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In Reply to: RE: "IM distortion almost as bad as the orginal Bose 901"... posted by Ivan303 on May 20, 2017 at 10:00:03
Paul Klipsch won a Silver Medal from the Audio Engineering Society. Before that happened (about 40 years ago when I was a kid), he sent me autographed copies of a collection of his papers and his dealer newsletters called "Dope from Hope."
Here's a scan from the AES papers on IM distortion, using the Bose 901, which RAMMED bass and treble into 9 small 1 ohm drivers in series in a small box via an outboard "smiley face" active EQ box.
You can see the gross sidebands that are produced and NOT in the original signal. This is why BIG HORNS RULE when you want low distortion and full dynamics at the "proper" SPL for all music.
Edits: 05/20/17Follow Ups:
Yes, we are all aware of the Bose 901. Most of us never owned them.
Did you measure the speaker that you linked to?
Is your position that all speaker utilizing 8-9 in. drivers produce the same distortion?
It's my position on all speakers that use 8" driver as a direct radiator WOOFER, whether sealed, ported, or open baffle, since a 41 Hz. bass would cause severe FM and AM distortion at 2 Khz, where the $50,000 speakers cited. Horn loading would drop that type of distortion by 15-25 db but would also limit the bandwidth, which would further reduce distortion. Back loaded horns being the exception, since the bass is extended by the horn and NOT over excursion by the driver being EQ'd down low. A reasonable compromise by many.
I own a pair of popular "studio monitors" which have an 8" mid woofer and 1" tweeter.but I use them for computer speakers, not for a main system.
Since in my application is bandwidth limited to the upper vocal range and PWK's IM distortion measurements on the drivers included a bass signal, I'm bypassing those issues. Besides I don't intend to listent to my resultant OB speakers at the same SPL as my all horn system.
To quote the late Gene Czerwinski of Cerwin-Vega vame: "Loud is beautiful, if it's clean!"
Which is why I listen to direct radiators at 75-80 db at my sweet spot and 85-90 db with my all horn setup.
My tapped horn sub bass is 3 db down at 18 Hz. and coupled to Danley Synergy horn's dual 12" woofer, crossed at 40 Hz. Together they run flat to 200 Hz. bass detail that is hard to believe, allowing every not to be tracked distinctly and to realize what kind of beater or sticks the drummers use.
People who try to use a single 8" driver from 40-2,000 Hz. are subject to a glaring reminder of the laws of physics. they are also missing over an octave of additional information down below.
Even the venerable Klipschorns need a subwoofer.
Also, I forgot to point out that the 8" Lowther drivers were specified by Paul Voight and his patents back in the 1930's to work in his ported corner horn, which at the time, bested all other designs.
He was also the first to use Tractrix horns while the rest of the world was hung up on (inferior in many ways) Exponential horns for decades.
The best of direct radiator designs use an ARRAY of drivers (3-4 way with subs) of various sizes to achieve lower distortion and FULL Audio bandwidth. I'm not saying they are worth the money to a DIY guy like me, but to ask FIFTY GRAND for an 8" woofer and 1" tweeter in a fancy box is almost criminal. The guy who's selling one used is just passing on his mistake to some other foolish buyer...........IF he can find one.
I took my Series I sans EQ outside for some graphs - if music is real good, it will survive a 901
look at the response of the rear 8 group vs the single front driver
here's what I got for the EQ box separate
Yep, ramming treble and bass into a midrange speaker will cause it to SCREAM in agony. 15 db of bass boost is what yields the gross IM distortion in Paul Klipsch's award winning papers.
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