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How to Achieve Awesome Mid Bass.


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speakermakers 
Copper - Posts: 231
Copper spacespace
Joined: January†02, 2003
Location: United States
Posted: April†24, 2008 at 2:59 AM / IP Logged  
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 thatís a whole story in its self!
SlayerpUNKclint 
Member - Posts: 1
Member spacespace
Joined: November†12, 2004
Location: United States
Posted: April†25, 2008 at 7:48 PM / IP Logged  
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?
speakermakers 
Copper - Posts: 231
Copper spacespace
Joined: January†02, 2003
Location: United States
Posted: April†25, 2008 at 11:52 PM / IP Logged  
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 itís 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.
brianthechemist 
Member - Posts: 17
Member spacespace
Joined: August†16, 2007
Location: United States
Posted: May†16, 2008 at 10:16 AM / IP Logged  
So am I correct in assuming that the old school Precision Power Phase shift controller (PSC-221, the manual is here http://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)
badboyjt 
Member - Posts: 1
Member spacespace
Joined: May†13, 2008
Location: Oregon, United States
Posted: May†16, 2008 at 3:54 PM / IP Logged  

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

dah buzzman 
Member - Posts: 1
Member spacespace
Joined: May†24, 2008
Location: California, United States
Posted: May†24, 2008 at 7:30 AM / IP Logged  

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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DYohn 
Moderator - Posts: 10,735
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Joined: April†22, 2003
Location: Arizona, United States
Posted: May†27, 2008 at 1:07 PM / IP Logged  
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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bigkevo 
Member - Posts: 1
Member spacespace
Joined: May†27, 2008
Location: California, United States
Posted: May†27, 2008 at 1:10 PM / IP Logged  

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 .

jmelton86 
Gold - Posts: 1,228
Gold spacespace
Joined: February†07, 2007
Location: South Carolina, United States
Posted: May†27, 2008 at 6:40 PM / IP Logged  
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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fuzzcar 
Member - Posts: 4
Member spacespace
Joined: June†23, 2008
Location: Kentucky, United States
Posted: June†28, 2008 at 10:30 AM / IP Logged  

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?

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