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post #7321 of 7328 Old Yesterday, 11:31 PM
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Originally Posted by steveting99 View Post
Use the following web app to determine the Sound Pressure Level (SPL) that can be achieved in your room with the Q900: http://myhometheater.homestead.com/splcalculator.html the goal is to reach 105dB peak at the Main Listening Position (MLP) - i.e. where you sit. Are you able to achieve this just in stereo mode?
That calculator is worthless, unless one is talking about listening outdoors or in an anechoic chamber. For more, better to point you here than to repeat myself.

Bottom line is really that Q900's demand very little from an amp, and chances are excellent that one's subwoofers are the limiting factor when using main speakers of that size and efficiency.

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post #7322 of 7328 Old Today, 12:53 AM
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Originally Posted by DS-21 View Post
That calculator is worthless....
Do you have a better method / calculation to determine the relationship amp power, number of speakers, seating distance to MLP and speaker placement?

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post #7323 of 7328 Old Today, 09:56 AM
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Originally Posted by steveting99 View Post
Do you have a better method / calculation to determine the relationship amp power, number of speakers, seating distance to MLP and speaker placement?
My method is simply not to obsess about things that are generally non-issues in real life with modern equipment and bass management.

But on Q900s, a friend of mine owns a pair. He, as many people affected by nonsense audiophool marketing claptrap, heard them on his AVR and insisted he needed a separate amp to get the best out of them. So he bought a Parasound amp that cost I think more than the speakers did. Objectively an excellent amplifier: high power, low noise, attractive faceplate. I offered to help him dial in the system after with the new amp. In the process, I snuck one of these cheap, old zone amps behind the thing and connected the Q900s to it. (I bought that amp for nearly nothing, and use it as a test amp for measurements, etc.) Needless to say, he enthused the amazing improvement offered by the amp - in everything from output to treble air to image centering! - over the AVR and wanted me to eat crow. I said I heard something that sounded like a bad connection, and asked him to check the connections. Red faces and valuable, four-figure-USD-saving lessons ensued.
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post #7324 of 7328 Old Today, 10:46 AM
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Boy that's quite the story, it's almost believable. You had me up until "I snuck in a zone amp". Hahahaha

Now back to your regularly scheduled programming...

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post #7325 of 7328 Old Today, 10:55 AM
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Originally Posted by DS-21 View Post
My method is simply not to obsess about things that are generally non-issues in real life with modern equipment and bass management.

But on Q900s, a friend of mine owns a pair. He, as many people affected by nonsense audiophool marketing claptrap, heard them on his AVR and insisted he needed a separate amp to get the best out of them. So he bought a Parasound amp that cost I think more than the speakers did. Objectively an excellent amplifier: high power, low noise, attractive faceplate. I offered to help him dial in the system after with the new amp. In the process, I snuck one of these cheap, old zone amps behind the thing and connected the Q900s to it. (I bought that amp for nearly nothing, and use it as a test amp for measurements, etc.) Needless to say, he enthused the amazing improvement offered by the amp - in everything from output to treble air to image centering! - over the AVR and wanted me to eat crow. I said I heard something that sounded like a bad connection, and asked him to check the connections. Red faces and valuable, four-figure-USD-saving lessons ensued.
All that does...is prove; even a lowly, stand-alone separate amp...sounds better than an AVR. Just imagine, how much better his more-expensive Parasound unit would have sounded.

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post #7326 of 7328 Old Today, 11:02 AM
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Originally Posted by Tom Grooms View Post
Boy that's quite the story, it's almost believable. You had me up until "I snuck in a zone amp". Hahahaha
Of course a salesman would interject something like that.

(The salesman who processed the return on the Parasound amp was not happy, either. )

A thinking person who understands what a 90+ dB/W/m speaker in a fairly standard size living room with bass management employed actually requires would understand why I did what I did, and that the result was inevitable. (The one question a thoughtful person might have is how I made the switch quickly and inconspicuously, considering that little amp has Phoenix terminals that require a screwdriver to terminate the speaker leads and not banana jacks or binding posts. The answer is a pigtail lead connected to one of these. I use this amp as a test amp when I'm measuring a loudspeaker outdoors, because I have no concerns about throwing it around. And the binding posts mean I don't have to use a screwdriver if I need longer speaker wire.)

The bottom line is that any marginal AB amp will be able to drive Q900's in a bass managed system to deafening levels just fine. They're efficient and a somewhat tough load. And a competent (load invariant, e.g. Hypex, Icepower, Anaview) Class D amp can too. Even one based on the little Icepower 50ASX2 (~25W/ch) in stereo mode.

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post #7327 of 7328 Old Today, 04:25 PM
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Originally Posted by DS-21 View Post
My method is simply not to obsess about things that are generally non-issues in real life with modern equipment and bass management..
Think I've highlighted the key words in DS-21 point of using 25W per channel amps for his speakers.

Most modern receivers do have well implemented bass management system, the question then becomes what % of the power requirement is re-directed to the bass and is this dependent on the crossover freqeuncy.

There are readily available functions and a feature that would put the 25W per channel amp into risk of clipping and possibly damaging the speakers with high distortion.

(1) Room Equalization (REQ) that can reduce the gain stage by up to 9dB - if usiing a modern room correction algorithm such as Audyssey.
(2) PURE DIRECT mode. This is where the receiver disables bass management and sends the full range signals to the front left and front right amps.
(3) Party mode and/or all channel stereo mode. This where the 2.0 signal is sent to the surrounds and downmixed to the center channel.

I did an experiment with (1) + (3) and set the volume limit to 0dB (reference level) with the Marantz NR-1504 receiver. The setting on the receiver was bass management enabled, all channel stereo. Had the sub crossover frequency on the high side - 100Hz. Maximum distance to MLP was just over 10'. The NR-1504 is rated at 50W per channel in stereo mode with very low distortion and was placed in an open area with sufficient space around it for cooling. Was playing around with a few tunes during the evening and noticed the compression in the KEF E301, but it was late and had to work the next day.

Got a complaint from the wife the next day saying the receiver keep shutting down (due to thermal protection) while she was streaming tunes using Spotify and had the volume turned up. I repeated her experiment and shure enough she was right. Had to place a lower limiter on the receiver to -10dB so that the unit would not go into thermal protection. The wife is now happy since she can now stream her tunes.

When using the web app, found out that 50W per channel was NOT sufficient.

So my experience is very different from yours.

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post #7328 of 7328 Unread Today, 06:07 PM
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Originally Posted by steveting99 View Post
Think I've highlighted the key words in DS-21 point of using 25W per channel amps for his speakers.
For the record, they're not my speakers. (I do use the 8" Uni-Q from the Q900 in my desktop speakers.) The only KEF speakers currently in my main system are R800ds surroundThe Q900's have really great bones, but the cabinet quality is not sufficient for my living room, and the crossover needs to be reworked to let that amazing 8" Uni-Q shine. (Could probably get 90% of the way there with a notch filter to tame the midwoofers' breakup. One of those things I've planned to get around to doing at some point.)

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Originally Posted by steveting99 View Post
I did an experiment with [Audyssey] + [all channel "stereo"] and set the volume limit to 0dB (reference level) with the Marantz NR-1504 receiver. The setting on the receiver was bass management enabled, all channel stereo.
First, I assumed a standard mode (stereo, surround sound expansion by something like DPL2, discrete multichannel) not a no-fi sound spraying setup.

OK...now please explain to everyone how willfully
-using a tiny (and thus lower thermal capacity, given its Class AB amps) AVR
-in a no-fidelity mode
-to drive tiny low efficiency speakers with tiny cones backed up by basically no cabinet volume

has to do with

-using a standard AVR or AVR-grade AB amp (the Sherbourne I used in this particular case was below AVR grade, admittedly)
-in a mode worth of good audio gear
-to drive fairly large and high efficiency speakers with fairly large cone area operating in a fairly large cabinet volume?

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Originally Posted by steveting99 View Post
Had the sub crossover frequency on the high side - 100Hz. Maximum distance to MLP was just over 10'. The NR-1504 is rated at 50W per channel in stereo mode with very low distortion and was placed in an open area with sufficient space around it for cooling. Was playing around with a few tunes during the evening and noticed the compression in the KEF E301, but it was late and had to work the next day.
I can see how that must've sounded awful. The E301 eggs (I have a pair, FWIW, as well as a bunch of the predecessor HTS3005SE) cannot play that low without serious dynamic compression regardless of power in a space bigger than a BMW X5. It doesn't matter if there's a chipamp or an ATI AT6000 driving them. It's a matter of tiny tiny cone, and motor that gets very hot because the egg has basically no airspace in it. The older HTS3001SE was a little better in that regard, even though I believe the midrange's voicecoil was considerably smaller-diameter. There was just more room in there because the driver motor was much smaller. Neo slug rather than giant ceramic disk. But I still highpassed 'em at 120Hz. See "modest multisubs" thread.)


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So my experience is very different from yours.
I agree, but use your system like someone who cares about how music sounds (no all channel "stereo" silliness, a highpass appropriate to the mains speakers) and/or pick an AVR that's not inherently a marginal performer because of the design choices made (lotsa heat-producing stuff - HDMI boards, AB amps - in a very compact case) and you might come around to my view.

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