Help with Behringer EP2500

[pudgewack]

First of all, this forum is great. This is my first post, but I have been read tons of threads and got some great ideas about some speakers that I will be building in a month or so.

But what I am doing now is trying to get some bass in my room. I have two Elemental Designs (car audio company) e12o.14 (12 inch sub with a TC2+ motor....single VC 4 ohm) just collecting dust in my house. I thought they would be decent for HT....plus I did not have to pay any money or drivers since I already had them. I built one box (about 2.4 ft^3) and will be building matching box for the other sub shortly. I was running one sub off of a part express plate amp that pumped about 150 watts at 4 ohms. I just got a EP2500 which should give me more than enought power for two of these subs. I hooked one channel of amp to sub, but I am not getting the ouput that I though I would get. In fact, I am getting less output with the EP2500 that I was with the little plate amp, even when the EP2500 was at full gain! I then bridged the EP2500. I got more output, but much more than the plate amp.

What am I doing wrong? I have my receiver (HK AVR630) connected to the amp with a RCA to 1/4' cable purcahsed from markertek.com (the cable is 50 feet long...is that too long for this type of cable?). I have tried several different settings with the switches on the amp. I have also made several adjustments on my receiver. Can someone please porovide some ideas on how to get this working properly.

Thanks in advance,
Matt

[---k---]

Check dip switches on back for lowcut filters being on. IIRC, the EP2500 comes from the factory with the 50hz filters on. Which means, nothing (well okay, less) below 50hz is coming through.

[dyazdani]

It also depends on the relative gains of the amps themselves. I also have an EP2500 and I had to increase the setting on my pre-pro (to ~+6dB) to get to the right levels (with the knob on the EP ~2:00). With my other commercial sub (BagEnd), I ran the gain at 50% and a 0dB level on the pre-pro.

[pudgewack]

Check dip switches on back for lowcut filters being on. IIRC, the EP2500 comes from the factory with the 50hz filters on. Which means, nothing (well okay, less) below 50hz is coming through.

I have all of the switches set according to the manuel...the lowcust filter is turned off.

It also depends on the relative gains of the amps themselves. I also have an EP2500 and I had to increase the setting on my pre-pro (to ~+6dB) to get to the right levels (with the knob on the EP ~2:00). With my other commercial sub (BagEnd), I ran the gain at 50% and a 0dB level on the pre-pro.

I have increased the setting on my receiver. I have maxed them out and tired everything inbetween, but have not had any luck.


I tried something that I have used in car amps in the past. I played a 50 hz test tone and measured the voltage on the speaker wire. I measured 16.xx V. According to my calulations (V = sqrt (power * resistance)), I am only getting 64 watts @ 4 ohms. Is this a valid method to test the amount of power that my ep2500 is putting out?
Any other suggetions on how to get the amp working properly? Or ways to test to see if it is not working properly?

Thanks for your assistance so far....hopefully I can get this working soon.

Matt

[Dennis H]

Check the output voltage of the preamp, both at the preamp's RCA jack and at the other end of the cable. You need about 1.2 volts for full amp output with the gain knob turned all the way up.

[ThomasW]

Here's another HK receiver owner that had the same problem. His was solved by changing the main speaker setting to 'small'. There are other suggestions in the thread if that doesn't help

https://www.htguide.com/forum/showthread.php?t=20609

[pudgewack]

Check the output voltage of the preamp, both at the preamp's RCA jack and at the other end of the cable. You need about 1.2 volts for full amp output with the gain knob turned all the way up.

Sorry for the newbie question, but how do I measure the output voltage?

I grounded one of the sensors (do not know the correct name of the sensors things) and touched the other senor to the connector on the end of the cable. When I do this I get 0.04 v...even when no audio is being sent......I am clearly do something wrong, but I do not know what. ops:...please help.

Thanks,
matt

[ThomasW]

They're called probes.

You'll need to play something with reasonable bass content and have the sub out level setting as high as it will go (+10?). While the music is playing, use your probes as you described, one to ground, the other to the hot (center of the RCA). Raising or lowering the volume on the receiver show a change in the DC voltage out.

[Dennis H]

Edit: Thomas beat me to it. Small correction, set the meter for AC volts.

No problem. First let's make sure you have the right cable. It should have an RCA plug at the receiver end and a 1/4" plug at the amp end. The 1/4" plug should be like the unbalanced TS plug in the pic. If it's a balanced TRS plug, you've found your problem.

Assuming the plug is correct, leave the RCA plugged into the receiver and unplug the amp end. Measure the AC voltage between the tip and sleeve on the 1/4" plug. You'll need to play something with killer LFE and play it loud to get near full voltage.

If the voltage seems low at that end of the cable, it's always possible the cable is bad. So, take your meter over to the receiver and unplug the sub cable. Put one probe in the hole and touch the outer ring with the other while you repeat the experiment.

If the voltage seems low, you can double check whether the amp is working okay. The gain of the amp is spec'd at 50. That means the voltage on the speaker wires should be 50x what you measure on the 1/4" plug with the gain knob turned all the way up. If the amp's gain is okay, you're just not getting a strong enough signal into it for whatever reason.

[ThomasW]

set the meter for AC volts

For the sub out from the receiver? I think those are line level...

[Dennis H]

Right but the signal is AC -- 10 Hz to 120 Hz or so.

[ThomasW]

Gees, you're right for once .....:wink:

I just measured the sub out from an old pre-pro stored in the basement...output drive voltage was ranging up to +1.5VAC.

So in spite of old age, I learn something everyday.

Thanks.....:B

[Dennis H]

Chuckle, I can't tell you how much I've learned from you and Jon. Thanks bro'.... :T

[pudgewack]

Denis, dyazdani and Thomas, thanks you very much for your input.

I was able to measure the output voltage. Here are the results (all measured with a 50 hz test tone):
Voume Maxed ( - 0 db) - up to 3v at of the end of the 1/4 unbalanced plug.
Volume lowered (-5 db) - up to 1.5 v at the end of the plug.
Volume lowered (-10 db) - 0.9v at the end of the plug.

I also tested to get it the output that is on the speaker wire after amplification to see it was equal to 50 times the input voltage....it was acutally a little high, but pretty close.

All of those tests are WAY louder that I ever set my receiver. I then tested to about the abosolute loudest that I ever listen to it (-25 db) and the voltage would not even register....this is on the end of the plug and on the preout on the receiver.


Based on this info, it aprears that all of the components are working correctly. The amp is just noting getting enough voltage at the levels that I usually listen to (between -40 - -25 db).
What are my options so I can get a higher voltage to my amp (without buying a new receiver)? Or this there something else that I might be overlooking?

Thanks again,
matt

[Dennis H]

Matt, it looks like everything is working right so it's time for some in-room acoustical measurements. You'll need a mic, a mic preamp and some software like Room EQ Wizard. Measuring, and the gear it requires, is a long topic that has been covered elsewhere but it doesn't need to cost a lot of money. An RS SPL meter will do for the mic and preamp at low frequencies, and REQ Wizard is a free download. Perhaps you have just gotten used to bass that's way too hot? Measurements are the only way to know for sure.

Edit: I just read what you wrote more closely.

All of those tests are WAY louder that I ever set my receiver. I then tested to about the abosolute loudest that I ever listen to it (-25 db) and the voltage would not even register....this is on the end of the plug and on the preout on the receiver.

That's troubling. You should have been reading between 0.1 and 0.2 volts based on your other readings. Someone in another thread was getting strange readings and it turned out to be a problem with his voltmeter. Do you have access to another meter to double-check that?