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Sufficient Amp for M60s - Large Bedroom
#398309 10/31/13 05:49 PM
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Hey all - haven't been on the forums for quite awhile. I'm looking for some advice on a new low-priced amp to drive my Axioms.

I am moving my beloved M60s to an upstairs master bedroom that's about 350 s.f. in size, roughly 17.5 x 20 feet. They'll be playing streaming digital music from my Sonos, but I know from experience that the Sonos' built-in class D 50 watt amp can't drive the M60s well. (Actually, it can't drive anything very well, but it's okay at medium volumes on my M3s and Ascend Acoustic bookshelves.) I plan on passing the Sonos signal to a separate amp.

I like the prices and products at Dayton Audion/Parts Express, and they have this APA150 Power Amp for sale at $125:
Dayton Audio - APA150 Amplifier

In stereo mode, it's 75 watts a channel. Do you think this will be enough to drive the M60s? Key point - this is a bedroom. I like to turn it up sometimes in private, but this won't be a party room where we need high volumes often. I don't want to spend too much on this amp, but I also am strictly buying it to power the M60s, so I want it to work.


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Re: Sufficient Amp for M60s - Large Bedroom
austinbirdman #398312 10/31/13 06:37 PM
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I would think 75 watts should be more than plenty in a room that size. At least for safe listening levels. M60s are not that power hungry despite their intimidating size.

However, if you like it 'ear splitting' then proper amperage gets expensive quickly.

Edit:
Here is a calculator to estimate the amps required based on the speaker, distance and listening level. Plug in "91" for the sensitivity of the M60s.
Amp Calculator

For instance, at 6 meters, 75 watts would allow for brief peaks up to 95 db which is pretty loud. Some like it louder but you are hurting your ears.

Last edited by Murph; 10/31/13 06:47 PM.

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Re: Sufficient Amp for M60s - Large Bedroom
austinbirdman #398313 10/31/13 07:01 PM
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Thanks - awesome calculator. According to that, with a desired sound level / dBSPL of 85, I have plenty of power - only need 13 watts to do that. (Of course it rises quickly, exponentially, as the volume goes up.)


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Re: Sufficient Amp for M60s - Large Bedroom
austinbirdman #398314 10/31/13 07:17 PM
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But, if you only need 13 watts, why wouldn't the Sonos amp suffice?


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Re: Sufficient Amp for M60s - Large Bedroom
tomtuttle #398315 10/31/13 07:34 PM
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The answer to that is over my head, but I can tell you the Sonos digital amp (in the current Sonos Connect: AMP) just sounds crap-ass to my ears, whether it's pushing my M3s at above average or M60s at average. The 50W amps on the original Sonos 100ZP sounded better, but they still clipped when I pushed the M60s to any above average level (85-90 ish). Why that should be, I don't know - but IMHO Sonos is great for connectivity and all-room audio solution, can't be beat. But for sound quality, they don't deliver. So I try to get the critical listening into different amps and avoid their expensive mobile boom-box devices.


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Re: Sufficient Amp for M60s - Large Bedroom
tomtuttle #398316 10/31/13 07:37 PM
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PS - Also, I thought that amp calculator was a bit low-ball myself. My hunch is I certainly want more than 13 watts for good sound at 85dbs pushing M60s in a 350 s.f. room. But seems like a good 75 wpc of A/B design amp out to do it.


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Re: Sufficient Amp for M60s - Large Bedroom
austinbirdman #398317 10/31/13 08:02 PM
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I hear ya. Even before I asked the question, I was speculating that the Sonos class-d amp just might not be very well designed. It seems like that Dayton amp should do the trick.


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Re: Sufficient Amp for M60s - Large Bedroom
austinbirdman #398320 11/01/13 02:18 AM
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I've heard good things about the APA150, quite a robust and heavy little amp. Let us know what you think of it if you pull the trigger on it.


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Re: Sufficient Amp for M60s - Large Bedroom
austinbirdman #398324 11/01/13 04:07 AM
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Birdman, although it's been pointed out several times here that the Crown calculator gives a result far too high for home listening rooms, it continues to be cited occasionally. Crown is primarily a pro amp manufacturer and the calculator is designed for use in relation to open spaces rather than enclosed rooms. This fact isn't indicated in the calculator screen but only in a separate discussion here and only rather less than prominently under "Other Considerations". They suggest a 6dB correction for use in enclosed rooms rather than anechoic outdoor venues. Without this 6dB correction the calculator result is 4 times too high.

You don't mention the key factor, listening distance, but at a typical 10 feet, your M60s use about 1 watt for a 85dB sound level. 75 watts would supply a peak of about 103dB.


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Re: Sufficient Amp for M60s - Large Bedroom
JohnK #398329 11/01/13 02:14 PM
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Thanks, John - I'll take that as a "Go for it!"


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