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How to Achieve Awesome Mid Bass.

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URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=100789
Printed Date: June 20, 2021 at 11:34 AM


Topic: How to Achieve Awesome Mid Bass.

Posted By: speakermakers
Subject: How to Achieve Awesome Mid Bass.
Date Posted: January 05, 2008 at 4:58 PM

How to achieve awesome mid bass

I have recently received many questions about mid bass. Instead of making several replies I have opted to make this post. Questions and additions welcome.

This is one of the most complex and misunderstood topics in car audio for the following reasons that I will explain.

1.     Phase
You must be able to grasp the concept of sound in the incremental phase domain as well as sound in the frequency domain. I will explain.
2.     The cars dimensions
The car itself conflicts with good mid bass response do to various interior dimensions of a typical automobile coinciding with the physical size of sound waves in this frequency range.
3.     The misconceptions
The misconception that poor mid bass is due to low amplitude in this range. More won’t help. I will explain.
4.     Futile attempts
Many of the attempts people make to increase mid bass response only make it worse including gaining up, expanding crossover pass band, adding more speakers, and placing the mid bass drivers in an enclosure.   

The term mid bass can be interpreted many ways. In car audio however this band is pretty much set as the band between 50hz and 250hz. This is due to many reasons that are beyond the scope of this article. What’s important to understand is that in the 50hz-250hz range humans are the very least sensitive to variations in frequency response but we are the most sensitive in this range to changes in phase. As frequency rises above 250hz the opposite becomes true. Humans become less aware of phase response and much more aware of frequency response.

Phase
Phase is the angle measured at a given point on a sound wave.
posted_image

Here you can see that from where Homer sits the sound wave arrives at his ear at one angle but below you can see that when he changes is position relative to the speaker the angle of the sign wave changes as well.
posted_image

he can’t hear any difference in the sound. But when you add a second speaker things change.
posted_image

Now his brain is picking up one sound coming from two different places. His brain knows its coming from two different places partially because the phase angle is not the same. When this happens your brain will red flag this sound information as “invalid” and discard it. In nature this helps us localize where a sound is coming from. By discarding conflicting information our brain can better hone in on non conflicting information. This is one major reason why boosting the volume of your mid bass drivers will not make your mid bass sound better or much louder. The more you crank up the volume the more your brain will refuse the information and the worse it will sound.

The second reason is that because the sound waves from both your speakers are colliding with each other and due to the phase angles not lining up with each other they will add and subtract from each other, not necessarily amounting up to more volume. Again more speaker and power will not alleviate this effect. This also causes severe deviations of amplitude at higher frequencies causing what is known as the comb filter effect. When comb filtering happens your brains ability to sample that sounds qualities is greatly diminished because much of the information is either physically being destroyed due to phase cancellation or being discarded by your brain as it is perceived as invalid. This will actually make your highs sound metallic and harsh not to mention trashing any chance that you have at good imaging or authoritive mid bass.

The cars dimensions.
All modern vehicles have been purposely designed to emit all of their noises in the mid bass range. From the engine to the rumble of the tires to the sound of the AC system, every device in your car has been designed to keep their noises with in the 50hz-250hz range. From Mercedes to Honda, auto manufacturers have done their homework and know that people have an inability to perceive sounds based on frequency in this range. By limiting noises to this range the car will seem much quieter and any noises made are much more tolerable. Because this frequency range is already so cluttered your mid bass drivers need to be in proper acoustic phase and all precautions taken to ensure that they are performing correctly in order to overcome this noise floor. When this is done the end result is that your brain will accept this information (music) and reject all of the cars noises.    

Misconceptions
We already know that boosting the volume, power, speaker, and equalization is not the answer here. So you might be wondering, what’s the answer. Who do I have to kill to get good mid bass.
The best way to understand this is to first under stand what we are really after. Humans perceive strong mid bass best when there is a sudden change in volume that is coherent with the rest of the sound systems volume level. And when this sound has a fast attack and decay rate with little phase distortion. Not a bunch of power in a very limited frequency range that causes phase distortion all the way up to 10khz, which is too often the case.

The solution
Choose speakers with a low Fs (resonant frequency). Closer to 50hz than 100hz. The fact is that as a speaker attempts to reproduce sounds that are to close to its Fs phase distortion and consequently comb filtering becomes a problem. You need to try to keep your speakers operating above this range. Fortunately the cars transfer function will help with this. Often times allowing a hi pass of 80hz while still allowing strong reproduction down to 50hz. There are many tricks here that can be accomplished by using asymmetrical crossovers and parametric equalization but all of that is outside the scope of this article. Maybe some other time.
Choose speakers with a low Qts. Lower than .5 closer to .35. Keep in mind that as your Qts value gets lower you must choose a lower Fs as well. For example a speaker with an Fs of 85 and a Qts of .52 might reproduce 50hz just fine but a speaker with a Qts of .35 might need an Fs of 60hz to do the same. There is more to this subject but I am limited on space. Just keep that in mind.
If your speaker ends up in a small enclosure (less than 1 cubic foot) there is a very good chance that you will end up with a sharp resonant peak that will cause many of the problems that we have already discussed as well as increase the lowest usable frequency that can be reproduced. This may cause a gap in the lower mid bass frequency where the fundamental of drum sounds occur. With out the fundamental wave off a drum all that is left is unconvincing upper harmonics.
Doors work real well as mid bass enclosures. Just make sure to seal off all opportunities for the rear wave to ever meet the front wave.
In kick panel speakers vent the rear of the enclosure with a large resistive hole. This forms an aperiodic enclosure. This is also a useful technique to utilize on mid range enclosures.
Always attempt to align the phase of your sub with the phase of your mid bass speakers, and your mid ranges and your tweeters. As dumb as it sounds this is rarely ever done. You know the destructive nature of phase cancellation from just the one speaker on the other side of your car. What do you think that a 10” speaker can do? The fact is that a lot of musical information bleeds past the crossover points between the sub and the mid bass speakers and the transfer function of the car amplifies this.
Last but not least the easiest, fastest, least expensive, and most effective way to improve mid bass response is to simply add .4-.9 milliseconds of time delay to the left speaker. Doing this will largely correct both phase distortion and comb filtering while simultaneously increasing volume by eliminating cancellation. The best way to get time delay is to choose either a head unit or amplifier that has it on board. Be aware though that head units that have factory preset positions are of little or no use. You will need incremental adjustability.

Questions welcome.   



Replies:

Posted By: sedate
Date Posted: January 07, 2008 at 7:00 AM

speakermakers wrote:

Last but not least the easiest, fastest, least expensive, and most effective way to improve mid bass response is to simply add .4-.9 milliseconds of time delay to the left speaker

I've noticed this but I thought I was crazy.



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"I'm finished!" - Daniel Plainview




Posted By: Alpine Guy
Date Posted: January 07, 2008 at 8:05 AM
I like this article very much, it clears up a lot of confusion that I had with the mid bass issue.

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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.




Posted By: crewwzin
Date Posted: January 07, 2008 at 8:47 AM
Thank you for posting this. Very informative and helpful. I plan on putting this to use.

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I'd rather be in the boat with a drink on the rocks, than in the drink with a boat on the rocks!




Posted By: Steven Kephart
Date Posted: January 07, 2008 at 8:27 PM
Great information Speakermakers!  I love the use of Homer Simpson; a true audiophile. posted_image




Posted By: speakermakers
Date Posted: January 07, 2008 at 10:46 PM
Thanks guys for the very positive feedback. Let me know if I left out any information that might make this an easier read. Questions welcome.




Posted By: jmelton86
Date Posted: January 07, 2008 at 11:31 PM

My midwoofers have an fs of 42Hz, a qts of .28, i've got them wired in phase with my sub, and i've got time-correction.

So, I guess i've got awesome midbass.posted_image

But really, nice write-up!



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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001




Posted By: Steven Kephart
Date Posted: January 08, 2008 at 12:44 AM
jmelton86 wrote:

My midwoofers have an fs of 42Hz, a qts of .28, i've got them wired in phase with my sub, and i've got time-correction.

So, I guess i've got awesome midbass.posted_image

But really, nice write-up!


Mine have a Qts of .332 and an Fs of 30 Hz.  They are also used in my home theater towers which produce impressive sub bass along with the midbass. posted_image  Baby's got back.





Posted By: jmelton86
Date Posted: January 08, 2008 at 12:56 AM
Steven Kephart wrote:

jmelton86 wrote:

My midwoofers have an fs of 42Hz, a qts of .28, i've got them wired in phase with my sub, and i've got time-correction.

So, I guess i've got awesome midbass.posted_image

But really, nice write-up!


Mine have a Qts of .332 and an Fs of 30 Hz.  They are also used in my home theater towers which produce impressive sub bass along with the midbass. posted_image  Baby's got back.

Nice! You realized this while watching Sky Captain, right? LOL.

Yeah, I'm gonna get the 8" versions of my 5.5's for my home stereo system... eventually.



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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001




Posted By: Steven Kephart
Date Posted: January 08, 2008 at 1:51 AM
jmelton86 wrote:

Nice! You realized this while watching Sky Captain, right? LOL.

Yeah, I'm gonna get the 8" versions of my 5.5's for my home stereo system... eventually.


It was King Kong tonight, and Apollo 13 last night.  I'll probably pop in Sky Captain pretty soon as I just got it on Hd-DVD.  But first will be We Were Soldiers.  That should be pretty much a non-stop subsonic fiasco, along with some amazing music.  My boss and I watched it at Adire in the warehouse and when the credits pop up and the male choir starts singing, it was absolutely breathtaking.  Imagine how it will sound in Dolby TrueHD. posted_image

BTW, if you want another option for a midbass, here's an excellent one using an XBL^2 motor: https://www.creativesound.ca/pdf/CSS-SDX7-data-261207.pdf





Posted By: khanhfat
Date Posted: January 12, 2008 at 11:13 PM
anyway.. components ratings are as low as 30hz and in real life testing when using a test tone CD, it can only perform 125hz and above... so who's trustable and which speakers models?   looking at 6.5" inch speakers.




Posted By: speakermakers
Date Posted: January 13, 2008 at 6:26 PM
Who’s trustable is a great point.
The most common reason that you will encounter frequency plots that show a 6.5” speaker with strong response at 30hz is that that response shows the typical in car response. And that’s valid, even with an Fs of 65hz. But you must be aware of what you are looking at. With mid bass speakers we are not concerned with its ability to play down to 30hz, we are concerned however with making sure that Fs is below the frequency that we are attempting to accurately reproduce. If the speaker can play down to 30hz but the Fs is at 65hz and the Qts is at .5 (for example) the speaker will not be able to quickly respond to any music in the 30-80hz range. Speakers are the least accurate at or near the resonant frequency (Fs). As Qts gets higher this inaccurate range broadens. This is why low Qts speakers are generally superior.
The reality is that most manufactures will either miss print specifications or print specifications from prototypes (not the speaker you buy). And some manufacturers will just flat out lie. It seems though that this is more of a subwoofer problem. Consumers don’t look at the specifications of high frequency speakers, so manufactures don’t even waste their time printing the lies. Also it seems that mid bass speakers don’t suffer the fate of constant reengineering that subs often do. Ever find your self wondering if you sub is a V1 orV2? Or 6 or 9?

With a laptop and a multi meter it’s quick and simple to test Fs and Qts your self. This is what I do. If it looks like the printed specifications are pretty close to my results then I assume that the rest (less critical) are also accurate.

I have entertained the idea of posting a how to on this subject, but I think it might be a little out of range for most viewers of this site. Let me know if any of you are interested. I just would hate to put a lot of my time into something like that and not have anyone read it.




Posted By: tp1182
Date Posted: February 07, 2008 at 12:41 AM
Great topic and info, I'm trying to figure out speaker placement possibilities in my '92 Accord Sedan. Any suggestions would be greatly appreciated as well as any speaker recommendations,

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Education, like life is a continuous journey.....




Posted By: speakermakers
Date Posted: February 09, 2008 at 12:39 AM
Two way or three way? What is the crossover frequency? If you are using a two way component set with a crossover frequency around 2.5khz (check your speakers documentation) then locating the tweeters in the bottom of the “A” pillars is a good option. If you are using a two way that has a higher crossover frequency (3.5khz or higher) the benefits of placing the tweeters up high is out weighed by the disadvantages of diffusing the human vocal range. In this case you are much better off keeping all drivers in close proximity to each other (tweeters in the kick panels or lower portion of the doors). 92 Accords have great line of sight to both kick panels and an excellent left to right distance ratio. In the event that you have a three way set up with a dome mid then I suggest locating both the mid and the tweeter in the “A” pillar. If you have a cone type midrange then I suggest locating it high and forward in the door (close to the tweeter in the “A” pillar) or in the kick panel with the tweeter also located in the kick.
As crossover frequency rises it becomes more critical to physically place drivers in close proximity to each other. Even digital time alignment becomes a less effective tool as frequency rises. Also always consider the dispersion characteristics of your particular speakers. Mount your mid basses in the doors and play with temporary tweeter positions. Pay attention to how your tweeters sound when slightly off axis. Is the sound degraded to an unacceptable level when slightly off axis? Or not? I can provide you with some absolute information on this if you provide me with some additional information. Ultimately though you will have to experiment with some elements.

As far as speaker recommendations, the Focal poly glass V2 165 is one of the best car audio two way component sets ever produced specifically for car audio for under $1,000 (they are sold for around $450 at most stores). The tweeters perform well even when aimed 20 degrees off axis and the poly glass mid is one of the best midbass-mid ranges that I have ever encountered.





Posted By: tp1182
Date Posted: February 09, 2008 at 9:54 PM
Thanks, speakermakers, that was very informative. I am looking at a couple different two ways and one or two three ways.  I've thought about possibly doing a dual component set up in the front but I was wondering if that would be overkill or just too tacky to pull off.  That way I can use the kicks and seal off the door panel for a 6 1/2 woofer and still do a tweeter in the "A" pillar to bring my highs up like you suggested (the component set I'm leaning towards has a 2.6kHz crossover frequency).  I don't really have passengers in the back so, I'm thinking how to get some pretty decent midrange there also with little to no freqeuncy  gap between the speakers and subs.  When I'm not beating down the block, I still want a full sound when I'm not playing the subs. Any ideas on that one??

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Education, like life is a continuous journey.....




Posted By: speakermakers
Date Posted: February 11, 2008 at 12:15 AM
Some things to keep in mind.

You want to achieve around 2.5khz and up at the “A” pillars as a minimum. Even at this frequency you must still manually manipulate both the amplitude and the phase (incrementally) in order to avoid a very disappointing defused human vocal range (this also covers many popular instruments). Because of this I strongly recommend not even attempting this unless you either have multi-channel/electronic crossover capabilities (ditching the passive crossovers) or you are willing to take a gamble with the odds of success stacked against you.
One example of how to do this.
In one of my own rides I have 1” tweets in the “A” pillars and 6.5” mids in the doors. I power the mids off an amp but I use the amplifier built into my Eclipse 8455 (CD player) to power the tweeters. This is plenty of power for my tweeters (speaker power requirements decrease exponentially as frequency rises). My Eclipse head unit also has electronic crossovers and digital time alignment built in to it and that makes this an ideal (and economical) arrangement.
If you want to use the passive crossovers that come with component sets then I urge you to go with a three way set that contains a dome type midrange. This way you can locate the dome mid in the pillar with the tweet and achieve fairly low frequencies up high on the dash. Of coarse this is also a great way to go with active crossovers as well. Point is that Tweets alone in the “A” pillars is great but requires some finesse. Be prepared.
What not to do.
Don’t put a 6.5” in a small kick panel with an identical 6.5” in the door. This is begging for phase issues and consequently poor mid bass. Even if they do not share the same pass bands.
Don’t use more than 1 pair of tweeters in the front of your setup. This will guarantee harsh comb filtering and no chance of decent sound quality.
As far as three way speaker sets with a dome mid go, I recommend the Hertz High-energy three way ($500) or if you have the dough the Zapco comp three way component set ($2,100).




Posted By: tp1182
Date Posted: February 11, 2008 at 1:14 AM
Wow, that's why its good to get a second opinion so , scrap that idea. I was actually considering getting the Eclipse CD5000 myself but I may opt for a Nav. unit and use an outboard processor. The Nav. unit I'm considering is the AVN 6610 but last I checked it didn't offer time alignment.  Since I was thinking in that direction I was trying to see if anyone actually makes an outboard processor that has time alignment capablity. Other than that I'm just weighing my options right now.

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Education, like life is a continuous journey.....




Posted By: speakermakers
Date Posted: February 11, 2008 at 9:56 PM
Last I knew Eclipse offered a nav with great DSP features in their line up, but I am not up to date on this years product. Audio control has great digital processors with time alignment that use RCA in puts and out outs, and Zapco makes a killer piece that can use digital input as well as RCA or balanced inputs. The cool thing about getting a dedicated out board processor is that you are free to pick and choose your headunit and amplifiers. Be aware though that many (most all) video/navigation units have inferior digital to analogue converters and weak pre-amps. This can ruin your best efforts.
If you can find a head unit with digital out and you get the Zapco processor you will be able to achieve one of the best possible signal paths, and precision control over every speaker in your system. All adjustments are performed by software on your PC.
This gives you a great visual tool. You can actually see in real time what modifications you have made to the signal. This makes things easy to understand.
posted_image
In the time alignment (lower right hand corner) the software even calculates distance for your adjustments, making it a snap!
But that’s just one of many great possible options.




Posted By: tp1182
Date Posted: February 18, 2008 at 10:23 PM
Ok, after your last reply I check out AudioControl to see what they offered that would be useful in my application.  I'm thinking that if I go with the DQXS processor.  How do you feel about 6.5" subs?? I've been looking at them and wondering what the possibilites are with those.

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Education, like life is a continuous journey.....




Posted By: trae08
Date Posted: March 16, 2008 at 6:12 PM
umm i bet this is a stupid question but how do you add a delay to the left side?




Posted By: falconyellow
Date Posted: March 31, 2008 at 9:01 PM
This is an awesome post, very informative.

Questions:

How far out of phase do the two speakers have to be before a difference becomes audible? I suppose that time arrival and phase differences would depend both on the frequency as well as the actual difference in path length?

I guess what I'm wondering, is how far off in path length can you get before the difference becomes audible (reflections excluded).

Also, can you use something like the phase plot in WinISD to determine where a mid bass/sub combo should be crossed over? Or does the install affect this too much?

Thanks for the great info!




Posted By: Steven Kephart
Date Posted: March 31, 2008 at 11:10 PM

falconyellow wrote:

This is an awesome post, very informative.

Questions:

How far out of phase do the two speakers have to be before a difference becomes audible? I suppose that time arrival and phase differences would depend both on the frequency as well as the actual difference in path length?

I guess what I'm wondering, is how far off in path length can you get before the difference becomes audible (reflections excluded).


About 3 miliseconds at around 1kHz and longer as you move up and down the frequency band.





Posted By: thadrizzle
Date Posted: April 09, 2008 at 10:43 PM
Thank you, that is easily the most unasnwered question in car audio.  This to me is more important than BASS BASS BASS!!!! and I was deafining myselg with my highs.  Thanks again.

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I love this stuff. Took me 34 years to find my calling but, I think this is it. I love pulling wires he! he!




Posted By: jfinks
Date Posted: April 10, 2008 at 11:33 PM

speakermakers wrote:

With a laptop and a multi meter it’s quick and simple to test Fs and Qts your self. This is what I do. If it looks like the printed specifications are pretty close to my results then I assume that the rest (less critical) are also accurate.

I have entertained the idea of posting a how to on this subject, but I think it might be a little out of range for most viewers of this site. Let me know if any of you are interested. I just would hate to put a lot of my time into something like that and not have anyone read it.

Um Please do! I have always favored the Dynaudio MW160's for mid bass. The Fs is 55 and QTs is .51 I tend to use very step (24 to 48dB) electronic cross-overs and run them higher than you are recomending 65Hz or 80Hz to around 200Hz. I prefer even order here vs odd order. Your information is great! If you are curious this is a link on the slow going processof system building I am currently in.





Posted By: DYohn
Date Posted: April 14, 2008 at 10:22 AM

jfinks wrote:

Um Please do! I have always favored the Dynaudio MW160's for mid bass. The Fs is 55 and QTs is .51 I tend to use very step (24 to 48dB) electronic cross-overs and run them higher than you are recomending 65Hz or 80Hz to around 200Hz. I prefer even order here vs odd order. Your information is great! If you are curious this is a link on the slow going processof system building I am currently in.

HERE's a good tutorial on measuring loudspeakers yourself.



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Posted By: jfinks
Date Posted: April 16, 2008 at 6:51 PM

DYohn] wrote:

A href="https://sound.westhost.com/tsp.htm">HERE's a good tutorial on measuring loudspeakers yourself.

OoO you know how to get my interest....

Thanks DYohn





Posted By: falconyellow
Date Posted: April 17, 2008 at 12:39 AM
So back to the midbass issue, if you have "rear fill" speakers playing in this same frequency range (or at least in the upper end of it) won't this potentially cause some major arrival time variations? I know some guys who like to delay the rear fill to give spaciousness, I'm guessing this can cause some bad cancellations at some frequencies?

Any takers? Or is this another topic in itself?





Posted By: jmelton86
Date Posted: April 17, 2008 at 12:43 AM
I would think that having the rear fill delayed (exact OPPOSITE of what you want...) would cause some kind of cancellation.

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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001




Posted By: DYohn
Date Posted: April 17, 2008 at 12:27 PM
Yes it's a topic unto itself but yes, any time you use multiple speakers to reproduce the same frequency ranges it can cause cancellation effects, but using time delay properly will allow yu to eliminate this effect.  If you'd like to discuss further, please start a new topic.

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Posted By: speakermakers
Date Posted: April 24, 2008 at 1:53 AM
I am currently working on a manufacturer show system that employs a single 5” driver in the rear deck that plays from 100-2Khz. The driver is delayed by more than 20 ms and is attenuated in such a way that the sound being emitted from it appears to the listener as a reflection from a distant (nonexistent) wall. This gives the effect of a large listening area. More importantly it gives me control over the apparent size of the listening area.

After just a couple milliseconds of delay the human brain is capable of deciding that a sound is being emitted from a disconnected source. This helps both with the illusion of creating a false reflection and avoiding phase issues. If your brain is not attempting to triangulate a single position of a single sound because it assumes that the delayed sound is a second though related entity then frequency becomes the dominant factor rather then phase.

Of coarse phase is still a factor. My approach is to attenuate the rear speaker to a convincing level (reflections are much lower in level then the source). Secondly I align the phase of the rear speaker to match the phase of the midbasses up front at the hi pass crossover frequency. At a given frequency such as the corner of a hi pass crossover at 100hz the phase will cycle from 0-360 degrees as the delay increases and becomes equivalent to the physical size of that frequency wave. Phase will eventually revert back to zero (360x2=720. 0,360,720 and so on are all essentially phase coherent). Once you delay more than a few times the wave length your brain will decide that it is now hearing two different yet related sounds. As frequency rises phase becomes less and less of a factor.

I have also found that eliminating peaks in the lower response of both the front midbass drivers and the rear driver is critical. A sharp knee and rise in the lower end response of any speaker will kill your efforts to fool your brain into thinking that a sound is located elsewhere. So small sealed enclosures are out. A well damped enclosure is key. In a car that usually means an infinite baffle configuration with dynasorb type materials behind the drivers. Alternatively aperiodic vented enclosures can work quite well.
posted_image




Posted By: speakermakers
Date Posted: April 24, 2008 at 2:59 AM
Some things worth mentioning to avoid confusion.
Changing path lengths physically or by DSP will affect phase across the entire frequency range of a driver but the degree of change is frequency dependant due to the physical size difference in wave length at various frequencies. Keeping in mind that the human ear is most phase sensitive at low frequencies and most sensitive to amplitude changes at higher frequencies it is easy to understand why phase is primarily a low frequency concern (1khz down). In the case of midbasses pay attention to the phase at the lower limit of the driver (crossover point).

Though phase angle changes with frequency it is not a concern. As long as phase is consistent with other drivers emitting that same frequency band at that frequency. Shifts in phase due to changing wave length (frequency) occur naturally and are undetectable by the human ear so long as they are not drastic shifts (like those caused by poor enclosure and crossover design). Use a wave length calculator to determine the wave length at the crossover frequency of a driver. Knowing the physical size of this wave will help you understand how much phase will be affected by any distance changes you might make.

At what point is a speaker to far out of phase? The human ear is quite tolerant of phase differences at all frequencies up to 90 degrees. As phase shift approaches 180 degrees near total cancellation occurs at that frequency. This causes both phase and amplitude red flags for the brain and will result in a gap at that frequency range. Regardless of the degree of phase shift be prepared to compensate for acoustic loss any time a phase shift is encountered. This is why there is typically a ripple in the frequency response at a crossover point. Even with a good crossover design.

Last but not least. Keep all of your phase sensitive drivers, such as mid basses and mid ranges (group delay afflicted might be a better term) crossed over (hi passed)at 12db or better and at twice the resonance (Fs). All speakers are least accurate at or near resonance (Fs). Subwoofers bend this rule because signal delays rapidly become less detectable below 75hz. But that’s a whole story in its self!




Posted By: SlayerpUNKclint
Date Posted: April 25, 2008 at 7:48 PM
I am having a hard time finding any devices: amps, head units, or otherwise, that have a time delay function built into them. What kind of device should I be looking for? Also, can I achieve this .4 ms time delay by using excessive lengths of speaker wire for the left speaker?




Posted By: speakermakers
Date Posted: April 25, 2008 at 11:52 PM
No. Excessive lengths of speaker wire will not have the same effect. My favorite brands for these types of devices are Zapco, Audiocontrol, and Eclipse. There are a ton of great products out there made by many different manufacturers that can do this. Personally I prefer products that are strait forward in their function. Zapco, Audiocontrol, and Eclipse are very good about this.

My advice to anyone looking for both a head unit and a preamp/EQ combination, is to seek out a head unit with digital out and a preamp/EQ with digital in. This alone can resolve many problems. Equipment with digital in/out is generally designed with performance in mind. Head units with digital out usualy output digital information in its purist form (no resampling) because it’s easier and cheaper for the manufacturer to do so. Once a digital signal has been converted to analog it must be reconverted back to digital in order to be processed by a digital preamp/EQ and then re-reconverted back again to analogue. Though the benefits of DSP can by far out weigh the losses from the conversions, the fact of the mater is that the signal suffers audible quality loss every time it is converted. By only converting to analog once you side step this and about a dozen more issues in one cost effective step.




Posted By: brianthechemist
Date Posted: May 16, 2008 at 10:16 AM
So am I correct in assuming that the old school Precision Power Phase shift controller (PSC-221, the manual is here https://narbi.free.fr/manuels/Autoradios%20-%20Proc/Precision%20Power/psc221.pdf ) is really just some type of analog delay? I'm thinking of picking one up to help my imaging and came across this thread.

Would you be able to use this to rephase the midbass? (the manual specifically states that it is for use on the midbass frequencies)




Posted By: badboyjt
Date Posted: May 16, 2008 at 3:54 PM

so i wanted to upgrade my stock speakers to better ones. i want to get good mid-bass but i don't with which speakers to go with. any recomendations. thanks





Posted By: dah buzzman
Date Posted: May 24, 2008 at 7:30 AM

speakermakers wrote:

How to achieve awesome mid bass
 , , ,
The solution
Choose speakers with a low Fs (resonant frequency). Closer to 50hz than 100hz.

. . . Choose speakers with a low Qts. Lower than .5 closer to .35.

. . . Doors work real well as mid bass enclosures. Just make sure to seal off all opportunities for the rear wave to ever meet the front wave.
Questions welcome.   


This is a well written post, but I have a question regarding the above statements.  You suggest using speakers with a low Qts.  But if they are going to be mounted in doors, shouldn't the speakers have a higher Qts because the doors do not provide a completely sealed enclosure, and the speakers are essentially mounted in an infinite baffle configuration? 

One very knowledgeable car audio afficionado recently advised me as follows when I asked for his thoughts on an 8" woofer I was considering using in my car doors which had a Qts of .36, and Fs of 26 Hz, Qes of .41, Qms of 2.8, Vas of 71 Liters:  "it will do OK as midbass with low to mid power, but resolution looks like it will suffer due to low internal damping resistance to being mounted free-air. Low Qts drivers tend to unload at high volume and become sloppy and prone to over-excursion. Your saving grace is the limited bandwidth you will be playing. Also a neg is the low res freq. if this is to be a midbass driver. Look for a res freq above 50Hz and a Qts above .45 and you will have a driver that will sound great in that freq range!"  Your thoughts would be much appreciated!!



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It's The Music That Matters!




Posted By: DYohn
Date Posted: May 27, 2008 at 1:07 PM
Qts above 0.5 will always work better in an IB alignment.  Lower fs will sound better at the lowest FR extreme.

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Posted By: bigkevo
Date Posted: May 27, 2008 at 1:10 PM

I wish I would have come across this info years ago. I just spent $$$ on some Alpine spx-17refs but i would have bought some Focals had I known better. I drive a 04 Mustang and I just finished dividing the factory rear enclosure for the Alpines when I found this post and found out they should not be in small sealed enclosures. How should I go about installing them? Should I mount them in the rear deck with those baffel cups?

I just remembered I did it on my boat too, I built small sealed enclosures for them. Should I open them up or port ithem? Should I use baffles? Thanks .





Posted By: jmelton86
Date Posted: May 27, 2008 at 6:40 PM
bigkevo wrote:

I wish I would have come across this info years ago. I just spent $$$ on some Alpine spx-17refs but i would have bought some Focals had I known better. I drive a 04 Mustang and I just finished dividing the factory rear enclosure for the Alpines when I found this post and found out they should not be in small sealed enclosures. How should I go about installing them? Should I mount them in the rear deck with those baffel cups?

I just remembered I did it on my boat too, I built small sealed enclosures for them. Should I open them up or port ithem? Should I use baffles? Thanks .


If you use sealed boxes for speakers designed for IB they have to be really big. Otherwise you could just have it in an open chamber. That is, the driver mounted on one side on this 'chamber', with the other side open. You would use a good amount of deadening on the inside of the chamber..

In your case, you could just open the other side of these boxes you made for them, and add some sound deadener.



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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
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Posted By: fuzzcar
Date Posted: June 28, 2008 at 10:30 AM

Where do I find a manufactuerers specs on Fs and Qts of their speakers? I dont see it on their website.

Whats some less expensive brands and models that have good specs in this area?





Posted By: bwket
Date Posted: June 30, 2008 at 10:16 AM
Lots of good information Speakermakers. Thanks. You mention in the post using an "enclosure with a large resistive hole." for midbass and midrange speakers. Midrange enclosures is a topic I've been researching and can't really find even a general rule of thunb for. Or I guess I should say, the proper way to mount them for best SQ and accuracy. Subs are easy enough using software, speaker parameters, and listening experience but with mids, what is "accurate" for their reproduction? I've used sealed back mids and regular open back. They've been door mounted, kick panel, door pod, and dash mounted and all sound pretty good while covering the required frequency spectrum. But I've also noticed that changing the enclosure size, stuffing, even the enclosure shape all have an effect on the sound to an extent. How do I know what the mid is producing from the enclosure is truely accurate musical information, and not adversely affected BY the enclosure?




Posted By: nickdahl
Date Posted: July 14, 2008 at 9:05 PM

This is a very interesting thread, and I hope I'm getting the right ideas, as I dial in my newly-installed car stereo.  Please help me with the following questions.

speakermakers wrote:

In the case of midbasses pay attention to the phase at the lower limit of the driver (crossover point).

If my crossover point is 85Hz, does this mean I'd want to pay particular attention to the 85Hz wavelength, and where my listening position is located within the phase of the 85Hz wavelength?

speakermakers wrote:

Though phase angle changes with frequency it is not a concern. As long as phase is consistent with other drivers emitting that same frequency band at that frequency. Shifts in phase due to changing wave length (frequency) occur naturally and are undetectable by the human ear so long as they are not drastic shifts (like those caused by poor enclosure and crossover design). Use a wave length calculator to determine the wave length at the crossover frequency of a driver. Knowing the physical size of this wave will help you understand how much phase will be affected by any distance changes you might make.

Do I understand this right?  If a given frequency has a wavelength of "x," and I move the driver 1/2x (one-half x), the wave's phase would be 180 degrees different from where it was originally.

speakermakers wrote:

Regardless of the degree of phase shift be prepared to compensate for acoustic loss any time a phase shift is encountered. This is why there is typically a ripple in the frequency response at a crossover point. Even with a good crossover design.

In this case, do you compensate by boosting the affected frequency?

speakermakers wrote:

Keep all of your phase sensitive drivers, such as mid basses and mid ranges (group delay afflicted might be a better term) crossed over (hi passed)at 12db or better and at twice the resonance (Fs). All speakers are least accurate at or near resonance (Fs).

Again, do I have this right?  My speaker's Fs is 42.5Hz, so I'd set the high-pass at 85 Hz and at least 12dB (would 24dB or higher be even better?).





Posted By: theignorantone
Date Posted: July 25, 2008 at 12:33 AM

speakermakers wrote:

Misconceptions
We already know that boosting the volume, power, speaker, and equalization is not the answer here. So you might be wondering, what’s the answer. Who do I have to kill to get good mid bass.
The best way to understand this is to first under stand what we are really after. Humans perceive strong mid bass best when there is a sudden change in volume that is coherent with the rest of the sound systems volume level. And when this sound has a fast attack and decay rate with little phase distortion. Not a bunch of power in a very limited frequency range that causes phase distortion all the way up to 10khz, which is too often the case.
 

Your very eloquent post, is this spoken based on experience or theory based expectations?  Are you discussing dedicated midbass or the usual 2 way front set up?  I am very curious why you say more is not better?  Maybe ENOUGH is the right answer?  In real world, road noise seems to be the king, given the typical urge to run a pretty strong sub bass section, achieving a balanced sound may very likely warrant very strong midbass, capable of producing levels sufficient to make the sub bass and midbass transition very smooth (I think this may warrant a lower subwoofer lo pass filter point?)  From what I know (and I know very little), humans perceive strong midbass when there is a strong midbass, not through the sudden changes but through sheer output within frequency band that is needed).  Not sure why too much power is bad?  Considering music dynamics and energy needed to support output in lower freqs, having more is considerably safer than having just enough (what do you do trying to deal with 6dB peak in midbass region?)

[QUOTE]
The solution
Choose speakers with a low Fs (resonant frequency). Closer to 50hz than 100hz. The fact is that as a speaker attempts to reproduce sounds that are to close to its Fs phase distortion and consequently comb filtering becomes a problem. You need to try to keep your speakers operating above this range. Fortunately the cars transfer function will help with this. Often times allowing a hi pass of 80hz while still allowing strong reproduction down to 50hz. There are many tricks here that can be accomplished by using asymmetrical crossovers and parametric equalization but all of that is outside the scope of this article. Maybe some other time.
Choose speakers with a low Qts. Lower than .5 closer to .35. Keep in mind that as your Qts value gets lower you must choose a lower Fs as well. For example a speaker with an Fs of 85 and a Qts of .52 might reproduce 50hz just fine but a speaker with a Qts of .35 might need an Fs of 60hz to do the same. There is more to this subject but I am limited on space. Just keep that in mind.
If your speaker ends up in a small enclosure (less than 1 cubic foot) there is a very good chance that you will end up with a sharp resonant peak that will cause many of the problems that we have already discussed as well as increase the lowest usable frequency that can be reproduced. This may cause a gap in the lower mid bass frequency where the fundamental of drum sounds occur. With out the fundamental wave off a drum all that is left is unconvincing upper harmonics.
Doors work real well as mid bass enclosures. Just make sure to seal off all opportunities for the rear wave to ever meet the front wave.
In kick panel speakers vent the rear of the enclosure with a large resistive hole. This forms an aperiodic enclosure. This is also a useful technique to utilize on mid range enclosures.
Always attempt to align the phase of your sub with the phase of your mid bass speakers, and your mid ranges and your tweeters. As dumb as it sounds this is rarely ever done. You know the destructive nature of phase cancellation from just the one speaker on the other side of your car. What do you think that a 10” speaker can do? The fact is that a lot of musical information bleeds past the crossover points between the sub and the mid bass speakers and the transfer function of the car amplifies this.
Last but not least the easiest, fastest, least expensive, and most effective way to improve mid bass response is to simply add .4-.9 milliseconds of time delay to the left speaker. Doing this will largely correct both phase distortion and comb filtering while simultaneously increasing volume by eliminating cancellation. The best way to get time delay is to choose either a head unit or amplifier that has it on board. Be aware though that head units that have factory preset positions are of little or no use. You will need incremental adjustability.

Questions welcome.   
[/QUOTE]

This solution, what size of drivers are you discussing?  There may be some drivers out there capable of functioning perfectly in a tiny sealed enclosure (if you pick the right driver) that do not have the issues you mention, in fact, I am pretty sure there are a few ... Seems to me this solution may be just another band aid to avoid the only realistic solution which would involve some larger (make the greater sensitivity your friend when efficiency is at stake) decoupled from the typical door cavity, unless you prefer to post another article with advise how to deal with interior limitations due to flexing and rattling door skins?  And of course, there is resonance to deal with but parts of your advice, discussing filter points and eq should take care of this rather easily?

About that left side delay, this sound like another trouble waiting to happen, considering the relative distances between other drivers and then the subwoofer itself... What can 10 inch driver do while being used as a dedicated midbass?  You tell me... For one thing, it should allow you to produce enough low end extension and output to allow the subwoofer to function merely as a filler without supplying too many directional cues that can cause way more headache than issues you mentioned... Or have you tried those 10 inch midbasses already? 






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