Preamp Output Question

deronb1

When setting speaker levels, is that, in a sense, increasing the output voltage to the amp? The reason I am asking is that my new speakers are 4 ohm and 86db. I have to increase volume to get same spl as previous set up. Was thinking that maxing out speaker levels might lesson strain on the amp, reducing distortion a bit. Am I correct in this thinking?

msg

What were the previous speakers and specs? Which preamp?

I think this may have to do with gain?
Going to follow along, good question, and I don't know the answer either, though have wondered what effect boosting speaker levels has on sound quality. I have only ever used this in HT systems.

deronb1

Yeah, that's probably correct, an internal gain as opposed to a mv output change

msg

I'm just parroting something I read here once in passing. I think it was Skip talking about the difference. I don't understand what's going on in the system when we bump speaker levels or tone controls.

mhardy6647

There are (or may be) multiple gain stages from source to loudspeaker, and they're frequently independently adjustable. There is probably an optimal setting (balance, so to speak) of preamp output (i.e., preamp gain setting) and power amp input attenuation that will optimize signal to noise ratio and dynamic range... and I know much has been written on the topic. It's not one of my shibboleths, so I don't have much else to offer.

One other comment, which might be completely irrelevant in the context of this thread. In traditional two-channel stereo hifi, the volume control setting isn't calibrated per se, and is somewhat arbitrary depending on the (maximum) resistance and the 'taper' of the volume control potentiometer (assuming it is a "pot"*) and the output level of the source (or whatever components are upstream of the 'volume control').

Oh... and... virtually always, a volume control is an attenuator -- it reduces the signal level (voltage) being supplied to the next stage.

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* Although the rate of attenuation (taper) of an autoformer or transformer volume control are also, practically speaking, often arbitrary, too. In home theater, the attenuators tend to be calibrated in dB relative to some reference.

deronb1

Good read Dr. Mark. I guess I'm just confused on the difference between the rated output of the outputs, if you will, and gain.

mhardy6647

Well, looking at your OP I realize I kind of mis-aimed my 'answer'.
So... I guess the question is, what did you have before your new "4 ohms at 86 dB" loudspeakers?

Even without that information, there are a couple of 'flags'.

1) First is the nature of the spec you quote: 86 dB at 4 ohms per... what? ... per watt, or per 2.83 AC volts (VAC)? If it is at 1 meter per 2.83 volts AC, that's two watts into 4 ohms (or 1 watt into 8 ohms). The difference is... 3 dB. In other words, if it's 86 dB @ 1 meter per 2.83 VAC, that's equivalent to 83 dB @ 1 meter per watt (at 4 ohms).

2) what does the impedance curve look like? It's almost certainly not ruler-flat at 4 ohms, and the frequency response may not be ruler-flat, either -- the net result of that is that the perceived loudness could vary greatly relative to one's expectation for "86 dB and 4 ohms".

Hope this is helpful, or, at least, interesting

deronb1

Its 86db at whatever the industry standard is. No idea what the impedance curve is but yes, im sure it varies. I was running 6 ohm speakers that had a 91db rating before.

txcoastal1

Long story short Dyns like power

My Pass XA35...35watts class A 180watts A/B bottomed out at at 85db listening levels with my Dyn C1’s

mhardy6647

deronb1 wrote: »

Its 86db at whatever the industry standard is. No idea what the impedance curve is but yes, im sure it varies. I was running 6 ohm speakers that had a 91db rating before.

That's the problem, there are two industry standards for input signal (i.e., drive) -- either 2.83V (or) 1 watt. Doesn't matter at exactly 8 ohms (under which condition 2.83 V corresponds to one watt); matters at any other impedance (actual or nominal).

Your new loudspeakers are probably considerably less sensitive than your old ones (not just 5 dB, but perhaps nearly 7 dB, depending on the reference conditions for the two loudspeakers' sensitivity ratings) -- and (again, depending on their impedance curves) perhaps also much more demanding on top of the sensitivity difference.

So, what does 7 dB mean? Well 5 watts is 7 dB more than 1 watt.

All of which means, you may have to turn the volume control higher to get the same perceived "volume" -- and it may sound better, worse, or the same, than it did with the same amp and the old speakers.

deronb1

mhardy6647 wrote: »

deronb1 wrote: »

Its 86db at whatever the industry standard is. No idea what the impedance curve is but yes, im sure it varies. I was running 6 ohm speakers that had a 91db rating before.

That's the problem, there are two industry standards for input signal (i.e., drive) -- either 2.83V (or) 1 watt. Doesn't matter at exactly 8 ohms (under which condition 2.83 V corresponds to one watt); matters at any other impedance (actual or nominal).

Your new loudspeakers are considerably less sensitive than your old ones, and (again, depending on their impedance curve) perhaps also much more demanding.

Well, further down the rabbit hole I go. Im thinking a 200 wpc high current amp at 8 ohms is going to be necessary.

deronb1

I have to go to about -25db to get to where I am used to watching movies. Not a big deal I guess.

mhardy6647

deronb1 wrote: »

I have to go to about -25db to get to where I am used to watching movies. Not a big deal I guess.

As opposed to what level before?

Yeah, it is not a big deal at all if it sounds good and if the amplifier isn't roastin' under any added stress.

The thing to remember about the decibel (dB) -- always, always, always it's a relative measurement.

mhardy6647

So, are these the speakers in question (just saw it in another thread)?



so, yes, that sensitivity is relative to 2.83 V or 2 watts into 4 ohms -- 83 dB SPL @ 1 meter per 1 watt.

Depending on how low the impedance dips and at what frequency, that could be a darned hard to satisfy loudspeaker (e.g., if it dips to 2 or 3 ohms at 200 Hz, which it might well).

deronb1

That is it! I swapped back in my Yamaha and re-ran YPAO. Made a big difference. Powering with a BK av5000ii. 185 wpc @ 4 ohms. I think it will be fine for HT, but for 2 ch, might need a bit more umph.