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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: RE: Show me a current monitor posted by Inmate51 on March 29, 2025 at 09:45:23:
Woof woof!!
Oh boy!! Where do we start? This is a doozy!!! of a post.
Ok Inmate51 you say, "Angling the woofer panels by 20 degrees or so has little to do with diffraction around the sides, but will affect the dispersion pattern, by possibly reducing lobing" Ok what is lobing? Lobing is when two or more speakers emit the same frequency at a distance greater than a quarter wavelength of the sound. Ok how to minimize lobing as it pertains to the KEF KM1 speaker? Angling the sides like you say will not do anything to stop lobing. If you want to reduce lobing there are several things you can do. First place the woofers close together like the KM1 does. Speakers playing the same frequency spaced far apart create more lobing placing them closer together will reduce lobing. Second Using steep crossover slopes like the KM1 does. The KM1 is an active speaker with electronic crossovers that have a very steep 24 dB per octave slope greatly reducing lobing. Unlike shallower 12 dB and 18 dB textbook passive crossover slopes that are never textbook because they do not include the acoustical properties of the drivers, and all drivers are different that's why we measure. Third way to reduce lobing on the horizontal axis is to stack the drivers vertically which the KM1 does.
So, it seems KEF knows how to design speakers. They have the woofers close together and stacked vertically and have a steep 24 dB per octave slope electronic crossovers. Also, if we look at the KM1 from a designer's viewpoint we will understand why they angled the sides. Because it narrows the center baffle where the midrange and tweeter live and that will help minimize baffle interactions with the midrange and tweeter. Not to make the box look less boxy like you say, remember this was a speaker not intended for home audio, so they did not care about looks. Most of the time when talking about speakers the form is for function not looks. But in this case sacrifices firing the woofers off axis to narrow the baffle for the mids & highs.
Then you say (Using 1129 feet per second as the speed of sound, the wavelength at 350 Hz is about 3.22 feet. With a nominal woofer diameter of 9 inches and an effective radiating diameter of about 8 inches, it is likely that the dispersion pattern is "adequate") Wow this really makes no sense its pure gibberish. Ok please explain how determining the wavelength of a given frequency can tell you the dispersion pattern is adequate by adequate I guess you mean wide to give a good soundstage. There is only one way and one way only to determine a speaker's dispersion pattern and that is by measuring on axis then measuring 15,30,45,60 degrees off axis these are the measurements you must take to upload into software to produce a polar plot and a polar plot is the only thing that will show you a speakers dispersion pattern. You also said the woofers are a nominal 9" nominal means "in name only" so are the woofers 9" or are they 9.4" and KEF just rounds them off? You also said the 9" speaker has an effective radiating diameter of about 8". There is no such thing as a speaker having a 8" radiating diameter. The radiating surface of a speaker is measured in cm squared and it is only counting the cone not the surround. So a 8" diameter circle has about 322 cm squared or 50 square inches surface area. However, the average 8" speaker cone not including the surround has an average 211 cm squared or about 32 square inches radiating surface.
And the paper you pictured has the name Olsen. I wonder if that's Henry Olsen. Henry Olsen is an audio pioneer, a very important pioneer to say the least. He was the first person to measure diffraction I think in the mid to late 1930's and the first person to use a curved baffle also in the 1930's. And that picture you posted. You said " Just as a sort of add-on to the discussion, here is a page about diffraction, as applied via an opening in a wall. The same concept applies to baffle edge diffraction " Oh no that paper does not apply to baffle edge diffraction at all read what you posted carefully. Here is the actual definition of edge diffraction verbatim " A phenomenon where sound waves, upon encountering the edges of a speaker cabinet/baffle are scattered and readiated, creating secondary sound sources that interfere with the original sound waves. potentially key word potentially leading to coloration or blurring of the sound. So how does a paper on the concept of sound traveling through a hole in a wall relate to the concept of a speaker cabinets edge diffraction?
Extraordinary claims need extraordinary evidence and what can be asserted without evidence can be dismissed without evidence. However, I provided ample evidence to not only dismiss but debunk the preposterous claims you have asserted in this doozy of a post.
Everything in your post is wrong and all of it is covered in that book. You say you own the Vance Dickason loudspeaker cookbook so either you have not read it or you do not own a copy.
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Follow Ups
- RE: Show me a current monitor - seancuster71@gmail.com 05:21:34 03/30/25 (1)
- Harry F. Olson - Inmate51 11:23:22 03/30/25 (0)
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