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Old 5th January 2011, 08:53 PM   #1
polop1 is offline polop1  United Kingdom
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Join Date: Apr 2010
Default low power helper sub.

(this was posted in the other forum but i think the question should be in its own thread in the appropriate section)

I have built some sterio speakers and now I am willing to look into adding some strength to the bottom end. but being in a student room, I am looking at subwoofers from an incredibly reserved way (i.e. i would only be interested in low power compact subwoofers)

The route that I am looking to take at the moment is to use a PA type driver, and maybe a subwoofer amplifier from a car (as i have a high power 12v supply avaliable and it would keep costs down.) Idealy i would like to avoid car amplifiers as i am so happy with my amp 6 from 41hz.com for the mains. What is the standard way round adding the channels together and cutting the high frequencies before inputting into a diy-type amplifier.

How much difference will choice of amplifiers make to the quality of the music? as far as i am aware it is less of a problem at low powers and low frequencies.

so hypothetical system as it stands:

-tangband / ikea bowl speakers driven by amp 6 (finished already)
-8 inch PA speaker (undecided)
-sealed enclosure (perhaps the larger ikea bowls ?)
-driven by a low power car amplifier (for the low cut and bridgeing ability)


any suggestions to improve that, driver suggestions, amp suggestions, enclosure suggestions.
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Old 5th January 2011, 11:01 PM   #2
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Join Date: Feb 2009
Things to note.....
1. 8" pro audio drivers generally speaking will not yield subwoofer range bass, their Fs is much too high for a sub application IMO......most are considered lower midrange.
2. Low power and sealed enclosures are not your typical cocktail. Most sealed subs benefit from being slightly overdriven.
3. The bowl idea, albeit a good one for your likely small space, probably will not be rigid enough without some bracing creativity in a sub application.
4. make use of the car amp you have, feed it a clean signal and it should provide good results.

Not to trounce on your creativity here, but I would suggest looking at some of the small tapped horns.......perform well in low power, most use cheap drivers, and have relatively small footprints. Of course this would require more building skill/tools, but I've been sold ever since I built one of these http://www.volvotreter.de/pics/TH_38...fold_klein.jpg The downside is TH's don't usually play very high, which could present a problem integrating with the TB loaded bowls you've already built......I presume 3 or 4".

You could scan through this thread as well
The Smallest Tapped Horn

Last edited by steviedon; 5th January 2011 at 11:27 PM.
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Old 5th January 2011, 11:45 PM   #3
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got to surfing after my initial reply for 8" PA drivers with low FS .......this driver could work, sealed w/ a bit of eq @ 35-40hz. Beyma Speakers - Beyma 8BR40 8" speaker - Beyma 8BR40 100 watt 8" woofer for all hi-fi and studio monitor bass speakers. Beyma 8BR40 and other Beyma 8" speakers here.

I'll do some modeling in the meantime.
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Old 6th January 2011, 09:34 PM   #4
polop1 is offline polop1  United Kingdom
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Join Date: Apr 2010
thank you for your help. It is good to see that you think a car amp will work cuts cost and hassle with the inbuilt features they offer. idealy any sub i build will be around the size of 10inch cube ish, very small i know but i am not looking for rediculously low or loud, down to 45 to 50hz and to balance out a handfull of watts from the ikea bowls (literaly between 1-4W total)

I want to avoid the pitfalls of building a system that goes louder than I am aloud to play it, just a very full and polite sound is my goal.
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Old 6th January 2011, 10:11 PM   #5
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Quote:
Originally Posted by polop1 View Post
thank you for your help. It is good to see that you think a car amp will work cuts cost and hassle with the inbuilt features they offer. idealy any sub i build will be around the size of 10inch cube ish, very small i know but i am not looking for rediculously low or loud, down to 45 to 50hz and to balance out a handfull of watts from the ikea bowls (literaly between 1-4W total)

I want to avoid the pitfalls of building a system that goes louder than I am aloud to play it, just a very full and polite sound is my goal.
It might be cheaper to buy one of the "buyout" subs available from Parts Express and modify it if necessary.

However, if you want to build your own around a small driver, consider the subwoofer amps available from PE. While you're visiting PE, you might want to look at one of the TB long-throw drivers as well, which leaves you with only the box to build - or you could buy that from PE too, e.g. this box might work for a 6.5" driver that requires a 0.5 cu.ft. box - Dayton TW-0.50BK 0.50 ft³ 2-Way Cabinet Gloss Black | Parts-Express.com
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Old 6th January 2011, 10:20 PM   #6
polop1 is offline polop1  United Kingdom
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Thanks for the advice regarding PE, but i live in the uk and as far as i can remember there shipping costs are huge, something like 70 dollars, meaning if i get a bottom of the range driver there i could afford a much better one (as far as i am away)in the uk, though the choice here is abismal.
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Old 6th January 2011, 10:51 PM   #7
joe58 is offline joe58  United Kingdom
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Location: England
A link link for the Beyma. Don't know if it helps but here it is. I know, I too agree choice here is shocking. I wish we had a PE or Madisound. So cheap on them websites.

Beyma 8BR40
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Old 7th January 2011, 01:22 AM   #8
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Quote:
Originally Posted by joe58 View Post
A link link for the Beyma. Don't know if it helps but here it is. I know, I too agree choice here is shocking. I wish we had a PE or Madisound. So cheap on them websites.

Beyma 8BR40
I ran that Beyma through my spreadsheet - that thing wants some big box sizes, given its size. Even if you get two for an isobaric loading, minimum box size still needs to be above 0.75 cu.ft. to avoid a boomy bass response.

What about car audio drivers? Do you have access to any JBL or Infinity drivers, for example? While designed for car audio use, the t/s specs for some of them suggest that, in the correct box size/tuning, they will work well as a home subwoofer.
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