Looking for some advice on building a HT subwoofer - Page 3 - AVS Forum
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post #61 of 66 Old 11-15-2012, 05:26 PM
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Do you guys think it would do any good to complain to the customer service department at Parts Express? I specifically asked them about them about the HPF and the girl that I spoke to said it was 19hz. If I had known that it was 30hz, I most definitely would NOT have purchased it! Only thing is, even if I do complain, I doubt they would take the amp back in exchange for a new Bash or give me credit towards an EP4000/EP2000, right? I am done with these "questionable" plate amps, its going to be nothing but Behringer EP's for me from here on out. I cant afford a Lab clone, the best I can afford is going to be something in the $300 to $500 price range. I am seriously PO'd about this!
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post #62 of 66 Old 11-17-2012, 11:52 AM
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ah, i see where all the confusion is now...i think.

here is how i understand it:

the BLUE line represents the frequency response of the AMP by itself.

q=2, second order highpass at 30hz.

the AMP is down -3db at 20hz relative to where it is at 100hz. that is probably where the confusion is coming from as we normally equate the -3db point with the crossover point for a second order crossover.

the RED line is an arbitrary sealed subwoofer, this one happens to be the alpine swr in 1.5 cubes.

it has the characteristic second order rolloff with an f3 around 40hz.

now COMBINE the response of the amp (the BLUE line) with the response of the the driver (the RED line) and you get the net effect which is the YELLOW line.

the net effect is a -3db point of around 28hz and a very steep 4th order slope below that.

now let's compare that to a 2nd order butterworth high pass at 19hz and +6db of boost at 30hz with a 1.4 q. that is the GREEN line.

i was kind of surprised, but the YELLOW and GREEN don't appear to be as different as it might have seemed at first blush.


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post #63 of 66 Old 11-27-2012, 12:51 PM - Thread Starter
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Well, I finally made up my mind.
Thanks everyone for your input (as well as topics in various other threads).
I decided to go with the THT LP design and already bought the plans and ordered the driver and amp. Thank goodness for the Black Friday sale at P-E. Even though the shipping was $105 I was able to save some money.
I'll start another thread of the build at some point.

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #64 of 66 Old 12-10-2012, 02:45 PM - Thread Starter
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Well I just got finished my THT LP build. I didn't take pictures along the way as there are several very good build threads and I would basically be doing the same thing. This thing is a beast at 72 x 36 x 18!
Here are a couple of pics with a tube of PL on top for reference.





I am just waiting on the glue to dry and tomorrow I will be picking up some cap screws of the correct length to install the driver after I get it in position. By tomorrow night it should be up and running.

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #65 of 66 Old 12-10-2012, 04:45 PM
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That's huge. Is it 2 15's?
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post #66 of 66 Old 12-10-2012, 04:57 PM
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One 15

Xbox One Gamertag = The Barbeerian

PS4 PSNID = The-Barbeerian
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