Assembling a Subwoofers

I'm putting a subwoofer together with parts I've been saving. I've never had a 15" subwoofer and now I have the stuff to put one together. This will just be the speaker and cabinet, no mounted amp. I thought putting these parts together, they will take up less space. I'm using a crossover from the circuit board from a Cervin Vega VR-15 which I had purchased damaged from a thrift store. The carpeted cabinet I've had for a few months with the plan of mating the 2. It is new, but the hole is too small and the cab is rather thin, so I worry about vibrations. But it seemed like it would be easier to buy one, and especially cheaper than to build one.

Grill

I also bought a waffle grill, I hope it won't vibrate either. I also am still collecting baffle material to glue to the inside. I'm using 3M spray glue.

Crossover

I mounted the crossover next to the input on the positive side. I had to ditch the small black finish ring due to the grill. I lined the inside with all the deadening material I could find, but forgot to take pics.

Testing

Well I'm ready to test, I purchased a QSC USA 400 Amp to power the subwoofer some time ago, but the Vega subwoofer is 4 ohms. The amp running mono bridged only runs at 8 ohms. So I'll be testing it with a Kenwood SW-32HT plate amp. I cannot find the wattage output, but the pull from the wall is 160 watts max.

What is a VR-15 and where did the driver come from? Do you know the correct airspace for that driver and is that box the right size?

Soundjunky said:

Well I'm ready to test, I purchased a QSC USA 400 Amp to power the subwoofer some time ago, but the Vega subwoofer is 4 ohms. The amp running mono bridged only runs at 8 ohms. So I'll be testing it with a Kenwood SW-32HT plate amp. I cannot find the wattage output, but the pull from the wall is 160 watts max.

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I'll stay out of the fracas regarding the sub, but personally I wouldn't be too worried about running that amp 4 ohms bridged. After all, it does have 2 ohm rating in 2-ch mode which to the amp is like 4 ohms in bridged mode.

whoaru99 said:

I'll stay out of the fracas regarding the sub, but personally I wouldn't be too worried about running that amp 4 ohms bridged. After all, it does have 2 ohm rating in 2-ch mode which to the amp is like 4 ohms in bridged mode.

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Thanks for the advise on the amp, I may try it. But I tested the (sub)woofer and at 40 Hz and the box thundered. I am very satisfied, but you'd have to hear it yourself, no vibrations, deep and clear. Also I did misquote the type of speaker this driver came from, it was a VE-15 Cervin Vega. I feel I scored on this project. I may still use the Kenwood plate amp, but I'm not cutting into the cabinet. I will build a frame and put the plate in it. The thundering it created was great, but I did have the Kenwood amp maxed at 100%. If I want more power I will have to use a larger amp, the QSC USA 400 is still on the table, but I must make sure it's OK to run it at 4 ohms in the bridged mono selection. It is not listed in it's manual I downloaded.

Sorry soundjunky, Botrytis is 100% correct. You can't take a woofer and decide it's a sub woofer and throw it into a random box with the wrong crossover and expect it to work like a real sub woofer.

JoeESP9 said:

Sorry soundjunky, Botrytis is 100% correct. You can't take a woofer and decide it's a sub woofer and throw it into a random box with the wrong crossover and expect it to work like a real sub woofer.

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I'll bet the Fs is lower and the Xmax is higher than many of the crappy drivers sold as "subwoofers" today. The classic big ass C-Vs didn't need no stinking subwoofers to bring the cops to the door. :yes:

Yes, most likely some room for improvement in the box size and tuning...duplicating the VE-15 dimensions (volume) would be a good place to start 16.6" x 20.8" x 36" (exterior). It won't dig as deep as some subs but will be stupid loud >30Hz.

Does the OP know what frequency their alleged subwoofer is being crossed over at?

Put the poor Woofer back where it was!!! (along with that random useless inductor) Do a lot more research, save up, and build something worthwhile.

donprice said:

I'll bet the Fs is lower and the Xmax is higher than many of the crappy drivers sold as "subwoofers" today. The classic big ass C-Vs didn't need no stinking subwoofers to bring the cops to the door. :yes:

Yes, most likely some room for improvement in the box size and tuning...duplicating the VE-15 dimensions (volume) would be a good place to start 16.6" x 20.8" x 36" (exterior). It won't dig as deep as some subs but will be stupid loud >30Hz.

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Thank You!!!

The cabinet could also use some bracing. I didn't notice any.

Subwoofer---
From Wikipedia, the free encyclopedia---
Jump to: navigation, search---
A 12" subwoofer driver without an enclosure
A subwoofer (or sub) is a woofer, or a complete loudspeaker, which is dedicated to the reproduction of low-pitched audio frequencies known as bass. The typical frequency range for a subwoofer is about 20–200 Hz for consumer products,[1] below 100 Hz for professional live sound,[2] and below 80 Hz in THX-approved systems.[3] Subwoofers are intended to augment the low frequency range of loudspeakers covering higher frequency bands. That's a direct quote from Wikipedia, from the 2nd address given above in botrytis post.
The Vega VE-15 reaches 26Hz, below the ability of human hearing. Along with the ported box, it rattles stuff all over, except for the windows, they're double pane. I have EV Interface Ds, they make the most bass of any speaker I've ever owned, although a few have come close, my MTX C-12s come close and my Polk Audio PSW 404b powered subwoofer with a Sunfire sub driver,(the Polk was blown out). I have a pair of Orion 10" HCCA Subwoofers with a M.B. Quart DSC1500.1D mono block D amp: 1500 WRMS 3000W Peak. I trying to tell you I know bass and I answered an ad in CL for some CV gear and a Crown amp. I was allowed to open the sub because It was shorting, the speaker was similar in every way: basket, motor(magnet), coil, spider, cone and surround. That's why I didn't go ahead and stuff it in a box and sell it. Enclosure dimensions are: 21" (W) x 16-1/4" (H) x 18" (D), not quite as large as suggested, but it was prebuilt and I must consider the space I have. The feet are from a JBL SUB 135 that died. I did test before deciding if bracing was needed, no vibration, so I didn't brace it.

Final touches.

I found the CV emblem last night and glued it on the grill. This finishes the project. I did find out why QSC did not rate the USA 400 at 4 ohms, basically the amp doesn't have the proper cooling ability, in their opinion. It will operate at 4 ohms, but it needs better cooling. I can add a computer fan inside the case as well as the power supply and connect to the main power switch to cut it on. But I'd rather have a thermal switch to cut the cooling fan on instead of it being on all the time. However I don't have that type of circuitry knowledge. So it limits my options. If anyone knows what type of circuits I should use, please let me know. I'd really appreciate it, Thank you.

I'm glad you're enjoying it. Here's a pic with an example of good sub cabinet bracing, should you decide to reinforce the cabinet structure.

Bracing

I thought of bracing, but when I tested my enclosure with 200WRMS @ 30Hz, 40Hz and 60Hz. There was no internal vibration, so unless it begins to vibrate internally or externally, I feel no reason to put bracing in it. I see yours is braced very well, but I'd bet you have a more powerful sub and amplifier. Mine is probably much milder than yours, but it rattles things all over the room, I've been testing the subwoofer and removing items that vibrate, moving them or putting little felt stick-on pads on the bottom of some things to control the vibrations. This is the first time I dealt with this issue, but it's the first time I've had a subwoofer that will sustain 30Hz so powerfully.

Soundjunky said:

I thought of bracing, but when I tested my enclosure with 200WRMS @ 30Hz, 40Hz and 60Hz. There was no internal vibration, so unless it begins to vibrate internally or externally, I feel no reason to put bracing in it. .

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What type of tests were done?

Take it easy on the guy. If he puts together a bass cabinet out of found parts and likes what it does, let him enjoy it.

It looks great, and it's obviously fun and satisfying.

I think it is good for you to know, however, soundjunky, that there is a more specific approach to designing and building a sub that will result in a much greater level of performance. Regardless of how much you're enjoying what you have, there's more of that to be realized next time you get the urge to build.

If you have the thiel small parameters of the driver and use software like BoxPlot to size and design the cabinet, you're going to get even cleaner, more musical bass. It's good to decide how big you want (or don't wat) a cabinet to be before selecting the driver. (Drivers of the same size, say 12", don't all require the same size cabinet for instance.) It can be a lot to chew through, and I was quite resistant at first, but the learning curve went rather quickly.

But again, you're obviously enjoying what you've built. If you're looking to just shake the room; fill it full of bass energy, then maybe you've reached that goal. Whatever you do, have fun and enjoy it.

Links:

http://en.wikipedia.org/wiki/Thiele/Small

http://www.micka.de/org/en/

http://www.members.shaw.ca/loudspeakerbuilder.ca/thiele-small.html

My project thread:
http://www.audiokarma.org/forums/showthread.php?t=511331

Good on you. You are starting out the way most of us did. Lots of enthusiasm, little if any money. Glad you are having fun / if it is fun and you want to continue there is a wealth of information out there (and here at AK) ...beware though : often sheer luck can get you to about the 80% mark ...... as you climb that last 20% of the ladder the rungs get more and more difficult to attain : but again / if it delivers fun/ the challenge IS the fun. Welcome aboard.