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Old 15th December 2005, 07:48 AM   #1
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Default why am I getting weak sub output?

Need some help here fellas. Am doing trial run of just completed DIY sub: 122L box (original design for 15 inch original tempest) with 15 in dvc dayton driver, using 240W dayton plate amp. Hooked up receiver via sub preout to plate amp low level input. I hear and feel some bass but have to turn the plate amp gain all the way up to have a so-so bass thump (though it is tight). Checked the box--no leaks. Think the amp to driver connection is right: positive to positive of each "red" coil and negative to each "black" coil (parallel wiring). Changing the plate amp crossover does nothing (note my receiver does have low pass filter as does plate amp but I have heard keeping the plate amp's crossover turned all the way up to 160Hz should solve any problems. I have not tried my receiver's automatic MCACC set up for surround sound--could this have an effect?
Any ideas why I'm getting basically low volume would be greatly appreciated
M
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Old 15th December 2005, 08:01 AM   #2
DcibeL is offline DcibeL  Canada
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Is your reciever being used in some sort of Surround Sound mode? Most surround sound recievers will not send anything (or leak out very little sound)to the subwoofer ouput in 2 channel mode.
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Old 15th December 2005, 12:45 PM   #3
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Is the cone moving at all? What is your idea of "weak?"

My guess is that there isn't enough gain. So you need to trace through the signal chain and find all the possibilities, starting with the CD or DVD - does it have bass? Then moving to the receiver, check all the settings including sub volume. Disable bass management or check crossover point. If none of this works then try driving the plate amp from "speaker level" or "high level" outputs.
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Old 15th December 2005, 02:33 PM   #4
rabbitz is offline rabbitz  Australia
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First thing I would be doing is checking the sub levels in the Receiver and checking is the low bass is shared with the main speakers or sub only.
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Old 15th December 2005, 08:27 PM   #5
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Thanks for the quick replies
1. My receiver is set up for surround sound-but I notice the same weak sub output with 2 channel use, so maybe my receiver allows sub output with 2 channel (pioneer 1014)
2. The cone is moving a little but not a great deal. "weak" meaning my 8 inch fostex are putting out more bass than my 15 in. sub. But I do have several settings that might be affecting output including:
A. I have front speakers on large setting (vs small)
B. I do have "yes" on sub output line vs "no"
So those are good ideas to check next. I did call Parts Express tech help and was told that the vast majority of poor sub output is due to the settings on the receivers nowadays; also said that the 240 W plate amp should "rock" the room on that particular driver. He recommended set the front speakers to "small" and not use the automatic set up feature.

M
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Old 15th December 2005, 09:27 PM   #6
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Setting your fronts to large and your processor to 2 channel will send no bass to the sub.

The 'usual' way to integrate a sub into a surround setup is to set all speakers to small, with the crossover on the receiver set to ~80Hz. This will redirect the low bass from all speakers to your sub.

Cheers,

Rob.
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Old 15th December 2005, 11:29 PM   #7
morbo is offline morbo  Canada
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With your current setup, only the LFE track will be sent to the sub when present. You should either set the mains to small (recommended, why run these drivers fullrange?), or you could set sub to the 'pls' setting (thats what its called on my pioneer, may be different on yours) which sends bass both to the mains AND the sub.
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Old 16th December 2005, 12:29 AM   #8
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This site has so many helpful members...thanks again.
One reason I set the front speakers to "large" is based on some literature I got on bass management from the polk community. I'll find the exact download if anyones interested. It stated that setting the fronts to large (IF your fronts can produce decent bass that is) while using the sub allows better integration among speakers--presumably b/c you're getting some bass notes dispersed around the room. But alas for me that didn't work and I'll try the recommendations. Will let you know--thanks again
M
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Old 16th December 2005, 01:10 AM   #9
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Mark, do you realise you sent 3 identical posts?

Setting speakers to small may help with small vented speakers in particular in protecting them, but may not provide the integration you want. If it's only a first order rolloff, then that's not likely to cross to the subs correctly.

I tend to think that you won't get it right unless you use something more powerful such as an active crossover properly designed for the speakers in mind.

Based on what you have said, its clearly not getting enough gain. Have you got it to work yet? I suggest again using speaker outputs - if nothing else works, then that should. But try the other suggestions first.
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Old 16th December 2005, 04:50 PM   #10
rabbitz is offline rabbitz  Australia
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I have to agree that most HT speakers are best set to small and let the sub do the low stuff.

You still haven't mentioned anything about subwoofer level adjustments in the Receiver. There should be a setting with adjustments in dB for all the speakers as well as the sub. This is normally done with the test tone. Some Receivers have another LFE adjustment as well as this.

Check also that you don't have dynamic range compression on to suit late night listening or some other option.

Get the manual out and have a good read.

You don't say what you are using as a source and how it's connected. If it's a DVD with on board processing, then bass management is done within the player with 5.1 coming into the Receiver via RCA leads.

I use a PE 250W amp and it's got plenty of grunt in conjuction with Peerless 10"XLS.
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