Building a sub, sealed or ported?

mike.hutch · 13-08-2009, 8:21 PM

I'm planning on building a sub for a new home cinema/gaming room project. I have a few bits, including a 200w panel amp and a few speakers to choose from.

Now most of them are car subs, I have an old Adire Shiva, a Magnat XTC1000, an MB Quart DWC308 and 2 8" REL subs.

Now to the point, I'm planning to use the MB Quart DWC308 sub that I have. I think its really designed for a car but its 8ohms. The spec on the box says its suited to a smallish sealed box, but plotting it up in Bassbox show it may be better in a ported enclosure.

The thing is I'm not sure if a sealed sub will be any good for movies and games, will it go low enough? The plot of sealed subs never looks very impressive in Bassbox.

Any thoughts guys?

tony brazao · 13-08-2009, 9:04 PM

So long as the driver you choose is happy to work in a ported box, I would go ported. Down sides will be more room taken up by larger box and slightly harder to build well, with a correctly tuned port. Ported boxes will go louder though!

micb3rd · 13-08-2009, 10:36 PM

Use the AdireAudio Shivia it is a good driver.

I happen to have copies of the original Adire Applications documents.

http://micb.talkaudiohosting.co.uk/n...plications.PDF

http://micb.talkaudiohosting.co.uk/n...plications.PDF

I would go for one of the Vented alignments, which ever one you can fit.

mike.hutch · 14-08-2009, 5:33 AM

Cheers for that, I've been looking for that Shiva info. I think I may build a test box for the MB Quart sub to see what it sound like sealed first. I do like the look of the ported designs for the Shiva there though.

micb3rd · 14-08-2009, 8:00 PM

It is your choice but I can't see the MB Quart being as good as the Shiva.

What impedence does your plate amp run best at 4 or 8 ohms?

You average small sealed enclosure will play down to low 30hz then roll off, it won't dig deep into the low 20's with much authourity, unless you have a lot of displacement from the driver and a large enclosure.

Output may be ok sealed but not a patch on a larger ported enclosure which will be 3-6db louder (maybe more) for most of its range with the same power.

I did a test 500 WRMS plate amp into single high excursion 10 (18mm xmax each way) inch woofer in a optimally damped low Q (0.5 qtc) 0.9 cubic foot enclosure and it did sound really good down to 30hz.

I doubled the cone area with same woofer so 2 x 10's, and put them in 2.6 cubic foot uned to 25hz and I gained 8db across the range it played lower and louder.

Sealed is great when you have lots of cone area like 2 x 15's or 4 x 12's where you can make up for the lost displacment from not having a port.

Moonfly · 14-08-2009, 8:11 PM

Out of interest,

Would sealed be just as good though if you used 2 15's, but in a push pull design ?

mike.hutch · 14-08-2009, 8:47 PM

I think the amp will run best at 4ohms. Its a 200w one I think, from CPC a few years ago I think. I think the Shiva is twin 8ohms voice coil if i remember rightly.

The Shiva is probably the safest bet, but I've had the MB Quart driver for ages and not found a use for it- its still in its packaging.

micb3rd · 14-08-2009, 9:31 PM

Quote:

Originally Posted by Moonfly

Out of interest,

Would sealed be just as good though if you used 2 15's, but in a push pull design ?

Yes it would be fine.

Quote:

Originally Posted by mixmanx

I think the amp will run best at 4ohms. Its a 200w one I think, from CPC a few years ago I think. I think the Shiva is twin 8ohms voice coil if i remember rightly.

The Shiva is probably the safest bet, but I've had the MB Quart driver for ages and not found a use for it- its still in its packaging.

Well if it does 200 WRMS into 4 ohms then it will do 100 WRMS into 8 ohms that is not much power really.

The MB Quart in a sealed run with 100 WRMS and a Shiva ported from 200 WRMS will be night and day difference.

mike.hutch · 17-08-2009, 5:47 AM

I'm looking at building the biggest ported design in the Shiva paper above. In the design it refers to a cut out in the front for a passive radiator and a cut out for a reflex port, I'm guessing it means one or the other but the design is not that clear.

micb3rd · 18-08-2009, 7:07 PM

Quote:

Originally Posted by mixmanx

I'm looking at building the biggest ported design in the Shiva paper above. In the design it refers to a cut out in the front for a passive radiator and a cut out for a reflex port, I'm guessing it means one or the other but the design is not that clear.

Yes the Vented designs were done so you could swap a PR inplace of the port so it is an either situation.

You only want to cut the hole for the port.

mike.hutch · 18-08-2009, 8:34 PM

Thanks! Thought as much.

mike.hutch · 05-09-2009, 6:50 AM

Thought I would update this thread. I've been busy building the Shiva sub, I changed the design of the bracing slightly to fit the amp I have, and I'm not going to use a flared port, because I haven't got one.

Sorry for the crappy pictures.

The first one show the sub put together.
Attachment 135337

The second has had the holes filled and the edges routed over.

Building a sub, sealed or ported?-sub2.jpg

Next it had a coat of primer and a few coats of black.

Building a sub, sealed or ported?-sub3.jpg

Then the inside has has a coat 'liquid rubber' this stuff is excellent for sealing all the cracks, and it helps with the resonance of the box. It will have another coat

Building a sub, sealed or ported?-sub4.jpg

The box will be sanded down to get rid of any lumps and bumps before having a top coat of black applied with a textured roller to get a stippled effect. I've found this is a goo way of getting a nice even finish without seeing any marks where screws have been filled over.

I'll get some better pictures when its finished.

micb3rd · 05-09-2009, 3:25 PM

That looks really good mixmanx.

Moonfly · 05-09-2009, 5:14 PM

Sweet, whens the amp and driver going in.

mike.hutch · 05-09-2009, 8:59 PM

Quote:

Originally Posted by Moonfly

Sweet, whens the amp and driver going in.

Still needs a lot of work yet to get a decent finish on it. Plus the room its going in still doesn't even have foundations yet, so it won't get used properly for a couple of months at least anyway. The wife is not too keen on having it the lounge, it is pretty big so I don't blame her really.

mike.hutch · 09-10-2009, 10:20 AM

A bit of an update on this, I've been off work yesterday and today so even though it still needs to have the final finishing coats of paint, I decided to put it together and run some test tones through it via my laptop and Cool Edit.

I can confirm it works down to about 18hz, at which point it rattles everything in the house but you cant really hear it.

MODS: Can this thread be moved to the DIY section please?

**IronGiant** · 09-10-2009, 10:50 AM

No problem

mike.hutch · 09-10-2009, 12:46 PM

Thanks!

micb3rd · 09-10-2009, 5:26 PM

Cool, it is a good subwoofer.