DIY Sub enclosure

[bre's dad]

I'm looking to build a sub cabinet. The sub I've ordered is a 10". I don't know the specs on it as nothing was advertised. Its an inexpensive driver, but something to play with. I've got a couple of low pass chokes I bought several years ago I believe cut off around 100hz (need to look up the exact specs on those too.)

What can I use to determine optimum cabinet size? Like I mensioned earlier, I don't have specs on the sub yet. I was thinking of a sealed box, but if it wouldn't be too difficult to figure, a ported box would work too. Math was never my strong point, so something not involving coplex formulas rivaling some of Einstein's work is preferred.

I've got a decent wood shop & have built cabinets, shelves, etc. so constructing a good box isn't an issue... just figuring the size is.

 

[dc270]

This is rather a tall order to fill as knowing the driver parameters is paramont to designing a proper enclosure! Generally speaking the 10" can be fit into a cabinet from about 1 cubic feet to a few cubic feet, vented and non vented. If you are lucky maybe there is an AK member nearby that can measure your 10" woofers parameters and suggest a proper box size and type. FWIW Parts Express sells a nice Woofer Tester that can measure your parameters and aid in the design work. The days of putting a speaker in a box has evolved for the better-but maybe you could still get lucky!
DC

 

[bre's dad]

What I need to do is see if I get the T/S parameters with the sub then go from there. If not, I'll try to look the up online. I've built boxes before, but mainly shooting from the him, guesstimating cubic volume then go from there.

 

[Zilch]

Yes, once you know the T/S parameters, you can put them into a box modeling program like the free WinISD or others, and try different box sizes and tunings in computer simulation. That'll tell you what to build and how well it's going to work, basically. :thmbsp:

 

[jocko_nc]

If you cannot find the parameters for the "cheapo" subwoofer:

Make the cabinet suitable for one of the Dayton Reference subwoofers. Use the Dayton parameters and make the cutout large enough to accomodate one. Use the "cheapo" and see how it goes. If and when you are done playing around, order the Dayton. You'll have a seriously kickass subwoofer and a ready-made home for it.

How do you plan to amplify? I had plate amps, but switched them out for an external amp. Much better, IMO.

jocko

 

[bre's dad]

How do you plan to amplify? I had plate amps, but switched them out for an external amp. Much better, IMO.

jocko

Unless it dies, I've got a NAD 2600A I'm going to bridge to drive it.

I'ce got a lot of scrap plywood laying around. Not the best material, but there's plenty of it. Once I get it fine tuned, I'll give it a nice oak finish to match the rest of the setup.

 

[jocko_nc]

You already have an amp, cool. I switched out the plate amps soon after I found a beasty H/K Citation 22 at the Goodwill. I really believe putting the amp in the subwoofer enclosure is a dumb compromise that defies common sense. External amp designs are much more flexible, easier to build, easier to use, and will probably last longer.

I am using mostly plywood enclosures right now. Plywood holds a screw (or T nut) better that MDF ever could. Be sure to brace it well and line with deadening material. The front baffle will need to be double-thick. I used plywood and MDF together. For the back panel it was MDF.

You could have a seriously kickass sub in short order. You're looking at 400 watts from a good amp? A 12.00 Dayton Reference driver won't cost all that much and will sound oh so sweet. A single 10.00 would probably feel a little small, once you get into it. For the amount of effort you are considering investing, don't skimp on the driver.

A ported design will have further benefits. I used these: Precision Ports by Precision Sound Products, psp-inc.com. PartsExpress sells them too. They have a nice port size and length calculator at the website.

Also, calculate resonant frequencies with a shareware program that I unfortunately do not have on this computer. Crap.

Man, you could amaze yourself with this project..................

jocko

 

[jocko_nc]

The program is called "boxnotes". It is shareware.

The Dayton Reference HO is $129.00. Good driver.

This is what I came up with over the winter. I would put these up against any subwoofers I have ever heard.

I posted like a fiend during the project: http://www.audiokarma.org/forums/showthread.php?t=106757 I take it back, those were MDF with plywood laminate. I forgot.

GO FOR IT!

jocko

 

[JimJ[VT]]

You'll need something more substantial than a 100Hz low pass choke as a crossover, otherwise you're going to get a lot of sloppy midbass coming through the sub, never a good thing.

 

[bre's dad]

Of course, about 2 months ago I gave away a nice 2" Cerwin Vega sub I figured I'd never use again, after sitting around for about 10 years... used for about 6 months.

 

[bre's dad]

I dug out the chokes I have (2). Here are the specs:
Inductance:........................................................4.25 mH
DC Resistance:.............................................Less Than 1 Ohm
Max. Current:.......................................................2 Amps
Cutoff Frequency:
With 4-Ohm Speaker:..............................................150 Hz
With 8-Ohm Speaker:..............................................300 Hz

If hooked in series, how would that change the cutoff? Its a 4 Ohm sub.

 

[GordonW]

In series, they'd be 8.5mh... which into a 4 ohm load would give around 75 Hz crossover frequency. Not a bad place for a sub...

Regards,
Gordon.

 

[auplater]

Measuring the T/S parameters isn't all that difficult.. I've got an excel sheet to plug in the Fs, with and w/o a sealed test box, along with the high/low -3dB resonance freqs. All you need is a computer with a sound card, a DMM, a 6 - 8 ohm 5 watt resistor, and a share (or freeware) signal generator program (I use NCH tonegen), and your amp, take a few voltage vs. freq. measurements, plug them into the spreadsheet, and voila! Fs, Vas, Qms, Qes, Qts result, from which you can then plug into Boxplot, WinISD, etc. to give proper box dimensions and tuning data.

You could use the 2 chokes in series to get ~ 2x inductance and lower xover, and add a parallel cap to make a 2nd order xover, but 2 amp current rating is pretty low, the xover won't handle much power.

I've become partial to sonotube subs, the enclosure's already built for you...

http://www.audiokarma.org/forums/showthread.php?t=116930


John L.

 

[bre's dad]

that's one hell of a sub! I built a few tubes in college, one out of 12" PVC 'compliments' of a late night visit to a construction site. Built another out of 12" cardboard builder's tube/concrete form. The carboard sounded much better than the pvc, not as boomy. The fun really began when I put a second sub on the other end & reversed the phasing, so they weren't pushing against each other.

 

[bre's dad]

OK, the sub arrived yesterday (cheap 10" Advent... no reason to spend big $$$ for first time out, at least first time in several years. I've built boxes before, but far more primative: no t/s params, just taking an educated guess. Anyhoo, I used a design that was already included in the manual which worked out to be about 14x13x19, with a 3" port 10" long. The box I built is crude but functional. The duct tape with a speaker wire? I didn't have and terminal plates and was eager to hook it up tonight, so I just drilled a hole and ran the wire through and covered it with duct tape. That will be corrected when I find a terminal plate. I may have a line on some better 12" subs and will build something nicer with a better X-over if I get them.

Oh yeah, the first test cd I ran through it didn't sound all that hot, but it doesn't have much bass. I ran Hotel California and some random stuff on the iPod and was amazed. After spending about 15 minutes balancing both amps (Carver tfm-15cb as the main and an NAD 2600A bridged driving the sub), it sounds pretty good. It needs to be crossed over lower than what it is. I took the 2 chokes I have and I think someone said that would put it around 75hz. I'm thinking 60 would probably be better. Its not as boomy as the powered Infinity 12" I have, but doesn't have quite the punch either. But thats a 10" vs. 12" speaker.

 

[Analogdino]

I would stick to a sealed, closed box. Easier to design and more forgiving of errors. For a 10 inch sub, use about 1.5 cu.ft. Also, the result will be a "faster" subwoofer.
Use thick wood and/or brace well internally. Add damping to taste. <g>
Cheers,
Roger