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Newbie trying ot build subwoofer..please help

post #1 of 13
Thread Starter 
Guys,

I am trying to build a new subwoofer and have been reading the posts but had a question. I have a 12" ported backfiring enclosure and was thinking on getting a driver and amp plate. However, I noticed that people are recommending an external amp. Is the amp necessary if I have a subwoofer plate? Also I noticed that the subwoofer plates are extremely expensive...somewhere close to 200 bucks. Is that correct? I might as well buy a new subwoofer if I have to spend 500 for a 500watts amp. Then why build your own. Sorry for the newbie questions but its a start. Thanks.
post #2 of 13
Quote:
Originally Posted by sdrm View Post

Guys,

I am trying to build a new subwoofer and have been reading the posts but had a question. I have a 12" ported backfiring enclosure and was thinking on getting a driver and amp plate. However, I noticed that people are recommending an external amp. Is the amp necessary if I have a subwoofer plate? Also I noticed that the subwoofer plates are extremely expensive...somewhere close to 200 bucks. Is that correct? I might as well buy a new subwoofer if I have to spend 500 for a 500watts amp. Then why build your own. Sorry for the newbie questions but its a start. Thanks.

Because what you can build for $500 is much better sound quality and SPL than a consumer subwoofer of the same price.

A $1000 subwoofer budget is the butter-zone for 95% of people.

A plate amp is fine if you are trying to save money.
They aren't expensive, they are actually cheap, and a good way to go if trying to conserve money.

Most people who need external pro amps need them because they are powering more than 1 subwoofer, in many cases 4 to 8 18inch subwoofers off 1 amp.

We consider these to be good amps, but with a price tag that matches.
http://www.ebay.com/itm/POWERSOFT-K20-DSP-AESOP-2-Channel-K-Series-Touring-Power-Amplifier-9000W-New-/380416501322?pt=US_Pro_Audio_Amplifiers&hash=item589297264a

http://www.ebay.com/itm/LAB-GRUPPEN-PLM14000-14000W-PROFESSIONAL-POWER-AMPLIFIER-B-STOCK-NEW-COND-/140892002787?pt=US_Other_Pro_Audio&hash=item20cdd159e3

http://www.ebay.com/itm/Crown-ITECH-I-TECH-IT12000-12000HD-12000-HD-Power-World-Touring-Amp-Amplifier-/360533853960?pt=US_Pro_Audio_Amplifiers&hash=item53f17e0708

http://www.ebay.com/itm/CREST-AUDIO-2500-W-Ch-Stereo-Pro-Power-Amplifier-CA18-/280618078853?pt=US_Pro_Audio_Amplifiers&hash=item4156241285

http://www.speakerpower.net/order.html
post #3 of 13
"I have a 12" ported backfiring enclosure and was thinking on getting a driver and amp plate."

the size and tuning of the enclosure affect the performance once you plop a driver in the box.

"However, I noticed that people are recommending an external amp. Is the amp necessary if I have a subwoofer plate?"

if you have a plate amp, you do not need another one.

"Also I noticed that the subwoofer plates are extremely expensive...somewhere close to 200 bucks. Is that correct?"

they can actually cost over a thousand dollars. as for if that is expensive, that is up to each person to decide.

"I might as well buy a new subwoofer if I have to spend 500 for a 500watts amp. Then why build your own."

because you might like the performance of something that you cannot buy for the same money. if you want a cheap sub tuned to 33hz or so, then you are probably better off buying.
post #4 of 13
Quote:
Originally Posted by sdrm View Post

Guys,

I am trying to build a new subwoofer and have been reading the posts but had a question. I have a 12" ported backfiring enclosure and was thinking on getting a driver and amp plate. However, I noticed that people are recommending an external amp. Is the amp necessary if I have a subwoofer plate? Also I noticed that the subwoofer plates are extremely expensive...somewhere close to 200 bucks. Is that correct? I might as well buy a new subwoofer if I have to spend 500 for a 500watts amp. Then why build your own. Sorry for the newbie questions but its a start. Thanks.

First thing, if you want to reuse the box you're going to have to give us the enclosure dimensions, and the inner port diameter + length, then we can tell you the approximate internal volume and tuning point.

Chances are if it's a cheap commercial product it is tuned around 30-40hz, and the amp will have a filter around the tuning point to protect the woofer. This will let us know what you have to do to reuse the enclosure, and whether the amp is suitable for reuse.
post #5 of 13
I understand that you want to reuse a box you already have. Other box designs like transmission lines and bass horns are more or less very small production or full custom since they are difficult to build hence not easy to mass produce and sell to the public.

Amps are dirt cheap for the amount of power they can deliver. At least compared to a decade ago. Lol...
post #6 of 13
Thread Starter 
The enclosure dimensions are length 15", width 15.5" and height 15.75". It has a cut out for 12" and mdf width of 3/4 inches. I also see wood separations inside the enclosure. Thanks.
post #7 of 13
Quote:
Originally Posted by sdrm View Post

The enclosure dimensions are length 15", width 15.5" and height 15.75". It has a cut out for 12" and mdf width of 3/4 inches. I also see wood separations inside the enclosure. Thanks.

What's the port dimensions?
post #8 of 13
Right now, I think the box size is too small for 90% of the DIY 12" subs for a ported box. Looking at the popular 12" Dayton Audio RS315HF-4 subwoofer in a vented box, the dimensions would be about 22" cubed. Even in a sealed box you would be looking at a 18-19" cube.
post #9 of 13
Thread Starter 
Quote:
Originally Posted by Jay1 View Post

What's the port dimensions?
12" port
post #10 of 13
Thread Starter 
Thanks. This is actually the polk psw505 enclosure that went bad a couple of years back and I was trying to use the enclosure. Is there nothing I can do with it?
post #11 of 13
Quote:
Originally Posted by sdrm View Post

12" port

How about the diameter?


Either way your best bet is likely going to be to completely plug the port and get a different plate amp, as I can already tell the box is going to be tuned to high. What is the dimensions of the plate amp?
post #12 of 13
If you really want to reuse that box you can try replacing the driver with an Infinity 1260W or 1262W. It look like it should work in that box assuming the port diameter is 4". The recommended box size is 2ft3 with a 12.25" x 4" port so that box is pretty close. For a plate amp you can select something from this site. You should be able to reuse your box and get better performance than what you had before for under $200. If you're patient you should be able to get the Infinity driver for under $50.

Caveat: I've never built or modeled a ported enclosure before so I can't tell you how well this will work. I'm only going off what is recommended by the manufacturer. Keep in mind that these recommendations to be used in a car which is a completely different environment than a house. I've built several sealed subwoofers using this very same driver with much success in a couple of modest HT environments with good success.

Since you are in the DIY forum if you tell us you budget, goals and size constraints there are very knowledgeable people that can help you.
post #13 of 13
what's wrogn with the original sub? Is the driver or amp bad? You could probably contact Polk to get replacement parts.
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