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In Reply to: RE: compromises - at what frequency is the first horn in the system most critical? posted by Bill Fitzmaurice on October 16, 2015 at 09:30:52
Mr. Fitzmaurice is right: all the distortion generated by the lowest frequency horn is audible - first, second, third ...tenth harmonics all convolve themselves into modulation distortion products (see pgs 7-8 of the link below to the Nelson Pass article on the subject), especially with any sort of direct radiators since they in particular suffer between 15-25 dB higher modulation distortion, especially the higher order products which the human hearing system (ears+brain) hears most clearly without masking effects. With bass frequencies - all the generated higher order harmonics are audible, unlike tweeters or even midranges, where at some frequency, the higher order distortion products become inaudible. And the bass frequencies are at much higher amplitudes than midrange or tweeters - (i.e., 1/f power characteristic of music).
PPSL and other direct radiating designs all suffer from the effects of moving mass and nonlinear motor/compliance suspension that horn-loaded bass bins don't. This is especially true when playing back transients or even average SPL anywhere approaching actual concert levels...or even 10-20 dB below those levels...even for acoustic (i.e., non-amplified) instrumentation.
Direct radiator cones must move at least 5x further to produce the same acoustic power as compared to those same drivers used horn-loaded. That horn loading advantage never goes away.
Chris
"As far as the ear can tell, consistently clean and spacious bass can be reproduced only by a driver unit coupled to a horn-type acoustic transformer..."; Jack Dinsdale, May 1974
Follow Ups:
"PPSL and other direct radiating designs all suffer from the effects of moving mass and nonlinear motor/compliance suspension that horn-loaded bass bins don't. This is especially true when playing back transients or even average SPL anywhere approaching actual concert levels...or even 10-20 dB below those levels...even for acoustic (i.e., non-amplified) instrumentation. "
You talk a good game, but why does a dual 15 PPSL go lower than a Klipschorn, have less distortion than a Klipschorn, and is more efficient than a Klipschorn?
(same amplifier, same room, the dual 15 PPSL has to be crossed out at 200hz~250hz).
"You talk a good game, but why does a dual 15 PPSL go lower than a Klipschorn, have less distortion than a Klipschorn, and is more efficient than a Klipschorn?...(same amplifier, same room, the dual 15 PPSL has to be crossed out at 200hz~250hz)."
Dennis, I have a lot of respect for your opinions both here and on the K-forum, and in terms of your PPSL and your electronics knowledge.
However, the point is obfuscated in "have less distortion". What kind of distortion are you measuring? Dual-tone modulation distortion with the drivers used as direct radiators and the same drivers used in a FLH? Harmonic distortion is approximately the same whether using direct radiating drivers or FLH at equivalent cone displacement travel, but modulation distortion (non-harmonic) piles up at the highest frequencies as sidebands on the direct radiating configuration and just sounds opaque with that "DR sound". I also feel that you know this to be true, but you must assume that it doesn't matter. For me, it makes all the difference in the world.
Use those same two 15" woofers in a well-designed FLH, and do the dual tone tests at equivalent acoustic output power. The FLH configuration will have a great deal less cone travel for the same output power.
Let's compare apples-to-apples, and not some arbitrary design to another, and different, arbitrary design.
Chris
"As far as the ear can tell, consistently clean and spacious bass can be reproduced only by a driver unit coupled to a horn-type acoustic transformer..."; Jack Dinsdale, May 1974
Sure. Horns rule. But the ppsl device can not be grouped in with
"typical direct radiators"
Night and day difference.
Unless built to military tank standards, wooden horns (esp folded)
will always impart a huge colouration factor compared to a properly built
ppsl. They will also play deeper for a given footprint. Also, the bigger the (mid)/or bass horn, the larger the room requirements for a proper blend.
Recent listening experiments yielded the fact that my ppsl mid bass is much cleaner than a LaScala mid bass.
A ppsl device for the lowest frequencies is a fine compromise if you wish to call it a compromise. I call it a very wise solution.
To each their own & happy listening to all :)
what you said probably holds true for front loaded horns with well chosen compromises which have not cheated too much in size vs path and cutoff.I would think a poor or overly compromised horn/driver combo to possibly be as poor or worse than a well chosen direct radiator in the region of the direct radiator's tuning frequency. (?) 6th order tuning and boost could be used in the PPSL to milk some extension.
Here's a JBL double 15 4648 box at 100 watts - H3 at ~1/2 octave above tuning has risen to ~ - 30dB - what horns might one build in 10.2 cubic foot overall bulk limitation to outperform this box? (my FH1 is about this size)
here's the effect of a cheap weak motor Beta15cx speaker in the old spec Karlson vs the same speaker in a reflex the size of the Karlson's rear chamber with reflex tuning around 50Hz - I'm not positive how far this would hold up on a scale say descending from 100Hz on the lower note to 40Hz but have noted cone motion reduction on the Karlson to ~37Hz - either a fluke or something can happen below tuning not indicated with simple bandpass box predictions. Unfortunately a regular Karlson 15 is pretty much limited to around 50Hz practical with the rear chamber and system tuning dominating response.I have K-horn, Heresy I and Peavey's FH1 so am familiar with Klipsch from that standpoint.
Here's at the time a brand new UCS1 vs a homemade 225l (overall bulk) Karlson at 20v/50Hz loaded with a buyout Eminence 18" - the horn was 20dB worse at this frequency.
Perhaps there was shipping damage to the woofer?
Karlson Evangelist
Edits: 10/16/15 10/16/15 10/16/15 10/16/15
Why would you refer to extremely poor drivers on poorly designed horns vs. something that is clearly not anywhere near an apples-apples comparison?
Using a driver direct radiating vs. the same driver in a reasonably designed and built horn that matches that driver is a fair comparison.
Chris
"As far as the ear can tell, consistently clean and spacious bass can be reproduced only by a driver unit coupled to a horn-type acoustic transformer..."; Jack Dinsdale, May 1974
The Nelson Pass piece is interesting, but where speakers are concerned this is more appropriate:
http://www.readresearch.co.uk/loudspeaker_papers/klipsch_modulation_distortion_article_1.pdf
I've posted a link to all three parts of that article below. I usually avoid using the PWK articles when talking to those that might like to argue about validity of sources due solely to the date that the article(s) were published.
More people nowadays seem to listen to NP, even though you might consider his arguments to be inapplicable to loudspeakers...I don't, however. YMMV.
Chris
"As far as the ear can tell, consistently clean and spacious bass can be reproduced only by a driver unit coupled to a horn-type acoustic transformer..."; Jack Dinsdale, May 1974
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