How much Watt amplification for 4 Ohm speaker at 65 DB SPL?

[Goldhamster916]

Hi!

I am looking to buy KEF LS50 Meta (4ohm) as FR/FL in a 11channel home theater system with a Denon X3800h and a high end sub. I am in a very small room and usually set the AVR to 65DB. What kind of wattage would I need to drive the Metas at 65DB listening level? Would the Denon be enough or do I need a powerful amplifier to drive them properly?

Thanks for any responses!

 

[Brian Hall]

Depending on your definition of "small room", it will be hard to get 11 channels in there. Some more physical separation is needed or you are going to have one big mush of sound regardless of room treatment.

Maybe scale it back a bit for a small room.

 

[staticV3]

With the KEFs placed near a wall and at 8ft listening distance, you will need 0.05W per channel to drive them to 65dB SPL Peak:


Here's the calculator in case you want to customize placement, listening distance, and desired SPL: http://www.hometheaterengineering.com/splcalculator.html

 

[Goldhamster916]

nice, that calculator really helps!

My listening distance is even closer, rather 6 feet. I guess the denon will do fine then, it delivers 70 watt even if all channels are active at same time.

Thanks for your reply!

@Brian Hall
For music listening, where I care about fidelity the most, I use stereo mode only. For movies/games sound effects I do enjoy having coming sound from so many sources. I tried less number of speakers but it was more immersive with more. But thanks for your Perspective!

 

[AnalogSteph]

With the KEFs placed near a wall and at 8ft listening distance, you will need 0.05W per channel to drive them to 65dB SPL Peak:

Note, I'm pretty sure that the 65 dB SPL was supposed to be average, not peak. So what you want to enter into such a calculator would be that plus crest factor... somewhere around 80, maybe even 85 dB. That's still no more than about a watt, mind you.

 

[Goldhamster916]

I see! Thank you for taking time to reply.

Would there be any benefit in getting a good external AMP, aside from being able to play them louder? Or is the X3800H fine for my listening levels?

 

[Sokel]

You should also define the way you came to that 65db SPL figure.
Is it A,C or Z weighted?What did you use you measure it (device,app) ?

Depending on these factors differences can be big.

 

[mhardy6647]

Note, I'm pretty sure that the 65 dB SPL was supposed to be average, not peak. So what you want to enter into such a calculator would be that plus crest factor... somewhere around 80, maybe even 85 dB. That's still no more than about a watt, mind you.

Go for 2 watts and have an extra 3 dB of headroom.

A (semi) serious question: I know that stereo (more to the point two channels vs. 1) should add 3 dB of SPL, all else being equal. How, then, does one (or does one?) allow for having eleven channels?

 

[DVDdoug]

and usually set the AVR to 65DB.

The AVR doesn't know the loudness in the room. And you are likely listening louder than 65dB SPL.

Most AVRs have plenty of power for most listeners/situations.

The powered sub can also add to the "feeling" of power & loudness. If the room is rumbling and you can hear the dialog in movies it's probably loud enough.

 

[RayDunzl]

A (semi) serious question: I know that stereo (more to the point two channels vs. 1) should add 3 dB of SPL, all else being equal. How, then, does one (or does one?) allow for having eleven channels?

Maybe this...

Adding acoustic levels summing sound levels 10 combining addition summation sum decibel levels or SPL of up to ten incoherent sound sources audio logarithmic decibel scale identical summing 1/3 octave spl full octave sum sound pressure level noise so

Sound level adding addition summing summation sum decibel dB of 10 acoustic sources sum combining decibels or SPL of incoherent sound identical pressure levels audio logarithmic decibel scale sum summing 1/3 octave spl full octave noise sound pressure acoustic pressure volts - Eberhard Sengpiel...

sengpielaudio.com

Or this, for up to 30 sources

Adding up to thirty 30 incoherent sound sources acoustic sound levels SPL - combining 30 decibels sound pressure level noise - sengpielaudio Sengpiel Berlin

Sound level adding 30 thirty acoustic sources - combining decibels or SPL of incoherent sound pressure levels noise decibel dB - Eberhard Sengpiel sengpielaudio

sengpielaudio.com

For eleven sources of +3dB it give a 13.39dB total SPL increase, for incoherent (not identical, as with music) souces.

 

[DonH56]

Go for 2 watts and have an extra 3 dB of headroom.

A (semi) serious question: I know that stereo (more to the point two channels vs. 1) should add 3 dB of SPL, all else being equal. How, then, does one (or does one?) allow for having eleven channels?

Assuming they are not all in phase every instant then you would convert to raw levels (not dB), RSS the levels (root sum square, net = sqrt(S1^2 + S2^2 + ... + S11^2), then convert the result back to dB. Note rarely are all speakers at the same levels.

Edit: The Scrutinizer @RayDunzl provided a nice set of links.

 

[Zapper]

Would there be any benefit in getting a good external AMP, aside from being able to play them louder?

No

is the X3800H fine for my listening levels?

Yes

 

[Goldhamster916]

I appreciate the discussion!
If you don’t listen in multichannel stereo, I think in real world terms you barely get much SPL increase from having multiple speakers because there is rarely more then 2-3 speakers active at the same time. At least with movies and games. There most effects pan between speakers, so if one goes active the other goes quieter/silent. You maybe have some quiet ambience sounds coming from the surrounds, but that’s it in 99 percent of content.

 

[Philbo King]

Go for 2 watts and have an extra 3 dB of headroom.

A (semi) serious question: I know that stereo (more to the point two channels vs. 1) should add 3 dB of SPL, all else being equal. How, then, does one (or does one?) allow for having eleven channels?

Assuming all speakers are the same and have equal signals:
2 speakers +3dB
4 speakers +6dB
8 speakers +9dB
With 11 it'll come in somewhere around 10dB