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Old 24th April 2012, 01:09 PM   #4701
dvv is offline dvv  Serbia
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It seems reasonable to me to assume that a driver, sold as capable of accepting 150 WRMS, or (since it's a nominally 8 Ohm driver) 34.6 Vrms. Let us, for the moment, assume that this is indeed so.

Does it then not stand to reason that this driver, if properly implemented, should feel little or no compressions at 20 Vrms, i.e. the point where those small speakers started to go nuts?

My point is this - if we generally think of a nominally 100 WRMS amp as simply a "safe" 50 WRNS amp, since we have to allow for transients and do not want any clipping thank you, why should be think of speakers completely out of that idea?

I agree that giving a loudspeaker in general any truly meaningful power rating is one hell of a fiddly job, but by and large, it should be safe to assume that it can handle about half the rated power without undue distress.

Ultimately, in a home enivornment, we all rarely use large power levels, we are typically well below 5 watts conitnuous, which could become much more in transients, and people erroniously think that a transient requiring say 40 watts to be properly (i.e. as the producer intended it to be) reproduced will sound much louder. This is simply not so, but if done properly, your tympani will maintain its sonic balance as it should, simply using much more power to be able to do so.

No doubt the voice coils will heat up after an hour of higly dynamic music, but let's give some credit to the designers of that driver, these people are neither complete fools, nor professional thieves, and let's assume they do know what they are on about.

In the end, I think much more than is usually assumed falls squarely on the field of the customer; I find that far too many times, they don't really know what they want.
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Old 24th April 2012, 01:37 PM   #4702
a.wayne is offline a.wayne  United States
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After an hr I usually let the amplifier rest ....
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Old 24th April 2012, 01:50 PM   #4703
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by gk7 View Post
From Sound On Sound:
"The final input level of 20V RMS is pretty loud, but it was important to drive the speakers hard in order to reveal any differences without any ambiguity."

Thorsten, do your 300Bs reach 20V RMS (without clipping) ?
One must beware of single numbers in comparison when comparing apples and oranges.

The speakers I used with my 300B Amplifiers where 97dB/1W/1m efficient (and 16 Ohm). So 20V was not required to reach high SPL's hence 20V output capability was not a design requirement. It may be if I was using lower efficiency speakers.

As the Speakers in the Sound On Sound test varied between 86 and 88.8dB/2.83V/1m, we can take a mean of 87dB vs. 97dB or 10dB difference in SPL with level for ease of calculation.

In other words, my 300B Amplifier only needed to produce 6.3V (2.5WW) for the same SPL that 20V in the Sound On Sound test would produce, except the 2.5W in this case are much less likely to cause significant compression compared to 50...100W

Also, you may be surprised by the actual levels such a simple 300B SE Amplifier is capable of. You may wish to peruse the article "Measurements of Amplifier Peak Output Voltages Under Dynamic Conditions and Into a Real Loudspeaker Load" - by Peter van Willenswaard.

Part 1

Part 2

BTW, my current tube amp manage around 18V without gross distortion, my current speakers are around 89...90dB/2.83V/1m and a near resistive 6 Ohm Load.

Ciao T
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Old 24th April 2012, 02:17 PM   #4704
gk7 is offline gk7
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"97dB/1W/1m efficient" quite different from a LS-3/5 you proposed as an "example" no ?.
As always you just use whatever seems to support your position, this makes a discussion somewhat tiresome.
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Old 24th April 2012, 02:58 PM   #4705
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by SY View Post
Perhaps the word "domestic" is unfamiliar? So, any contrary data to share?
It is not unfamiliar, it is merely a weaselword that allows the user to claim anything they like, without the ability to falsify any such claim as there is no definition.

Instead I would propose we apply the only known standard for Home Audio (domestic audio) THX.

This specifies 85dB SPL PER CHANNEL at the listening position for a -18dBFS signal. It implies a maximum SPL at the listening position of 103dB SPL for "domestic levels".

If we consider a common listening distance of 3m it means we require around 110db/1m from each of the Speakers. For a 87dB/2.83V/1m sensitive Speaker (which according to John Atkinson's work represents an "average" sensitivity for HiFi Speakers) this means +23dBW Power input, or 40V or 200W per speaker.

If we use instead a 97dB/2.83V sensitive speaker the same condition is fulfilled using only +13dBW or 12.7V or 20 Watt.

We may now debate how much compression and distortion we wish to allow under these conditions as "low impairment" and this can be a mega meta thread in itself.

However no matter how we look at it, the numbers are not going look good next to any semi-competently designed Amplifier. But what are these numbers?

Soundstage measures at 2m distance, usually at 90, 95 and in extreme cases 100dB, single speaker for compression and distortion, note their distortion plots cut off -45dB, so this is only around 0.5% HD... So my previously noted 110dB SPL would be 104dB SPL in the measurements that Soundstage does

Let's see what we have, shall we?

Dynaudio Focus 110

Nearly no (< 0.5dB) compression at 90dB from 70dB, worsens a bit at 95dB to -2dB but only below around 300Hz, mid/hi unaffected. Distortion is a mixed bad, fairly low from 500Hz-4Khz, rises a lot at either end though. Considering that is is basically a "toy" speaker with a 5.5" Woofer not a bad results.

SoundStage! Measurements - Dynaudio Focus 110 Loudspeakers (12/2006)

Magico V2

A -1dB broadband response variation at bass and treble variation between 70dB and 90dB... Distortion is very low.

SoundStage! Measurements - Magico V2 Loudspeakers (5/2009)

NHT Classic Three

A -1dB broadband response variation at bass and treble variation between 70dB and 90dB, but gets notably worse at 95dB with > -2dB... Distortion is comparably low.

SoundStage! Measurements - NHT Classic Three Loudspeakers (3/2007)

Paradigm Reference Signature S1 v.2

A -1dB broadband response variation between 70dB and 90dB, but gets much worse at 95dB with +1/-3dB... Distortion is comparably low but rises at high and low frequencies.

SoundStage! Measurements - Paradigm Reference Signature S1 v.2 Loudspeakers (12/2007)

Paradigm Studio 60

A -1dB broadband -2dB narrowband frequency response variation between 70dB and 90dB, but only gets a little worse at 95dB... Distortion is bad.

SoundStage! Measurements - Paradigm Reference Studio 60 v.5 Loudspeakers (5/2009)

Revel Concerta F12

This is a low compression Speaker! A <<-1dB frequency response variation between 70dB and 90dB, ~-1dB frequency response variation between 70dB and 95dB, even at 100dB frequency variation to 70dB is only around 2dB... Distortion is reasonably low, excepting a nasty spike at around 3khz, could be acoustically bothersome.

SoundStage! Measurements - Revel Concerta F12 Loudspeakers (3/2006)

Usher Audio Technology Be-718

A <-1dB frequency response variation between 70dB and 90dB, quite broadband with bass and upper mid/treble being turned down, no measurement at 95dB... Distortion is reasonably low.

SoundStage! Measurements - Usher Audio Technology Be-718 "Tiny Dancer" Loudspeakers (10/2007)

Wilson Audio Watt/Puppy 8

A <-1dB frequency response variation between 70dB and 90dB, but looses it to ~-2dB frequency response variation between 70dB and 95dB, saving grace is that this is quite narrowband around 5KHz... Distortion is reasonably low.

SoundStage! Measurements - Wilson Audio Specialties WATT/Puppy 8 Loudspeakers (3/2007)

YG-Acoustics Anat

A +/-1dB frequency response variation between 70dB and 90dB, +1/-2dB frequency response variation between 70dB and 95dB... The less said about distortion the better.

SoundStage! Measurements - YG Acoustics Anat Reference Main Module Loudspeakers (4/2007)

QED

Ciao T
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Old 24th April 2012, 03:11 PM   #4706
SY is offline SY  United States
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OK, so how are those data related to thermal compression? Do you have any data contradicting Howard's that thermal compression is of any concern?
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Old 24th April 2012, 03:11 PM   #4707
gk7 is offline gk7
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"maximum SPL at the listening position of 103dB SPL for "domestic levels".

If we consider a common listening distance of 3m it means we require around 110db/1m from each of the Speakers. "

How did you calculate that ? Would this not depend on the room size ? Or are you listenining in free space ?
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Old 24th April 2012, 03:18 PM   #4708
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Thermal compression is real and my worry is more that it wacks passive xovers out of alignment. Good reason to filter actively.
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Old 24th April 2012, 03:19 PM   #4709
gk7 is offline gk7
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Quote:
Originally Posted by ThorstenL View Post

QED
Yes really ? From your post #2998581: "Three to four dB thermal compression is nothing unusual ..."
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Old 24th April 2012, 03:23 PM   #4710
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by gk7 View Post
"97dB/1W/1m efficient" quite different from a LS-3/5 you proposed as an "example" no ?.
As always you just use whatever seems to support your position, this makes a discussion somewhat tiresome.
Anyone who would use an LS-3/5 with a 300B SE Amp would be in a very questionable position indeed.

What I am giving are data-points, not what supports any "position".

Lets look:

System 1 - 300B-SE 6W & Tannoy Monitor Red - 10W/108dB/1m sans Compressison

System 2 - 50W (20V) & 87dB "Monitor" - 50W/104dB/1m sans Compressison

System 3 - 100W (30V) & LS-3/5 - 100W/103dB/1m sans Compression

If compression is approximately linear to applied power we can see which system will be subject to more compression...

We know that the "Monitors" had between around 2 - 5dB Compression, as the SE Amp High Efficiency Speaker system operates at 1/10 of the power of the Monitor (and is actually blessed with a much larger voice coil and most of the Monitors) it is safe to consider that thermal compression will not be measureable at SPL's below 100dB.

The same cannot be said about the smaller systems.

Incidentally, I also happen to have distortion measurements for the TMR 15", this driver that went out of production in 1967. It is below -46dB (0.5%) in the midrange at 100dB/1m (that is 1 Watt power input) and stays below 1% all across the band.

In fact, as the distortion is H2 dominant it can be lowered considerably by using an amplifier with appx. 1% HD at 1 Watt H2 dominant with the correct phasing of distortion components. Usable bandwidth in my system was < 30Hz-18KHz.

So, using 1930's Amplifier Technology and 1940's Speaker technology we can easily make a system that is low compression, low distortion and wide bandwidth, something that seems to present considerable problem to 21st Century technology.

Amusing, innit?

Ciao T
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