SHL5 with Mcintosh C220 & MC452 (450w available power)

[jtc_1968]

Hi to all HUG members. This is my first post here, I'm interested on these SHL5 for my 2nd set of speakers. I'm using a 450watts amplifier for my MG1.7's, and as of now, i have no plans of buying another amp.

would there be a problem if i use a 450watts amp on SHL5? my concern is it might damage the speakers .... your thoughts are highly appreciated.

Harbeth+Mcintosh user's please share your experience.

thanks!

jim

[jplaurel]

Jim-

There is no problem using your MC452 with your Harbeths. Just keep the volume to a reasonable level.

[Thanos]

I'm using an MA6500 integrated to drive them. The issue here is the Mac sound, which I love together with the built quality & looks. All you have is to play lower than most amps do, due to the very big power of your amp. But it will pay you back with the excellent bass control and the headroom. You couldn't go better with this superb marriage, Good old American power and pure classical British speakers... All time classic! And this is a point where all experienced HiFi lovers agree...

[thurston]

I thought that technically every amp will put the very same amount of watts into the speaker when driven at the same level.

As 30 watts (in may case) are enought to drive the SHL5 to deafening levels I guess you are unlikely to come to the point that your Mac will send much more than 30 (maybe 40) watts to the speaker. Which means there are about 420 watts that will simply never be used.

{Moderator's comment: again, we have covered this before here (where?). The speaker DRAWS power from the amplifier. The amp DOES NOT force power into the speaker. It is vital you appreciate the correct sequence of events. What defines how much power is actually being drawn from the amp (for any given speaker) is the music waveform and the setting of the volume control, under under's command. So, even if the amp can in the lab produce a million watts, if the user only commands a certain volume level such that the speaker is drawing a few watts, the remaining power is just not being drawn from the amp. So it is useless to have it available. Is this completely understood?}

[A. E.]

I thought that technically every amp will put the very same amount of watts into the speaker when driven at the same level.

As 30 watts (in may case) are enought to drive the SHL5 to deafening levels I guess you are unlikely to come to the point that your Mac will send much more than 30 (maybe 40) watts to the speaker. Which means there are about 420 watts that will simply never be used.

{Moderator's comment: again, we have covered this before here (where?). The speaker DRAWS power from the amplifier. The amp DOES NOT force power into the speaker. It is vital you appreciate the correct sequence of events. What defines how much power is actually being drawn from the amp (for any given speaker) is the music waveform and the setting of the volume control, under under's command. So, even if the amp can in the lab produce a million watts, if the user only commands a certain volume level such that the speaker is drawing a few watts, the remaining power is just not being drawn from the amp. So it is useless to have it available. Is this completely understood?}

no doubt… it is useless to have it available if it just helps to warm the room :-)

What happens in audiophilic terms, when an amplifier (high powered) is set to lower volume level and the other’s (low powered) volume level is up relatively, to get the same sound pressure level? forward sound ? larger soundstage? less dynamics? smaller images?

{Moderator's comment: why on earth would any of those subjective judgements alter just because the amp had more *reserve* power even though you just couldn't ever actually deliver that power to the poor little speakers? No correlation whatsoever. Why should there be?}

[A. E.]

no doubt… it is useless to have it available if it just helps to warm the room :-)

What happens in audiophilic terms, when an amplifier (high powered) is set to lower volume level and the other’s (low powered) volume level is up relatively, to get the same sound pressure level? forward sound ? larger soundstage? less dynamics? smaller images?

{Moderator's comment: why on earth would any of those subjective judgements alter just because the amp had more *reserve* power even though you just couldn't ever actually deliver that power to the poor little speakers? No correlation whatsoever. Why should there be?}

There could be... not because of the amp had more *reserve* power, but because of different levels of volume... Setting the volume level down (and up for the weaker amplifier) -keeping the SPL equal- may alter something in sound quality.

Anybody can hear it?

[A.S.]

There could be... not because of the amp had more *reserve* power, but because of different levels of volume...

With respect, you are nullifying your own argument.

For a given, fixed loudspeaker with a given, fixed, certain sensitivity (i.e. loudness out for power in) at a given replay loudness in the listening room (i.e. a known spl) there will be a certain current drawn from the amp. That current will be sucked by the speaker from the amp as the speaker traces the music signal. It will not be pushed by the amp into the speaker: it will only be pulled by the speaker from the amp. If you unplug the speaker there will be zero current flowing out of the amp so it would be immaterial whether the now disconnected amp was rated at 1W or 1000000W: no current would be flowing regardless of how much you turn up the volume control.

If all you need to get a certain speaker playing at a certain loudness with a certain music in a certain room is 10W, if the amp is rated at 450W, then 450-10W= 440W is not being drawn and is power potentially but not actually usable by those speakers. It would seem rather daft to pay for such a huge unusable power reserve with the elevated risk that component failure or misuse could destroy your speakers in a flash.

As for sonic perception of 'quality' yes, of course this is directly related to loudness. But that applies equally to turning the volume up and down on an amp rated at 10W or 450W. And as there is absolutely no standardisation as to what actual listening loudness (say) 11 o'clock volume on amp A produces compared to 11 o'clock setting on amplifier B (i.e the gain of the amp from the input to output terminals), those who have constructed careful A-B amp tests where the loudness is measured with a microphone at the listening seat and not guessed, usually report that the subjective differences between amplifiers regardless of power rating almost or actually vanish.

If you are going to test drive an Aston Martin and a Ford run-around, logically you should test them at exactly the same road speed. Testing amplifiers (or speakers for that matter) without knowing how loud they are is like covering-up the speedometer and then test driving two cars: a useless comparison likely to result in erroneous and expensive conclusions.

[BAS-H]

There is one point that hasn't been mentioned in this discussion. I agree that, in principle, if 10 Watts are required for the desired SPL, any more available Watts are wasted. However, putting this principle into practice, a fatal assumption is being made.

You're assuming your amplifier has a linear response from zero to ten Watts. Many don't: proportionate rise in SPL with increasing input level often peters out at the upper end of an amp's power capability. This is a form of level-dependent distortion. In these cases, it is beneficial to have an amp with an unused reserve of power.

In my very limited experience, I have found this to be particularly problematic with low power, single-ended class A amplifiers. (I imagine the reason to be that the upper half of the output waveform may not be an exact mirror of the lower half, due to this non linearity towards the upper end of power output. If I had access to an oscilloscope, I would expect the upper half to be visually shorter).

[Pluto]

A lot of the foregoing discussion has been complicated, possibly, by a confusion between the concepts of amplifier sensitivity and gain.

The two terms are kind of synonymous, with the latter being somewhat less ambiguous in its meaning, but the hi-fi industry tends to prefer the former, which tends to need rather more qualification to remove ambiguity.

Let's assume that we are dealing with a power amp without a volume control. It will have a particular amount of gain - let's say, 30dB. This means that any voltage present at the input will appear at the output 30dB greater, up to the point at which the amplifier can drive no further. It is this point that, more or less, defines the amplifier's maximum output and maximum input, which will be a voltage 30dB less than the output clipping point. The key is that the input and output are tied together with 30dB of difference, always.

The problem with the definition of sensitivity is "what is the relationship between input and output?" If I'm told that the sensitivity is 500mV, is that RMS or peak or even peak to peak? Is that to achieve full output or, say, 50W output or 1% distortion? It is unlikely that you truly know how much voltage and current are required to drive your speaker to a given loudness and even less likely that you can relate this to power (Watts) as the relationship is a complex one (in the mathematical sense).

Introduce a volume control into the mix. Does the sensitivity or gain relate to the volume control flat out, or what? A useful "standard" sometimes used is where a volume control is 180° off minimum, it ought to be 10dB below maximum. In reading the specification of an amplifier, you need to know the reference points - a minimalist specification is not really worth the paper on which it is printed.

[BAS-H]

The key is that the input and output are tied together with 30dB of difference, always.

Only within the amp's linear range. This may or may not cover the whole range from zero to clipping, depending on the design.

{Moderator's comment: maybe this needs to be explained. Can we assume that all readers understand what 'clipping' is and how it is inevitable?

[Pluto]

This may or may not cover the whole range from zero to clipping, depending on the design.

I assume you are referring to the potential non-linearities of a tube amplifier at or near the top of its output??

I think it's safe to assume, for the sake of argument, that a well made solid state amplifier will be linear up to clipping at which point all bets are off.

I have a (slightly) interesting theory about the nature of some valve amplifier designs relating to this, which possibly explains part of the attraction of such designs:

It is well understood that tube amplifiers exhibit soft clipping compared to the catastrophic clipping of most solid state designs. But many tube amplifiers become slightly non-linear remarkably early. This too is widely acknowledged and understood but its significance is not. Once you start driving into an amplifier's non-linear region you reduce the dynamic range of the signal - in other words, loud elements in the signal increase less with rising amplitude than quiet elements that remain entirely within the truly linear region. This effect is exploited, to good effect, in classic tube-driven compressors such as the Fairchild.

So what we have with some tube amplifiers is a mild compressor which causes the low level content to be proportionately higher in the "mix" than was intended hence, "more revealing of detail".