jwgorman Posted December 20, 2015 Share Posted December 20, 2015 In searching the forum, I came across Chris' corner horn imaging primer. When I read the part about the 400/401 losing control of 400-1.7Khz region it made total sense. Long story short, a quick trip to the local fabric shop to get some soft foam and heavy duty two-sided tape and about an hour of work provided a very valuable mod. I have vaulted ceilings that go up to about 10' but I also have wood floors and that mod did wonders for the reflections I was getting off the floor. Thanks for posting that many years ago Chris. The pic of the peavey horn was a big help. So with the foam on the 401's mouth and the CT120 tweets, I'm really digging my khorns again. I cranked up a live Muddy Waters record last night and played it loud. I was front and center in the club. I'd strongly recommend this mod if you have 400/401 horns. 1 Quote Link to comment Share on other sites More sharing options...
Chris A Posted December 20, 2015 Share Posted December 20, 2015 Cool. Quote Link to comment Share on other sites More sharing options...
jimjimbo Posted December 20, 2015 Share Posted December 20, 2015 Please post the link Quote Link to comment Share on other sites More sharing options...
Chris A Posted December 20, 2015 Share Posted December 20, 2015 https://community.klipsch.com/index.php?/topic/131163-corner-horn-imaging-faq/?p=1464525 1 Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 21, 2015 Author Share Posted December 21, 2015 (edited) So one thing I should mention about the 401s: when I first applied the two sided tape it did not adhere. The tape would come off easily and was covered in flakey plastic. I took clear sealing tape and applied it to where I wanted the two sided tape to adhere to and pressed it firmly onto the horn. I'd pull off the tape and it would be solid black with plastic flakes. After that the two sided tape would adhere. Just FYI. Edited December 21, 2015 by jwgorman Quote Link to comment Share on other sites More sharing options...
Chris A Posted December 21, 2015 Share Posted December 21, 2015 Can you describe where you applied the foam and tape relative to the bolted surface of the horn's mouth? Quote Link to comment Share on other sites More sharing options...
jimjimbo Posted December 21, 2015 Share Posted December 21, 2015 Or a photo? Quote Link to comment Share on other sites More sharing options...
tromprof Posted December 21, 2015 Share Posted December 21, 2015 Or a photo? Pictures worth a thousand words. Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 21, 2015 Author Share Posted December 21, 2015 Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 21, 2015 Author Share Posted December 21, 2015 I trimmed a bit before reinstalling the motorboard. Quote Link to comment Share on other sites More sharing options...
Chris A Posted December 21, 2015 Share Posted December 21, 2015 Can you describe the differences in sound? Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 21, 2015 Author Share Posted December 21, 2015 Well, my room is somewhat reverberant. Splashing 400-1.7K around in that room was bad for imaging and tonal balance. I threw down area rugs and put up heavy insulated drapes on the walls to tame it. That made it better but installing foam on the mouth of the horn was a better solution for convenience and it sounded better than trying to absorb it. My memory of how the Khorns sounded in our previous house is what these guys are sounding like now. The imaging and tonal balance were both improved. It was a good $15 experiment! 1 Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 21, 2015 Author Share Posted December 21, 2015 Oh and I didn't think I'd be able to see that green through my cane grill cloth. I was wrong. I don't really care, but if you don't want a fashion blunder, you might want to get some dark gray or black foam. Quote Link to comment Share on other sites More sharing options...
JJkizak Posted December 21, 2015 Share Posted December 21, 2015 What is your normal listening volume? JJK Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 22, 2015 Author Share Posted December 22, 2015 I don't really have a "normal" volume. If I'm listening later at night, it's fairly quiet. Last night, I spun Neil Young Harvest when my youngest was sleeping, so the volume was down pretty low. It's also depends on what I'm listening to. I can tell you that last Saturday I was spinning some Muddy Waters live and it got pretty dang loud, in that ball park of "I'm old enough to know better but this sounds really good." I like a lot of music, like Frank Sinatra, Tony Bennet, The Who, Led Zeppelin, Neil Young, Joni Mitchell, John Coltrane and The Ramones, so I wouldn't listen to all those artists at the same volume. I use a Luxman SQ38u, which, I suppose puts a limit on how loud I can play music, but I've made the EL34s start to compress before and that's already waaaaay too loud. My listening room is about 16x24. Why do you ask JJK? Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 22, 2015 Share Posted December 22, 2015 Anyone ever take any measurements of adding foam inside the horn? I'd be really surprised if it affected the polar response - especially at lower frequencies. There's a lot of talk about how the wavefront in an exponential isn't actually planar, so in reality we get reflections due to the curvature of the wavefront - especially at higher frequencies. I wonder if the foam is helping attenuate some of that craziness? Looks like a simple low cost mod. I've done similar experiments with folded bass horns in the past to help clean up some of the standing waves at higher frequencies. I wonder what would happen if you did a similar thing to the khorn bass bin? Would that tighten things up there too? It wouldn't be very PWK like though because it would ultimately be reducing efficiency a bit... Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 22, 2015 Author Share Posted December 22, 2015 Anyone ever take any measurements of adding foam inside the horn? I'd be really surprised if it affected the polar response - especially at lower frequencies. There's a lot of talk about how the wavefront in an exponential isn't actually planar, so in reality we get reflections due to the curvature of the wavefront - especially at higher frequencies. I wonder if the foam is helping attenuate some of that craziness? Looks like a simple low cost mod. I've done similar experiments with folded bass horns in the past to help clean up some of the standing waves at higher frequencies. I wonder what would happen if you did a similar thing to the khorn bass bin? Would that tighten things up there too? It wouldn't be very PWK like though because it would ultimately be reducing efficiency a bit... That would be the way to do it Mike. Maybe someone interested in this mod could do a before after? What frequency range do you think that foam effects? If it was effecting the polar response of 1-2K I guess that would make sense. But you are quite correct, a real measurement would be the way to know. So who has the gear to do such an experiment??? I thought it was interesting that Peavey did it. I'm sure they wouldn't just throw foam at a horn for no reason. Whatever frequency range is being controlled via the foam, I think it's a good thing. But yes, it would be cool to have some data. http://www.bhphotovideo.com/c/product/1017036-REG/peavey_00493560_ch_642qt_constant_directivity_horn.html 1 Quote Link to comment Share on other sites More sharing options...
robotc Posted December 23, 2015 Share Posted December 23, 2015 I did some testing of foam in the horn of my RF3 speakers a while back. The results I got might not apply to the horns you are modding but the results might interest you. I decided not to use foam inside the horn because I thought it might affect the geometry too much. Instead I stuck felt on the surface covering about half the depth of the horn. I also stuck a strip of open cell foam around the outside of the mouth. The effect on the frequency response is shown in the attached graphs. The measurements are at 80cm with no crossover attached. I didn't like the effect on the sound produced by the felt but I have stuck with the foam around the horn mouth. Robert 1 Quote Link to comment Share on other sites More sharing options...
jwgorman Posted December 23, 2015 Author Share Posted December 23, 2015 Thanks for posting that Robert. Quote Link to comment Share on other sites More sharing options...
djk Posted December 23, 2015 Share Posted December 23, 2015 (edited) The foam in the mouth of the Peavey horn is recessed into the walls of the horn, the horn is stepped back where the foam is. Edited December 23, 2015 by djk Quote Link to comment Share on other sites More sharing options...
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