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Rolyasm
06-15-2005, 01:10 PM
Okay, I am looking at some amps for my subwoofer. I am using four 15" Avalanche drivers in a large box system. That is another forum. It has been recommended that I use Behringers's EP2500 amplifier, which I am happy to do, but wanted to compare some others and learn something at the same time. So... specs on the Behringer are Features:

2 x 1200 watts in 2-ohm/2400 watts in 4-ohm bridged operation

2-channel, parallel or bridged mono operating modes for flexible application

Independent limiters for each channel offer dependable protection against distortion

Precise signal and clip LED indicators to monitor performance

Selectable low-frequency filters (30 Hz or 50 Hz) remove distracting infra-sound frequencies

Professional SpeakonŽ and "touch-proof" binding post loudspeaker outputs enable secure operation

Balanced XLR and 1/4 in. TRS inputs

Connection option for extra amps in parallel operation

Ultra-reliable ToshibaŽ/FairchildŽ high-power transistors

High-quality components and exceptionally rugged construction for long life and durability

High-current ToroidŽ toroidal transformer for absolute reliability and lowest noise emission

"Back-to-front" ventilation system including air filter with automatically adjusting fan speed for smooth operation

Independent DC and thermal overload protection on each channel automatically protects amplifier and speakers

My Question is 1)what does all this really mean? Some specs I see are listed as Stereo mode, some listed like the Behringer as 2x1200. If the system simply says 600w @8ohms, but is a 2 channel amp, is that the same thing as 2x1200?
2)What does RMS X2 mean? 3)How do I compare apples to apples? 3)Why do some amps list frequency? Isn't this more a factor of the driver you are using? 4)Does "peak power" matter. One amp says 2000 w peak power but shows :
600 WATTS@2 OHMS
460 WATTS@4 OHMS
240 WATTS @8 OHMS.
How are they calculating peak power from that? 5)Is THD really a factor when using the amp for this application?
Thank for all the information. If you know of any good deals like the Behringer EP2500, please give me a website so I can check it out. I think the Behringer is around $300.00.
Roly

Glen B
06-15-2005, 05:06 PM
I visited the Behringer website and looked at the specs on this amp. My comments are on the specifications that are of importance in your case. The other "specifications" you listed are really just features of the amp.

The EP2500 amp can be used as either a regular two-channel amp or bridged as a single channel amp. When operated in bridged mono mode, an amplifier will usually deliver into a single channel, an output that is several times that of both channels combined.

The frequency specification has to do with the frequency range of the music signal that is being amplified, not the speaker used. For full range music, the commonly accepted range is 20 Hz to 20 kHz, which covers most of the range of human hearing. This manufacturer lists outputs at both 20Hz - 20kHz and 1kHz respectively, at 0.1% THD. Maintaining rated output at all frequencies (in the 20Hz to 20kHz range) is usually more difficult for an amplifier than at a single frequency of 1kHz. At the single frequency, an amp will usually deliver a bit more power.

In stereo mode at the full frequency range of 20Hz to 20kHz, the EP2500 delivers 450/650 watts per channel into 8 and 4 ohms respectively. At a frequency of 1 kHz, (usually considered as near the clipping point) the amp delivers greater power of 500/750/1,200 watts into 8/4/2 ohms respectively. At the frequency of 1 kHz you get more power from the amp but this spec is a bit unrealistic as no one listens to music at only 1 kHz (midrange).

In bridged mono mode, at 20Hz to 20kHz the EP2500 delivers 1,300 watts into 8 ohms. At 1 kHz the amp delivers 1,500/2,400 watts into 8 and 4 ohms respectively. Again, you get more power but at an impractical frequency range.

Peak power usually means "dynamic" power or what the amp will deliver for a short burst (a fraction of a second) as opposed to continuous power.

I am not saying this is not a good amp but some manufacturers play a numbers game with specs in an attempt to make the unit seem more powerful than it may be in actual use. Focus your attention on the performance at 20 Hz to 20kHz.

SteveL
06-15-2005, 07:00 PM
My Question is 1)what does all this really mean? Some specs I see are listed as Stereo mode, some listed like the Behringer as 2x1200. If the system simply says 600w @8ohms, but is a 2 channel amp, is that the same thing as 2x1200?

No. If it's a 2 channel amp, and it's saying 600w @ 8 ohms, you'll have to dig deeper to find out if it's 600 x 2 (@ 8 ohms), i.e., "600 watts per channel," or if it's 300 x 2 (@ 8 ohms), i.e., "600 watts total." Do some digging on the amps you're interested in and read the specs carefully, and generally speaking, avoid the amps that claim things like "9500 watts peak power!" without explaining much more.




2)What does RMS X2 mean?


In layman terms, RMS means "continuous power" - meaning, that's what the amp is supposed to deliver over a continuous time period. The "x2" means the number of channels that the amp has.

So, for example, if I had a 2 channel amp (i.e., "Stereo"), I may say it has 100W x 2 @ 8 ohms. The __ ohms = the resistance at which the power is measured. (again, this is in general, layman terms) If I had a 5-channel surround sound amp, I may say it has 100W x 5 @ 8 ohms. The 5 refers to the # of channels (i.e., speakers) it can drive.



3)How do I compare apples to apples?


That is the $1MM question. You have to dig and check out the specs, ask around, etc. But it's pretty safe to assume that a $150 amplifier that's rated at 500-watts per channel won't perform the same as a $1500 amplifer that's rated at 500-watts per channel.



3)Why do some amps list frequency? Isn't this more a factor of the driver you are using?


The frequency refers to the range of sound at which the amplifier's power measurements were taken. Many mfg's will list their power ratings at 1kHz, and may appear to make more power when compared to other amplifiers who take their measurements at 20Hz - 20kHz. It's much easier for an amp to deliver power to a single frequency than across the entire spectrum (generally speaking).




4)Does "peak power" matter. One amp says 2000 w peak power but shows :
600 WATTS@2 OHMS
460 WATTS@4 OHMS
240 WATTS @8 OHMS.
How are they calculating peak power from that?


Peak power doesn't really matter. I may be able to get 1000 peak horsepower from my Honda with the appropriate nitrous kit, but I: a) won't sustain that 1000 hp for long, and b) I'll probably cause some damage sooner rather than later. Don't go by peak ratings.

My guess is that the 240 W @ 8 ohm rating is also at 1kHz, meaning true power is probably around 175 - 180 W @ 8 ohms, full spectrum, but it's hard to say with any certainty.



5)Is THD really a factor when using the amp for this application?


I'd argue yes. A "dirty" amp (i.e., higher THD) isn't something I'd use in my systems, but I'm probably more picky than most. Noise is noise, even at 20 Hz...



Thank for all the information. If you know of any good deals like the Behringer EP2500, please give me a website so I can check it out. I think the Behringer is around $300.00.
Roly

The EP2500 gets a lot of good press from folks, and it's definitely a bargain. I just bought the Feedback Destroyer, and am anxious to try it out. But for power, I couldn't bring myself to use the EP2500, so I went with a Crest CA-18... Were I to spend only $300 on a sub amp, the Behringer or a Nady would be my only choices. I wouldn't trust anything else that (supposedly) delivers so much power for so little money.

Just my $0.02.

ThomasW
06-15-2005, 11:37 PM
Given the passband where subs amps are operating, watts are watts... The Behringer amps are fairly built and reliable. They're made in China and that's why the price is low. The build quality is on par with any of the low cost switching amps with analog power supplies.

The really nice thing about IB subs, is that next to horns they are the most efficient subs around. As a result, cubic amounts of horsepower and massive cooling systems aren't needed, since the demand on the amps is quite low

taz13
06-17-2005, 03:49 PM
Here is an interesting review on the ep2500

http://home.mn.rr.com/hometheater/Beh2500.htm