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View Full Version : Any way to tell how speakers perform IB?



heyman421
08-17-2006, 12:06 AM
I've still been scouring partsexpress for components for a DIY setup, and i've been looking at a couple different drivers. The amplifier i'm using will give 120w rms @ 8 ohms, or 240w rms @ 4 ohms, CEA2006 certified, so either of these drivers will work fairly well with the amplifier.

can anyone tell me which (if either) of these speakers will work in an IB install?

Or at least what i should be looking at to pick better drivers?

I need something that will be comfortable playing down to 60hz infinite baffle, without the suspension wussing out and self-distructing, my substage is most likely going to be a pair of Dayton Reference series 15's in 2.5 cubes each.

Here's the two drivers i've been looking at. I can't afford morels, but i think these two speakers look like the best for my money.

They'll be playing 60hz-500hz, btw, in a 3-way configuration.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=296-432

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-368

my midrange and tweeters are most likely going to be dayton reference as well, which is why the dayton reference 10 is in consideration, but the dvc ac woofer would make better use of my available 4 ohm power to bring the midbass home with some grunt.

Let me know whacha think.

GordonW
08-17-2006, 11:36 AM
The most important things to look for in an IB woofer, IME:

-Qts of AT LEAST .40 (.5 or greater is better)

-Large X-max

Given these two parameters, the Aurum Cantus will most likely work better.

Regards,
Gordon.

heyman421
08-17-2006, 03:12 PM
awesome, i really had my eyes on that one

now to find someone to build me some nice doorpods....

squeak9798
08-17-2006, 07:40 PM
I would have to agree with Gordon's assessment that the Aurum would probably be the better option of the two from a Q/Xmax point of view. And the lower inductance for a midbass application is icing on the cake.

That said....unless your door has 5cuft of volume, neither speaker would truly be in an infinite baffle alignment. The resulting Qtc of the Ref would very likely be pushed up to an acceptably high value (not that a low Q system can't have decent results for certain personal tastes, since that's what it mainly boils down to, personal taste).

But I would say if the Aurum tickles your fancy, and you can afford it...go ahead and give it a shot.

heyman421
08-17-2006, 07:47 PM
Hmm, i guess it never even crossed my mind that the full volume of my doors could actually still be too small. This is the first venture i've attempted into drivers larger than 6.75" for components.

Do you think the behavior in the door would be violent enough to shake my door? Not due to vibration, but due to actual vacuum/Pressure?

squeak9798
08-17-2006, 07:59 PM
Nothing that couldn't be taken care of with a little ingeniuty with sound deadening.

Also, FWIW, it seems that for any given volume the Aurum has a much lower F3 than the Ref....talking ~20hz difference.

This is using the T/S off the PE website and the formula:
F3 = Fb*((1/Qtc^2-2+((1/Qtc^2-2)^2+4)^0.5)/2)^0.5

For example, in a 3cuft enclosure the Aurum has an F3 of about 38hz, whereas the Ref has an F3 of about 55hz. Qtc for the Aurum would be .75 and the Ref .58. Used 3cuft because it seemed like it could well be a close approximation to how much airspace could be had from your door.

Disclaimer: Ofcourse the above assumes I didn't make any errors when inputting things into Excel.

heyman421
08-17-2006, 08:09 PM
38hz is a lot better than i expected.

I've been reading fiberglass DIY's so long that i'm getting dizzy.

i'm gonna chill out on this for a bit and go outside, haha

squeak9798
08-17-2006, 08:14 PM
Well, I double checked my calculations and I was right :p:

WhoSayWho?
08-17-2006, 11:29 PM
Wow, I think I had a similar question, but now that I have heard the answer, I am not so sure.

Why can't you just say, this speaker owns that speaker? Or, this speaker blows the other away?

Those are both very acceptable responses.

Just kidding of course. I will go back and read for comprehension.

GordonW
08-18-2006, 12:32 PM
38hz is a lot better than i expected.

I've been reading fiberglass DIY's so long that i'm getting dizzy.

i'm gonna chill out on this for a bit and go outside, haha

Keep this data point in mind, too:

My doors have Genesis Physics 8" woofers... calculated "anechoic" f3 (as in what a box program predicts in a sealed box the approximate size of the door internal volume) is about 40 Hz. HOWEVER... MEASURED, IN CAR response (measured with LEAP/LMS... not some cheesy SPL/RTA setup!) was STILL RISING in level, going BELOW 15 Hz. As in, the F3 was probably around TWELVE Hz or so.

Cabin gain is a MONSTER, with door speakers!!

Regards,
Gordon.

squeak9798
08-18-2006, 07:10 PM
^^ Good point.

That number I listed was anechoic (no enviornment affects), whereas the vehicle will have some nice cabin gain to help you out and push the F3 even lower.