How many watts?

[Filterlab]

As I’m sitting here reading more and more about the Aleph 5 amplifier (60wpc) - an amp which I’m seriously considering, I wonder how many watts do I really use?

My power amp has ludicrous amounts of power; 250wpc into 8Ω and 500wpc into 4Ω. Given that my speakers are 95dB/W/m and that my active sub has an input impedance so high it barely presents a load, I’m sure I never even tickle the surface of the available oomph.

I rarely listen at high volumes, mostly I listen at low to moderate volumes.

So, my question is, how would one actually find out how many watts are being ‘used’ during listening? Is there a device one can connect to the speaker terminals to monitor such a thing?

[Mand]

Been thinking about this as well. Get a decibel app for your phone.
If the speakers are rated at 88db per 1watt at 1m sensitivty and the app shows 88 db, then does that mean you’re using 1 watt?

[Filterlab]

I guess it would. I never even thought about doing that way. I was thinking of a method to measure AC RMS voltage.

I suppose that once set up as a reference, one could see how much one watt was actually doing.

[Barry]

How far away from your speakers do you listen?

If you listen 2 metres away then you reduce the speaker sensitivity by 6dB, thus 89dB/W.

Orchestral peaks can be as high as 120dB, so you would need 120 - 89 = 31dBW. Call it 30dBW, or 1,000W. But since you have two speakers, a 500W/channel amplifier would suffice. But as you say, for the great majority of the time the average power called upon is less than 0.5W, so you only need the high power reserve for volume peaks of very short duration.

If you assume a typical speaker impedance of 8 Ohm, 0dBW (= 1W) corresponds to a r.m.s voltage of 2.83V. Thus an amplifier producing 20dBW (or 100W) will present a voltage of 28.3V across the speaker terminals.

[Macca]

For a pair of speakers you get an extra 3dB

For watts it is always better to have too many rather than too few.

[Filterlab]

I’ve got ya. The speakers are 3m from my listening position so if the first equation is linear then that would be 83dB/W.

I don’t really listen to orchestral music and the source is only digital. Most of the time it’s sound from Netflix and Prime (so not dynamic at all), my girlfriend listens to YouTube music during the day (mostly electronic, if not entirely), and my listening is mostly electronic but also acoustic and prog or similar. Redbook maximum dynamic range with dithering (which I have enabled on Fidelia) is 115dB (IIRC) so would be 115 - 86 (including the 3dB for the pair) = 29dB/W.

The Aleph 5 is rated at 60wpc into 8Ω and has a maximum output of 30v at 8a. I’d imagine this would be ample for my needs given the lack of dynamic peaks in the choice of audio and the relatively moderate volumes?

[Macca]

Yes should give you plenty of headroom assuming the speaker sensitivity rating is correct, usually you can deduct a couple of dB from what the manufacture claims. Even so you'd still be good.

Don't really understand why you want to swap to the Arcam though?

[Barry]

Sound pressure level (SPL) falls off as the inverse square of the distance. So compared with that at 1m (as quoted in your speaker sensitivity of 95dB/W), listening at double that distance of 2m will reduce the SPL by a factor of 4, or 6dB, to 89dB/W. Thus trebling the distance to 3m will reduce the SPL by a factor of 9, or 14dB, to 81dB/W.

Your amp can produce 60W/channel (or 17.8dBW), so the maximum SPL from each speaker will be 81 +17.8 = 98.8dB, and since there are two speakers an SPL of 101.8dB in total.

102dB (above the threshold of hearing) is classed as very loud (https://audiology-web.s3.amazonaws.c...5.32730330.pdf) and if maintained at that level (assuming the amplifier doesn't overheat) would cause some hearing loss after about 10 minutes.

Or to put it another way - you have plenty of power for your needs, provided you don't listen to continuous sine waves at a high level for long periods of time.

[Light Dependant Resistor]

As I’m sitting here reading more and more about the Aleph 5 amplifier (60wpc) - an amp which I’m seriously considering, I wonder how many watts do I really use?

My power amp has ludicrous amounts of power; 250wpc into 8Ω and 500wpc into 4Ω. Given that my speakers are 95dB/W/m and that my active sub has an input impedance so high it barely presents a load, I’m sure I never even tickle the surface of the available oomph.

I rarely listen at high volumes, mostly I listen at low to moderate volumes.

So, my question is, how would one actually find out how many watts are being ‘used’ during listening? Is there a device one can connect to the speaker terminals to monitor such a thing?

Unlike the majority of amplifier manufacturers Pass, does not appear to state the input sensitivity - Volts or fractions of a Volt RMS that allows full output from the amplifier from a input signal, making it very difficult to reliably assess the 60 watt output figure, relative to a input signal.... one is just left to guess I suppose ?

[Filterlab]

Don't really understand why you want to swap to the Arcam though?

Aleph 5, not Alpha 5. The Aleph 5 is a Nelson Pass design. If I wanted an Arcam I'd get my A85 out of the office.

Or to put it another way - you have plenty of power for your needs, provided you don't listen to continuous sine waves at high level for long periods of time.

Thanks Barry, that was my feeling too.