Infinite baffle

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doublespaces

Administrator
Oct 18, 2016
7,945
AZ
Seems like a 12" sub can fit in that spot. Infinite baffle or otherwise, I guess that is a place to start?

1573189683305.png
 

Torgus

Captain
Nov 6, 2016
1,381
Boston
I don't think you could fit an 18 on that rear seat -maybe if you installed it with the seat closed (have fun), my 15 is pretty close.

And yes, with DSP cone size doesn't matter as much any more, as long as the drivers are located close enough to couple as one (in a car, with low freq's, they do). Just remember making a driver excurt further is the least efficient means of getting more bass. it's what most sane people do though (vs. my "few dozen 12's but who is counting" home projects)



If you target a rising low end response, and want things to go pretty deep, you will run out of capability quick. These cars aren't a true IB, sort of cross between open baffle and lossy big sealed, meaning they have a lot of low end cancellation, so doing it like I have (and Rob is), you'll tend to need a little more ooomph to reach normal levels. A sealed box in trunk with same driver would be louder, never mind a ported or bandpass.
I was really just kidding about one of those 5000w RMS 18s. They are on a whole other level of crazy. I don't think the BMW electrical system would like the draw from the amps. Not to mention no room for batteries or multiple alternators etc. Not the right platform for SPL IMO.

I've always heard good things about the tang bangs. Maybe I will just do 8 6.5s of those vs. 4 8s. Same cost basically for more cone area. The JL amp will do 750 rms x1 1.5 to 4 ohms.
 

Rob09msport

Major
Oct 28, 2017
1,850
Monroe CT
You need Cones within quarter wavelength and ya I agree more subs move more air but if you want true sub like 20hz your gonna want a 12 or 15. I loved the sound of my 10s back in day but we have 8s under seat so I really was looking to just fill out sound.
I am thinking of doing similar with a l2i converter on my b and 0 in the 5 but I may just get a musicarv enclosure. It's just a jl w3 but that system is already great .
 

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800HP Club (N54)
Platinum Vendor
Oct 24, 2016
894
Scottsdale, AZ
I was really just kidding about one of those 5000w RMS 18s. They are on a whole other level of crazy. I don't think the BMW electrical system would like the draw from the amps. Not to mention no room for batteries or multiple alternators etc. Not the right platform for SPL IMO.

I've always heard good things about the tang bangs. Maybe I will just do 8 6.5s of those vs. 4 8s. Same cost basically for more cone area. The JL amp will do 750 rms x1 1.5 to 4 ohms.
They're great, and 4 ohm single coils, so with 8 of them you could wire to 2 ohms easily. That'd give you about 100 watts each, which is more than enough to have fun with them (IIRC they're rated for 50watts).
 

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800HP Club (N54)
Platinum Vendor
Oct 24, 2016
894
Scottsdale, AZ
You need Cones within quarter wavelength and ya I agree more subs move more air but if you want true sub like 20hz your gonna want a 12 or 15.
This is a myth. Reference; headphones. You're right though, that typically big cones with more mass and lower Fs can more easily reproduce the bottom freq's. With DSP we can change that (somewhat).

The wavelength of a 20hz tone is ~56 feet. That would mean you'd need about a 15 FOOT driver to reproduce it. I'm sure you heard this from someone else though, there are a lot of poorly understood concepts audio wise that still make the rounds. In the end it's about displacement, although greater cone area does tend to "couple" with the air better vs. one smaller driver throwing further.

Chris
 

KevinC39

Corporal
Jun 27, 2017
189
I am thinking of doing similar with a l2i converter on my b and 0 in the 5 but I may just get a musicarv enclosure. It's just a jl w3 but that system is already great .
That's the route I went. Just had Musicar send me the whole thing plug and play. It's a single 10w6 in mine. I believe their E92 box fits a 12.
 

Rob09msport

Major
Oct 28, 2017
1,850
Monroe CT
This is a myth. Reference; headphones. You're right though, that typically big cones with more mass and lower Fs can more easily reproduce the bottom freq's. With DSP we can change that (somewhat).

The wavelength of a 20hz tone is ~56 feet. That would mean you'd need about a 15 FOOT driver to reproduce it. I'm sure you heard this from someone else though, there are a lot of poorly understood concepts audio wise that still make the rounds. In the end it's about displacement, although greater cone area does tend to "couple" with the air better vs. one smaller driver throwing further.

Chris
Once again reread my post please you have alot of knowledge but your to quick to correct someone
If you would like 2 speakers to act as one they need to be within a quarter of the wavelength, yes this isn't exact but it goes with the logarithmic 10x power for double in volume and 6db is double sound pressure which is not perceived volume so as much as I almost quoted 50ft for low frequency cause i wouldnt have bothered looking up and writing 56, I didnt cause I am more about real world applicable info not tech jargon. Your dsp works great for high frequency but when dealing with cabin gain and low frequency it goes out window. Ever wonder why high end systems don't delay the trunk sub yet their is the saying the driver was on the dash. A properly blended xover will get true sub frequencies on the front of your soundstage but you cant get a reg woofer to do that without time delay . Also human ears cant localize below 50hz and last but not least the real prob with dsp is with 2 forms of sound at low frequency in car, you have the sound wave and you have pressure in cabin and this is why subs cant be to far apart for low frequency. I believe even stock subs are high passed at 63hz .

My entire post equates to you can't have small drivers to far apart or they will cancel out each other
 
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[email protected]

800HP Club (N54)
Platinum Vendor
Oct 24, 2016
894
Scottsdale, AZ
Once again reread my post please you have alot of knowledge but your to quick to correct someone
If you would like 2 speakers to act as one they need to be within a quarter of the wavelength, yes this isn't exact but it goes with the logarithmic 10x power for double in volume and 6db is double sound pressure which is not perceived volume so as much as I almost quoted 50ft for low frequency cause i wouldnt have bothered looking up and writing 56, I didnt cause I am more about real world applicable info not tech jargon. Your dsp works great for high frequency but when dealing with cabin gain and low frequency it goes out window. Ever wonder why high end systems don't delay the trunk sub yet their is the saying the driver was on the dash. A properly blended xover will get true sub frequencies on the front of your soundstage but you cant get a reg woofer to do that without time delay . Also human ears cant localize below 50hz and last but not least the real prob with dsp is with 2 forms of sound at low frequency in car, you have the sound wave and you have pressure in cabin and this is why subs cant be to far apart for low frequency. I believe even stock subs are high passed at 63hz .

My entire post equates to you can't have small drivers to far apart or they will cancel out each other
Sorry if the tone was off a touch -not being rude, I love this stuff.

You can have small drivers pretty far apart with no real issues but you might have to adjust phase/etc. Could be we're saying similar things differently. No biggie.

Not many people delay subs for a few reasons. First is they're furthest away. Secondly with high output systems you typically have more group delay (inverse derivative of frequency response). Having two speakers within a quarter wavelength is easily done in the bass frequencies, to the extent in a car it's a non-issue. You wrote that you need larger diameter drivers to reproduce the lowest frequencies; this was and is untrue. Finally, you have a slow sub, and can't speed that up, so typically you delay everything else to match. This can be a giant pain in the ass to dial in.

Delay and frequency response are completely separate issues, unrelated unless you're getting huge cancellation due to odd phase response, which would be unusual in a car in the deep bass frequencies as shroeder frequencies begin pretty high up. This is a good thing, and why cars can have insane low bass output with relative ease. To reproduce similar output and visceral impact in a 5000 cuft living room I use the better part of 10kW and an usual amount of drivers.

DSP works FANTASTIC at low frequencies in the cabin gain area. In fact if you have to eq anything at all, it should be the bottom end -things get weirder as you increase in freq due to off axis responses, reflections, reverb, etc -I tend to be more cautious above 200hz. All you need is an inexpensive DSP like a minidsp 2x4, freeware like Room Eq Wizard, and a calibrated mic. I'm fond of the UMIK-1. For $300 and a little learning time you can transform your system night and day. There are other DSP's with more channels for not much more money.

IMO any system that doesn't use DSP is in the stone ages. I can make nearly anything sound good given a couple hours, assuming the drivers have some power and low(ish) distortion. Night and day difference. I don't target flat, I target something like the Harmon Target Curve, but that's a whole different chapter.

If you were local I'd love to give you a demo. I can put visible ripples in the leather couch. ;)

Chris
 
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Rob09msport

Major
Oct 28, 2017
1,850
Monroe CT
No you dont need a larger driver their are exceptions to the rules but if you have 8 inch subs that go to 30 hz then you need them to be within quarter wavelength to lower their fs and act as one. They can be far apart and you can use dsp but you wont increase sub bass extension and you will always need window down to prevent cabin pressure cancelling out sound waves or you dont use dsp and then you will have opposite . Car is unique environment. My point was if you take a series of subs and look as t the 8 to 15 usually the 15 is the only one close to 20 hz response and in a infinite baffle that is extremely important as their is no air spring so it will overload the suspension unless sharp cutoff at the sub fs. That's why I went with a 12 cause the kappa perfect goes to 23 hz 10 was 26 and I belive 8 was 33 . But yes I wasn't saying you were wrong I was saying you were correcting a statement that you were misinterpreting. That's why I said please reread . I love your posts but sometimes I feel your really quick to correct and then people only read the last posts so they assume that my statement was wrong and then causes confusion.
 

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800HP Club (N54)
Platinum Vendor
Oct 24, 2016
894
Scottsdale, AZ
Hey Rob,

Putting drivers close together doesn't drop Fs. That's one of the basic driver parameters and is a function of cone mass and suspension. You're correct that opening a window changes things (significantly) within the vehicle interior though. Kinda makes the whole car a bandpass enclosure. Car is really a unique environment.

IB doesn't unload underneath driver Fs, but you do have to be careful not to mechanically overexcurt the driver. Ported boxes unload a few hertz under the port tuning -in those cases it's a good idea to use a high pass filter (DSP makes it easy) to save the driver from unloading. That is definitely a quick way to wreck a driver. Sealed boxes also don't unload, I sometimes still use a HPF on them so I can get aggressive on boost down low without totally going bananas in the infrasonic territory.

Most of my acoustics knowledge is centered around home audio, for me the car stuff is a (distant) hobby. I put a 15 in the BMW for some fun, but the logic 7 system sounds pretty decent for a stock system out of the box -especially with some judicious tweaking of the provided eq. Def not perfect but good enough for casual use/enjoyment anyway. Same with my Ford, I added DSP just for fun (and I had a spare minidsp not being used). By far most of my efforts are in the main system and the computer audio system, both of which are pretty advanced.

Music is important stuff, there are many ways to enjoy it. It can be hard for new guys to sift through marketing vs. wives' tales vs. flat out bullshit. Still, at the end of the day if you have fun and like how it sounds, it's not wrong. Keep doing your thing, curious how you end up liking that infinity.

Personally, I like a heavy low end and upper bass needs to be controlled or it sounds too boomy/smeary (technical term lol) and I don't like it. It's been very difficult for me to figure out upper bass -which is necessary for impact. It's a fine line. Keep having fun!

Chris
 

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