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Old 17th February 2008, 09:32 PM   #1
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Default Am I doing something wrong with my amp?

Hello all,

I just bought a Behringer EP-2500 amplifier to power a stereo subwoofer setup. I have a Dayton Reference HO 12 inch woofer in a ported enclosure hooked up to one channel. This 4 ohm load should give the woofer 650 watts rms. I have hooked up my ipod and my computer directly to the amp using the large headphone jack looking input. Playing music out of the ipod and using a signal generator on the computer, neither method gave me loud results. At all, the signal light barely came on, so nowhere near to clipping. Are my input sources too weak? I notice the amp at my church does the same thing, meter lights barely register only that is someone talking. I have the volumes on my devices turned all the way up and the gain on the amp to at least 3 o'clock.

With 650 watts I figured the sub could reach full excursion, but it's not even moving hardly. I know the amp puts out what it states so its alot of power.

I'm lost

thanks
Dan

If this needs to be moved to subwoofers I'm sorry
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Old 17th February 2008, 09:59 PM   #2
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Hello Dan, I would say that you need a preamp between the input(s) on the power amp and your ipod or computer output. I'm a little surprised about the computer. The thing that you need to take into account is that the Behringer says it can output 650w, but there is probably a specification in the manual somewhere that says what the input voltage is to produce the 650w output. It's quite likely that the ipod and computer sound card can't create this level of voltage necessary.
A question I have is you say you are using this amp in a mono configuration. Are you just using one channel on the amp, and leaving the other one floating, or is the amp capable of being set as a bridge mono amp. If it is capable of bridge mono, there is probably a switch on the back of the amp that needs to be set for this, and if you look in the manual, it probably says something about using the positive terminals of the two channels as the places to hook up your single driver.
I am also curious, do you have any sort of crossover in the system, or are you relying on the natural rolloff of the subwoofer driver to provide the cutoff frequency. I personally would suggest an active low pass filter between the output of your preamp and the input of the power amp.

Sorry it's so long winded.

Peace,

Dave
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Old 17th February 2008, 11:44 PM   #3
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Hello Again Dan, I was taking a look at the manual for your amp, downloaded it from Behringers website. Besides having to set switches and hook the speaker wire to the positive terminals from each channel for mono mode, it says that only the channel 1 controls are used for input control, and to keep the channel 2 input level control set to minimum (all the way left or counterclockwise), otherwise there could be cancellation of signals due to phase inversion. If you have the amp configured for mono, but the channel 2 input level turned up, this could also cause a problem like you describe.

Peace,

Dave
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Old 18th February 2008, 02:09 AM   #4
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Hi Dave thanks for the help. I have one channel hooked up and the other one is floating. There is no crossover inbetween, I just wanted to test it out. How can I figure out how many volts my devices are putting out? I hooked my ipod up to my Onkyo m-504 power amp with no problems but maybe the behringer needs a higher voltage input. I'll take a look at the manual to see what it needs. I'll see if I can borrow a preamp also. Should a home audio preamp give a strong enough signal?

Thanks again
Dan
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Old 18th February 2008, 02:29 AM   #5
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Hello Dan, I would suspect that any conventional home audio preamp should be able to provide the voltage input level necessary to get the Behringer going. If you were able to drive the Onkyo, I would think that you should get decent volume with the Behringer.
Looking at the Behringer manual, make sure that the switches for Bridge mode are set to off, since you are only plugged into one channel for now. Also make sure the settings for Stereo/Parallel are in Stereo mode for now. And make sure the other switches are set to off.
Also, make sure that the cable you are using to connect between the ipod and the amp is wired correctly. You will need a cable that goes from the stereo 1/8" plug for the ipod, to a pair of 1/4" mono plugs to plug into the inputs on the Behringer. One of the things different here is that the Onkyo is most likely an unbalanced input and the Behringer is setup for either balanced or unbalanced. To get the unbalanced inputs to work correctly, the incoming connectors need to be wired correctly. Page 11 of the Behringer manual shows how to wire the connectors for either balanced input or unbalanced input.

Hope this helps,

Dave
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Old 18th February 2008, 02:37 AM   #6
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alrighty I'll take a look at the behringer manual when I get home. I may be back if I can't figure it out.

Thanks again
Dan
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Old 18th February 2008, 02:47 AM   #7
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No problem. If you need more help, I'll see what I can do.

Peace,

Dave
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Old 19th February 2008, 05:39 AM   #8
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Alrighty I hooked the amp to my NAD 7155 and used the preamp from that and it helped alot. I was still not able to bring the sub to full excursion because the amp started clipping. Will it help when I get a crossover.

Thanks
Dan
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Old 19th February 2008, 05:13 PM   #9
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Hello Dan, The crossover might help a little, but I doubt it will have a great effect on what you are experiencing. I suspect that now you have too much voltage gain from the preamp of your NAD 7155, this is driving the input stage of the power amp to clipping. What I would suggest is to use the input level controls on the front of the Behringer to limit the maximum level that the input stage of the power amp will see. This will give you greater usage of the volume control on the NAD, while still keeping clipping to a minimum.
The advantage to the active crossover in line before the power amp is that you will be able to adjust the cutoff frequency of the subwoofer so that there is less interference with the bass/midbass drivers in your main listening speakers. Without the crossover, it's possible that there will be too much output in the region where the sub and midbass overlap, making it boomy and unrealistic.
Is the Dayton driver you are using as a SUB a single or dual voice coil design, and what are the specs on this driver? Knowing these can help adjust things better.

Peace,

Dave

P.S. How are you and your wife doing handling your loss? Hope things are improving.
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Old 19th February 2008, 08:04 PM   #10
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http://www.partsexpress.com/pe/pshow...TOKEN=18044367
Here is a link to the driver. It was very kind of you to ask about our loss. I think we have moved on, my wife already has another kitten. I had the volume nob on the nad at about 3 o'clock when it started clipping. If I turned the gain down, it wouldn't clip but wouldn't I get less volume (db)? I am going to take the amp to my brothers because he is a dj and has a bunch of equipment to help me test it. I just don't understand how I can't get full power out of the amp.

If you get any other ideas let me know, thanks again youo have been VERY helpful.

Dan
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