new 15 inch sub

so you are going to swap 1 15 for 4 8's. the 8's have it in cone space but the 15 probably has it won on excusion. Let us know how it works out.

 

sweet!!! pics pics pics!!!

 

Not only would the 15" likely have the 8" on excursion, that single large cone with that single larger, heavier voice coil will have a tremendously lower resonant frequency compared to four individual tiny, light cones...

It'll be a totally different animal - this sub should not only be as loud as the eights in the frequency range they were [Fs and excursion] limited to, but it'll DROP way lower than those eights, and shake you up. The eights just kicked nicely, I'm sure.

But it's an interesting point about the eights and 15... in an SPL contest context, where you only have to tune it for a burp at a higher frequency, you might be able to make a box that would eek out the 15" in SPL. It would be sweet if classes were done by cone area... way more fun.

But in a street car, tuned anywhere below 45hz, this 15" should be a winner in more ways than (but including, if only perception) SPL. Let us know how it turns out...

 

damn the 15 has a high QTS....more suited for IB and large sealed enclosures.

Ported it will likely sound very peaky and muddy.

Ok well well after crunching some numbers the 15 can sound decent in a 4th order bandpass if you wanna try one Pedro.

 

Actually there's a lot that's noteworthy about that comparison...

Just a generalization, but by the specs, those look like some beefy, high capability eights.
And, by the specs, the 15" looks like a cheapo, save for having high powerhandling.

The eights have strong motors - very low Qes and Qts. Of course, they don't have much mass to push, even though it looks like they have pretty heavy cones as eights go. And, the suspension on them is pretty soft, very high mass - gives it a very low resonant frequency, that's very low for an eight. And, it must have a pretty wide diameter spider and long voice coil (I'm assuming it's overhung), because a 14mm Xmax is very long for an eight - if that's a real (meaning one-way) Xmax that's listed there. With a coil that long, I'd also guess it handles a decent amount of power - more cooling area, and I'd guess with that kind of moving mass, a good part of that is a heavy duty voice coil... the efficiency is pretty low for an eight, so that all adds up. Bottom line - those are some really nice eights, at least by design (apparently not by execution).

The 15" by comparison... I'm not the slightest bit impressed by a 15mm Xmax on a 15" sub... even purpose-built nearly even-hung SPL subs have that for excursion. And, that Fs is pretty middle of the road... seems like there's not much moving mass there, usually that means the components used are light, maybe cheap... very surprised to see 750w powerhandling even. It's not a strong motor, that is a tremendously high Qts and ludicrously high Qes... which, if nothing else, means that sub is going to sound bad in a vented box. That sub says "seal me" all over it.

I agree with asnboi3644... a 4th order bandpass might be one way to get around that last issue there... in a 4th order bandpass box the rear chamber IS sealed, and you can manipulate the SPL skyward by playing with the tuning on the front chamber (the vented one). I didn't model this up in anything, but I'm guessing that regardless, this sub is going to be wanting a pretty huge box... and in this case, these weird specs might mean you wouldn't want to send 750w into it at any rate, in an enclosure that large.

Really interesting comparison...
Now I'm really curious, because there's no advantage at all in excursion, Fs is virtually identical between them, and if you end up going from four eights vented to one fifteen sealed.... the four eights will definitely have the single fifteen in SPL, by these specs. ;-)

 

that would work...but the 4th order would be 5 cu ft net (both chambers) using two 6" round ports.

 

I assume that's a different sub, not those cheapos?

Also, as an option, I know the owner of Pro Tech, and he's basically ending life on the company... he's got these very nice beefy eights (I used two in a dual-chamber vented enclosure, and it was easily as loud as a twelve) that I can get my hands on to you for $30 each I'm sure. They were sold for $99.

Site is down, I'll have to get you the new page with the specs... but they rock in vented boxes, and four of them would replace yours. I think they are single 4 ohm IIRC.

 

I'm interested in those 8's