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Re: Maximum amperage for M50's?
jamin3d #195355 02/07/08 05:51 AM
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Jamin, both the amplifier in the 875 and the amplifiers in the 2400 and 906 amplify transparently within their power limits, so there's no reason why any of them would sound any better than the others.


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Re: Maximum amperage for M50's?
jakeman #195356 02/07/08 05:56 AM
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 Originally Posted By: jakeman
Presumabley he meant bridged output at clipping as as in excess of 300W at 4 ohms not 8 ohms.

I'm not sure if this makes a difference regarding the 4 ohms vs 8 ohms thing, but the 875 manual on page 24 states in bold:

• Use only front speakers with an impedance of 8
ohms or higher for bridging. Failure to do so may
seriously damage the AV receiver.


It also states the following (which is why I made my original post):

• When using bridging, make sure that your front speak-
ers can handle the additional power.

Since that S&V test says "over 300W" in bridged mode, then it sounds like it would NOT be safe to run the m50's with the 875 bridged... correct?

Re: Maximum amperage for M50's?
JohnK #195357 02/07/08 06:00 AM
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 Originally Posted By: JohnK
Jamin, both the amplifier in the 875 and the amplifiers in the 2400 and 906 amplify transparently within their power limits, so there's no reason why any of them would sound any better than the others.

Thanks JohnK! It sounds like I can replace both NAD amps with the receiver! Very exciting. I just hope it sounds at least as good as the NAD pre/pro (S170). I'm mainly getting it because I want uncompressed audio from my Blu-ray's via HDMI.

Re: Maximum amperage for M50's?
jamin3d #195358 02/07/08 06:04 AM
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I think you'd probably be ok with the M50s; it's not likely that you're going to be hitting that 300W very often (if at all). I know that Axiom tends to be very conservative with its speaker ratings--although the M80s are rated at 400W maximum, they have been tested (by Axiom) at well above 1000W!


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Re: Maximum amperage for M50's?
jamin3d #195359 02/07/08 06:14 AM
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Jamin, the 875 has plenty of maximum power capacity in its standard operating mode, as the S&V lab tests indicate, so you shouldn't be worrying about still more maximum capacity from bridging(incidentally, the S&V article correctly mentioned that the bridging was at 8 ohms; bridging can't change the impedance of a speaker or other load which is being driven). But no, if you did it, the M50s can handle brief bursts of maximum power in excess of the conservative number given in the Axiom specs. So again, you should worry about your ears more than your M50s.


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Re: Maximum amperage for M50's?
JohnK #195360 02/07/08 06:27 AM
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I just didn't want to chance ever damaging my precious Axioms! \:\) You've been a big help -- thank you very much.

Re: Maximum amperage for M50's?
jamin3d #195412 02/07/08 08:36 PM
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 Originally Posted By: jamin3d
Thanks for the thoughts everyone.

Currently I'm running the m50's with a 2-channel NAD amp (2400), and the rest of the speakers with a multi-channel NAD amp (906), and was hoping to be able to get rid of an amp to save some space.

But if the Onkyo's amps didn't sound as good as the NAD amps, then I would just keep using the NAD amps.


If budget is the main concern what you are doing makes sense. I've experimented with that receiver and it clips at not that high volumes and at loud transients. If you are planning on using it at low to moderate levels its OK.

However if you are asking are you giving up sound quality by selling the separate NAD amp and relying on the very hot amp inside the onkyo receiver box then the answer is that it would be a mistake. Do not believe the over-simplistic statements that a receiver amp is the same sonically as a capable separate amplifier. The high heat (hot to touch) along with the radiation from the amp inside the box will affect sound quality.


John
Re: Maximum amperage for M50's?
JohnK #195415 02/07/08 08:48 PM
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When bridging which I do with my Bryston and McIntosh amps, the power output for 4ohm loads will be different than with 8ohm loads. With well designed efficient solid state amps the 4ohm power output will be nearly twice the power output with an 8 ohm load. That's why its important to know the ratings at both those impedances or ideally have a graph. The published data is inconsistent. 300w output at 8ohms bridged implies around 600w bridged at 4ohms. No way with that amp. 300w at 4ohm bridged is believable though I doubt even that is achievable given the high heat that receiver generates.


John
Re: Maximum amperage for M50's?
jamin3d #195419 02/07/08 08:58 PM
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 Originally Posted By: jamin3d


Since that S&V test says "over 300W" in bridged mode, then it sounds like it would NOT be safe to run the m50's with the 875 bridged... correct?


No it would be safe. The rule of thumb I have always used when matching speakers and amps is to use a minimum amp power of 2X the speakers nominal power handling. That way you avo.d clipping in all but the loudest passages.

Another thing to keep in mind with that receiver is to NOT set the speaker impedance in the menu to 4 ohms as it will limit power output to 55 wpc all channels driven. No reason given for this except I suspect its related to its different design with few capacitors and kept low in order to get certified. That means it will clip more easily. I don't like the amp in that receiver primarily for that reason. Capacitors and how they are arrayed are important determinants to how fast the amp can respond to voltage demands and how much spare power is held in reserve.


John
Re: Maximum amperage for M50's?
jakeman #195478 02/08/08 07:38 AM
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Uggh... all this is so contradictory and a lot to think about. One guy says the amp doesn't matter, one guy says it does... everywhere I read, it's always something different. \:\)

I've never had my current system so loud that it clipped; it always sounds great & gets plenty loud. And right now my mains are 'only' powered by 100W, the center with 90W and the surrounds with 30W. Before I went separates I had an Onkyo 787 receiver and it never ran out of power either (and honestly, after going separates the improved audio quality was only noticed with SACD / DVD-Audio, and then only marginally).

So I guess I just don't see how this new Onkyo 875 would not have enough power. Can it really be any hotter than these NAD amps now? They get pretty darn warm, but I've never felt I needed to measure their temps.

Thanks again for everyone's input!

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