Class A 30 Watt Amps: Are they enough to drive my book shelfs?

@kijanki

Hi Kijanki,

Two speakers vs. one will add 3 db, but both speakers will have the same distance-related loss, so as I indicated the second speaker will not compensate for the distance-related loss. It will just make the sound 3 db louder at any given distance.

If 2.83 volts is applied to one speaker rated at 90 db/2.83 volts/1 meter, neglecting room gain the SPL at 3 meters will be 90 db minus 9.54 db.

If 2.83 volts is applied to two of the same speakers, neglecting room gain the SPL at 3 meters will be 93 db minus 9.54 db.

In the second case the SPL at 3 meters will be 3 db louder than in the first case. But the distance-related loss in both cases is 9.54 db. Room gain will compensate for around 3 db of that loss, resulting in a loss of about 6.54 db in both cases. The 6.54 db subtracts from 90 db in the first case, and subtracts from 93 db in the second case.  While the Benchmark statement implies that 0 db should be subtracted from 90 db in the first case, and 0 db should be subtracted from 93 db in the second case.

Best regards,
-- Al

@almarg 
Yes, loss will be 6.54dB, but from rated sensitivity of one speaker it will be only 3.54dB.  For 2m listening distance, that they likely assumed as an average, there will be no error.  Sound level at listening position will be the same as rated sensitivity.

In case on hand each speaker sensitivity is 86dB. Two of them playing at the same time add +3dB, room adds +3dB and distance of 2m causes 6dB drop resulting in 86dB sound level at listening position when 2.83V is applied to both speakers.  Am I missing something?

@kijanki

OK. I see what you are saying. What it comes down to is that we have been interpreting the Benchmark statement differently. And both interpretations are reasonable, IMO, as long as each interpretation is properly understood and applied.

You are interpreting their statement such that:

In case on hand each speaker sensitivity is 86dB. Two of them playing at the same time add +3dB, room adds +3dB and distance of 2m causes 6dB drop resulting in 86dB sound level at listening position when 2.83V is applied to both speakers.

I agree with this statement, but I have been interpreting Benchmark’s statement differently, with my interpretation having been indicated at the end of my previous post. As I say, though, I think neither interpretation of Benchmark’s statement (yours and mine) is unreasonable.

In any event, though, the 101.7 db and 107.7 db numbers I originally stated in my response to the OP do in fact reflect the presence of two speakers.

Best regards,
-- Al

If you have to ask, you dont have enough!

In my own personal experience, "enough" never does the trick with amps. Having the most quality power has always given me the most satisfaction - maybe it's the extra ability of the amp, extra headroom...or maybe it's all just in my head.