New Behringer EP1500 problem

[scubasteve2365]

Hello all,

I do not yet have an infinite baffle arrangement but Im slowly working towards it. I have a baby on the way late next month.

Currently in my theater I have 4 12" Sony power subwoofers, I technically have 5 of these guys but the plate amp went belly up. I got them really cheap. Now the plate amp has gone out on another. I thought I could go ahead, disconnect the plate amp and power all 4 subwoofers with a Behringer EP1500 that I picked up brand new off of ebay., with the intent of later buying some FiCar 18s. The drivers themselves are a single 6-ohm coil. 2 drivers in parallel would present a 3-Ohm load. I planned to run two 3-ohm loads, one for each channel instead of a 6-ohm bridged load. I measured the impedance of the drivers at rest and measured 3.5-ohms so I know I'm wired correctly.

Channel 1 of the amplifier barely has any output, it is however, not completely dead. If I play with the dipswitches I can discern with the low-cut (high-pass) filter is turned off and on so I don't think that is the problem.

Channel 2 of the amplifier has plenty more power, but I still have to set the gain knob about 85% just to make the subwoofers have a decent output. The subwoofers were rated at 150W/ea, at 3-Ohm stereo load from the EP1500 should move these things with the gain at a much lower level, or at least I anticipated.

Putting the same 3-ohm load in bridged mode is comparable in output to Channel 2 by itself.

I'm thinking the amplifier is faulty. I'm an Electrical Engineer and I've been in audio (both Home A/V and Car Audio) industry and I cannot see anything that I have done wrong.

One last thing is about the input, I picked up a simple RCA to Mono 1/4" adapter for the input. Is it possible that the amplifier, having a "balanced" input feature may be somehow not compatible with this 1/4" adapter? How do most of you guys get the RCA sub preout on your AVR into your Behringer amps?

Any ideas, I'm I missing anything?

[ThomasW]

Mar 21, 2010 10:31:30 GMT -7 scubasteve2365 said:

Channel 2 of the amplifier has plenty more power, but I still have to set the gain knob about 85% just to make the subwoofers have a decent output. The subwoofers were rated at 150W/ea, at 3-Ohm stereo load from the EP1500 should move these things with the gain at a much lower level, or at least I anticipated.

Regardless of the label it's not a gain knob, all it does is attenuate the incoming signal.

I'm thinking the amplifier is faulty. I'm an Electrical Engineer

What do the different channel waveforms look like on an O-scope?

One last thing is about the input, I picked up a simple RCA to Mono 1/4" adapter for the input. Is it possible that the amplifier, having a "balanced" input feature may be somehow not compatible with this 1/4" adapter?

This should be apparent to an EE that none of the Behinger equipment is truly balanced (i.e. has dual complementary symmetry circuits). If it did things would have to be changed internally (usually jumpers changed) before a singled ended plug could be used. And it would be significantly more expensive.

How do most of you guys get the RCA sub preout on your AVR into your Behringer amps?

Just like you're doing it some use 1/4" mono adapters others use a special cable with an RCA on one end and mono 1/4" plug on the other.

The most common mistake people make with Behringer amps is they look at the makings on the dip switches instead of the big white graphics printed in the chassis for switch settings. On occasion these are in conflict. If there's any doubt follow the printing on the chassis not the little marks on the dip switch that say on/off

[scubasteve2365]

Mar 21, 2010 11:06:53 GMT -7 ThomasW said:

Regardless of the label it's not a gain knob, all it does is attenuate the incoming signal.

Good to know, now I'm not as concerned about having it turned over as far.

Mar 21, 2010 11:06:53 GMT -7 ThomasW said:

What do the different channel waveforms look like on an O-scope?

Don't know, I don't have access to a scope. I work in manufacturing, as an automation engineer and project manager. I haven't used a scope or diagnosed PCBs since college.

Mar 21, 2010 11:06:53 GMT -7 ThomasW said:

This should be apparent to an EE that none of the Behinger equipment is truly balanced (i.e. has dual complementary symmetry circuits). If it did things would have to be changed internally (usually jumpers changed) before a singled ended plug could be used. And it would be significantly more expensive.

I don't see why it should be apparent. An EE doesn't necessary deal with Amplifiers or even component level circuitry in their profession. I deal with the programming of manufacturing equipment (PLCs) and power feeding for equipment. I would eventually determined as much had I taken the amplifier apart but it's hardly worth my time especially since I purchased it brand new, from a supposed authorized dealer and should have a warranty.

edit: I see from my post above that it made like it sound like I was an engineer in the A/V Industry, I am not. While in college I worked in sales and custom installation for a local high-end retailer. That is the experience I was referring to. Since finishing college I have not worked in that field.

Mar 21, 2010 11:06:53 GMT -7 ThomasW said:

Just like you're doing it some use 1/4" mono adapters others use a special cable with an RCA on one end and mono 1/4" plug on the other.

Thought so, but wanted to make sure there was something that I didn't account for.

Mar 21, 2010 11:06:53 GMT -7 ThomasW said:

he most common mistake people make with Behringer amps is they look at the makings on the dip switches instead of the big white graphics printed in the chassis for switch settings. On occasion these are in conflict. If there's any doubt follow the printing on the chassis not the little marks on the dip switch that say on/off

Given the confusion on the matter I didn't even trust the the printed diagram on the chassis. It's easily apparent when the high-pass filter is engaged. I may have one of the latest EP1500s produced because there are no marking on the dipswitches themselves.

Time to contact the seller, this is the first bad amp I've ever had in my life. I guess that's not so bad, I just hate to pack stuff up and mail it off.

[ThomasW]

Something to check

If you accidentally have the amp in the bridged mode, only the channel with the input signal should have the 'gain' knob turned up. The other knob should be completely down/off