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Discussion Starter #182
If anyone outside of the MECA circle in the south and midwest, Ben Vollmer (who is a good friend to many of us and owns Audition Audio and Electronics) bought what was once Harry Kimura's Acura Legend and after it spending many years in limbo around Tennessee with it's previous owner, Georgia and here in North Carolina, and it made it's way to Mobile Soundstage Engineering in Bixby, OK where it underwent a COMPLETE rebuild by Mark Eldridge...including an array front stage.
That's the second 'horn dude' I know of that switched over to the dark side. (IE, "line arrays")

The first was D.B. Keele

 

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well.

so far, there are certain bandpass that play up on the dash that really make you try to hear it coming from behind, and there are certain areas that pull back around my shoulders or the headrests. i have not done any EQ, and only have basic time alignment and levels set. ive been driving around for about two weeks with it so far.

theres times where i am like 'holy crap this is awesome' and times where im like 'i wonder what frequencies this is becuase its pulling back a little'. most of the time, the tight punch of a kick-drum will be way up front, maybe because the incident sound is from the midrange, followed by the midbass? and most of the time i end up hearing rolling bass guitar pulling backward toward the "rear" midbass.

i have not had much time to expierment.







 

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Req,

What frequency do you have them crossed?

My sub manifolds are going in the same spot, but will only play up to 150hz, where the mids will take over. The experiments I have done in my living room, the manifold does not pull my ear back as long as I have mids taking over from 150hz, and tbose mids are placed to the left and right Opsodis style.
 

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I have a question.

Vertical arrays have better horizontal dispersion and vice versa.



Every time you sit in the car your ears position will vary more on the x axis while on the y axis they will more or less be at the same height. Hence you are looking for an array that gives better lateral dispersion, i.e. vertical arrays.

the same should apply while mounting a mid and tweet on dash/pillars. Tweeters above the mid (vertical array) should work better than tweeters besides the mid (horizontal array). Is this reasoning correct?
 

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i could have put a larger speaker, like an 8 or a 10 in there, but the opening+grill for the OEM speaker is still less than 6.5 inches. plus i didnt feel like buying new hardware to test and see if this even worked. i didnt buy anything besides a few bolts for this expierement - i had some wood laying around and i just re-located the midbass speakers. plus, technically, i could fit into a lower competition class due to using the OEM speaker locations and sizes haha (if i didnt have the carPC) but im not bothering with competition anymore - so i guess its a moot point.

orion - iv been playing with the slope and xover point between 150~300hz, and it seems that a steeper slope closer to 150hz mitigates it more just as you have said (i just lowered it yesterday actually). i have to do some more playing around with it and re-listening to the same material though... as well as make sure i dont push too much bass to my midranges.

ill see what i can do about lowering it to 150 and playing with it a bit more, and ill get back to you.

is there a specific track you are listening to that i could use so that we may be on the same page?
 

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orion - iv been playing with the slope and xover point between 150~300hz, and it seems that a steeper slope closer to 150hz mitigates it more just as you have said (i just lowered it yesterday actually). i have to do some more playing around with it and re-listening to the same material though... as well as make sure i dont push too much bass to my midranges.

ill see what i can do about lowering it to 150 and playing with it a bit more, and ill get back to you.
You can start locating front/back around 70hz. If you're using the rears as subs I'd keep them ~60hz and under on 6th order slopes. If it still pulls to the rear play with TA between the rear and front mid bass. Low end on bass guitar is 80-125hz.
 

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Discussion Starter #189
well.

so far, there are certain bandpass that play up on the dash that really make you try to hear it coming from behind, and there are certain areas that pull back around my shoulders or the headrests. i have not done any EQ, and only have basic time alignment and levels set. ive been driving around for about two weeks with it so far.

theres times where i am like 'holy crap this is awesome' and times where im like 'i wonder what frequencies this is becuase its pulling back a little'. most of the time, the tight punch of a kick-drum will be way up front, maybe because the incident sound is from the midrange, followed by the midbass? and most of the time i end up hearing rolling bass guitar pulling backward toward the "rear" midbass.

i have not had much time to expierment.








Use this picture as your guide. It was setup by the Opsodis folks, and I have a heck of a time reading their papers, likely because Japanese is their native tongue.

Our perception of frequencies below 500hz is determined by phase. Due to this, we have a few options. The first option is to put the speakers hard to the left and hard to the right, like the Opsodis folks did above. Note that it's not sufficient to get the angle right; you have to get the distance right too. But here's the important thing; if you CAN'T get the distance right, you can 'fake' the distance using DSP delay. IE, you CAN'T fake the angle, but you CAN fake the distance.



TLDR : With the midbasses located to the left and to the right you'll need some delay for the left channel. Without delay, your center is going to shift to the left. You'll also want to cut the level of the left midbass by a few decibels, to compensate for how close it is to you.

 

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Discussion Starter #190
On second thought, you *could* fake the angle of the midbass using crosstalk cancellation. But doing that really nukes your dynamics, and the only way it's 100% effective is if you're able to nuke the crosstalk 100%... which is physically impossible.

I am using crosstalk cancellation in my home setup, and it works nice in the midrange but I don't find it to be worth the trouble below 250hz or so. I use it from 250hz (54") to 2khz (6.75") Basically I use it in the frequencies where the wavelengths are too long for waveguides, but not so long that the crosstalk cancellation is totally ineffective. To me it seems like you get the most 'bang for the buck' in the two octaves from 500hz to 2khz.
 

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Discussion Starter #191
is there a specific track you are listening to that i could use so that we may be on the same page?
One really easy way to determine width is to record some pink noise at various locations in the stage. Basically here's how you'd do it:

1) get a wav of pink noise (google it)
2) load that wav into Audacity
3) and then pan from the left to the right. Something like ten steps would be optimum
4) Once you have your ten wav files, record them on a CD

If you really wanted to go nuts, you could do this for every octave too. Basically chop up the pink noise into ten octaves, and repeat steps 1-3.


The ambiophonic VST plugin has a tool built in that does this. It's really a trip, because you can *immediately* tell if your stage is set up right. For instance, in my setup, I can tell that the left channel is better than the right... When it pans to the right there's a 'hole' next to me. This 'hole' is due to geometry. Basically I'd have to fiddle with DSP and EQ to fill in that hole.

 

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i could have put a larger speaker, like an 8 or a 10 in there, but the opening+grill for the OEM speaker is still less than 6.5 inches. plus i didnt feel like buying new hardware to test and see if this even worked. i didnt buy anything besides a few bolts for this expierement - i had some wood laying around and i just re-located the midbass speakers. plus, technically, i could fit into a lower competition class due to using the OEM speaker locations and sizes haha (if i didnt have the carPC) but im not bothering with competition anymore - so i guess its a moot point.

orion - iv been playing with the slope and xover point between 150~300hz, and it seems that a steeper slope closer to 150hz mitigates it more just as you have said (i just lowered it yesterday actually). i have to do some more playing around with it and re-listening to the same material though... as well as make sure i dont push too much bass to my midranges.

ill see what i can do about lowering it to 150 and playing with it a bit more, and ill get back to you.

is there a specific track you are listening to that i could use so that we may be on the same page?
In regards to music and tracks, nothing real specific. For tracks I listened to Radiohead -Weird Fishes and Rusted Root - Cruel Sun. For entire albums it was more EDM/electronic/ambient type stuff. Aioaska - Into the Cosmic Jungle and Sysyphe - Under the Wood. Might be some better reference tracks than what I used.

As far as my whole system design, it's a bit different. The subs are eight 8" manifold PPSLs and will be mounted in the quarters. They vent back over the shock tower and exit into the trunk. I was planning on sealing the trunk, but my experiments with manifold OB has taught me that sealing the trunk may not be needed or wanted. Those subs will play to 140hz.

I have four PM180-8 for midbass. They have very good sensitivity, but don't play too low. But, because of the subs, they don't need to do so. One pair will go in .16 cu ft sealed pods (F3 150hz) in the doors at the hard left and hard right positions. The other pair will go in .16 cu ft pods at essentially the location of the stock system at the front of the door. There are many reasons why I decided on this arrangement, but I was trying to get some benefit of Opsodis and the theoretical benefit of midbass arrays. I was worried about localization cues from midbass in the quarters, but I also realized that placing large midbasses at the back of the door in the hard left and hard right positions would be a very bad idea on multiple fronts.

Crossover points: So this is were things get a bit different. The subs are in the quarters, stereo crossed at 140hz. The midbass to the hard left and hard right pick up from 150hz and play to 600hz. Now the front midbass, play from 150hz all the way out to 2200hz. The upper end has not been determined. I may use just a tweeter, or I may use some small midrange, and then super tweeter inboard of that or even centered on the dash.

Sounds like a mess, no?

So I did a test in the house, which differs slightly from what I plan to do in the car. I had one pair of PM180-8 in front playing from 150-2200hz crossed to tweeters. I placed the other pair of PM180-8 to my hard left and hard right. I placed one of the sub manifolds directly behind me. 8 channels of processing. I played the front stage (PM180-8 + tweeter) with the subs crossed at 150hz. It sounded good, but at 150hz I could detect some rearward pull with some bass notes. Stage was just outside of the speaker width.

I then turned on the channels to the PM180-8 at the hard left and hard right. These midbasses were time aligned to play just ahead of the rest of the drivers. I immediately noticed a much wider stage, a la Opsodis.

Can anybody guess what else happened?
 

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Discussion Starter #193
In my experience this type of a setup sounds more 'spacious', but a lot will depend on the directivity of your drivers and how 'live' your room is.
 

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In my experience this type of a setup sounds more 'spacious', but a lot will depend on the directivity of your drivers and how 'live' your room is.
Some other observations:

1) Yes definitely more "spacious". A bit more "enveloping" but not at all headphone like

2) I could not hear the position of the midbasses to my sides at all. Even though I immediately heard a huge difference in the stage when the channels were flipped on and off, I literally had to reach down and feel the cones to make sure they were moving. They were played at the exact same levels as the front midbass.

3) In reaching down to the cones and turning my head in the process, I noticed that head turning was not an issue. I could turn my chin from my left shoulder to my right shoulder, and the image stayed in front without localization.

4) Not only could I not localize the side midbass drivers with them on, the front drivers became much more transparent also.

5) Here is the neat bit that I alluded to; The bass cues I was getting from the sub manifold mounted behind me disappeared. I turned the side midbass drivers on and off several times on several tracks just to be sure, and everytime the rearward bass cues disappeared. I think the side midbass were pulling the cues forward in way that the front midbass could not. The big question is, why?
 

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Discussion Starter #195
Think about it this way:

1) Let's say you're in a room with one person talking. It will be easy to tell where they are.
2) Now do the same thing in a room with ten people. You can still pick out the location of the person, but the additional cues will make it more difficult.
3) Now try and listen to someone who's ten feet away from you, while someone else who's five feet away is talking to you. The cues from the nearer person are going to obscure the cues coming from the farther person.

I'm kinda curious to try varying the height to see if multiple midbasses can make the stage higher. IE, you don't want multiple tweeters because they're going to interfere with each other. But midbass frequencies are so long, you have a lot more freedom to vary their location. (As you found.)




It's complex though. The other day I went to a restaurant in Del Mar that was fifty feet from the ocean. Seated outside, I found that it was nearly impossible to hear people, even people five feet from me. My hypothesis is that the sound of surf crashing is so loud, and the sound so random, that it was drowning out conversations happening just five feet from me. It was truly distracting; some of the worst acoustics imaginable.

 

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^ All of this :D.

Its not that the side midbasses are so loud that they are drowning out the other cues (as stated before, I can't actually hear the side midbass playing) it is more of an arrival thing and saturation. I did state that I TA'ed the side midbass to arrive just a tiny bit ahead of everything else.


Lots to play with here.

FYI, the side midbasses were on the floor to either side of my office chair (not optimum angle, in fact, a sharper angle than will be in the car) and the front midbass were at desk height with the tweeters.
 

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So, I've got the same factory locations as in the OP and have found them to be very good.

When I had the system tuned the center image ended up being a little bit to the right for me when I placed my head on the head rest. After a discussion with the tuner I found out that his head was a few inches ahead of mine while the seat was in the same position. Now what I have found interesting is that when my head is back the center is solid and focused, but a little to the right. If I move my head closer to where it was tuned, it is still solid and focused now more dead centered.

Could this have anything to do with the location of the midbass??
 

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Discussion Starter #198
So, I've got the same factory locations as in the OP and have found them to be very good.

When I had the system tuned the center image ended up being a little bit to the right for me when I placed my head on the head rest. After a discussion with the tuner I found out that his head was a few inches ahead of mine while the seat was in the same position. Now what I have found interesting is that when my head is back the center is solid and focused, but a little to the right. If I move my head closer to where it was tuned, it is still solid and focused now more dead centered.

Could this have anything to do with the location of the midbass??
The answer to that question is really going to depend on the frequencies in question.
 

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Discussion Starter #200
HP 90Hz w/ 12db
LP 315Hz w/ 24db
No I mean the frequencies you were playing, not the crossover points :)

That's why pink noise is so invaluable in testing. You can spend an hour listening to fifteen music tracks, and most of the imaging cues will likely be in the midrange. Pink noise covers all the bands.

 
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