Opinion on the Behringer KM1700 Class-H amp - diyAudio
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Old 26th January 2017, 07:41 PM   #1
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Default Opinion on the Behringer KM1700 Class-H amp

Hey everybody!

Since I just ordered a Behringer iNuke 3000DSP for my subwoofer, I thought I'd look at my options for an amplifier for my fronts. I stumbled across the KM1700 because I know that it's basically like Class A/B but with a variable and dynamic voltage rail. Correct me if I'm wrong!

They're slightly (and that's a mild expression) overpowered at 2x500w into 8Ohms. My speakers are barely 90 Watts RMS (if they're set as fullrange. They can take slightly more when not in fullrange, I suppose. Or less? Less movement is less cooling hmmmmm.)

Since I'm not very good with the specification-sheet reading, what would your opinion be? I can't actually find a specsheet.

Any input is greatly appreciated.

Cheers,
Anna

https://www.amazon.com/Behringer-KM1.../dp/B01MAY7S7W

[spoiler]
Behringer KM1700
limiter is switchable
front-to-back ventilation
frequency response: 20 Hz - 20 kHz (@-10 dB), 10 Hz - 80 kHz (@-3 dB)
THD: <0.03%
signal-to-noise: >100 dB
sensitivity: 0.77 V/26 dB/1.4 V (switchable)
dimensions: 482 x 375 x 88 mm (w*d*h)
weight: 12.5 kg
[/spoiler]

Last edited by HumbleDeer; 26th January 2017 at 07:43 PM.
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Old 26th January 2017, 10:57 PM   #2
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This looks like a very interesting amp to me, and I have mentioned this in another thread in the PA forum about it's little brother, the KM750.

The KM1700 reminds me of the EP2500. It's a class-H amp which, like you mentioned, is more like class AB than the class-D of the iNUKE series. It has two fans versus one on the EP2500 (I would do a fan mod if I bought one). The price is quite affordable at $199 for 500W/ch into 8R. While this might be "overkill" for your mains in terms of average power, it's not as overpowered as you might think for "peak power". You can think of it like a 100WPC amp with a good amount of headroom. This means your amp will not clip on peaks, unless you really listen to compressed music at very high levels. And yes, it does have the capability to fry your speakers, so don't play it too loud too long.
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Old 26th January 2017, 11:43 PM   #3
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Thanks for your extensive reply!

The amp states an RMS wattage that I said. Is that an overrated spec?

I'm always very cautious with power. I have never accidentally damaged a speaker and I wish to remain innocent

I like having a good headroom anyway to allow for taking it to a rig or upgrading to more powerful speakers. Even though I doubt I've ever pushed these speakers over 40-60watts as they're already painfully loud at that power level.

Cheers,
Anna
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Old 27th January 2017, 02:34 AM   #4
PRR is offline PRR  United States
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product sell-page

"front-to-back ventilation"

You realize this means it has a FAN ?

On some amps, the fan lays dead until the amp gets hot. Others run the fan on full all the time. Others vary the fan speed as needed. No details on the sell-page.

This is a low-price PA amp, for bands and DJs. In a crowded room the fan whirrr is not an issue. In a home listening room, it may be.

Why are you looking at THIS amp?

Yes, it is covered with buzz-words. G-mode, ATR. Some of these may even be good ideas. For somebody. But any good idea can be done wrong.

Rail tracking.... do you listen to the rails?? What it really means is they get more output with less heat (and money). OTOH this is more Watts for your bucks. On the third hand, IMHO this is an insane amount of Watts for most homes.

Knowing B-ringer, I am sure it meets all specs and reproduces music fine. B-ringer got where they are by making low-low-price stuff that does work OK.

At $200 for 1000-1700 Watts it is at the lower end of what Watts cost today. There are enough other amps at this $/Watt point that I don't think B-ringer has done it especially good or bad.

General gripes against B-ringer tend to be that the pots and jacks don't last forever especially in hard use (traveling band). In fixed home use it may last 10-20 years no problem.

If you really want a Thousand Watt Amplifier, this is a safe bet and about as low-price as you can find.

If the fan turns out to be disturbing, you can probably pawn it for half what you paid; near-new kilo-watt PA amps have good resale value.
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Old 27th January 2017, 06:11 AM   #5
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Quote:
Originally Posted by PRR View Post
product sell-page

"front-to-back ventilation"

You realize this means it has a FAN ?

On some amps, the fan lays dead until the amp gets hot. Others run the fan on full all the time. Others vary the fan speed as needed. No details on the sell-page.

This is a low-price PA amp, for bands and DJs. In a crowded room the fan whirrr is not an issue. In a home listening room, it may be.

Why are you looking at THIS amp?

Yes, it is covered with buzz-words. G-mode, ATR. Some of these may even be good ideas. For somebody. But any good idea can be done wrong.

Rail tracking.... do you listen to the rails?? What it really means is they get more output with less heat (and money). OTOH this is more Watts for your bucks. On the third hand, IMHO this is an insane amount of Watts for most homes.

Knowing B-ringer, I am sure it meets all specs and reproduces music fine. B-ringer got where they are by making low-low-price stuff that does work OK.

At $200 for 1000-1700 Watts it is at the lower end of what Watts cost today. There are enough other amps at this $/Watt point that I don't think B-ringer has done it especially good or bad.

General gripes against B-ringer tend to be that the pots and jacks don't last forever especially in hard use (traveling band). In fixed home use it may last 10-20 years no problem.

If you really want a Thousand Watt Amplifier, this is a safe bet and about as low-price as you can find.

If the fan turns out to be disturbing, you can probably pawn it for half what you paid; near-new kilo-watt PA amps have good resale value.

I know these have a fan, yup! I have near dead silent fans laying around that I can put I'm, but they'll be behind the other wall anyway

I'm not per she interested because of the power input. Rather because no matter how cheap I go on Beringer, it'll be better than Logitech.

I have a 30day full refund warranty at the shop I'm buying my materials.


Perhaps I'm cheap because I'm not old enough, but for now cheap is fine.

Thanks for your reply, PRR.

Cheers,
Anna
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Old 13th May 2017, 01:07 AM   #6
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Default Would like to see internal pictures.

Based on the weight of the amp, i would say the toroidal transformer is underrated somewhat.

Once someone posts some internal pics i would have a better idea.
Hopefully she has at least 10 150 watt output transistors per channel.

Certainly a great opportunity to have 8 subs on 8 bridged amps for 1700 per sub for only 1600

2 of these look like a much better value than inukes
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Old 13th May 2017, 03:03 AM   #7
wg_ski is offline wg_ski  United States
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Underrated somewhat? Understatement of the year. Most 'pro' and otherwise audio uses toroids (or switching supplies) designed only to deliver 1/8 power on average. Wall socket current ratings are based on the same assumption. It isn't a Behringer thing. The one in the QSC GX5 isn't much bigger.

To do it 'right' (deliver 500 per channel indefinitely, and more into 4 ohms) would require TWO 1.5kVA toroids weighing thirty pounds each. And a heat sink the size of a small car. And a 30 amp plug. As efficient as the inukes are even they will fold back the power after a few seconds at full sine output. Whether or not it is needed is subject of debate. Whether or not it sounds better done the old fashioned way is unmistakeable. But no one wants to pay $4000 for a 500 watt amp, do they?
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Old 13th May 2017, 07:13 PM   #8
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The 2500va toroidals in all my amps weigh 31lbs. Seriously doubt a 1500va toroidal will weigh as much as a 2500. And you might need one 1500va toroid to do 500 rms sine wave forever, if the output stage could put up with that. I doubt it. On regular music signals no problem.

Im not a fan of SMPS at all and would agree with any deficiencies you describe.

However at a price of 200 bucks each, and based on the amplifier weight , I am betting on a 800 vA TO 1000 va toroidal.

Like i said i would love to see the amplifier channels on the inside. Even with the under rated toroidal in bridge mode this thing could actually do some amazing things into an 8 ohm subwoofer, but again have to wait for some internal pics. I really do not want to buy a couple, just to satisfy my interest as i almost did last week.
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Old 13th May 2017, 07:32 PM   #9
wg_ski is offline wg_ski  United States
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At that price point and weight I'm betting a 500VA. I did pop the hood on a GX5 (similar power class, $300) and that's what it was. 800's from Antek or Plitron are much (not just a little) bigger. And the heat sink looked like it belonged on a 1990's era Pentium or 80486 CPU. Being class H they are a lot more efficient than old Peaveys or BGWs. But you can't beat on these modern amps near as much. They count on you toasting the speakers long before the amp gives out, which is usually the case.
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Old 15th May 2017, 08:04 AM   #10
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Hmmm...

FWIW, 1/8th power is pink noise with a 9dB peak-to-average ratio run so the amplifier is just clipping. Sine wave testing is still technically only half-power, since it has a 3dB peak-to-average ratio. If you want to really cook an amplifier, you'll need square waves, where the peak-to-average ratio is 1.

I happen to think the 1/8th power rating is just fine. It's pretty close for modern pop music. Live music will have a much larger dynamic range (and therefore average power draw will be low), while some EDM can have extremely compressed bass resulting in exceptionally high power draws.

The old iron amps (Macrotechs etc) are designed and rated for sine wave testing, which is very demanding and rarely occurs. Seems a bit silly to optimise for it, then.

I'd rather have an amplifier that'll do 500w sine waves and 5000w peaks than something that'll do 1000w sine waves. The first one is much more aligned with the program material I work with, and would offer more headroom in that usage. Someone that's doing raves would probably want the 1000w sine-wave-amp for their subs, but likely still the peaky amplifier for the mid-high range.

Chris
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