Speakers cut out briefly at high volume

[admin_exported]

I'm using a Cambridge Audio Azur 340SE Amp with Q Acoustics 2010 speakers, and if i turn up the volume to high the speakers tend to cut out briefly (for about half a second) and resume normal function when i turn down the volume again. I posted about this a year back and the general consensus was that I was putting too much strain on the amp and it was cutting out to protect against damage. The solution suggested was to get an amp that was capable of driving my kit. This made sense as the 'Max power handling' of the Q2010 is listed as 75 watts, and my amp's tech specs list its power output as 45 watts.

However, my flat mate has just brought a pair of B&W P6 Floor speakers - These are much larger, have a higher impedience (8Ohm as opposed to the 6Ohms of the Q2010), and their power handling is between 30-150 watts. Regardless of what i assume would place a far larger strain on the amp, when we tried the amp with those speakers, i could turn it up far louder without the music breaking out, way beyond the level i can with Q2010's. Could anyone suggest why this is the case, and perhaps explain what's going on (i don't understand what impedimence is/how it effects your set up.)

I'm thinking of upgrading to some larger floorstanders, but at the moment i don't know if that means having to buy a new amp or speakers. Hopefully you guys are able to elucidate.

Thanks.

 

[John Duncan]

Forget the power handling figures, they're usually a bit of a misnomer.

An 8ohm speaker is 'easier' to drive than a 6ohm one, because the lower the impedance, the higher the current. So (simplifying wildly) at the same volume setting on the amp, more current will be pumped out into a 6ohm speaker than an 8ohm one, therefore the amp will run out of puff earlier.

 

[Overdose]

There is also the speaker sensitivity issue, although I don't know what the figures are for each of the speakers mentioned.

In basic terms, the sensitivity of a speaker, determines how loud it will sound when fed a certain amount of power.

Whatever, it's not good to be regularly pushing your amp to it's limit in this fashion, it won't end well for your amp. It could even damage your speakers when clipping occurs.

 

[dannycanham]

Something to do with impedance matching between the amplifier output and speaker. Impedance isn’t constant with speakers but they are given a nominal value (8 or 4 ohms). The lower the actual running value varies and drops the harder the speaker becomes to drive.

Or something like that. Never my strong point.

You also have speaker sensitivity. Usually given in db. The higher the value the louder the speaker for the same power.

So usually with more budget intergateds its a good idea to go for high impedance, high sensitivity speakers.

 

[dannycanham]

B&W P6

Sensitivity:

90dB spl

Nominal Impedance:
8 ohms (minimum 3.5 ohms)

Q 2010

Sensitivity:

86dB spl

Nominal Impedance:
6 ohms (minimum 4 ohms)

 

[John Duncan]

I didn't bring up sensitivity just so I could 'simplify wildly', but the P6s were 90db and the 2010s are 86db, so the P6s will be more than twice as loud than the 2010s at the same volume setting (3db = double the volume), and will use less juice from the amp while doing so...

 

[John Duncan]

(jinx@dannycanham)

 

[dannycanham]

At least it looks like we all agree.

 

[Andrew Everard]

(3db = double the volume)

Surely a 3dB increase requires twice as much power from the amp, or in this case 3dB greater sensitivity means half as much power is required for the same level, but to get double the volume you need to achieve a 10dB increase in level, requiring about more than eight times as much power (doubling of power for each 3dB gain)?

 

[John Duncan]

Dunno. But then i'm not an engineer.

 

[eggontoast]

10 Watts into 8Ohms = 8.944Vrms = 19.03dBV

20 Watts into 8Ohms = 12.65Vrms = 22.04dBV

100 Watts into 8Ohms = 28.28Vrms = 29.03dBV

 

[John Duncan]

OK, I'm officially confused by dB, SPL and 'perceived' volume now. I still contend that a 90dB sensitivity speaker will be 'some' louder than an 86dB sensitivity one with the same amp set to the same volume. But there's clearly only one way to sort this out...