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Need design help and advice - Building sub enclosure


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10 replies to this topic

#1 of 11 OFFLINE   Firelime

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Posted April 24 2012 - 09:58 PM

Well we got the theater done. Turned out very well for my first one I think. Learned a lot for the next one. Still have a little touch up to do but it is operational. The box came together well and the other 2 subs will be on the way later this week. The only problem I have are they are very quiet. The signal light on the amp rarely lights up unless the receiver is cranked and even then the subs sound very weak. I have played around with the gain a little. Set it to 75db when audyssey asked. My towers are currently producing more bass than the subs right now and my Polk 505's work just fine when they were hooked up. I am thinking that the signal to the amp is weak. I have tried 2 different cables. I am using a RCA to XLR for the signal. I also tried a RCA with a XLR to RCA adapter with the same effect. Are these the correct cables? Or should I be using a RCA to TS? I would not think it would make a difference. But up till this project I had never heard of a XLR connector. If not what cable would you recommend? This is the adapter - http://www.parts-exp...tnumber=240-438 This is the RCA to XLR cable - http://www.monoprice...&seq=1&format=2 I am also looking at getting the FBQ1000 you listed earlier with the subs this week. Once the new subs come in would you recommend I wire them in a series-parallel configuration to achieve 4 ohm?

#2 of 11 OFFLINE   Robert_J

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Posted April 25 2012 - 02:36 AM

The signal light on the amp rarely lights up unless the receiver is cranked and even then the subs sound very weak.
My sub signal light rarely comes on as well. What are the attenuators set to? What are your DIP switches set to? Cables shouldn't make a difference. I use RCA to 1/4" mono phono for my EP-2500 and BFD.
Once the new subs come in would you recommend I wire them in a series-parallel configuration to achieve 4 ohm?
I like to run mine in stereo mode, 2 ohms per channel. In testing, it performs better. It should be the same as mono but for some reason it isn't.

#3 of 11 OFFLINE   Firelime

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Posted April 25 2012 - 10:03 AM

[quote name="Robert_J" url="/t/316510/need-design-help-and-advice-building-sub-enclosure#post_3919811"][QUOTE]My sub signal light rarely comes on as well. What are the attenuators set to? What are your DIP switches set to? [/quote]

The DIP's are set to:
1- right
2- right-N/A
3- right
4- right
5- right
6- left
7- left
8- right
9- right-N/A
10- right

The receiver is set to +2db on the subwoofer. The gain on the amp is set about a 1/3 of the dial above the bottom. I dont have it here in front of me or I could give you a more accurate number.

#4 of 11 OFFLINE   Robert_J

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Posted April 25 2012 - 10:15 AM

I'll check the DIP switches against mine.
The gain on the amp is set about a 1/3 of the dial above the bottom.
It's not gain. It's an attenuator. That means you get 1/3 the input power of your +2 receiver setting. I crank the knobs full blast and back off 2 detents so there is no hum. Then I run the MCACC auto calibration.

#5 of 11 OFFLINE   Firelime

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Posted April 25 2012 - 12:11 PM

When I get home I will try that.

#6 of 11 OFFLINE   Mike Thomass

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Posted April 25 2012 - 01:32 PM

the problem is very likely the receiver setting for the sub that robert mentioned. i was having the same problem as you, and then i changed my sub setting from 0 to +3db, and whammo!

#7 of 11 OFFLINE   Firelime

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Posted April 25 2012 - 07:18 PM

I got it fixed. Sounds freaking awesome. It will be nice to have 2 more. Thanks guys for all the help.

#8 of 11 OFFLINE   Mike Thomass

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Posted April 26 2012 - 04:05 AM

I got it fixed. Sounds freaking awesome. It will be nice to have 2 more. Thanks guys for all the help.
was it the subwoofer dB setting on your receiver?

#9 of 11 OFFLINE   Firelime

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Posted April 26 2012 - 12:07 PM

was it the subwoofer dB setting on your receiver?
-8.5 db was where it ended up at. The problem was when I wired up the subs I put in series not parallel. So simply fixed that. It had been so long since I had been on here I had forgotten Rebert_J said to wire them in parallel.

#10 of 11 OFFLINE   Firelime

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Posted April 26 2012 - 12:11 PM

Robert you werent kidding about the fan. It gets loud! What fan did you use to replace it with and was there any modding that had to be done?

#11 of 11 OFFLINE   Robert_J

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Posted April 26 2012 - 06:34 PM

Digikey part # P9739-ND You have to pull the plug on the old fan. Normally, it is hot glued to the main board of the amp. Not that difficult to pull off though. Then you need to put a plug on the new fan. You can re-use the one from the original fan if needed. I just used a plug from a PC power supply (the 3.5" floppy plug cut down to 2 connectors). Reverse the flow. Originally, it pulls air from the rear and blows out the front. I now pull from the front where the air filter resides and blow the hot air out the rear. The entire process took about 30 minutes.




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