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

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Flavio

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Flavio

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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.
Would you care to explain the calculation?
 

mhardy6647

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I will opine, based strictly on empiricism, that the quality of the power trumps the quantity with such loudspeakers (especially).
 
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Flavio

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I will opine, based strictly on empiricism, that the quality of the power trumps the quantity with such loudspeakers (especially).
I think this is pretty clear to me now, but the question is what would be the minimum quality I should look for to avoid audible noise and hiss?
 

restorer-john

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This is another example where the residual noise is the key number. work back from the full rated power S/N number to obtain your residual noise on uV.
 

sarumbear

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With the supplied wall mounts. You can swivel and tilt them.
I had them too but I was using them upside down positioned on custom stands so that the curve was pointing up. I only had the tops, I couldn’t imagine how much tilt was going to be possible with the bass unit attached, and how far up the speakers will be mounted.
 

mhardy6647

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I think this is pretty clear to me now, but the question is what would be the minimum quality I should look for to avoid audible noise and hiss?
I'd encourage you to think more about the quantitative performance of the amplifier at power output levels below 100 mW (realistically, in the range of ca.10 to 100 mW), rather than just worry about S/N per se.

I can tell you what kind of amplification I use, quite happily, with loudspeakers of 104 dB/watt @ 1 meter sensitivity, but I'd have to also tell you that it wouldn't (and doesn't) meet ASR approval in any way, shape or form. :)
 
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Flavio

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I had them too but I was using them upside down positioned on custom stands so that the curve was pointing up. I only had the tops, I couldn’t imagine how much tilt was going to be possible with the bass unit attached, and how far up the speakers will be mounted.
I have the center of the lower unit at about three feet from the ground.
 

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Flavio

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This is another example where the residual noise is the key number. work back from the full rated power S/N number to obtain your residual noise on uV.
If only I knew how to do this....

For mono amps and to stay within my budget I can choose between used Hypex NC400, used NC500, new NC250MP or new NC500MP and among others used ICEpower 50AXS2 based amps.
 
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Chrispy

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Thx. With two speakers and 100 W the SPL is 117.7 dB. I don't think my neighbours will tolerate that for long. And this does not even take into account my four subwoofers.
Let alone your ears. Curious, why the mono amps?
 
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Flavio

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Let alone your ears. Curious, why the mono amps?
Because I like them and they fit my physical setup better. I use the 70 Hz high pass output of the Sunfire subs for the JBL's and with the mono amps close to the Sunfire subs the cabling is much neater.
 

kemmler3D

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

The 100W amps I am talking about are ICEpower 50AXS2 based (bridged).
The more expensive option would be Hattor Audio NC500MP based.

You will want to look at SINAD but mostly SNR (signal-to-noise ratio).

Topping PA5 has really good SNR for the money (under $400)

The hypex amps are your next best option for the money, although they are pretty overpowered for your use.

what would be the minimum quality I should look for to avoid audible noise and hiss?

I'd say realistically anything in the high 80s, low 90s SNR at low power should be good. Once you are in the 100s, there's a good chance you will never hear any noise at all under any circumstances.
 
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Flavio

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You will want to look at SINAD but mostly SNR (signal-to-noise ratio).

Topping PA5 has really good SNR for the money (under $400)

The hypex amps are your next best option for the money, although they are pretty overpowered for your use.



I'd say realistically anything in the high 80s, low 90s SNR at low power should be good. Once you are in the 100s, there's a good chance you will never hear any noise at all under any circumstances.
Topping PA5 can't be bridged and has a power brick which I don't want.
 

kemmler3D

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Topping PA5 can't be bridged and has a power brick which I don't want.
If you definitely want monoblocks and you want low noise, then I would try to find the lowest-power NCORE you can find. I run some Nord NC500 monoblocks and like them, but my speakers are only maybe 86dB/W... got them on Craigslist for $600 total.
 
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Flavio

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What is the relation between the output noise value and amp hiss?
I have found these maximum values (all in uV):

NC500 - 10
NC400 - 25
NC500MP - 40
NC250MP - 30
50AXS2 BTL - 70
MA5332MS BTL - 350 (this is in my noisy Sabaj A20a 2022)
 
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Blumlein 88

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What is the relation between the output noise value and amp hiss?
I have found these maximum values (all in uV):

NC500 - 10
NC400 - 25
NC500MP - 40
NC250MP - 30
50AXS2 - 70
In relative terms half the voltage is a 6 db difference. 17 db between the highest and lowest on your list. What that means for hiss you'll hear is a bit more complicated. The simple calc I did assumed 20 uV and a 4 ohm speaker, putting that at -100db approximately referenced to 1 watt (-103 db for 8 ohm speaker). So should be about 0 db SPL. Since you have room noise it would have to be somewhat higher to hear it at worst. This is because 1 watt would presumably produce 100 db at 1 meter in your case. So 100 db spl (at one watt) minus 100 db equal 0 db spl.
 
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Flavio

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In relative terms half the voltage is a 6 db difference. 17 db between the highest and lowest on your list. What that means for hiss you'll hear is a bit more complicated. The simple calc I did assumed 20 uV and a 4 ohm speaker, putting that at -100db approximately referenced to 1 watt (-103 db for 8 ohm speaker). So should be about 0 db SPL. Since you have room noise it would have to be somewhat higher to hear it at worst. This is because 1 watt would presumably produce 100 db at 1 meter in your case. So 100 db spl (at one watt) minus 100 db equal 0 db spl.
How do you calculate from 20uV and 4 Ohm to - 100 dB?

Never mind, I already figured it out.
 
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Elitzur–Vaidman

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What is the relation between the output noise value and amp hiss?
I have found these maximum values (all in uV):

NC500 - 10
NC400 - 25
NC500MP - 40
NC250MP - 30
50AXS2 BTL - 70
MA5332MS BTL - 350 (this is in my noisy Sabaj A20a 2022)
If you switch to the NC250MP your hiss will be ~20dB quieter than your Sabaj A20a. Hiss is just amplified noise
 

fpitas

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I'd encourage you to think more about the quantitative performance of the amplifier at power output levels below 100 mW (realistically, in the range of ca.10 to 100 mW), rather than just worry about S/N per se.

I can tell you what kind of amplification I use, quite happily, with loudspeakers of 104 dB/watt @ 1 meter sensitivity, but I'd have to also tell you that it wouldn't (and doesn't) meet ASR approval in any way, shape or form. :)
Right? I'm a pariah too, even though my horn amp has 0.008% THD. Not good enough around here!
 

sarumbear

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I have the center of the lower unit at about three feet from the ground.
According to @amirm's measurements there is a very narrow vertical listening window. It is expected to affect people at different heights or at different seating, upright or laying back. How is it in your experience?

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