JohnA Posted May 21, 2005 Share Posted May 21, 2005 I enjoy these discussions. I have just a touch too little education in these areas (Civil Engineers rarely apply electrical filters to stormwater structures or railroads) and I find this stimulating. Personally, I want my own Robbie and a few seconds on the Krell Teaching Machine. It is hard for me to see that the 3" x 13" slot does NOT create a compression chamber. It clearly would not create the compression ratio of a conventional compression driver, but restricting the entrance to the throat from 137.9 sq in to 39 sq in has to increase pressure and velocity if the output is held the same, does it not? Did you see the Myth Busters show about breaking a wine glass with the human voice? They did it! A Rock tenor was able to, finally, break a glass with only his voice. In order to do it with an amplified speaker they had to place a board with a 2" diameter hole in it against the speaker and put the wine glass a few inches away from the hole. Didn't this hole form a compression chamber (I couldn't tell it it was sealed and they didn't either) and/or a filter? The glass's resonant frequency was about 525 Hz. Then, the mass of air trapped between the cone and motorboard and its compressibility surely would behave like a weight on a spring, absorbing energy here and giving it back there. Isn't that a filter? Quote Link to comment Share on other sites More sharing options...
dragonfyr Posted May 21, 2005 Share Posted May 21, 2005 Might anyone have the link to Gil's posting of the DBKeele article? Many thanks... Quote Link to comment Share on other sites More sharing options...
WMcD Posted May 21, 2005 Share Posted May 21, 2005 In recent months, I put technical articles in Technical Questions. I include in the subject the word "article" even if it is not quite an article. Therefore you should use the menu search function for "article." That is how I keep track myself! I've not quite kept up with making it for your weekend reading, which was my goal. I.e. there hasn't been one every Friday. Sorry. Gil Quote Link to comment Share on other sites More sharing options...
dragonfyr Posted May 21, 2005 Share Posted May 21, 2005 Thank you sir! Quote Link to comment Share on other sites More sharing options...
djk Posted May 21, 2005 Share Posted May 21, 2005 "Might anyone have the link to Gil's posting of the DBKeele article?" You want #11 http://www.dbkeele.com/papers.htm Quote Link to comment Share on other sites More sharing options...
D-MAN Posted May 23, 2005 Share Posted May 23, 2005 ---------------- On 5/21/2005 10:03:11 AM djk wrote: The impedance of the driver has NOTHING to do with the slot size. The 16 ohm number comes from taking the root mean of the minimum impedance and the maximum impedance at the first peak above the Fc of the bass horn (as explained by PWK in one of the Klipsch papers reprints of his various technical articles, not DFH). ---------------- In terms of a Khorn application, the 8-Ohm vc driver is enough to indicate that it is NOT a K33E, which the narrow 3" slot was exclusively used for "adjusting" its frequency response in the horn. In that sense, it DOES effect the slot size, i.e., the slot should be somewhat wider in most cases up to the full 1:1 match with the Khorn throat cross-sectional area of 78 sq. in. (6x13"), depending on the application, of course. So I would go with the Bruce Edgar saying that IN GENERAL, 8 Ohm woofers should use the wider slot when used in a Khorn, which was were I got this in the first place. In the strictest sense, though, yes, I agree, the impedance of the vc itself does not INDICATE the size of the optimal slot-size by itself. Other parameters do, INCLUDING the vc impedance (i.e., "certain driver parameters including suspension compliance, effective circuit resistance, and back cavity compliance" - Keele, "Low Frequency Horn Design Using Thiele/Small Driver Parameters"). The vc would presumably be a part of the overall circuit resistance. I think that PWK used Barenek's (sp?) law to calculate the impedance of the horn-loaded woofer, as mentioned above. What it has to do with the "modern" 15" 4 Ohm (3.2?) vc driver is another question. That is, why and to what effect? DM Quote Link to comment Share on other sites More sharing options...
Klewless Posted May 23, 2005 Share Posted May 23, 2005 It seems to me that to get "true" answers to all these points/counter-points is to build a Khorn such that the motorboard can be altered by the insertion of a reducer board like they had in speakers when I was a youngster. Then measure, measure, and measure some more. I would not be surprised if PWK didn't do that himself. To heck with theory when you have the tools to build and measure. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted May 23, 2005 Share Posted May 23, 2005 You mean like this? Unfortunately, I can only listen to the "changes", can't actually measure them. That sucks. DM Quote Link to comment Share on other sites More sharing options...
Klewless Posted May 23, 2005 Share Posted May 23, 2005 Yep, It is hard to imagine that PWK didn't do something like that and he eventually did have the tools to measure what was coming out. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted May 24, 2005 Share Posted May 24, 2005 I'm sure he did. I believe that the older Khorns all were stock this way. It was later changed with the narrower slot in 1961 and direct screw mounting of the woofer to the baffle. Sort of a proprietary move on PWK's part. DM Quote Link to comment Share on other sites More sharing options...
Deang Posted May 25, 2005 Share Posted May 25, 2005 Fantastic thread, thanks guys. Quote Link to comment Share on other sites More sharing options...
djk Posted May 25, 2005 Share Posted May 25, 2005 What year did they drop the angle iron braces on the motor board? Quote Link to comment Share on other sites More sharing options...
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