First Home DIY Subwoofer - questions (1 Viewer)

Hi all. This is my first post here, though I've been reading the forum for a couple weeks now (and I've spent more time over at avsforum).

As the title indicates, I'm about ready to do my first HT DIY subwoofer. (I have done boxes for cars in the past.) Anyway, in order to upgrade my sub and garner the needed WAF, I've decided to go the DIY route. The wife does not like the box look (wood or black) and the tube look isn't any better. She has seen subs (innovativeaudio.com) that look like endtables and likes those. Thus that is what I'll be building.

The first problem? The more I research, the more possibilities I come up with. First I was going Shiva sealed, then Tempest sealed, then ported. After that I thought Tumult, then AV12, AV15, even SVS stuff. You get the picture.

I guess (at this point) I'm looking for some recommendations. The room the sub is going in is the family room (but is "attached" to the kitchen). Total dimensions are approx. 15' X 30' x 9'. In the corner that the sub will go, I have approx. enough room for up to 5 c.f. (though 3-4 would be preferred). Listening use will be approx. 80% HT 20% music.

The basic scenarios I see working are 12" sealed, 12" vented, 15" sealed. (PR won't work as the front and side need to be solid to have that furniture look.)

Drivers in the running are: Shiva, Tempest, Tumult, Brahma, AV12, AV15, SVS orig 12" (I'd look at upgraded drivers, but haven't found the T/S params anywhere). As far as budget I can go to about $1,000 (though $500 would be better.)

Thanks for the help.

p.s. Once we've worked out the sub, I'm still undecided about the amp.

For something as small as 3-4 cu.ft. but that will deliver the performance for movies in that size of room you may have to go with the sealed Tumult. If you can go a little bigger a vented Tempest would fill the bill nicely and leave money for a good amp and a BFD. Here's my sealed Tempest for inspiration. Tim's Sealed Tempest Table

An AV15 in 4 ft^3 tuned to 21Hz with a 4" flared port would probably get you to decent levels in your sized room. Downfire the driver and vent and make the enclosure any dimensions you want. The port will be a full length flared port kit which finishes to ~18" (I think). Use either a 350W plate amp or maybe a pro amp like the QSCs or Samson. You may get some port noise if you throttle it up, but downfiring should help. A larger port would be better, but may be too long (~42").

Pete

Thanks for the replys so far.

I'm upgrading from an Energy XL:10, which puts out decent-ish levels, but with a ton of port noise. In fact that is the major reason I'm upgrading and why originally I was looking at a sealed system.

Bob,

Anything you build should be a huge step up from the Energy sub. Pete's recommendation is a good one and it shouldn't exhibit any port noise.

Brian,

Thanks for 2nd to Pete's post. I'd seen your work in my research and the picture on your website looks very similar to what I have in mind (w/o the faux marble though).

Looks like 2 votes for the AV15 so far.

Bob,

I'm currently building an AV15-based sub for a customer, but it's twice this size!

Bob,

I'm looking at a similar project. I'm also thinking of the Stryke AV15 but in a sealed enclosure. You might also consider the AV15 with dual 18" PRs ... something like the Power 15.2 from www.stryke.com.

I figure I start with sealed first. And then decide if I need the greater extension of the dual 18" PRs, which add another $200 or so to the project.

For amps, I've been reading about:
* Rythmik 380 watt plate amp
* QSC MX1500a available for around $350 in eBay

There are many others in between: PE, Hypex for plate amps... Crown, QSC and Crest for pro-amps.

Good luck... and use the search feature to get lots of info.

Al

Given that I need to make this *really* look like an endtable, I don't believe I can go the PR route.

Thanks though, the AV15 is looking like the way to go.

What about even an AV-12? It should provide way more output than the Energy sub, and be easier to work into a smaller box, shouldn't it?

Looks like the AV15 should work. I'm just making my final decision between 4 c.f. and 5 c.f. -- and I'm leaning towards the 5 c.f.

Should have my design done by the end of the weekend.

OK, maybe I lied. Now I'm thinking about the Tumult- vented, 92L, & tuned to 19 Hz. Looks like it should outperform the AV15 by at least 4-6 db across the board.

Questions I have about the Tumult:
Is it suitable for downfiring?
Would the loss due to sag be significant or would it still outperform the AV15?

Thanks.

P.S. I do believe I've settled on the HS500 as the amp I'm going to use.

It may be. I used the ported.xls spreadsheet from http://www.diysubwoofers.organd its given me fairly reliable results before. The Tumult page at www.adireaudio.com talks about porting, so I didn't think it was a problem.

Can you elaborate? Or can someone else?

How do you figure that? With the amp you've chosen the AV15 would outperform the Tumult in my sims. 720 watts is just about perfect to get an AV15 to near max excursion, but the Tumult needs much more power to reach its limits.

Well, alright then. I guess I am set on the AV15.

I personally would recommend the AV15. I just finished a 5 cu ft ported (to 23 hz i think) and its great. I used 2 4" ports and noise is not a problem at all. I posted a pic in the AV15 enclosures thread if you want to see it (its still MDF for now). The AV15 is a much better deal than the AV12 and for just that little extra money you get more displacement and more efficiency, as long as you can handle the bigger box. Good luck in your choice, I don't think a Tumult would be bad either, but the power requirements are much more intense.
--Ryan

"720 watts is just about perfect to get an AV15 to near max excursion"

That sounds about right. But the max power handling specified on the Stryke website is 500 watts. Its always bothered me that to get the benefits of the extra excursion of the AV12 and AV15 you'd have to go beyond the electrical/thermal limits specified by the manufacturer (in all but the largest enclosures). Anyone know what Stryke's stance is on this? Are they underrating the voice coils? Will they void your warranty if you push 700 watts?

My Dayton DVC is rated up to 600 watts RMS (300 per coil) but needs only 250 - 300 watts in most applications. And I wouldn't really expect it to survive long at 600 watts even if you weren't exceeding Xmax.

As you can probably tell, I'm pretty excited to get the planning done and on to the next phase.

But I've thought of a couple of questions that I couldn't answer after doing a few searches:

1. How much room is necessary between the end of the port and the opposing wall of the sub? For example, if the port length is 18" and the internal height is 21", is that enough?

2. I'm not planning on stuffing with polyfill, but just using sound deadening material on the walls. What is the best approach- egg crate, spray on, or something else?

Thanks again.

The Tumult should work well in a 5ft^3 ported enclosure with the 720W amp. Dan recommends slot porting the enclosure with a 15" x 2" port, 50" long. The biggest difference is that the Tumult will easily be cruising with 720W while the AV15 will be near it's excursion limits.

Also, IIRC, John said the thermal power handling figures for the AV12 and AV15 are pretty conservative.