Tweeters in-phase?

Have a pair of Quart tweeters mounted in the dash firing straight up to the glass, then reflecting back to my ears.  Does this put them out of phase?  I haven't played with it much, but I presumed I'd never hear a difference in-phase or not when they're crossed at 1k.

There's a second set in the rear doors firing inwards, actually at a 90 degree angle to the dash tweeters off the glass.

I guess this will be a pretty theoretical question if anyone can even answer it.  Thanks.

This will not effect the phase. Usually  hooking one up backwards will do that.

To be honest, I don't think you would be able to tell anyway.

The easiest way to see if they are out of phase or not is to play them as is, then switch the polarity on one of them, and try again.  Whichever is louder highs is in phase since when you put speakers out of phase, they effectively cancel a good portion of themselves out.

Sound quality is excellent - very crisp & defined, excellent staging, no fatigue at volume for long periods.  It constantly amazes me how good it sounds.  that said, I'm not really trying to solve a problem, just curious about phase "theory" after the waves reflect off of a 45 degree angle, then head towards a different set of drivers playing in a different axis.

The setup is this - '99 Jeep Gr Cherokee w/2 sets Quart 6.5 seperates (the "Reference" series) in F&R doors, the front tweeters in the dash, driven by 2 Soundstream 10.0 class A's @ 4ohm/100wpc.  X-over frequency is whatever the passive Quart x-overs set it at, I think it was 1k, could be 2k?   It's the same front & rear.  JL Stealthbox with a 10" W3 & a Soundstream Rubi throwing another 4-500w that way, actively crossed at 90hz.  Front tweeters are bright, so they're set to -6db.  Rear drivers aren't directly in line with my ears, so I play with the fader a bit to dial them in.

I've no doubt what the consequences of the low end being out of phase & how that cancellation would sound.  I've never known much about how the tweeters would sound out of phase, but I agree that it would probably result in long-term fatigue at the least.  So again, kinda lookin' for some theory from someone smarter than me. 

One day I may get around to pink-noise-ing the set-up, but a little afraid that I'd find a new problem & have to fix that, being a perfectionist.  Can anyone relate to that?  Thanks for the feedback.  Can anyone help with the turn-off thump?  That's really bugging me - check other posts.

Have a great weekend.

boulderguy wrote:

---

Can anyone help with the turn-off thump?

---

geepherder pointed you in a direction that will solve the problem.  As Nike says - "just do it".

Yeah, there have been numerous anal compulsive perfectionists frequenting this board (I'm not one of them) and some still lurking and contributing gold.  Sometimes it takes that kind of mentality to solve problems from afar, like over the internet.  Sometimes, though, it goes too far like when it's your own audio system and you are too severe of a critic.  Your first two sentences in the above post spells out your findings clearly:  don't keep messing with it.  Time to relax and enjoy!

boulderguy wrote:

---

Sound quality is excellent - very crisp & defined, excellent staging, no fatigue at volume for long periods.  It constantly amazes me how good it sounds.  that said, I'm not really trying to solve a problem, just curious about phase "theory" after the waves reflect off of a 45 degree angle, then head towards a different set of drivers playing in a different axis.

The setup is this - '99 Jeep Gr Cherokee w/2 sets Quart 6.5 seperates (the "Reference" series) in F&R doors, the front tweeters in the dash, driven by 2 Soundstream 10.0 class A's @ 4ohm/100wpc.  X-over frequency is whatever the passive Quart x-overs set it at, I think it was 1k, could be 2k?   It's the same front & rear.  JL Stealthbox with a 10" W3 & a Soundstream Rubi throwing another 4-500w that way, actively crossed at 90hz.  Front tweeters are bright, so they're set to -6db.  Rear drivers aren't directly in line with my ears, so I play with the fader a bit to dial them in.

I've no doubt what the consequences of the low end being out of phase & how that cancellation would sound.  I've never known much about how the tweeters would sound out of phase, but I agree that it would probably result in long-term fatigue at the least.  So again, kinda lookin' for some theory from someone smarter than me. 

One day I may get around to pink-noise-ing the set-up, but a little afraid that I'd find a new problem & have to fix that, being a perfectionist.  Can anyone relate to that?  Thanks for the feedback.  Can anyone help with the turn-off thump?  That's really bugging me - check other posts.

Have a great weekend.

---

I can relate to the perfectionist thing, but really... if it sounds fine, I wouldn't worry at all about phase.  There are a bunch of people that want phase to perfect, but there's another school of thought that says phase doesn't matter too much if the resulting frequency response is in the right ballpark.  I'm with the second school, especially in-car. 

On the crossover frequency, the passive Quart Reference set is much higher than 1khz.  Try 4.2khz.  See here: https://www.mbquart.com/2003/en_US/mbtech/car_cross_specs.asp  This is actually a -really- good thing for you.  Why?  Because any phase problems based on tweeter positioning are outside of the critical 250-3000hz listening range that really shapes the music and where are ears are the most sensitive.  Your tweeters won't be a full 12db down by 3khz, but they'll be quite attenuated compared to the midrange.  I wouldn't worry about the phase problem.

What one thing might I worry about with a crossover frequency that high and your tweeters positioned like they are?  A frequency response dip between where your midrange starts to rolloff when it is off-axis and where the tweeter picks back up.  This gap could have the tendancy to make your tweeters seem even brighter than they should be relative to your midrange and make your sound seem a bit separated.  In many systems set up the way you describe, there's a tendancy to really be able to pick out the fact that the midrange and tweeters are coming from different sources.  This shouldn't be noticable.  Anyway, I think this actually probably a more serious problem for you than phase, depending on how off axis your midrange speakers are.  How off axis are they?

On both issues, it will all probably boil down to how nuts you become over car audio and getting it perfect.  If either issue is important enough to you, you'll move the midrange and tweeter to the kick panels, with the tweeter as close to the midrange as possible, and both as on-axis as possible.... So, how badly has the audio bug bit you?

Cheers  :-)

Good info KFR01, sounds like you really know your stuff.  The passenger door mid is dead-on axis, my door is about 60 degrees off.  that creates a bit of a hole, but not too bad.  You may have something about a dip at the xover point tho, the tweeters do tend to be bright up there.  Maybe I should do that pink noise test.

there is a lot of seperation in the sound, but in a good way, not annoying - more like a good soundstage presence.  The signal processor I use is an Audiocontrol HPX, basically an expansion circuit.  It's the only one that brought life back to MP3's without making it sound too "hot" and annoying.  I like to believe this is creating a lot of the seperation I hear. 

I do hear a different location for mids & tweeters, but the net effect feels more like instruments being spreadout on the stage rather than listening to equipment spread across the stage.  Does that make sense?  My goal is ultimately to listen to the music, not the gear reproducing it.

BTW, nice system you've listed there.

I'd say the bug bites me on occasion over the last 20 yrs or so, I play with it until I like it, then leave it alone around the time it starts to own me more than I own it.  What started this episode was the idea of moving the entire music collection to MP3 & having it live permanantly in the car for trips.  Been thru 3 head units in the last month, finally found the right combo in the Alpine 9855 & a big Ipod.

Thought I'd found the holy grail with an in-dash MP3 player w/a hard drive - Dension DH100ix.  Unfortunately the SQ wasn't there at all, reminded me of a cheap CD player.  I imagine that's the direction it'll all go in a few years - a hard drive & electronic music collection.  Exciting to see all the new options in car audio, but disappointing waiting for them to come up to quality listening standards.  Also kind of sad to see all the hype directed towards the equipment over the music.  Heard Bruce Hornsby's "Gonna Be Some Changes"?  Or Verve [records] Remixed 3?  Wow.  Other new favs - Remy Shand, Mars Volta, Joss Stone, Jem, Jamiraquoi, Alana Davis, Maktub.

Pretty happy with the sound & functionality right now, will probably leave it alone for a few years.  Then again I'm due for a new car, probably a Subaru, that'll likely start the whole process over again.  anyway, enough, I'm getting on the bike for a while.  Good luck fiberglassin' those kicks.

stevdart wrote:

---

Yeah, there have been numerous anal compulsive perfectionists frequenting this board (I'm not one of them) and some still lurking and contributing gold.

---

I mentioned it before, I think in a few years we'll have gone mostly to an entirely electronic music collection, meaning MP3's or such on hard drives & toss the CD's out the window.  I'm referring to mainstream of course - I still have some virgin vinyl in my collection, but never use it anymore.

Music purchases will be thru the web, downloaded like Itunes.  Satellite radio will feature limitless internet radio choices.  HD-digital radio will go the way of Betamax.  Our home stereo/TV and car stereo will be an extension of the home PC.  Head units will be modelled after this.  (don't get that one, sound quality ain't good).  You will be able to grab the 200gb HD from your headunit, snap it into the computer thru USB (or hell, wireless in your driveway), transfer all your new music in 30 secs & be done.

By 2015, having a CD hanging from your rearview will be the equivelent of fuzzy dice today.  Before all that, I think we'll go to DVD's from MP3-CD's, roughly 10x the size.  Just waiting on the DA converters to be taken seriously.

Just looking in the crystal ball.  I added tweeters to the dash b/c I like the sound there.  Had to play with the angle to get dispersion right, but it works well.

I just re-read this, think I'll make a new thread to stir the pot...

haemphyst wrote:

---

kfr01, I just found out that the (blech) Kenwood MusicKeg supports flac! Available in 10G and 20G flavors, there are apparently 40, 60 and 80G cartridges available for it as well! The unfortunate part is they can only interface with our units via an RFModulator...

This unit looks like the same thing, but there are apparently adapters for various OEM head unit manufacturers... No Eclipse 8443 or 8051... dammit!

This information came from the Sourceforge website. I don't recall seeing it there before, do you?

The Neo does not support flac natively, but I am hoping soon they might have a plug-in for it...

---

Wow!  Those are new and were not on the Sourceforge website as of our last heavy discussion on this topic.  It is encouraging that some car audio products are finally starting to support flac!  Eclipse?  Are you listening?  ;-)

On this topic, because I still do have a large mp3 collection that I'm slowly moving over to lossless, I have found, taking the advice mp3 nuts on other forums, that these two pieces of software can help make mp3 sound the best it can be.

1)  Shibatch mpg123 input decoder - supports 24-bit upsampling and output, nice if you have a 24-bit soundcard.  The 16-bit output is also regarded as cleaner than the default winamp decoder.

2)  ASIO output plug-in.  Allows the bypassing of the windows API and communication directly with the sound card.  This cleans things up some.  Check that you have an ASIO compatable soundcard before using this.

Boulderguy, you asked what Redbook Audio and Tweeter Lobing are.

Redbook Audio is just the standard retail cd format.

Tweeter Lobing:  (slightly more complex)

I've been searching for a nice graphical representation of tweeter lobing, and finally found one.  Look here:  https://www.kettering.edu/~drussell/Demos/BaffledPiston/BaffledPiston.html

Alright.  Speakers beam energy in lobes.  (A lobe is just some sort of rounded projection).  Scroll down on the linked page about 3/4 of the way down to the heading of "High Frequency."  You'll see that in contrast to low and medium frequencie radiators a high frequency radiator (your tweeter) produces multiple lobes.  Between these lobes are dead spots.  The main lobe is relatively narrow.  In the pictures on that page, you can see that it is optimal to locate the tweeter under 20 degrees off axis.  The dead spots are caused by cancellation.  The side lobes and main lobe have different phase relationships.  As you can see in this next link, here:

https://www.kettering.edu/~drussell/Demos/superposition/superposition.html

under the heading "Two sine waves travelling in the same direction: Constructive and Destructive Interference," "when two waves have opposite-phase [180 degree difference], they interfere destructively and cancel each other out." 

This cancelation can also happen near the crossover point if your tweeter and midrange driver are not as close as possible.  This happens because your midrange and tweeter are essentially playing the same frequencies with similar amplitude near your crossover point.  You have two radiating sources.  Their waves head out and are either constructive or destructive.  At and around the crossover point you want constructive interference - keeping the frequency response flat i.e. briding the gap between the drivers.  Constructive interference is easiest to obtain if the drivers are on-axis and close together. 

Haemphyst once had a nice plain-language explanation that went something like this.  Two speakers are two radiating sources - like two stones thrown into a pond.  If thrown some distance apart they create two distinct circular ripples.  When the ripple edges meet, assuming the stones were the same size, they cancel out.  However, if two stones are dropped very close together they seemingly create one circular ripple together.  This is similar to the additive or constructive effect we want near our crossover point between the midrange and tweeter. 

Haemphyst, Dyohn, others, let me know if I can add to any of this.