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Very efficient speakers (100 dB), how important is amplifier power?

Flavio

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I have a pair of JBL CBT 70J-1 / 70-JE1 as my main speakers and four JBL CBT 50-LA1 as surround speakers, all in my living room and want to buy some class D mono amps for the main speakers.

According to JBL they are 8 Ohm, have a sensitivity of 100 dB/1m and can take 1000 W low-Z (whatever that means?).
My main listening position is at 12 feet. I use the system for home theater 90% of the time.

I don't pretend to be able much difference (if any) between different amplifiers, but I do hear noise and hiss and can hear difference in dynamics.
Currently I have a pair of Sabaj A20a amps, but to get rid of the hiss I have to turn down the volume knob so much the ARC measurement of my Anthem MRX 720 has trouble reaching Dolby reference level.
The left and right speakers are set at +12 dB whereas the rest of the speakers that are powered directly by the Anthem are set at almost at - 12 dB!

I was looking at NC400, NC500 and NC500MP based mono amps because they have measured very well and have decent power (400 W or more), but I am wondering if I am not kidding myself and should save a bunch of money and should just get some 100W ICEpower or similar mono amps and spend the $800 difference somewhere else? Or would I still run the risk of getting amplifier hiss by going the cheaper route?

I am obviously never to going to stress the JBL speakers as they can play to peaks of 136 dB!

Any advice would be appreciated.
 
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Sokel

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5 modules of Ice Power edge 300a2 (about 720 euro for all) who measure more that decent.
Plus an 1500S PSU (the 57V variant) or two if you want more juice for about 500 euro each or something similar from Micro audio) plus a case,connectors,etc and someone to make it for you if you can't do it yourself,can't get better and cheaper than this for 10 channels of quiet amplification.
 
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Flavio

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I only need two channels, why do you think I need ten?
The built-in Anthem amps are more than sufficient for the four surround speakers.
 

Sokel

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I only need two channels, why do you think I need ten?
The built-in Anthem amps are more than sufficient for the four surround speakers.
Oh,I thought you wanted to change them all,sorry.
Does it have to be monos?
 
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Flavio

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Yes, two mono amps.
 

Mr. Widget

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I'm sure 100 watt amps will give you enough headroom. I don't know if the Anthem is quiet enough on its line outs though.

How do you like the CBT 50s for your surrounds? I have used the CBT 70Js in a few theaters and they work quite well... surprised you also used the add on JE-1s, but I guess if you have the space. Only two monos? Are you using a CBT 70J with the JE-1s as a center or are you going phantom?
 
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Flavio

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No center speaker, I always sit in the middle. :)
I was offered the 70J's as a complete set and they fit nicely wall mounted on the sides of my projection screen.
Because of space and money concerns I chose the 50's for surround and Atmos ceiling duty.
 

kemmler3D

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100W gets you 123dB @ 1m with 2 speakers http://www.hometheaterengineering.com/splcalculator.html ... far too loud for any real listening. 400W gets you 129dB. Far, far too loud.

The battle is pretty much won the minute you hook up a 100dB/w speaker... 110dB is so loud that people start to close their eyes in response, let alone cover their ears... You can probably get away with 50W and be pretty happy.

Since hiss is a problem I'd prioritize high SNR above all and not worry about power. Unless you're trying to get the cops to show up, you're never going to be using much of a 400W or even 100W amp.
 
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Flavio

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So how can I judge potential amp hiss from specs or measurements?

The 100 W amps I am talking about are ICEpower 50AXS2 based (bridged), SINAD 81 dB.
The more expensive option 400 W amps would be the Hattor Audio NC500MP based, SINAD 97 dB.
 
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Bob from Florida

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So how can I judge potential amp hiss from specs or measurements?

The 100 W amps I am talking about are ICEpower 50AXS2 based (bridged), SINAD 81 dB.
The more expensive option 400 W amps would be the Hattor Audio NC500MP based, SINAD 97 dB.
Benchmark ABH2 should solve your hiss issue.
 

sarumbear

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Flavio

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Elitzur–Vaidman

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For speakers as sensitive as yours, the amplifier noise level is more significant than its max power. Something like the Topping LA90 could drive your speakers to 117dB each with absolutely 0 hiss at any volume.
 

Blumlein 88

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Datasheet is linked to here:

According to this datasheet and a bit of calculation, idle noise should be -100 db referenced to 1 watt. SINAD is said to be -86 db at one watt output. So shouldn't be a noise problem. The Benchmark would be quieter.
 
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radix

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There's a calculator "Amplifier power required" where you can enter your desired SPL (e.g. 100 dB) and headroom (e.g. 10 dB, depends on your music), listening distance, speaker sensitivity and it will tell you the required amplifier power.
 
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Flavio

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For speakers as sensitive as yours, the amplifier noise level is more significant than its max power. Something like the Topping LA90 could drive your speakers to 117dB each with absolutely 0 hiss at any volume.
I don't want to spend Topping LA90 money, I want two mono amps and I don't want amps with a power brick.
 

DVDdoug

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No center speaker, I always sit in the middle
Of course it's your choice but the phantom center isn't the same as an actual center speaker. And, that's where most of the movie dialog comes from.
 
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Flavio

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There's a calculator "Amplifier power required" where you can enter your desired SPL (e.g. 100 dB) and headroom (e.g. 10 dB, depends on your music), listening distance, speaker sensitivity and it will tell you the required amplifier power.
With 105 dB at 12 feet, I would have 4 dB headroom with 100W. More than plenty I should think. And that's for one loudspeaker.
 
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Flavio

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Of course it's your choice but the phantom center isn't the same as an actual center speaker. And, that's where most of the movie dialog comes from.
I have used a phantom center for a very long time and if you are in the sweet spot it sounds better than a REAL center IMHO.
Even if you are using the exact same speakers for LCR, you will still hear a difference between them as a result of placement and acoustics.
But this is getting off topic.
 
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