DrWho Posted July 25, 2007 Share Posted July 25, 2007 DOC....Chuffing for a HF horn??? come on its a compression horn design... Chuffing in the sense of random chaotic motion of air - not as in the audible air swooshing sound typically associated with overdriven ports. Are you saying that it is impossible to introduce turbulence to higher frequencies? Do,nt forget to collect some good professional Not the cheap crap. testing equipment along the way....and dont throw away the mistakes. I'll have to wait for that when my purpose of measuring actually requires more reliable resolution. But at the same time, I remind myself that all the audio giants had far less measuring capability back in their day - and they whipped out some insanely awesome designs. I don't pretend to be as good as they are/were, but I can still try to apply methods to work around the limits of the measuring capability. Heck, gotta start somewhere. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted July 25, 2007 Share Posted July 25, 2007 I can do some chuffing on a Tuba..... When good measuring equipment comes along dont pass up the chance to aquire it. Some of the early guys had to make there own....Like PWK s famous string and coil to measure complience of a cone...But he also had to buy and collect his wiggle tube measuring instruments. Quote Link to comment Share on other sites More sharing options...
Deang Posted July 25, 2007 Share Posted July 25, 2007 Really nice work on those horns Jeremy, it'll sound great when you get it all together. Mike/Maron -- below posted at the Asylum back in 2002 by DJK For all intents and purposes horn distortion is a function of how hard you squeeze the air and how much bandwidth you try and cover. I'm going to use a Klipschorn as an example that we all love/hate. The K55V (Atlas) midrange driver has a 5/8" (nominal) throat. This driver (and most drivers) have a 10:1 compression ratio. Distortion is proportional to pressure per square unit of area and the square of the bandwidth in octaves (bandwidth to be covered later). Loosely put: a 2" throat has over 10X the area that a 5/8" throat has and thus the air distorts less. Dedicated midrange drivers also exist that have lower compression ratios, ie: 2~5:1 rather than 10:1 or higher. For a given sound pressure level the larger the throat and the lower the compression ratio, the more 'relaxed' or 'easy' the sound is. The shape of the horn throat is also important. Long narrow necks on horns also suffer from air overload. I remember the first time I heard this sound. It sounded like somebody was frying bacon in my horns. Some describe it as 'quacking'. It wasn't the crossover. It wasn't the amplifier. It was the air in the throat of the horn. Replacing the horn with a different type allowed a big increase in level before the same thing happened again. This time it was the air between the diaphragm and the phase plug. Horns without long necks generally have limited dispersion at high frequencies and drivers with lower compression ratios generally have less high frequencies too. Going to a two way top end gets rid of the problems (the square of the bandwidth thing goes away too). People that are interested in the square of the bandwidth thing should refer to figure 7.8 Acoustic Engineering, Olson. "for constant sound power output, the distortion is proportional to the frequency"... "the nearer the frequency is to the cutoff frequency (of the horn) the smaller the distortion"..."for a certain allowable distortion the power output is directly proportional to the area of the throat". The problems of frequency intermodulation distortion due to variations in the volume of air between the diaphragm and the phase plug also become moot with a two way top end. Quote Link to comment Share on other sites More sharing options...
DrWho Posted July 25, 2007 Share Posted July 25, 2007 Thanks Dean. That's trippy that you get the least amount of distortion at the Fc of the horn - I wonder if that's because at Fc the horn has its greatest efficiency. I wonder how that plays out with the K402... Quote Link to comment Share on other sites More sharing options...
consistent Posted July 26, 2007 Share Posted July 26, 2007 Nice work...I would love to possess such skills so I must work on what little skill I have! Well done. Quote Link to comment Share on other sites More sharing options...
bluesboy Posted August 10, 2007 Share Posted August 10, 2007 Jeremy, you have a PM Quote Link to comment Share on other sites More sharing options...
capo72 Posted August 14, 2007 Author Share Posted August 14, 2007 Hey Don, I replied to your PM. Jeremy Quote Link to comment Share on other sites More sharing options...
capo72 Posted August 14, 2007 Author Share Posted August 14, 2007 As an update to all who are interested, I have purchased some equipment to get some frequency response measurements on these horns. I'm still trying to work out the bugs on my measurement rig, and i'll get some charts posted as soon as I figure it out. I've also started working on the direct radiator bass bins for my 18" JBL 2245's. I just received some of Bob Crties' tweeters via Greg Roberts. I will be doing some testing with these as well as some JBL 077 tweets, maybe some JBL 075's also. I think Bob's have a big advantage in that they will reproduce quite a bit lower than the JBL's, and since my mid drivers reproduce down to 300hz, they just don't cover the high end as well. I can't wait to get to the point where I can get all this stuff tested. Unfortunately that may be a little while off as my work has picked up, so between 12 hour work days and taking a couple classes at the local community college, and the kids activities, my time is pretty limited. I will give it my best though! Thanx to those of you who have followed along or helped out along the way. Jeremy Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted August 14, 2007 Share Posted August 14, 2007 Jeremy, Ahhh, The age-old problem is that there are only 24 hours in a day. I will be quite interested in seeing the measurements that you are making and hearing about how you made them. Good Luck, -Tom Quote Link to comment Share on other sites More sharing options...
Marvel Posted August 16, 2007 Share Posted August 16, 2007 Unfortunately that may be a little while off as my work has picked up, so between 12 hour work days and taking a couple classes at the local community college, and the kids activities, my time is pretty limited. I will give it my best though! Jeremy Wow Jeremy... don't you think you could also squeeze in a few hours on a part time job to help pay for all the audio gear, too? [8-)] There will come a day when you will wonder how you did it all. More than anything, make sure you spend time with the kids. Bruce Quote Link to comment Share on other sites More sharing options...
Rob H Posted December 16, 2008 Share Posted December 16, 2008 Jermy Great pictures and nice job. My question is i would like to build a pair to fit in my klipschorn corner speakers. Do you measurements or drawings for these? Thanks Rob Quote Link to comment Share on other sites More sharing options...
Rob H Posted December 16, 2008 Share Posted December 16, 2008 Speakerfritz Do you have drawings or measurments for the ALK's Trachorn? I want to build a pair. Thanks Rob Quote Link to comment Share on other sites More sharing options...
pocket.change Posted December 27, 2008 Share Posted December 27, 2008 What were the results of this little exercise. Quote Link to comment Share on other sites More sharing options...
capo72 Posted December 28, 2008 Author Share Posted December 28, 2008 Not much to tell yet. GotHover built some of these horns and sent one to JWCullison for some testing. You can read about it in his thread about 2" 223 HZ Tractrix horns. I just sent him one of my JBL 2482 drivers to do some testing on that horn. He should be getting it tomorrow and probably have some results within a week or so. I have some testing equipment, but have had no success getting good data. I gave up for a while but the fire has been relit recently. This project has moved down the priority list for me, but I may get back to it soon. I just need to figure out how to add a few more hours to the day. Jeremy Quote Link to comment Share on other sites More sharing options...
dkalsi Posted December 3, 2009 Share Posted December 3, 2009 Jeremy, Any progress on your build? D Quote Link to comment Share on other sites More sharing options...
Kalifornian Posted May 22, 2019 Share Posted May 22, 2019 Did anything ever come of this??? Quote Link to comment Share on other sites More sharing options...
Schu Posted May 22, 2019 Share Posted May 22, 2019 4 minutes ago, Kalifornian said: In the last TEN years... Did anything ever come of this??? Quote Link to comment Share on other sites More sharing options...
Kalifornian Posted May 22, 2019 Share Posted May 22, 2019 Yes, thats correct. But since you are here Schu, got any resources for building a plywood horn? Quote Link to comment Share on other sites More sharing options...
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