Sealed TC-12 OEM Project

**Geoff St. Germain** · **03-03-08, 08:46 PM**

I've only had ported enclosures up until now, so it's time for a venture into sealed subwoofers. I have a total of four TC-12 OEM drivers that I will likely be using for this project. My initial thoughts are using the drivers in two enclosures, so 2 drivers per enclosure. For the design I'm between an opposed driver setup and a setup similar to the JL Gotham. I would like to keep the theme between these subwoofers and my mains to be the same, so in that regard, something like the Gotham will work better. The mains are going to be towers with curved sides similar to the center channel I built.

For size I've been thinking 4.5 cu ft fully stuffed. I have limited experience with stuffing and enclosures. WinISD says that with full stuffing 2.25 cu ft per driver gives a Q of .577 which is what I'm shooting for. I am also considering using something like the Marchand Bassis EQ.

At this point I'm looking for thoughts on this. Like I said I don't have much experience with sealed subwoofers. The emphasis will be on getting good response down to 20 Hz, hence the idea of using an EQ. I think that with 4 drivers there should be a fair bit of opportunity to use EQ and still maintain a good max output.

**Warmon** · **03-03-08, 09:49 PM**

I had to go see what a Gotham looked like. So this is it, right? Are the four posts on the front baffle there for a grille? Will you be recessing the top?

**TheEAR** · **03-03-08, 10:04 PM**

Geoff,

Superb work on the center channel ! Quality and dedication to a project are always great to see.

**Geoff St. Germain** · **03-03-08, 10:38 PM**

Quote:

Warmon wrote:

I had to go see what a Gotham looked like. So this is it, right? Are the four posts on the front baffle there for a grille? Will you be recessing the top?

Yeah, that's the Gotham. I probably wouldn't do the recessing on the top or the front where the grille should go (on the four posts you mentioned). Basically it would be the curved cabinet and the two vertical drivers.

The finish will be the same as the center channel, oak veneer and the textured black baffle.

Thanks for the kind words Arthur. My opposed firing idea is like your sealed TC-3000 and TC-1000 boxes.

**Warmon** · **03-05-08, 07:45 PM**

Geoff, what advantage does a .577 critically damped offer you over .707 maximally flat? I know the box will be bigger - is it efficiency? My understanding is .707 will have some punch and .577 won't have much, if any...is that what you're after?

Should be a cool build...a bit of a challenge on the woodworking side.

**Geoff St. Germain** · **03-05-08, 08:11 PM**

.577 is actually max flat delay, .5 is critically damped. I'm after maximum accuracy, and from my understanding a Q of near .5 is best. Also, a lower Q alignment has better low end efficiency.

**eyekode** · **03-06-08, 06:49 PM**

Quote:

Geoff St. Germain wrote:

WinISD says that with full stuffing 2.25 cu ft per driver gives a Q of .577 which is what I'm shooting for.

Sorry for the silly question... but how do you enter stuffing into WinISD?
Thanks!
Salem

**Warmon** · **03-06-08, 07:19 PM**

Quote:

Geoff St. Germain wrote:

.577 is actually max flat delay, .

Oh yes, you are right...

4.5 cf is a good size for two 12's. These 10" NHT Sub2's I'm playing with want a box bigger than that - I'm thinking pull pull isobaric max flat for a 2.1 setup in the bedroom...gotta shrink them down to nightstand size.

**Geoff St. Germain** · **03-06-08, 07:41 PM**

Quote:

eyekode wrote:

Sorry for the silly question... but how do you enter stuffing into WinISD?
Thanks!
Salem

If you look in the help files you can simulate by changing Q_a.

**Geoff St. Germain** · **03-09-08, 03:16 PM**

I'm starting to lean toward an opposed driver setup with the drivers arranged in a push-pull setup.

Does anyone know where I could get my hands on some magnet boots (those rubber things to cover the ferrite discs)? The TC-12s don't come with them and the ferrite slugs are pretty ugly. I'm looking to get two for the two drivers that will be mounted inverted with the magnet sticking out of the box.

In case I can't find anything, does anyone else have any ideas for covering the magnets?

**Geoff St. Germain** · **03-09-08, 04:58 PM**

Oh, a shot of the drivers. I'm still waiting for one that's supposed to be here next week.

Here's our Chihuahua. I think he's scared of it:

**Warmon** · **03-10-08, 07:04 PM**

Quote:

Geoff St. Germain wrote:

Here's our Chihuahua. I think he's scared of it:

Better he stay that way...or else he might get too comfortable and start using it as a trampoline. Bet he'd really freak if you thru the juice to it...

**F1 fan** · **03-11-08, 11:37 PM**

Quote:

Geoff St. Germain wrote:

I'm starting to lean toward an opposed driver setup with the drivers arranged in a push-pull setup.

As in a closely coupled Isobaric to reduce cabinet volume requirements, or just a standard compound arrangement like M&K used on some of their designs?

I must say that that stack of drivers looks rather sweet,

and the puppy is a little cutie too.

**Mike P.** · **03-12-08, 12:14 AM**

Geoff, did you find any magnet boots that you were looking for?

**Geoff St. Germain** · **03-12-08, 07:29 AM**

Quote:

F1 fan wrote:

As in a closely coupled Isobaric to reduce cabinet volume requirements, or just a standard compound arrangement like M&K used on some of their designs?

I must say that that stack of drivers looks rather sweet,

and the puppy is a little cutie too.

It'll be a standard compound arrangement. Yeah, our puppy is a cutie. I wasn't in favour of getting a little dog when my wife proposed it (we have two German Shorthaired Pointers I use for hunting). He actually quiet, well behaved and very affectionate. I figured he'd be yappy and annoying but I was wrong.

**Geoff St. Germain** · **03-12-08, 07:31 AM**

Quote:

Mike P. wrote:

Geoff, did you find any magnet boots that you were looking for?

Hey Mike, no I haven't. I guess it has the same size motor as the TC-3000 but from posting on AVSforum it seems that the boots are from a vendor that I wouldn't be able to buy from (they make the gaskets and boots on a lot of subs). It was suggested to paint the slugs which is what I'm exploring. I may try to fill the small gaps in the slugs with something to get a smooth surface and then use a texturized paint of some sort.

**Robert_J** · **03-12-08, 05:32 PM**

Pic 1 below is my OEM12 with the magnet boot I offered you at AVS.
Pic 2 below is the OEM12 beside a sub I built with a surplus TC9 motor. See the difference in the number and size of the magnet slugs as well as the diameter of the top plate.

-Robert

**Exocer** · **03-12-08, 10:58 PM**

All these woofer pics are making me want a new driver...We all know I have way too many as it is...so i need to not buy another until i sell some of the ones laying around.

Anyway Geoff, another reason to consider the opposing fire drivers is to minimize panel resonances. But sure, you already knew that. While the Gotham does look cool, opposed firing drivers do make for a more neutral setup.

As far as Qtc, i've had anywhere from slightly above .707 down to below .5 in my sealed box. The midpoint of about .55 did sound the best to my ears. A perfect trade-off of higher frequency "thickness" to lower frequency efficiency. In this room having the lowest anechoic f3 simply didn't matter for me due to room gain.

**Geoff St. Germain** · **03-14-08, 06:40 PM**

Here's a couple of shots of the modeled enclosure:

Any thoughts?

**F1 fan** · **03-14-08, 07:22 PM**

Quote:

Geoff St. Germain wrote:

Any thoughts?

I really like those rounded sides and the pedastal.It looks more labour intensive but the results will be worth it.I have never atempted rounding panels as you are intending so I will be watching your progress to get some tips on how its done.Are you planning on veneering or painting?

**Geoff St. Germain** · **03-14-08, 07:59 PM**

I'm planning to veneer, but I may also do a combination with painting, perhaps veneering the upper part and painting the base.

**Warmon** · **03-14-08, 08:05 PM**

Quote:

F1 fan wrote:

I have never attempted rounding panels as you are intending so I will be watching your progress to get some tips on how its done.

Like the design...looks good. Best way to do those sides is three layers of 1/4" MDF.

**Geoff St. Germain** · **03-14-08, 08:10 PM**

I'll likely take a similar approach to how I built up the sides on my center channel.

I'm probably going to be using void-free baltic birch for these guys since I am really sick of dealing with MDF dust. I may use an outer layer of 1/8" hardboard since it seems to be a nice substrate for veneering.

**eyekode** · **03-14-08, 08:20 PM**

Those will look great with your center channel. I am still trying to figure out how to mount my center over my plasma like you did... very slick.

I will say however that balancing 2 subs is not so fun. I have 2 crappy ones now. I have been using them as speaker stands for my fronts. But it was tough to get them to play nice in that location. Oddly enough I found that putting one of them out of phase made for nice FR. I am replacing these two subs and I will go with one larger ported sub directly between my mains.

Good luck!

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