Loudspeaker compression (why a 200+ WPC amp doesn't help KHorns)

[stereohermit]

I do have another catalog...

[stereohermit]

KP600 glossy

[stereohermit]

The front of the Theatre Catalog

[stereohermit]

140 db, not bad for the size!

msl-4_ds.pdf

[Don Richard]

In The Dope From Hope, Vol.16 No.1, Jan. 1977 D.B. Keele gave the absolute max SPL for the Khorn, LaScala, and Belle as 122.7 dB with 375 watts input.

This rating is higher than what he called the "TOO DAMN LOUD LEVEL"

Note that these are average levels in the reverberant field of a 3000 cu. ft. room, with peaks 10 dB higher.

Do not try this at home, children, as hearing damage will ensue.

[stereohermit]

One metere on axis would be approx129.5, so that figures out just 'bout right!

[twistedcrankcammer]

I do have another catalog...

The K-1132 was used in both the KP-450 and the KP-600. My KP-600 stacks have the earlier pair of KP-60s attached to the manifolds, but I would like to upgrade to the KP-1132s My KP-600s are the A version with the Flyware though. []

Roger

[twistedcrankcammer]

In The Dope From Hope, Vol.16 No.1, Jan. 1977 D.B. Keele gave the absolute max SPL for the Khorn, LaScala, and Belle as 122.7 dB with 375 watts input.

This rating is higher than what he called the "TOO *** LOUD LEVEL"

Note that these are average levels in the reverberant field of a 3000 cu. ft. room, with peaks 10 dB higher.

Do not try this at home, children, as hearing damage will ensue.

Don,

I have four Nakamichi PA-7 stereo amplifiers to push the seve TSCMs at 200 watt RMS per channel after I find two more TSCM tops to buy, does this qualify a too **** LOUD?

Roger

[twistedcrankcammer]

140 db, not bad for the size!

That sure puts out the dB, but god is it ugly!!

Roger

[Don Richard]

Don,

I have four Nakamichi PA-7 stereo amplifiers to push the seve TSCMs at 200 watt RMS per channel after I find two more TSCM tops to buy, does this qualify a too **** LOUD?

Roger

I dunno. Open the windows and turn 'em up. If I can hear them from here, probably []

[psg]

As for running a larger amp, as previously stated, more Bass authority, even at lower volumes, more headroom, better build quality. Your 100 watt RMS amp may be capable of pushing it up to the continuous wattage rating, but where does that 100 watt RMS amp begin to CLIP at?? Further, that 100 watt amp will probably never ever be capable of reaching peak power threshold.

More bass authority? Maybe but I can't hear it.

More headroom? That was my point. If doubling the power doesn't add 3 dB to sound output, then the speaker is compressing and you best to avoid this for good sound anyway. So the extra power isn't really needed if it is never used.

[psg]

In The Dope From Hope, Vol.16 No.1, Jan. 1977 D.B. Keele gave the absolute max SPL for the Khorn, LaScala, and Belle as 122.7 dB with 375 watts input.

Note that these are average levels in the reverberant field of a 3000 cu. ft. room, with peaks 10 dB higher.

I don't understand. You can't add 10 dB for peaks if that number is the absolute max SLP. That should correspond to maximum peaks.

[Islander]

In The Dope From Hope, Vol.16 No.1, Jan. 1977 D.B. Keele gave the absolute max SPL for the Khorn, LaScala, and Belle as 122.7 dB with 375 watts input.

Note that these are average levels in the reverberant field of a 3000 cu. ft. room, with peaks 10 dB higher.

I don't understand. You can't add 10 dB for peaks if that number is the absolute max SLP. That should correspond to maximum peaks.

Don uses the term "absolute max", but the spec in other places uses a similar number for "max continuous", which would leave room for a higher "max momentary" spec. PWK himself mentioned that the worst shock to a speaker driver occurs with a loose or intermittent connection, worse than any musical peak.

[Islander]

Islander,

"that this is only a few dB", 121 dB compared to 130 db is eight times the sound level.

Roger, I was referring to the difference between 121 and 124dB, as you'll see if you look at my post on Page 1 of this thread. You're right, 130dB is indeed much louder than 121dB and a difference like that would be more than a case of measurement methods.

[DrWho]

In The Dope From Hope, Vol.16 No.1, Jan. 1977 D.B. Keele gave the absolute max SPL for the Khorn, LaScala, and Belle as 122.7 dB with 375 watts input.

Note that these are average levels in the reverberant field of a 3000 cu. ft. room, with peaks 10 dB higher.

I don't understand. You can't add 10 dB for peaks if that number is the absolute max SLP. That should correspond to maximum peaks.

I'm pretty sure "With peaks 10dB higher" is another way of saying 10dB crest factor... so the RMS level was 10dB below the peaks that hit 122.7dB.

Also, was that measurement done in stereo or single speaker mono?

[garyrc]

• In the data sheets of the 1970s, the Klipschorn was rated at 104 dB @ 1 wt @ 4 feet, rather than the closer 1 Meter distance that everyone used later. This was said to be the equivalent of an old 54 dB EIA rating. The industry had yet to standardize on the measurement technique they used when publishing. I remember Klipsch and EV as being among the first to publish any useable figures in this area. I wonder if when they started to print the newer sheets (80s?) and changed the copy to 1M, they mistakenly failed to raise the 104 dB figure, or just considered it conservative, because when they did raise it to 105 dB, I remember hearing that the 104 figure had been in error. I believe all figures for the Khorn depended on it being pushed into the proverbial trihedral corner, in order to bring the overall SPL from the woofer/horn up to that of the midrange and treble.

• During the same years, they placed the "power input maximum" for program material at 105 watts.

• In a later catalog, they reported testing 5 "good" speaker systems, including their Belle Klipsch (same drivers as the Klipschorn), to see at what Sound Pressure Level, and at what wattage input they would fail. Since they inputted two unrelated "tones," I guess this was "continuous" (rather than "program" or "peak" power. You can bet that neither of these tones were in the delicate tweeter range (and orchestral music has SPL that is about 20 dB down in this overtone range, as well -- no guarantee with electronic and other kinds of music). As others have said, DON'T TRY THIS AT HOME! The Belle failed at 165 watts, but produced a much louder sound than the competing speakers at their max power (i.e., at the point of failure). For instance one speaker would take almost 350 watts, but put out sound about 23 dB lower in SPL than the Belle at 165 watts.

• I think that Keele's 10 dB peak figure pertained to some good amplifiers being able to produce the briefest peaks about 10 dB higher than at their (RMS?) rating without clipping, rather than being applicable to the Khorn's absolute maximum brief power input capacity --- I could be wrong, I don't have my copy at hand. I haven't seen any amplifier company advertise that much headroom, not even McIntosh, who claims 8,000 watt ultra brief peaks for their 3,000 watt RMS amplifier.

• Here are two questions I've wondered about:

  1) Does compression occur as much on instantaneous peaks as with continuous tones or white/pink noise?

  2) Do speaker frequency response curves resulting from measurements taken at a moderate SPL resemble frequency response at high peak levels? Can a speaker measure +/- 3 dB over its bandwidth at 90 dB, and be not nearly so smooth (e.g., +/- 9 dB) at 110 dB? I assume it would have to be measured with brief tone bursts to avoid blowing it out. Is this ever done?

[DrWho]

Hey Gary, I believe the answers to your two questions can be found here (if you want to get into some heavy reading):
http://www.klippel.de/pubs/papers.asp

Re #1: It depends on the frequency ranges of the peaks. Mechanical excursion related compression will be the same, but thermally induced compression will be worse with white/pink noise.

Re #2: The frequency response does change with SPL.

[grogB]

A speakers frequency response will change with SPL, at the lower frequencies the effect of the suspension stiffening and the BL dropping due to the coil leaving the center of the gap will increase the Qt and decrease the sensitivity, also the coil impedance will rise dur to thermal effects.

there is lots of data on this from klippel

the high frequency response can also change with level, I've seen prototypes where the high frequency roll of of a 6" driver changes from 4Khz at 1w(86dB) to 1.5Khz at 80w(102dB)

[Don Richard]

In The Dope From Hope, Vol.16 No.1, Jan. 1977 D.B. Keele gave the absolute max SPL for the Khorn, LaScala, and Belle as 122.7 dB with 375 watts input.

Note that these are average levels in the reverberant field of a 3000 cu. ft. room, with peaks 10 dB higher.

I don't understand. You can't add 10 dB for peaks if that number is the absolute max SLP. That should correspond to maximum peaks.

I think Keele was referring to the maximum continuous level and the maximum peak level capability of the speakers. Refer to the Dope From Hope for more info. There is a complete set somewhere on the forum.

[Islander]

The Belle failed at 165 watts, but produced a much louder sound than the competing speakers at their max power (i.e., at the point of failure). For instance one speaker would take almost 350 watts, but put out sound about 23 dB lower in SPL than the Belle at 165 watts.

1: Do you have any SPL figures for the sound level of the Belle at 165 watts?

2: Could you use regular-sized text in your posts? That big size is very "loud" and distracts from your message.