D-MAN Posted February 28, 2006 Share Posted February 28, 2006 As you guys know I'm running BMS 4590 driver on a P-Audio 4525 horn and it has been driving me NUTS with a tendency to GLARE (harshness at certain frequencies). Since I am running them unbaffled, I can change the angle any particular direction that I want but I could not actually tame the harshness by changing the angles. One of the main problems with horn-induced glare is that you cannot get away from it, it increases sibilance, sounds "electronic" or "solid state" by adding a high frequency "buzz" or "tizz" (sizzle), tends to be irritating to the listener upto the point where it induces flinching or a dread of certain frequencies, exagerates lip-smacking, microphone pops by putting an artificial edge on them, etc. - bottom line is that it can effect the choices of music (i.e., recordings) that one chooses to listen to. THAT IS THE SIGN OF A BAD SYSTEM SETUP! Then I changed the connecting wire from copper to pure silver between the crossover and the midrange driver which helped but did not totally eliminate the glare problem (right about 9K - sound familiar?). The silver has a "sound" or is it lack of "sound" that is refreshing all by itself, but the glare was still there although reduced, most of which I blame directly on the midrange horn being used. However any improvement in that arena by changing horns is "exponentially" expensive so I thought I would explore any and all other considerations. Additionally, moving to all-silver wire is expensive, too, and although certainly worthwhile, it was probably not going to resolve the harshness problem. Moving to a wood tractrix was going to be my next move out of necessity. Having read this short paper on horn boundary edge diffraction (attached), I thought I'd give that a try since I have done all that I could aside from using an active EQ on the problem. So as an experiment, I treated the outside edge of the horn mouth with a strip of felt, which I have handy. Experimented with different lengths, top, botoom, sides, etc, until I finally ended up with a felt strip all around the circumference of the horn mouth just on the front-facing flat edge. Tamed, smoothed, blended, quite a difference. The apparent "transparency" into the lower mid-range spectum has increased. Probably the flinch-effect from the previous glare covered this up. Strangely dynamics have increased especially in the low end which is rather unexpected, however, this could be the result of the increase in mid and high frequency attenuation I can now use. This change allowed me to go to DOWN further to the 0-1 setting on the ESN autoformer, which is something like over -16db down! That means my setup is quite a bit more efficient than stock Khorn! For example, I listened to Flim & the BB's "Tricycle" cd which suprized me by sounding a bit "muffled" in the midrange. A change to my fav Flim & BB's "Big Notes" cd convinced me that it is just an artefact of the recording. The Big Notes cd has all of the clarity and pazzaz that one would expect, along with the added bonus of increased low frequency response. Previously, I had not actually noticed any differences in the recordings - and I have listened to both for years, literally! The soundstage is now huge well outside the wall boundaries, depth increased. However, it is not overpowering or in your face - it is comfortable and unimposing - it is just "there" in a natural sense. The "FELT MOD" has finally givien me a glimpse into what the setup is capable of doing, which is quite a relief as I have invested alot of time and money into it and was getting what I would consider sub-standard responses. Anyway, I don't know what the effect would be on a baffled K400 but I will go as far as to recommend that it be experimented with because it's CHEAP, completely reversable, and suprizingly EFFECTIVE. DM diffraction_boundary_effects.pdf Quote Link to comment Share on other sites More sharing options...
intotubes Posted February 28, 2006 Share Posted February 28, 2006 DM, Did you place the felt inside the horn mouth to the ouside edge or did you put it on the front flange of the horn (in the same plane as the motor board)? Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 28, 2006 Author Share Posted February 28, 2006 Front flange only. Nothing inside the horn. DM Quote Link to comment Share on other sites More sharing options...
rockbobmel Posted February 28, 2006 Share Posted February 28, 2006 My drummer has these. He used them in his recording studio, now in his H/T & Stereo. UREI Quote Link to comment Share on other sites More sharing options...
rockbobmel Posted February 28, 2006 Share Posted February 28, 2006 more.... Quote Link to comment Share on other sites More sharing options...
BiggerIsBetter Posted February 28, 2006 Share Posted February 28, 2006 DMan, If you think silver will help the situation, I have a pair of 6" pure silver speaker cables and interconnects (1M RCA) that are not in use. The speaker cables are solid conductor braided conductors with bi wire termination on the speaker side. If you want to try them out send me your shipping info..better to know they are in use than sitting in my closet. Just send them back when you are done, I personnaly don't think you will like the change. In the rare event you do like them, you can have them real cheap....like $100 range... Jim Quote Link to comment Share on other sites More sharing options...
D-MAN Posted March 1, 2006 Author Share Posted March 1, 2006 I can't believe what a difference a few pieces of felt can make! Who would have thought! Sort of makes me wonder what some properly shaped pieces of acoustic foam could do, i.e., an after-market add-on for particular horns. Like the UREI tweets posted above... DM Quote Link to comment Share on other sites More sharing options...
sunnysal Posted March 1, 2006 Share Posted March 1, 2006 D-man, I know you must have seen these peavy horns before...BTW the spec mentiones "quadratic waveguide" earl geddes had something to do with these...earl is using foam in the throat area nowadays to reduce HOM...regards, tony read about it here: http://aa.peavey.com/downloads/pdf/qwp1.pdf#search='quadratic%20waveguide' Quote Link to comment Share on other sites More sharing options...
sfogg Posted March 1, 2006 Share Posted March 1, 2006 "..earl is using foam in the throat area nowadays to reduce HOM..." I think he mostly fills the horn with a very open foam. The idea being that the foam will reduce the higher order modes more then the direct sound because the refraction and such travel through the foam more times (at least 3 times for the reflections) compared to the direct sound. I tried a piece of 1" acoustic foam in the cells of my 805Bs (about midway down in the horn) and feel it was a worthwhile addition. I put more info about that in the thread about tri-amping the system. Shawn Quote Link to comment Share on other sites More sharing options...
D-MAN Posted March 1, 2006 Author Share Posted March 1, 2006 Yeah, I knew about this stuff for years, but didn't think it would make much of a difference, so I never got around to trying it being the lazy S.O.B that I evidently am! I am hestitant to do anything to the inside of the horn because of it being a coax and the high (tweeter) frequencies don't tend to cope well with obstacles. But we are all on the same page! DM Quote Link to comment Share on other sites More sharing options...
Q-Man Posted March 2, 2006 Share Posted March 2, 2006 I think that I would first fix the network. You need the right equipment to measure and test the driver and horn. I thought my 290-16K driver and 311-90 horn sounded good, untill I sent them off to John warren. He found a nasty peak in the 311 horn and used a notch filter in the network to correct it. I was floored with the difference in the sound when I did an A/B test with his network and the one that I was using. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted March 2, 2006 Author Share Posted March 2, 2006 Gary, I'm pretty sure that it's not the network or even the driver - it's the horn. And now I'm pretty happy with the sound I'm getting! But you're right, I'm starting to look for some testing gear. However, I did find this on adding a 9K notch filter for the midrange... but my impression is currently that I don't need it, of course that could change with time... DM Quote Link to comment Share on other sites More sharing options...
Kudret Posted June 15, 2007 Share Posted June 15, 2007 sorry, wrong place. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted June 16, 2007 Share Posted June 16, 2007 Useing foam on the edge of a horn mouth will eliminate some diffraction effects ,,,But inserting foam lineing into throat will interfere with proper horn propergation. Most of the UREI foam disign was to soften lip diffraction effect on surface of woofer cone. Now that was audible....But placing foam around a large mid horn like a 400 or K 401 is not that noticeable....And than again a Bob Smith DSH type horn that uses horizontal septas,,,Only the vertical lips could benefit.....also the K77 tweeter tweeter lips diffract....120 degrees worth vertically. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted June 16, 2007 Share Posted June 16, 2007 What high order modes are we talking about???? there ar,nt any on my charts. Short dips arnt audible...Short spikes are.. Quote Link to comment Share on other sites More sharing options...
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