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More speakers, less watts?

RichardL

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#1
I recently purchased a Denon AVR X3700H to replace my old Denon 3806.

My question involves how many watts get delivered to a speaker when 2 or more speakers are driven?

The Denon spec states “105W/channel with 2 channels driven”. So how many watts if more speakers are driven? I asked Denon and they stated that there is no loss of watts regardless of how many speakers are driven, “All get 105Watts”...then why does their spec state “2 channels driven”… Since the 3700 can drive 9 speakers, the amps can push 945watts?!? I believe the chart below, but not sure why 2 speakers being driven are coming in at 138 watts?

Denon AVR-X3700H AVR Review | Audio Science Review (ASR) Forum

So - generally, do receivers lose power with more speakers or not? Is Denon correct? If not, are there any “Watt charts” for the 3700 driving 2 thru 9 speakers at 4, 6, 8 ohms? I am looking to learn as I would consider adding external amps to lighten the 3700’s load.

Thoughts? Thanks in advance.
 

AdamG247

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#3
As this graphic shows as you add speaker the wattage per channel drops a little. This graphic is taken from the review thread you linked. So maybe you missed it.


 
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RichardL

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Thread Starter #6
When that tugboat gets too slow, I want to add more tugboats - but I don't know how slow it is going :)

Yes, the chart is exactly what I saw, note the bar for 2 speakers states 138 watts, but the receiver is rated 105. More importantly the chart confirms that a receiver will in fact lose per speaker power as you drive more speakers. Enter Denon who said "no"...

I have reviewed the power section in the manual a few times, and it is vague. They state the exact same spec for "front", "Center", "Surround", then "Surround Back / Height 1 / Height 2". Why are some specific and some combined? Why state it like that? No mention of how many speakers and how many watts...

Not looking to drive all at max, but for example if the 3700 drives the surrounds at 75 watts, and I can get an external amp for 125 watts, to handle those 2 speakers, I would do that.
 

DVDdoug

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#7
That's Watts-per-channel so with 5 channels driven at 100W per channel you get 500W. You're getting more total power (which means you can get higher SPL) with more speakers connected.

But it's rare that all channels will be driven with equal power at the same time... Most of the sound usually comes from the front. And if you're getting maximum out of the rear or other channels the front is probably reduced at that moment.

I can't guess how much power you need but if you add a powered subwoofer, that's usually where you need the most power.

Denon states the power consumption at 660W
That's the power it sucks out of the power outlet and since nothing is 100% efficient more power comes-in than goes-out to the speakers, with the difference converted to heat.
 

Chrispy

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#8
That's Watts-per-channel so with 5 channels driven at 100W per channel you get 500W. You're getting more total power (which means you can get higher SPL) with more speakers connected.

But it's rare that all channels will be driven with equal power at the same time... Most of the sound usually comes from the front. And if you're getting maximum out of the rear or other channels the front is probably reduced at that moment.

I can't guess how much power you need but if you add a powered subwoofer, that's usually where you need the most power.

That's the power it sucks out of the power outlet and since nothing is 100% efficient more power comes-in than goes-out to the speakers, with the difference converted to heat.
The listed consumption isn't even specified and likely relates only to a required govt/regulatory spec.....and if you look at even Amir's spec and think about amp efficiency....
 

beagleman

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#9
What need do you have of all channels driven to max simultaneously?

Actually a great point.

Years ago owned an earlier surround sound receiver and it spelled out in detail why only the 2 main stereo channels were rated "Full Power" and the center and surround were rated to half that power.

The explanation was that any typical surround system would rely on having the bass to the full size stereo left and right pair OR a dedicated sub or two, and therefore no bass would be routed to the surrounds or center, allowing them to be lower powered and still play loud enough, minus the bass.
 

beagleman

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#10
When that tugboat gets too slow, I want to add more tugboats - but I don't know how slow it is going :)

Yes, the chart is exactly what I saw, note the bar for 2 speakers states 138 watts, but the receiver is rated 105. More importantly the chart confirms that a receiver will in fact lose per speaker power as you drive more speakers. Enter Denon who said "no"...

I have reviewed the power section in the manual a few times, and it is vague. They state the exact same spec for "front", "Center", "Surround", then "Surround Back / Height 1 / Height 2". Why are some specific and some combined? Why state it like that? No mention of how many speakers and how many watts...

Not looking to drive all at max, but for example if the 3700 drives the surrounds at 75 watts, and I can get an external amp for 125 watts, to handle those 2 speakers, I would do that.

In THEORY that might be better, and would take some "Work" off the power supply of the receiver, but in practice, the difference between 75 watts (bass limited) and 125 is not all that much really. And I think most would not even notice the difference, especially in surround channels.

For the main stereo and maybe center channels that would be a positive, to some degree perhaps.

In my experience in my TV room, even with a lowered powered entry level AVR, using a Sub, I have NEVER ran into noticing not enough power, ((and my receivers is rated quite low with 5 channels driven)) even at fairly loud levels. There is just not tons of power needed when the bass is removed and sent to a dedicated powered sub.
 

Trell

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#11
...
In my experience in my TV room, even with a lowered powered entry level AVR, using a Sub, I have NEVER ran into noticing not enough power, ((and my receivers is rated quite low with 5 channels driven)) even at fairly loud levels. There is just not tons of power needed when the bass is removed and sent to a dedicated powered sub.
There is quite a bit of musical content in the upper bass that the subwoofer does not cover.
 

steve59

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#12
waay back in the day I had a 4 channel system rated at 55wpc and when I added a second pair of stereo speakers and turned the dial to A+B sound pressure in the room increased. 5 years later I bought a receiver with the same 55wpc rating from the same manufacturer and sound pressure decreased when I went to A+B and they were the same speakers. My point? good question.
 

Chrispy

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#13
waay back in the day I had a 4 channel system rated at 55wpc and when I added a second pair of stereo speakers and turned the dial to A+B sound pressure in the room increased. 5 years later I bought a receiver with the same 55wpc rating from the same manufacturer and sound pressure decreased when I went to A+B and they were the same speakers. My point? good question.
Different gain structure?
 
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#14
The 105W/channel is the maximum power for 2-channels being driven into an 8-Ohm load at a low distortion level. When driving more channels simultaneously an AVR's total output becomes limited by what it's power supply unit (PSU) can deliver to the amps so the power per channel will naturally fall.

For its higher end AVRs, Denon guarantees at least 70% of the 2-channel power output rating will be available per channel when 5-channels are driven which is 73.5W/channel for a X3700 model. This guarantee is often stated in the specifications.

The 5-channel driven wattage figure is useful/conservative because in practice, movie content shouldn't require more total power than the equivalent of 4-channels being driven to their limit at any one time.
 

gsp1971

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#16
Everytime you double the number of speakers (from 1 to 2, from 2 to 4, etc.) you gain 3dB in sensitivity and, hence, you need half the power to achieve the same level of loudness. 100W per channel with 5 speakers is more than enough to fill a 25-30m2 room with music at ear-bleeding loudness.
 

Benedium

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#18
Everytime you double the number of speakers (from 1 to 2, from 2 to 4, etc.) you gain 3dB in sensitivity and, hence, you need half the power to achieve the same level of loudness. 100W per channel with 5 speakers is more than enough to fill a 25-30m2 room with music at ear-bleeding loudness.
Unless each speaker plays different sounds at different time like in a movie soundtrack?
 

fieldcar

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#19
I've got a X3700H too, but I highly recommend an AC infinity cooler and setting the HPF for every speaker, even your front pairs to SMALL @ 40Hz at the very least. I've got JBL 590's set as [email protected] despite Ausyssey suggesting 'large'.

https://www.amazon.com/gp/product/B078PQJSRY/

Once the receiver gets hot after a minute of loud music, sound gets muddy. Try that before considering external amplification.
 

peng

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#20
When that tugboat gets too slow, I want to add more tugboats - but I don't know how slow it is going :)

Yes, the chart is exactly what I saw, note the bar for 2 speakers states 138 watts, but the receiver is rated 105. More importantly the chart confirms that a receiver will in fact lose per speaker power as you drive more speakers. Enter Denon who said "no"...
To give the Denon rep the benefit of doubt, he might has misunderstood your question. He might just meant regardless of 1 or 9 speakers connected, each will get the full power if driven 1 at a time (so a case of "connected", vs "driven". He should have known what you meant though but you never know.:D

By the way, technically speaking "power" is really the wrong term to use because then you have to consider other factors such as impedance, phase angle, duration etc., and then there is the question of picking the distortion level at which the output is measured, ie. 0.05%, 0.1%, or at clipping etc., but I know what you are asking.., and you got the answer. In the end, Amir's chart is a good guide for all intents and purposes.
 
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