Anyone do a "free air" or infinite baffle subwoofer in their 6?

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Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

So I'm tossing around the choice of doing a infinite baffle type subwoofer in my M6. I'm not looking for boom, boom, boom. I want low freq. when the music is there and I want tight controlled bass with the emphasis on sound quality, not necessarily quantity. Though having both would be a plus. If you've done a IB, what driver did you use? What amp and/or wattage did you use. Did you do one driver? Or two? Where did you put it?

For those who did boxes, same sort of questions. What driver, what size box, sealed or vented/ported. Where did you mount it. I've seen the little 8" sub driver in the 6x9 box put into the space behind the M6 rear A/C console. I'm not sure that appeals to me.

Thanks for any input, Dennis
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by baders »

I run a 12" Alpine and originally installed in in a sealed box in the boot. Unfortunately it was extremely muffled and indistinct, even driving it with it's own 500w amp. I then took the plunge and installed it behind the rear seat centre section. Happy bass days ever since :D
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by dlvad »

Vintage "Brucey's AudioTech Post" link…
Simple.

viewtopic.php?f=11&t=49&p=233&hilit=subwoofer#p233
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by slofut »

Did this in my '87 years back. 6 in Hart subwoofers, 100db 1w/1m! I have 100wpc (old school zed audio amp) on them. Sounds like a million bucks.
Did the same a couple years ago with my '88. Found an inexpensive pair of 6" woofers that were high efficiency, I think 96db. Sounds great just off the yamaha head unit. Have a small Proton amp I'm going to put on them...

viewtopic.php?f=5&t=21104&p=150881#p150881
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Divad, seen that post a few times. It seems everyone links to that post. I'm doubting the effectiveness of that installation. I was even thinking about doing a miniture tube sub in that same space. But to hit low freq., one must be able to move air, and those two examples won't do that. The mid/woofer drivers I'm installing in the rear shelf, go lower than that one sub install. And they're only 5.25" (150mm) in size. That's why my question about the IB install. In today's drivers, you can put them in really small boxes, but then they don't go very low and don't have very much output. I think most of them need to be in a box, because they aren't very good drivers to begin with. They don't have any mechanical control over their own movement. Plus they needs lots of power to start and then stop them. IB's can be special in that way with the right drivers. But then again, a 30 year old coupe has a lot of holes in the interior and trunk. That doesn't make for much of a cabinet. I'm a little concerned about vibrating everything to death if I do the IB. How long are filament light bulbs going to last if a sub is vibrating and sending shockwaves in its direction that it wasn't engineered for. That's a question for the experts.

Baders and Slofut, do you have any photos of your installations? Or can you email some to me. I'm really interested in how you did what you did and what the install looks like. How did you mount the driver/s and other equipment. This is my first install in 37 or 38 years. So my skills are really rusty.

Thanks, Dennis
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by baders »

Some good info and photos in this thread Dennis;

viewtopic.php?f=5&t=26238&hilit=subwoofer
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by slofut »

baders wrote:Some good info and photos in this thread Dennis;

viewtopic.php?f=5&t=26238&hilit=subwoofer
Btw... Nice job there Baders. I've done LOTs of cars like that :o back in the 80's. Had a cool car stereo shop for 10 years. Back then my Volvo 242 turbo had three 10" Wagner/Hart subs like that, Dynaudio 7" woofers in a fiberglass box on the rear parcel shelf, and MB Quart in the front. This was back when you could only buy Dynaudio as raw drivers. With a 4x35 watt Hifonics amp it surprised everybody that listened to it. Those Wagner 10's were 100db/1w/1m and flat to like 30hz. Didn't take much to drive them pretty strong.
IB is pretty much my preferred way of doing most cars if you're keeping the interior intact and if you can get the right drivers. Think of all the cars I cut up! :-?
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Thanks guys. Baders, you mentioned that if the car were a M 635, you'd not cut that hole in the rear bulkhead. Care to explain?

I'm doing this install on a '87 M6. I'm using some of Scan Speak's best drivers all the way around the inside of the car. 4" full range in the kick plate area, silk dome tweeter in the oem location for the tweeter. Then a combo 5.25" and 3/4" silk dome tweeter in the oem rear shelf plate location. The 5.25" woofer fits perfectly inside the rear plate so that I can use the oem speaker grill. I couldn't ask for a better fit with this driver. I have experience with this driver in some of my home audio cabinets, and it is a fantastic little driver. I wasn't sure I was going to do a subwoofer, so I knew this driver would produce nice bass down to 50 Hz. or 60 Hz. Paired with the DSP, I figured I could shape the response to work. Now with the subwoofer addition, I'll be able to dial back the rear speakers so they are mostly fill or for rear seat passengers if desired.

What I’m going to be doing - still sitting on the fence - is using a Scan Speak Revelator 23W/4557T-02 9" aluminum cone subwoofer driver. I have the driver, but haven’t installed it yet.

Here: https://www.madisoundspeakerstore.com/a ... one/#tab-1

It is not the most efficient driver in the world at 82 db. at 1 watt, but if you look at the freq. response graph, it actually rises above its 82 db. efficiency starting point. It stays above that frequency down to 20 Hz. So with the DSP product I'm going to be using, hopefully I should be able to knock those peaks off and create a flat response down to 20 Hz or below without difficulty. HOPEFULLY being the key word.

I'm using other Scan Speak drivers for the front kick and high tweeter locations. Then another Scan Speak package for the rear shelf drivers. If you'd like to know what they are, I can list them. Perhaps before I re-install the interior I'll take photos and post them. I guess it depends on the level of interest.

On the subwoofer install, I'm planning on mounting the driver to a front baffle made up with 3/4" mdf times 2 and then a final back plate of 3/4" plywood. So the baffle will be nearly 2.25" thick. This will then be bolted up to the back bulkhead with at least 10 bolts around the driver and fitting the entire width of the rear bulkhead from inside the trunk. This should hopefully reinforce the bulkhead for the 8.5" (225 mm) hole cutout in the middle. It may be overkill, but then again.......

If I find I have too many rattles to make the IB install work, I'll pull the baffle back out of the trunk and make an add-on rear cabinet to surround the driver. I'm tossing around the thought of doing this upfront first, but I think I'd prefer the sound and response of the IB. Another sitting on the fence decision. But I'm making/taking measurements along the way so hopefully I wouldn't have to start over if the IB creates too many side effects.

Baders, did you find that the IB made too many noises after you installed your IB setup? Slofut, same questions?

My M6 has the rear AC unit, so firing a sub into the interior is going to subject these components to these frequencies. So besides what’s in the trunk, the inside of the car is going to be "hearing" these low bass frequencies that were never apart of the car's design. Concerns?
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Here's the 5.25" that I'm using in the rear shelf.

https://www.madisoundspeakerstore.com/a ... fer-4-ohm/

This is the slightly different model of that driver I'm using in a few pair of home mini monitor speakers. It’s a great little driver. I’m also using this driver in the MZ3’s kick panel:

https://www.madisoundspeakerstore.com/a ... r-low-qts/

Here's the tweeter in the front door and rear shelf.

https://www.madisoundspeakerstore.com/s ... 0-tweeter/

Here's the 4" kick panel speaker.

https://www.madisoundspeakerstore.com/a ... ull-range/

This the active crossover and DSP unit.

https://www.minidsp.com/images/document ... %206x8.pdf

Then I'm going to try this JL Audio 8 channel amp. I'm not certain it will provide enough power for the SS subwoofer though. Bridged I think it is 200 watts at 4 ohms. It will be partially dependent on how much power is used to EQ response flat. But given the sub's freq. response graph below 100 Hz., it might not be an issue.

Here’s the amp:

http://www.crutchfield.com/p_13698259/J ... 0-8v2.html

I can change this choice to a 6 channel for the other drivers and then pick a dedicated amp just for the subwoofer if needed or desired. Any thoughts on this question?

I still haven't cut the hole in the car yet. I'm going to do the baffle/bulk head boards first. Leave the nasty stuff for the end. Besides, I'm sitting on the fence about the size hole to cut in the car. The speaker driver cutout or the overall diameter of the driver. If I do the latter, I can install the driver from inside the car, which might be easier than trying to heft in the baffle board with driver attached. It's a pretty small cavity to get into the trunk of this car. I'm getting too old and don't quite bend as easily as when I was younger. That and the extra 50 lbs. I'm carrying around. It doesn’t help me get into little spaces.

I’ve ordered a Pioneer head unit - one of those pop out display models. I’m looking to install this basic setup in two cars. This M6 and my MZ3 roadster. So seeing something on the display might be beneficial. My eye sight isn’t what it used to be either. Eye surgery a couple years ago has changed my sight from near sighted to far sighted. So anything within arms reach requires reading glasses. The dash is ok, but looking down at a tiny display on a regular single din radio might be impossible. We’ll see if I like one of these things or not. Crutchfield has a 60 day return policy. So we’ll see what happens.

http://www.crutchfield.com/p_130X7800BT ... ml?tp=5684

Guys, please comment on any aspects of this install. I’m open to further suggestions and whether or not I will have issues with doing the IB with noises and/or rattles. Or drivers and/or crossover and DSP or amp choices. Nothing is written in stone. I’m hoping my “regular” speaker driver choices will perform as well or hopefully better than “car” audio speaker drivers. If not, it is a waste of good money. I’ve got my fingers crossed.

Thanks, Dennis
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Da_Hose »

When the day comes that I have time, I plan to use a pair of Tang Band 6 1/2" subs in a sealed .5 cu/ft enclosure.

http://www.parts-express.com/tang-band- ... r--264-832

They have the best performance specs I have seen for anything in the ~6" range of speaker, and they are pretty affordable (comparatively).

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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by baders »

DennisLJacob wrote:Thanks guys. Baders, you mentioned that if the car were a M 635, you'd not cut that hole in the rear bulkhead. Care to explain?
Quite obviously an M635 is more exclusive and rare. On a financial basis, an original, unmodified M635 is worth far more money. I'm actually glad in a way that I could not find an M635 and am now building my own version.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by GazM3 »

1 had a 12" in the boot and as badders said was ineffective. No bulkhead cutting so I just fitted a blaipunkt 8" compact subwoofer all in one under the front passenger seat. Great bass and no holes.

I ended up installing the 12" in my e23 and cut a hole in the rear bulkhead about 300x100 as there are bolts holding the rear arm rest in the e23.

I put some foam seal to seal up the hole to the subby and I have more bass than a 90's chemical taking party.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Da Hose, I've looked at that TB driver too. I was very tempted to use that driver in one of my cars. But then it was brought to my attention that it used a uncoated paper cone. So for car use, it would be a short-lived product choice. I've also talked to a couple speaker company makers who questioned the specs as being perhaps not realistic. Not having the ability to test drivers, I can't say if it does or doesn't do what it says it does. But they definitely have folks looking at their drivers for projects. The reviews on PE's site are all positive.

Damn Baders, now you have me questioning whether or not if I should make the big cut in the bulkhead. Crap. So is there anyway that one might make an install that you wouldn't judge as being detrimental? With the stamped shape of the steel panel, there isn't going to be a "clean" edge. So I suppose there is no good option.

So what are you doing with your “build your own" version?

What are you building? Are you using M parts or doing something else?

Are you doing audio in that car? Cutting into the bulkhead? Curious.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Gaz how the heck did you get anything under that seat? I can't see any space under my seats to put anything. What vintage M6 was yours? North American car? Euro? Manual or electric seats?

I thought about trying to put something in the kick panel of the left rear seat. But not sure if I'd get any meaningful bass out of it. Though, maybe I should try that Tang Band 6" driver? Though I'd still need to cut a hole in the kick panel. I suppose not as bad as cutting the rear bulkhead. But if it didn't work, I'd have a useless hole in the kick panel.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by GazM3 »

1984 euro manual seats.

I don't mind having it there as it keeps the weight low and well within the wheelbase. Also gives me all the trunk space which is compromised with the m635 due to the battery in there. The bass is not quite as good as the enclosed boxed 12" as per the e23 but it's better than 2 pairs of 6x4 speakers.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by baders »

DennisLJacob wrote:
Damn Baders, now you have me questioning whether or not if I should make the big cut in the bulkhead. Crap. So is there anyway that one might make an install that you wouldn't judge as being detrimental? With the stamped shape of the steel panel, there isn't going to be a "clean" edge. So I suppose there is no good option.

So what are you doing with your “build your own" version?

What are you building? Are you using M parts or doing something else?

Are you doing audio in that car? Cutting into the bulkhead? Curious.
Do a search for my build threads. Basically, I owned an imported '79 highly modified (Ray Gulson) 635csi for all the '90s. Loved that car. The ex punted it into a bridge pylon in '99. Been wanting another E24 again ever since. Three years ago began looking again. Was going to buy ChrisM6s lovely black M635 in the UK but idiot government regulations here forbade that purchase. Decided to build my own. Saw Vinneys great example of an '86 635csi and said WTF, I'll build my own version. Have been gradually refurbishing LOCUTUS and have just this weekend dropped her off at BMW Autohaus here in Perth. After I come back from work next week we will be getting into the conversion installing the S38B36 I have into LOCUTUS.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Brucey »

DennisLJacob wrote: I thought about trying to put something in the kick panel of the left rear seat. But not sure if I'd get any meaningful bass out of it. Though, maybe I should try that Tang Band 6" driver? Though I'd still need to cut a hole in the kick panel. I suppose not as bad as cutting the rear bulkhead. But if it didn't work, I'd have a useless hole in the kick panel.
It isn't as good an enclosure as the boot (trunk) is because

a) the volume is not well defined
b) it leaks air unless you spend a lot of time trying to seal it
c) many of the leaks are back into the cabin, which kind of defeats the object (with many designs of sub enclosure).

I'm no expert on the design of these things (and it pretty soon gets into the realms of deep mathematics, using parameters that are not always well known, if you approach it analytically.. :roll: .) but what I did was I tried to make it like a ported sub, on the basis that for the port to do any good, all it had to do was have less acoustic impedance than the leaks.

You can read about ported sub enclosures here;

http://www.diysubwoofers.org/prt/

and the port calculations are here

http://www.diysubwoofers.org/misc/portcal.htm

I couldn't work out the correct port length for sure (too many unknowns even for that...), plus any subsequent changes in the driver units and/or the sealing would affect that too, so I made my ports adjustable in length. I did that using custom fabricated aluminium exit flanges, to which I added push-fit plumbing waste pipe fittings, where you can't see them.

In practice adjusting the enclosure sealing (using pieces of foam etc, or just lowering the armrest.... :wink: ) makes as much difference to the sound as adjusting the port length. In truth I've not spent that much time fiddling with it; I'm sure I could get it to sound different/better if I wanted to, but as it is, it is good enough for me, anyway!

BTW with decent drive units and ports in the kick panels, the sound is absolutely transformed vs any sound from the standard speaker enclosures. There is simply no comparison. If you sealed the OEM speaker pod edges, mounted large drive units centrally and ported them into the boot (trunk) that would be better perhaps, but not if you have rear seat passengers, plus I like having the storage in the hinged pods. I also like the stealth look; that I've got the extra ports and speakers etc is not apparent until you either hear it or you hinge the seats forward.

FWIW unlike the rear bulkhead, I wouldn't worry about the car's structure in relation to cutting the rear kick panel about; all that panel does is support the rear seats. It is far too flimsy to do much else. If you don't want to cut your OEM carpet, you don't have to; that section of carpet comes separate from the rest anyway, so you could replace it with something else before you start cutting it about.

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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Well I've gone and done the nasty. Though I haven't finished cutting out my little circle, I'm half way round, so no turning back. I'm using a Rotozip tool with circle cutting jig and a steel cutting bit. So far, nice and clean even and round circle. So if nothing else, it won't look like someone took a sawzall and/or hack saw and had their way with it. I'll do my best to make it look professional and high quality. Lord knows the components I'm installing are worthy of the car if not more so. We will see, and hopefully how it sounds in the coming days or weeks. I'm still learning the software program for doing the active crossovers and defining what signals go where and which ones.

So I'm at a crossroad. I can stop now and convert the open baffle IB and change it to a sealed box. If a sealed box, Madisound recommends 1 cu. ft. Though I haven't put any of the TS parameters into a software program to see what it says. Anyone care to help out with that? Here's a link to the Scan Speak site with their TS parameters as well as additional info down below the normal data.

http://www.scan-speak.dk/datasheet/pdf/23w-4557t02.pdf

I'm not in a position to convert the open baffle into a ported enclosure without addtional cutting and making a larger box. The driver is actually pretty shallow as far as sub drivers with this amount of xmax and output. I am working with a 32" wide baffle by 12" tall. I'd like to keep the actual box width to 22" wide if built. That way I have room for the passive crossovers for the rear shelf speaker setup. Each passive XO is 4" wide by 10" tall. So I'd like to leave the two outer sections or wings available to mount those two XOs.

Let me know if you guys need any additional information. Help from this point forward is most appreciative. Oh, the reason I decided to go ahead and make the cut - is I hope I never have to worry about selling this car. So I decided to build the audio system that was going to give me the best performance from good stock of components. I'm doing that. So if I do a professional job, maybe it won't hurt the value. Or maybe the system will offset the negative side of a small circle cutout of the rear bulkhead. Who knows, only time will tell.

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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

They say the first cut is the deepest. Here it is:

Next up is finish fitting the baffle and expanding the mounting holes for the real bolts that will hold it to the bulkhead. So has anyone figured out if I should convert from IB to sealed box? Or should someone just put me in a box for doing this to a M6? Make it a nice box guys. I'll want pictures of the car before and after in my casket. I'll need to finish putting sound deadening material around, plus line the hole with proper trim covers around the circle's edge. I'll have to find that online somewhere.

Well have hole will travel. I'm too big to fit through this one, but a child could probably do it. Escape route.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Da_Hose »

First off ..... EEK! :shock: I love my //M too much to take out a big chunk of metal like that. :P

My exhaust is louder than stock, and I like hearing it. So an SQ competition setup is not what I want. I do want something that can be heard above the din of the exhaust and the 280 transmission, though. That is why I am going with the sealed enclosure, but I am building it into the seat back. My thinking is I start with one sealed enclosure behind the driver's seat and see how that goes. I could always add a second behind the passenger. Or do a combination of one sealed cabinet for response speed, and a t-line on the back of the passenger seat, to get booming bass as well.

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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Brucey »

I dunno how big your drive unit is but I figured out that in some cases you would be able to space the drive unit into the boot (trunk) a short way (eg on a wooden flange) and mount it 'the wrong way round' i.e. firing into the boot, with the magnet etc partially within the armrest housing. An IB layout can then preserve most of the luggage space. The sub can then be on show in the boot, with just something like a metal grille over it to protect the diaphragm from damage.

If you mount it the other way round and/or are prepared to make up an enclosure, you can make a sealed or ported system. IIRC I figured out that you can make box with plenty of volume just by adding a false panel behind the bulkhead.

Which is best will vary with the drive unit itself as well as how you drive it and (of course) how you like the sound to be.

It is a scary-looking hole, that!

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DennisLJacob
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Brucey, it would be possible to turn the driver around and have it face the trunk. I'm making the laminated baffle board now. All I need to do is rabbet and route the driver hole. The driver is approximately 5 1/2" deep (135mm). The baffle I'm making is from 3 boards 3/4" each. So it will be about 2.25" or almost half the depth of the driver. In rough measurements, it would appear that my minimum clearance depth is 3" to the back of the middle seatback cushion. So with the baffle I could turn the driver around and mount it backwards. That method would actually save a lot of space since I was going to use that thickness baffle no matter.

Of course I wouldn't be able to do a sealed cabinet if mounted that way. Or could I?

Hum, mount the driver backwards in the baffle. Then add a very shallow box that the driver would fire into?

Besides space saving, would there be a detriment in mounting it backwards? If you'd like to see the driver, I included links further up in my posts.

Thanks, Dennis
1987 M6, 1998 Dinan SC MZ3 Roadster
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Brucey
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Brucey »

if you mount the driver ' the wrong way round' I think you could still make a sealed box in the boot, but it might perhaps be possible to make it smaller than if you had the driver the other way round, if the unit can poke out less one way round vs the other.

I think that most drivers will happily push air in either direction (if they didn't, enclosures of any kind would surely never work...?).

Of course some folk would reject that scheme on the basis that there is no bling! But hey, it is a free world... :wink:

Image

It is quite a compact unit, that; I'm sure it will offer you many more mounting options than some others. I guess it is a bit late now but if it is to be mounted on a 3" thick flange firing into the boot, might it have been possible to install it into a somewhat smaller hole through the bulkhead?

A concern about any driver mounted behind the armrest is that when the armrest is 'up' the driver will be obstructed/damped, and even when it is down, if you try and shove enough air through small gaps, you might start to get 'chuffing' sounds from a big sub (c.f. 'port noise' ).

BTW I've not seen anyone wreck the centre armrest panel though having a big sub behind it, but I suppose that could happen, it isn't built that strongly.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
baders
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by baders »

With my driver mounted behind the rear arm rest, I cannot pick the difference with the rest up or down. Certainly far better than when it was mounted in the boot sealed box though.

I think your hole is bigger than my hole ? LOL.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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DennisLJacob
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Baders' in more ways than one on the "bigger hole".

So I won't have to worry about arm rest in the traditional sense for the NA M6's have the center rear A/C system. So this is what is there:
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1987 M6, 1998 Dinan SC MZ3 Roadster
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