Do I need an external amplifier? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 12 Old 02-24-2019, 07:16 AM - Thread Starter
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Do I need an external amplifier?

I would like to understand if I need an external amp to power my front channels or my AVR is sufficient. Let me give you some parameters as context:

- listening room is a bedroom size of 17 x 12; I usually do 50:50 movies and stereo music listening
- KEF Q300 speakers with 87 dB sensitivity (supposedly 8 ohms, but i read some places may go below 4 ohms)
- a 5.1 setup with an SVS sub
- listening position is 9 feet away
- Denon AVR rated at 105W for 2 channel
- when I listen to music my Master Volume is around 50 for heavily compressed (recent) music (out of 98) and that produces about 70 dB SPL I have measured it with REW
- when I listen to music mastered in 80s and 90s my Master Volume could be around 55 for similar 70 SPL
- when I watch movies my Master Volume is anywhere around 55-60
- I have never had to turn my Denon AVR higher than Master Volume 60

With that being said,

1) Do I need an external amplifier for my front speakers to sound their best at my MLP for when I listen to music only, still leveraging the sub?

2) Would I get better sound quality (not louder, but better) from using an external amplifier?

3) Does not audio quality degrade once you have AVR pre-out --> amplifier via analog RCA connectors? The chain is no longer all digital, so I assume loss of audio quality.

Last edited by KurtCocain; 02-24-2019 at 08:31 AM.
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post #2 of 12 Old 02-24-2019, 08:00 AM
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Quote:
Originally Posted by KurtCocain View Post
...
1) Do I need an external amplifier for my front speakers to sound their best at my MLP for when I listn to music only, still leveraging the sub?

2) Would I get better sound quality (not louder, but better) from using an external amplifier?

3) Does not audio quality degrade once you have AVR pre-out --> amplifier via analog RCA connectors? The chain is no longer all digital, so I assume loss of audio quality.
1. Given your usage and conservative volume level, it doesn't seem like you need any more amplifier power.
2. If you have a good AVR amplifier, which you seem to have, and aren't clipping due to needing more power, then adding more power won't affect the sound quality.
3. The digital signal in to your AVR is being converted to analog before it goes to the AVR internal amplifier, so that is happening whether it is sent to the internal or external amplifier.

I am sure others will reply, hope this helps,
Mark
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post #3 of 12 Old 02-24-2019, 08:33 AM - Thread Starter
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Originally Posted by markmanner View Post
and aren't clipping due to needing more power, then adding more power won't affect the sound quality.
How do I know if I am clipping? Would I only notice clipping if trying to produce 105 dB SPL?
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post #4 of 12 Old 02-24-2019, 08:35 AM
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Quote:
Originally Posted by KurtCocain View Post
I would like to understand if I need an external amp to power my front channels or my AVR is sufficient. Let me give you some parameters as context:

- listening room is a bedroom size of 17 x 12; I usually do 50:50 movies and stereo music listening
- KEF Q300 speakers with 87 dB sensitivity (supposedly 8 ohms, but i read some places may go below 4 ohms)
- a 5.1 setup with an SVS sub
- listening position is 9 feet away
- Denon AVR rated at 105W for 2 channel
- when I listen to music my Master Volume is around 50 for heavily compressed (recent) music (out of 98) and that produces about 70 dB SPL I have measured it with REW
- when I listen to music mastered in 80s and 90s my Master Volume could be around 55 for similar 70 SPL
- when I watch movies my Master Volume is anywhere around 55-60
- I have never had to turn my Denon AVR higher than Master Volume 60

With that being said,

1) Do I need an external amplifier for my front speakers to sound their best at my MLP for when I listen to music only, still leveraging the sub?

2) Would I get better sound quality (not louder, but better) from using an external amplifier?

3) Does not audio quality degrade once you have AVR pre-out --> amplifier via analog RCA connectors? The chain is no longer all digital, so I assume loss of audio quality.
1. Based on Crown Audio calculator, you need an amp supplying ~11 watts/channel, to produce reference levels 85 dB, at a distance of 3 meters (~9 ft), with 3 dB of headroom. I'm sure your existing AVR is more than capable of supplying 11 watts/channel, all channels driven, so no, you don't need an external power amp.
2. Not necessarily (mostly no) -- SQ is a complex function of not just the equipment, but also the physical enclosure (room), distances, and so on. You may get better results by playing around with the placement, toe-in, distance from backwall, etc. Experiment.
3. As others have already explained, no.
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post #5 of 12 Old 02-24-2019, 09:44 AM
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you can't measure the level with REW if you haven't calibrated it before. But if you have calibrated it why don't you use your reference directly instead of REW?
with a volume level around 50 you probably never used much more than ONE SINGLE WATT!
the volume control has a logarithmic characteristic, half the volume doesn't mean half the power but 1/10!!!
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post #6 of 12 Old 02-24-2019, 10:08 AM
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Originally Posted by KurtCocain View Post
How do I know if I am clipping? Would I only notice clipping if trying to produce 105 dB SPL?
I am not sure at what db level you would notice it, but for your AVR, with a vol. level at 50-60% of its range, it is not likely clipping. If it is clipping a lot, it would be noticeable I think. It would sound distorted and bad!

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post #7 of 12 Old 02-24-2019, 10:28 AM - Thread Starter
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Originally Posted by Mickey Mouse View Post
you can't measure the level with REW if you haven't calibrated it before.
I am using REW with a calibrated miniDSP UMIK-1 mic and a calibration file for it. Does it make sense?
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post #8 of 12 Old 02-24-2019, 10:32 AM
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I want to say power is like cowbell, you could always use some more... However, as everyone else said, based on your usage it seems you are fine with your current setup.
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post #9 of 12 Old 02-25-2019, 03:20 PM - Thread Starter
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Last question - what about my speakers - even though rated at 8 ohms - may be dropping to 4 ohms or even 3 ohms. I think I read somewhere that they may be dropping to 3.2 ohms on some frequency...

In that case, if my power from the AVR still enough? Or the Denon can handle only 4 ohms, ad potentially I am losing sound as speakers drop to 3.2 ohms?
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post #10 of 12 Old 02-26-2019, 09:05 AM
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"officially" the impedance shouldn't drop below 20% of the nominal impedance.
4Ohm - 20% -> 3.2Ohm
so a speaker with drops below 3.2Ohm isn't even a 4 but 3 Ohm speaker.

in the end it really doesn't matter, you probably never "squeezed" more than 1W out of your amp
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post #11 of 12 Old 02-26-2019, 09:32 AM - Thread Starter
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Quote:
Originally Posted by Mickey Mouse View Post
"officially" the impedance shouldn't drop below 20% of the nominal impedance.
4Ohm - 20% -> 3.2Ohm
so a speaker with drops below 3.2Ohm isn't even a 4 but 3 Ohm speaker.

in the end it really doesn't matter, you probably never "squeezed" more than 1W out of your amp
OK, so if the KEF Q300 are rated at 8 ohms nominal impedance... officially they should not drop more than 6.4 ohms?
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post #12 of 12 Old 02-26-2019, 10:03 AM - Thread Starter
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so a speaker with drops below 3.2Ohm isn't even a 4 but 3 Ohm speaker.
@Mickey Mouse Here is a German site which if I understand correctly, the speakers do drop below 4 ohms:
https://hifi-selbstbau.de/testberich...r/411-kef-q300

"Impedance minimum of 3.8 ohms around 200 Hz -> the manufacturer's impedance rating of 8 ohms is "buffed" to "simulate" a relatively high voltage efficiency"

Last edited by KurtCocain; 02-26-2019 at 10:06 AM.
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