My Idea

[chemicall]

Well I have an idea, I have searched here and the net net like crazy to not exactly find what I may want to do

down firing 15" or 18"(undecided still) cube sub with a 12" passive on either side of the cube and one 12" passive on the front. I'll be using it for music, so about 19hz lowest would be great due to the roll off of the PR design.

I just have a few questions about this before I start modeling

Will all 3 radiators react properly and the same? of course they will all match

will a rack power amp like a Peavey work properly with a active x over, aslong as the amplifier can support the power and frequency range I need? I don't remember the model of peavey the amp, it's away in storage. but It does 700 x 2 @ 4 ohm and can support to 20hz. Will this work?

Can you recommend a subwoofer that will work good in a downfiring PR design, with my amp 4 ohms is fine, Should be dvc.
how far from the floor does a downfiring sub need to be?

I was looking at radiators on parts express, they offer a dayton for $78, is there better for the price? http://www.parts-express.com/pe/show...number=295-192

Any info is appreciated. Thanks all. Have a great day!

[bear]

Imho of course.

Downward firing is a bad idea.
The mass of a subwoofer with a low Fs is high, and the suspension is not designed to support the mass. Over time it will sag out of the gap.

The three 12" passives are a bad idea too.
While you may have enough excursion (maybe not), they are not symmetric, so they will not likely resonanate in phase. Believe it or not the pressure nodes inside a box are not even. Maybe 4 would be ok.

The volume of the cabinet you envision is an issue. Because you are thinking of 3 x 12" passives, I suspect that you think the volume of the cabinet will be smallish. To match that 15" or 18" driver you will need a box volume that is fairly large - look at the VAS figure, and run it in a simulator.

I'd go the other way, a 12" driver and a 18" passive for example, neither doward firing.

You could EQ the driver to make it "flat" in too small of a box. But then you have to have a big amp, and a driver that is designed to take a huge amount of power - and they usually then do not have a low enough Fs, and they tend to have a very large VAS.

Soooo... anyhow when you downward fire a woofer, assuming it can handle aiming down (and it can't) you have the added issue of the makeup of the floor playing a significant role in the overall sound that you hear. Put it another way, the floor - something you can't control at all - becomes part of your speaker system. In case this isn't obvious, there is a huge difference in the way a downward firing woofer will sound on a wood floor, a concrete floor and also with and without carpeting... etc...

Rethink. Simulate the box + driver. Then you might come up with a good idea. There are likely some sub projects that have been "vetted" here, so do a search...



_-_-bear

[jbell]

3pr's at $75 each? that sounds expensive..

http://www.infiniteelectronix.com/in...OD&ProdID=1631

I've used the above slaps with the magma 15" driver in a 19" cube, with a PE bash 500.. which is basically a DIY supernova 15. It's kinda fun, just watching the excursion of the magma and the slaps...

As I recall, I called earthquake directly at the time (a couple years ago) because my wholesale co, had the magma, but not the slaps. They sold me a slaps for $65.. YMMV...

The good thing about that combo, is it's a tried and true, and retails for a bunch of $$$$..

http://www.hometheaterplus.com/easumkposub.html

[chris661]

The issue with cone sag is with speakers of 15" or bigger - you could down-scale this idea a bit, say 10 or 12" instead, with 1 or 2 15" PRs

And I don't understand why you want 19Hz, unless you listen or pipe-organ music, which goes to 16Hz, but not very often, due to the structural damage to the building this would cause.

Looking at the size of woofers you're thinking of using, you're going for high-SPL stuff. Most music has little data below 40Hz anyways, so you could go for bigger woofers, but not PR design, and go loud instead of low.

Alternatively, you could go for low stuff in a small box, using EQ - you need to say exactly what volumes and type of music you're going to be listening to.