# Lack of output: Rear deck sub mount



## AAAAAAA (Oct 5, 2007)

So I installed a pair of 8inch SLS subs in my 05 altima rear deck and they fire through the factory 6x9 holes. The speakers are mounted on 5\8 MDF rings and the cone can move freely without hitting anything. Between the mdf ring and the rear deck is a lot of silicone to "seal".

They are bridged to each side of a Planet audio bb175.4 so they should be
able to see somewhere around 200watts. SLS's in my doors of another vehicule with less power were able to give me a satisfying amount of base but in this configuration I can hear the deck rattle more then I can hear the subs. *There is basically zero output.* Like the subs aren't playing, I had to go phisically see the cone moving to confirm the setup was working.

Any ideas?

I haven't tried basic like flipping phase yet but can't see flipping only one or both helping at all. 

Any insight is welcome.


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## ErinH (Feb 14, 2007)

I had the same results in my wife's car, 2 rear mounted on the deck firing through the factory 6.5" holes.
Off of 200w each they didn't do much.


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## rommelrommel (Apr 11, 2007)

Checked everything basic like every VC in phase, crossover set right, all that stuff?

Is the rear deck very rigid?


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## AAAAAAA (Oct 5, 2007)

Haven't played with phase yet. I will be trying that tonight but I wired then both in phase with each other so I wouldn't think they could be canceling each other out as they seem to be doing.

Rear deck seems pretty solid, doesn't bend or move when I yank and push on the subs. I could put some sounddeadener on it but I almost need to have SOME output from them before I start laying it....

Bikinpunk: Did you simply give up on that project?


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## ErinH (Feb 14, 2007)

^ when I was testing mine, they were the only thing playing.


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## Andy Jones (May 12, 2006)

Did you just mount the speaker rings to the rear deck and that was it?

That is like having a sub enclosure made out of 1/8" MDF. 

Seal up all the leaks around the back seat, add some mass to the entire rear deck. 

The entire rear deck is now your "baffle". It needs to be stiffened up.


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## ErinH (Feb 14, 2007)

^ Check.


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## AAAAAAA (Oct 5, 2007)

^That is indeed what I did. Figured I would be able to get at least stock 6x9 type of output ouf of them hehe.

So to add mass... sound deadner or what would you recommend?

Thanks by the way.

BIKINPUNK:what did you end up doing with that project?


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## ErinH (Feb 14, 2007)

AAAAAAA said:


> BIKINPUNK:what did you end up doing with that project?



Scrapping it probably. It’s my wife’s car. I’m not going to keep putting hours into it trying to get it to work.

As of last weekend all the holes were sealed. The rear deck was re-inforced with a couple pieces of sheet metal attached to it here and there, with some deadener here and there as well. Holes were all plugged up with either silicone, ¼” birch ply, or great stuff. 
They were attached to the rear deck with ¾” MDF rings, which were also sealed up to the deck with Don’s butyl rope.

I’m going to try it one last time off a different amp to see if they simply need more power. At 200w @ 8 ohms they were moving but not a whole lot. Definitely not nearing xmax.

If the new amp doesn’t work then I’m pretty much going with the stereo integrity BM3 and molding an enclosure to the spare tire, or behind the trunk liner. If it will fit under the front seat, I’m going to do that, but I’m not sure that it will.


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## tanakasan (Sep 8, 2007)

Double check the speaker terminals for polarity with a battery...maybe factory mislabeled. Gains set correctly?

Robert


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## Andy Jones (May 12, 2006)

I would cover the top and bottom with a mat deadener (second skin is nice). Then sammich MDF on the top and bottom with bolts. 

If the back seat lets down, I would seal that opening. Then on the sides of the trunk is generally a big opening that needs sealing. 

IB enclosures, when done right, are VERY time consuming to get done. If you finish in under an hour, I would expect Funky Pup results.


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## sqshoestring (Jun 19, 2007)

Best thing to do is get a pair of 10s with a high qts/low fs, cut a piece of 3/4 ply or mdf if you want, mount it to the rear deck and the subs to that. Subs only need to take the power you want to use, most normal subs take half rated for IB use. Use thicker than 3/4 if xmax is huge. I cut cardboard and fit it to the deck, when done take pattern and cut wood once. The wood deadens and strengthens and seals the deck, poof, all done just seal anything left around the seat/etc. Use weatherstrip or whatever between the baffle and deck when you screw it in. Sometimes you make a frame around the deck to space the baffle down a little, if the deck has brackets/etc in it, make it part of the baffle.

8s just don't get it IB, only at low outputs. If you use a HD small box sub (low qts) they _don't work well _at all, model one once they have terrible rolloff and put out mostly at 100Hz plus. In fact you might put cheap pyramid/pyle 12s under the 6x9 holes and get significant bass if the qts was above say .5, on 200-300w amp is about all the cheap ones can take. That show car in another thread here the guy ran huge xmax triple 12s into factory 6x9 holes with a manifold under the deck. I still like paper cones for IB in the deck, but likely only an issue with the cheapest subs.

Got to move air with IB, bigger and more are always better. Look at your fs and don't expect to get much under that. Qts is your tuning, it should be .5 minimum unless you use 15s maybe 12s. My 12s are .46 with fs 24 (fairly low for a 12) and with some EQ they put out 20Hz well, but I have quads too. My eq is down at 50 and up 6db at 20, up 3db at 30. Is near flat maybe little more 30-35.

I've never put deck subs in without a board, and I used to put a lot of them in. Baffle can't be flexing any more than the front of a sub box its the same thing. You don't put deadening on a sub box right? You do put it on the metal parts of a car and maybe seal seams/etc with it too.

Anyway, thats my 02 I can tell you the above works I've put it in every car I owned if I could, providing I kept the car at least half a year. I put them in professionally 20 yr ago is how I got started on IB. It gets low. I used a lot of 10s because many cars that is all the deck will fit, but 12s have more cone area and lower fs, so they get lower with more output. Sometimes you can't do the baffle much larger than where the subs are, make it large as you can or space it whatever works. It will still tie the seat bar and bottom of the glass frame together to make it stronger.

This is an ancient setup I helped put in long ago, its been in storage and I don't know why the wires are hanging. Six 10s and pair of boxed 6x9 in the back of a maybe 79 firebird. The seat and deck are all 3/4 ply iirc. It got pretty loud too. He changed subs around and liked this setup. Been sitting for well over a decade I really gave him some crap the day I took the photos to show someone else. He ran three 300rms amps on the subs.









So could be you have a flexy deck, have low qts subs, or expect reasonable output from 8s. I tend to figure double the cone area for IB to keep my output. So for a box with pair of 12s, that is why I put quads in (was a little overkill though). In reality output should be the same as a large sealed, because that is what it is. Note your small sealed will push Q up for more output, at expense of low end extension while IB does not. You need a subsonic if you beat them hard. Look at the AE IB subs and try to match those specs, they are spot on for IB subs. You don't need good subs for low power, long as they don't have cone noise. Sorry for the book just trying to help maybe a search will show this, its not the first time I've seen this issue. IB can work great if done right.


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## ErinH (Feb 14, 2007)

I understand the premise for getting IB to work right. I'm running the ae ib15's in my car.
The sls8's were lent to me, figured I'd try them to see if they'd work in my wife's car. 
They don't. 
The standard case of 'specs can give you an idea, but testing tells you'. 

I appreciate the info, though. Maybe someone searching later will see this.


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## gijoe (Mar 25, 2008)

That's the thing they don't tell you about IB. You'll read that it's the simplest set up, but it's far from the easiest. If you have 2 8's IB, you should have some decent bass, but you'll need to completely seal off the trunk. This means you'll have to make the rear deck into a solid baffle AND put some type of baffle behind the seats. I had plenty of output from 2 10's IB (went to 3 10's for other reasons) so you should have decent output from 2 8's. 

Like other people have mentioned, check everything from your wiring to the crossovers on your hu and amp. It could be that you have a simple install error causing the majority of your problem.


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## sqshoestring (Jun 19, 2007)

Its not my intent to be an azz, but I keep seeing this. Part of it is that many subs now are for ported or sealed but IB subs are coming back some. The SLS look to roll off from 70 down http://www.parts-express.com/pdf/264-1102s.pdf
Fs 36.5 and qts .54 which is marginal for 8s. Larger subs will make up for it, but 8s should be more like .7.(any IB should be, but not quite as important for much larger subs) Even my 12s will play too high with no EQ, but they were cheap and had a low fs so I went for it. Plus I put too many in, lol. The SLS drops 3 db 80 to 60Hz, what you see in the chart is what you get. -3db is not good and it continues its down 8db at 40Hz, about as low as it will ever get. Add to that if the baffle is not solid, maybe the car has less cabin gain, it all means they are going to have to work really hard to make any low bass. Its at 82db at 40Hz. If you model the ~.7 qts 10" pyle subs at PE that cost same or less than the SLS, I bet they look a lot better at 40Hz. Not that you have to buy them mind you, just trying to make the point that the cheap sub made to do IB will outperform a sub not made for it. For a while I ran pyramids that looked a lot like the $22 pyles there, and they were impressive. They don't make the exact same ones now but I'm sure there is something out there.

Note how the people reviewing on PE replace a home speaker woofer with a high .7 qts woofer and complain how it does not sound good, well no a high qts needs a giant or no box. I used to run 2cf ported each 10 in a stuffed box and that was just enough to make them work with a LP crossover. Choosing the right tune sub is just like choosing the right box volume and/or port size. With enough power and EQ anything will work, but can be a pita.


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## AAAAAAA (Oct 5, 2007)

Thanks for the input. So my current plan is

1: Deaden the read deck and double check the seal around the SLS subs.
2: If no luck with the above I will make a woodden baffle and either use the 8's or some 10's that I already own that seem to model ideally for a 16cube box that is exactly the size of my trunk.
3: Eventually get around to sealing around the rear seats and the other mentioned areas.


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## thehatedguy (May 4, 2007)

Both of you guys have some major leaks going on.

Erin, I looked at the install page for your wife's car. There are quite a few large holes on the rear deck that you didn't seal up. You need to spray foam every hole back there that leads some way to the cabin.

And you could be leaking around the seats too.


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## gijoe (Mar 25, 2008)

thehatedguy said:


> Both of you guys have some major leaks going on.
> 
> Erin, I looked at the install page for your wife's car. There are quite a few large holes on the rear deck that you didn't seal up. You need to spray foam every hole back there that leads some way to the cabin.
> 
> And you could be leaking around the seats too.


Yeah, a lot of people think that you only need one baffle for IB. You need to completely seal the trunk off regardless of whether the subs fire into the seats or through the rear deck.


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## ErinH (Feb 14, 2007)

thehatedguy said:


> Both of you guys have some major leaks going on.
> 
> Erin, I looked at the install page for your wife's car. There are quite a few large holes on the rear deck that you didn't seal up. You need to spray foam every hole back there that leads some way to the cabin.
> 
> And you could be leaking around the seats too.


Those pictures were taken back in December, iirc.
Since then I've treated the rear deck and sealed up the holes. I used an amp on the bench and ran wires to the drivers. Gave them 200w @ 8 ohm (each) and it wasn't doing much. 

It's possible the rear wall needs to be sealed up and that's making all the difference, but I've also heard a couple IB installs without anything in the rear wall and they've done just fine. In short, if that's the real reason I'm not getting much then I'm not going to bother anyway. 

The purpose of me hanging the sls 8's was to see if they'd work with a reasonable install. I think I've gone beyond reasonable at this point and am not going to bother with going balls out on it. They aren't working in teh way I wanted to see if they'd work. So, it's not worth it to try any longer. That would defeat the purpose of _my_ intentions. 


Don't get me wrong, I appreciate the help. I've just gone the extra mile and it's not doing what I want and I'm not going to spend more time on it. I've pretty much made up my mind on going with the SI BMIII. 


And again, _my_ civic is SEALED THE EFF OFF. Spray foam, chunks of wood, bracing galore, etc, etc. I know what it means to fully seal the trunk because mine is. 
I've listened to Jason's car, though, with 2 12's hanging off the rear deck and only some LLP laying over the rear deck, no treatment anywhere else and the rear seat not sealed up and it works perfectly fine. (no, I'm not comparing my 2 8's vs. his 2 12's, I'm simply pointing out that the rear wall doesn't necessarily have to be barricaded)


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## audio+civic (Apr 16, 2009)

good stuff for us IB virgins


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## ErinH (Feb 14, 2007)

Welp, I now take back everything I said previously.

I just wrapped up the install in my wife's car (pics can be seen here for those who give a rip). They're now powered off a pdx-5 getting up to 400w @ 4ohm. I'm not sure if the PDX is rated the same at 8ohm or not, so I'll have to check. They're wired to a 4 ohm load, so probably getting about 200w each at that rated power. If that.

I don't know what was different about before that caused such the difference between the "bench testing" with them in the car powered off an amp on the bench, or now, but I do know that I've never been so happy to be wrong about my previous assertions. 

The 8's play pretty nice. They have some good bump to them, not major SPL levels, but nice nonetheless. No rattles in the car with minimal treatment (pictures of this are not updated in the build log, but you get the general idea). The wall is not sealed off as mentioned earlier.

I'll try to put them on the RTA tomorrow, since I"ve got to calibrate a couple mics ASAP anyway.

I'll try to add more details later if needed. Just wanted to jump in and add my new findings. I'm very pleased now with the output and integration. Going to have to work to get them not to pull to the rear (even crossed at 50hz/24dB ol' Chesky voice pulls to the subs), but for now I'm happy. My wife hasn't left the car in the past 25 minutes. She's jammin' out to Dave Matthews as I type this.


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## 01ws6 (Jan 9, 2010)

Bikinpunk- I would like additional details....I am one who is sometimes lead in one direction upon initial testing/install only to "hear" something totally different with only minor changes. Thank you for your consistent and frequent testing of equipment on this board...you always seem to follow up with honest and "real world" opinions. Glad to hear it worked out...any win with the better half is a plus....


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## AAAAAAA (Oct 5, 2007)

So all you did was swap out a different amp?


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## sqshoestring (Jun 19, 2007)

Glad it is working. They are still going to roll off some with the mild qts, that will show up as more output at 80Hz and above and force you to crossover lower than usual.

There are some more complex issues with sealing. If you have a panel, either the deck or the seat, it would have to vibrate with the sub to pass the output and thus cancel the output. If you have a leak it has to do the same, pass the signal in the range you are using the sub for. When it leaks you lose output typically at lower Hz. It will still work, just not as well. I mean a sub plays the same bass mounted to nothing, and as you make the baffle larger it plays louder at a lower and lower frequency because it cancels less and less. Or you make the sub put out enough to overcome some cancellation.


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## ErinH (Feb 14, 2007)

*2 of these wired in parallel to 4ohm final load on a pdx-5 sub-channel, rated at 408w @ 14.4/4ohm.*

Put the subs through its paces a bit on the drive to work (left my car with the mrs today). They play fine bandpassed from 31-71hz with a 24dB slope on each end. I have a few rattles that are exposed when I cross higher, but that’s a given. 
On most typical music, at mid-loud volume levels they do well. When I was playing some Black Eyed Peas (hey, point of reference, don’t judge me ) they would bottom out and higher volumes. 

I’m going to work the crossover some tonight and try to figure out the trouble spots with louder volume and see what I come up with. 
I’m also going to throw the RTA on the system and test the subs running full range. I’ll post up the results here.

IMO, for someone who doesn’t want a lot of bass, and you’re only looking to fill in the lower octaves, then they’ll work (assuming your install is up to task). 
Right now, with only minimal deadening and filled in holes in the deck and some in the trunk, they play well. 

Would I personally run them? Probably not. I listen to various music, and some of it is rap. On days I feel like going WFO, they couldn’t handle it.
Are they good enough in my wife’s c ar? I think so, yes.
Would they suit more moderate listeners? I think so. If your taste in music doesn’t trend toward rap or newer pop music where it’s bass heavy, then I think you’d be OK. As I said, they’re supplemental, which is all subbass should be, but you can’t expect much more from them than that.
If I had to guess, and subbass is not my strong point, I’d say they’re probably playing pretty flat from about 60hz down. Of course, playing flat isn’t (in my opinion) nominal for subbass. I’ll have to verify with the RTA later.

If anyone reading this plans to come to my GTG next month, you’ll have a chance to hear them for sure. I’m planning on working the tune in her car over the next week or so and try to get things ironed in. Not perfect, but at least get the kinks worked out. Feel free to demo the car.

I still may look into going with the SI BM3 at some point, but I’m not sure. I’m hoping that someone who comes to my GTG will have one and let me drop it in her car to test it out.


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## Yuck. (Dec 28, 2009)

noice...


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## 2upFZ1 (Nov 23, 2009)

Ed Zachary


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## sqshoestring (Jun 19, 2007)

You can't get much out of 8s, sounds like it is doing well. Hang some 10s or 12s and you will have significantly more output.


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## ErinH (Feb 14, 2007)

ran the RTA on the 8's today. Interesting results. Not necessarily because of the sub's ability to stay flat (within reason for 8's), but because of the serious suckout at ~160hz. The mic was positioned pointing straight up, pointing front and center, to the left, to the right *and even in the passenger's seat* facing up. There's a suckout there no matter what. I even used a mic mate instead of the mobile pre just to check the pre and the results were nearly dead on the same. 

In all cases there's a dip around 45hz, 65hz, 105hz, and 155hz (give or a take a couple hz). 
Resolution sat at 1/12dB to show a more realistic story. 1/3 shows roughly the same but hides a bit of the nasties. 

Car audio is fun.


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## thehatedguy (May 4, 2007)

Wow, you are having dips where most people are getting peaks.


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## ErinH (Feb 14, 2007)

I know, huh. Very odd.

80hz was just as surprising. Typically I have a dip there. 

I'm going to have to do some measuring tomorrow and see if I can figure out what's causing this. Probably the center console if I had to guess.


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## thehatedguy (May 4, 2007)

Try it with different seat positions too. 

Then try it SPL style on the dash.


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## ErinH (Feb 14, 2007)

^ check the above post (bolded). 
I had it in various directions in the drivers seat, and also measured from the passenger's seat. 

Unless, by 'seat positions' you mean literally positioning the seat differently. I wouldn't suspsect a difference, though. 


Forgot to note that the measurement was taken with the subs playing up to 200hz with a crossover of 12dB, iirc.


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## thehatedguy (May 4, 2007)

Yeah, move the seats back and forward.

You would be surprised that you may be hitting some sort of nulls. The Accord when IASCA changed SPL measurements from the driver's seat to the dash changed dramatically.


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## ErinH (Feb 14, 2007)

will do.


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## AAAAAAA (Oct 5, 2007)

Welp put some of that sealing tape between the wood ring and the SLS sub since the SLS has a rounded top not all that great for reverse mounting as well as a bit of deadening on the deck making sure to get the holes and the bigger areas ripe for resonating.

Results are great, I have output now. There is very little low end but some EQ work fixes it somewhat. It definitely excels for mid-base though, when I cross it at 250hz\24db, I can def feel it. The mid base from these are better in my rear deck then they were in the doors of my fj cruiser. They are in their element free air in that range for sure. Base though? Not so much.

All in all the SLS isn't all that great for rear deck sub-woofer duties.


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## ErinH (Feb 14, 2007)

^ agreed.
they'll work, but they're not great.

x2 on midbass performance, though. Would definately be a viable option for the 'midbass in rear deck' fanatics.


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## AAAAAAA (Oct 5, 2007)

Update, I ended up Modeling a crap load of 8's and see which one seemed like it would work best. And the results are below, surprisingly they all look very similar.










The top graph is the response of each woofer free air. SLS, pioneer, JBL,Polk and I forget the other one.

Surprisingly the one that looks best in that graph is the green line, that's the shallow mount pioneer 8 that pioneer actually recommend for IB use. It looks pretty good compared to the others.

I was trying to gifure out what parameters exactly to look at. seems like the pioneer is what one would be looking for. But after looking at the second graph, we can see that xmax trumps all. If one has enough, one can make it work.

You can see in the second graph where the line color change from bright to dark. 
Bright = playing within linear xmax
dark = no more xmax so it won't play or won't play well.

What we can see here is even though the pioneer has like 4mm of xmax, it can still take 200watts all the way down to the edge of the graph(geen). But so can the polk (purple line) and the JL (orange)but it uses up it's xmax. The polk 8's have an amaing 20mm one linear one way excursion like the W7 from JL!!

So I figured I would try the polks as I have used the pioneers before and the JL's are to expensive.

Essentially I slaped the polks in like I had the peerless SLS and gave them a couple of weeks to brake in, then I tuned them using the EQ liberaly to boost the low end. Thing is naturally they aren't great IB and EQ boost compensates a lot, these things can take LOTS of power according to bassbox and as it turns out, in the real world to.

I can't beleive the output I am getting out of these and they go low (with EQ work). I am amazed and glad I chose them. They exeed my expectations.

Whats cool is that they are damn punchy if I cross them over around 80hz to 250, they have tremendous impact. But I cross them between 63 to 80hz and boost them down to 30some hurts and it makes me feel the low lows pretty damn good.

**All opinions expressed here reflect those of a guy who isn't a bass head.


Green-Pioneer shallow
Purple-Polk MM840
red-Peerless SLS
Orange-JL w7
yellow-JBL


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## ErinH (Feb 14, 2007)

I'm not surprised they look similar. You're modeling a sealed box of the same size for all of them, and they're all roughly the same sd. It's rare that you find drivers of the same size that model vastly different.


IMO, it's not xmax, but sd that makes the biggest difference in an IB application.


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## AAAAAAA (Oct 5, 2007)

SD and xmax ... You can compensate for lack of one with more of the other.


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## ErinH (Feb 14, 2007)

I agree that both are important. But, IMO, cone area trumps xmax.


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## thehatedguy (May 4, 2007)

Cone area FTW


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## T3mpest (Dec 25, 2005)

bikinpunk said:


> I agree that both are important. But, IMO, cone area trumps xmax.


that's because down low it's really hard to get enough xmax to simply make up for more or bigger drivers. A 12 is over 2x the sd of an 8. If the 12 has 15mm of excursion, which is still pretty tame, you need 30mm of excursion on an 8 to keep VD constant. Step up to 15's and you at a little less than 4x an 8. One fifteen with 25mm of xmax which is realistic would need an array of about 7-8 eights to keep up with it, since very few 8's have more than 12mm xmax. Guys with 2 15's, shoot, forget about keeping up with that with 8's, even 10's and twelves might be a challenge, 12's work if you can fit 3-4 lol.

Realistically low bass is always about displacement, vd*xmax, so they are technically equally important. However, increasing vd is alot more realistic than increasing xmax.


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## 2upFZ1 (Nov 23, 2009)

The old hot rod saying applies here also... "There's no replacement for displacement."


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