(Aus) Biema pro amps for (sub)woofer use - diyAudio
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Old 24th September 2004, 01:54 AM   #1
tktran is offline tktran  Australia
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Default (Aus) Biema pro amps for (sub)woofer use

Has anyone had experience with Biema pro amps for (sub)woofer use?
http://www.biema.com/html/product/amplifiers/q.htm

Am looking for a moderate cost amplification to power the woofer section (2 x 12") in the NaO.

Someone at Madisound forums suggested the QSC RMX 850 as good value at USD$300, but here in Australia it costs USD$900.
:-(

Am considering the Q250 or Q400 (for Aussies, the Altronics product code is A4164 or A4170)
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Old 27th October 2004, 10:44 AM   #2
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I'm in fact looking into an Altronics amp which puts out 2x450w into 4 ohms, which is on special now for $450 and seems a bargain at that. The distortion seems low, however they didn't really specify it properly so it could be anything.

To me this looks like the best value sub amp in Australia. I was looking at the Behringer EP 2500 which has a bit more power and can be bridged, but it's only about 1.5 db more output for nearly double the cost. The response looks acceptable, which is another thing you have to watch with low cost PA amps.

I'm doing a search at the moment, but if you find anything out, or get some feedback, I'd be interested to hear your thoughts.
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Old 17th September 2006, 01:17 AM   #3
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A late reply, but I managed to have a look under the hood for these Q400 power amplifiers.

Separate power supply ie. TWO toroid transformers power supplies with 3x 8,200uF caps and 10 output devices per side attached to a tunnel heatsink...In total this thing weighs a massive 20kg beasts, and there's no fancy casework to add to that weight.

Will try to take photos next time I check it out.

Definitely adequate for subwoofer use, if only I could figure out how good they would be for full range work.
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Old 17th September 2006, 02:23 AM   #4
Hayden is offline Hayden  Australia
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Iím extremely interest in a cheap amp too but I need about 1000-1500wrms per channel for my subs, usually the weight tells you how much grunt the amp has some stereos state 3000watts and only weight 5-15kg and I know thatís a lie.
yes please take some photos
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Old 17th September 2006, 03:37 AM   #5
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Hayden, what impedance are you looking for?

I bought the Behringer EP2500 which has 650w into 4 ohms and is stable down to 2 with 1200w into a 2 ohm load, or 2.4 kw bridged into 4 ohms. It costs around $600 and you I doubt you could beat it.

The cheaper Biema amps supply no schematics, so if they fail, they can't be repaired. This came from a pro retailer who also did repairs. I'd say the cheap Biemas are for intermittent subwoofer use, not for continuous high power use. I hear the fan is quiet, and this would suggest they built in less robustness - most pro amps run loud in the home with the fans when it isn't needed.

If you need that much power, then perhaps two EP2500s. A pair of EP1500 would actually do it, 1.4kw bridged mono into 4 ohms. You could probably pick up a pair for ~ $1000.

If for home use, then the fan is a pest and you would want it in another room, if you use it for movies.

I wouldn't read too much into the weight. There are a lot of design issues there. It doesn't tell you how much grunt it has. There are heavy amps with only a few hundred watts, and there are lighter amps with a lot more. You have to look at the design of the amp, what method of cooling they use, the casing, and so on. Of course, if it is cheap and light and claims ultra high power, you would be skeptical. If its a Crown, light and powerful, then it will be expensive. An amp can be made lighter by using light gauge sheet metal on the case, by using class D or other similar technology, and by minimising heatsink size by multiple fans.
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Old 17th September 2006, 05:08 AM   #6
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Hi Paul,

Got any internal pics of the EP2500?
As far as power specs go, it's a winner, with thanks to it's Class H topology manages 500/750/1200W into 8/4/2 ohms. It's also bridgeable for a monster 2.4kW into 4 ohms.
Ref: http://www.partsexpress.com/pdf/248-747s.pdf

The Biema Q400 is rated to 400W/600W into 8/4ohms, at 0.1% THD, 1Khz. Bridged it can do 1.2kW into 8 ohms. No ratings for 2ohms, so probably not recommended for 2ohms (not a big problem, but real downside it that it's not bridgeable for 4 ohm operation)

I would think the Biema is a class A/B topology, though I can't be certain (I'm no power amp expert). It would explain why it uses two very large transformers and dual mono power supplies.
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Old 17th September 2006, 11:25 AM   #7
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tktran,

I haven't dared to open it up! I'm not thrilled about getting near those PS caps! If you don't use speakon connectors on the rear, there is a screw on cover to avoid contact with any bare wire, since this thing has so much juice! I must say I'd be curious to see it now you mention that. I will at some point need to clean the air filters, but I find it stays cool most of the time, unless I feel the urge to turn up the volume on loud rock music.

I have seen a review online on someone's personal website, where he did open it up and run it through some tests, where he confirmed that the power ratings were accurate, and that the quality of its construction was sound.

The first PA supplier I spoke to regarding this amp said that it was more reliable than the entry level crown amps. He gave numbers of units failing as backup. Whether this is a reflection on the amp, or how users tend to use them is another thing. I'd expect those who choose crown are more likely to be those who will push their equipment harder and insist on reliability. The entry level crown amps were quite a bit more expensive, they have two fans of the same size and run noticeably louder. The only advantages to the crown I could see was that the passive attenuators seemed better quality (firmer), and the fact that it was a crown with a 3 year warranty instead of one.

For most diy subs out there, I'd say the Biema is a great choice as the fans are quiet and they are very cheap. I also think that sub plate amps are rarely well designed in terms of having the right response - no rumble filter option, boost where you don't want it, etc. This is a great alternative
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Old 17th September 2006, 02:47 PM   #8
Hayden is offline Hayden  Australia
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How good is the EP2500 will it live up to a constant 1200wX2wrms without a lot of distortion and overheating? I donít want it to damage my subs.
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Old 17th September 2006, 04:19 PM   #9
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Into what impedance?

It is no different to any other amp. Pushed beyond its limits it will clip and you will get distortion.

Whether you will get the power you want depends on how you configure it. Bridged to drive a 4 ohm load you will get 2.4kw which is twice as much as you are looking for, however you would need two amps and this is probably overkill.

If you can find an amp that is better value for money for driving a high power sub, then I'd like to know what it is.

I have mostly answered your question in my previous posts, but I will add that I haven't pushed it to the extent that you might in a DJ situation where it might have to run all night. I'd expect that it would be up to the task, however I'm not experienced in this kind of context.

It does have thermal overload protection which should kick in before failure. You could test it out and if this becomes a problem with just one, you could use two. Then it would be running more comfortably with more headroom.
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Old 5th March 2008, 07:47 AM   #10
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Well i noticed that some people were asking questions on what the biemaQ250 amplifier could handle,

im currently running 2 speakers off it in parallel and i don't need to even turn the amp up full to get enough out of the speakers, and im running 2x 18" 800RMs speakers, and they get plenty loud,

As for clipping the only time it happens to me, is when there is too much bass pumping through the channel, and that is easy fixed in a min by either turning the amp down a tad or turning the input down,

and i would post some photos of inside the amp, but i forgot to take pictures when i had it open, and the fans a really good, and they are only standard computer tower fans, i can run my system for a few hours and no distortion, no clipping, just great music blaring out non stop,
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