jwc Posted April 26, 2009 Share Posted April 26, 2009 I want to thank greg for sending it to me. My curve was outside. I did inside curves too that look "nicer". That bump at 3 K was there outside...I assume that is the driver. All my curves inside went below 400Hz. Also note that my dB scale is 50dB like BMS and also the Freq scale 100Hz to 20KHz. You can see the similarities. Note that this horn isn't on a baffle for the curve. jv Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 26, 2009 Author Share Posted April 26, 2009 I want to thank greg for sending it to me. My curve was outside. I did inside curves too that look "nicer". That bump at 3 K was there outside...I assume that is the driver. All my curves inside went below 400Hz. Also note that my dB scale is 50dB like BMS and also the Freq scale 100Hz to 20KHz. You can see the similarities. Note that this horn isn't on a baffle for the curve. jv I don't know why you're thanking me! I'm thanking you for taking the time to test it for me. Someday I'll get set up to test them myself. Here's an inside curve from JC, on axis. Greg Quote Link to comment Share on other sites More sharing options...
jwc Posted April 26, 2009 Share Posted April 26, 2009 yep..notice only 30db scale on that onw and FR scale shortened. So the curve is "blown up". Therefore 2 dB changes look drastic. I remember the just off axis curve looking the best...... Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 26, 2009 Author Share Posted April 26, 2009 yep..notice only 30db scale on that onw and FR scale shortened. So the curve is "blown up". Therefore 2 dB changes look drastic. I remember the just off axis curve looking the best...... OK, here's 15 degrees off axis, inside. Greg Quote Link to comment Share on other sites More sharing options...
Deang Posted April 27, 2009 Share Posted April 27, 2009 Bob's curve looks a lot like the BMS published curve. Bob, how far from the horn did you have your microphone? JC, I don't think the driver is causing the peak. Move from 2 meters to 1 meter -- and make sure the mic is perfectly centered. Just a suggestion. "I think we could say that the average sensitivity of the BMS driver and your horn is about 3 to 4 db higher than the K-400/K-55V combination." That's what the plot appears to show, but it's a tough pill to swallow. The K-400/K-55 before attenuation is 107dB. The rated sensitivity of the BMS driver on their horn is 118dB. Craig has Greg's set up right now, and I've been on and off the phone with him for the last two days listening to him moan about how hot the set up initially sounded with his LaScalas. I had him drop in the networks I built for him which use the 3636 autoformer to give him more attenuation options. He ended up attenuating 13.64 dB before it sounded right to him. If we assume that the BMS on their CD horn really is 118dB like BMS says -- then that attenuation setting makes perfect sense: 118 - 13.64 = 104.36dB So, either we have roughly 8dB of loss when going from BMS' CD horn to Greg's Tractrix -- or Craig just really hates the sound of midrange. In case anyone's wondering, here's the turns ratio data with the resultant attenuation for Bob's UT 3636 -- using the swamping resistor (Al's networks). 0.08638 -21.27 X 4 0.09687 -20.28 Y X 0.10362 -19.69 2 1 0.10880 -19.27 5 Y 0.14519 -16.76 3 2 0.18325 -14.74 Y 4 0.20567 -13.74 5 X 0.20795 -13.64 4 3 0.24881 -12.08 3 1 0.25119 -12.00 1 0 0.29205 -10.69 5 4 0.29433 -10.62 X 3 0.35314 -9.04 4 2 0.35481 -9.00 2 0 0.39120 -8.15 Y 3 0.43952 -7.14 X 2 0.45676 -6.81 4 1 0.50000 -6.02 3 0 0.50000 -6.02 5 3 0.53639 -5.41 Y 2 0.54314 -5.30 X 1 0.64001 -3.88 Y 1 0.64519 -3.81 5 2 0.70795 -3.00 4 0 0.74881 -2.51 5 1 0.79433 -2.00 X 0 0.89120 -1.00 Y 0 1.00000 0.00 5 0 Quote Link to comment Share on other sites More sharing options...
Deang Posted April 27, 2009 Share Posted April 27, 2009 The off-axis curve looks nice -- makes me inclined to think the on-axis peak at 3kHz is being caused by a reflection. Greg -- is that horn truncated by any chance. IOWs, is the flare complete? Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 I've been on and off the phone with him for the last two days listening to him moan about how hot the set up initially sounded with his LaScalas. I've had to endure the moaning too. There is a difference in bass output between a pair of La Scalas that are not in corners compared to Khorns set up in nice corners in a room made for Khorns. Craig has the mid horns set at about 4db lower than I do on my Khorns. Last time I talked to him, he was thinking they might be a tad lower than they should be. Some people like their midrange a little hotter than others. Some purposely turn the midrange down to voice the speaker to having more bass. This does not mean that the person who likes their midrange up a little hotter needs to have their "ears checked". Geez. I think this is the beauty of having the attenuated midrange on the networks, so people can voice their own speaker instead of using tone controls. Craig also said something about having to buy two pairs of V-Tracs now because he has to have them in his shop as well as the living room. So I think he likes them enough! Greg Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 Greg -- is that horn truncated by any chance. IOWs, is the flare complete? Basically yes. It's trimmed 1/2" on each side, which hardly makes a difference. The horn side curve comes to a full 90 degree flare. I would like to experiment with extending the flare to see what that does to the sound, but I can't do this until I get set up to test speakers. I only put so much stock in curves. I view them as a starting point only, or for comparison between different horns. Greg Quote Link to comment Share on other sites More sharing options...
Deang Posted April 27, 2009 Share Posted April 27, 2009 It's trimmed 1/2" on each side, which hardly makes a difference. Well, that's a full inch. It's possible that it could be responsible for the peak at 3kHz. If the horn is mounted on a baffle, two things might happen -- the peak will go down, and the bottom end of the response will come up a bit. Bob, did you measure just the horn, or with a motorboard? Quote Link to comment Share on other sites More sharing options...
BEC Posted April 27, 2009 Share Posted April 27, 2009 Dean, I measured 1 ft. from the mouth of the horns. The K-400 is in a Lascala and Greg's horn is on top of the lascala without motorboard except that the Lascala cab may be providing a partial baffle. Bob Quote Link to comment Share on other sites More sharing options...
jwc Posted April 27, 2009 Share Posted April 27, 2009 Dean. The curve showing the most peak at 3K is the outside one at 2 meters dead on axis. I repeated that in other places in the yard with similar results. I also repeated with the mic up closer and also with the horn pointed "at the sky"...with the mic centered (that was a real PITA BTW). Same type results. When I was doing it different places in the room, I was getting reflections...no doubt and didn't save those. There is one way that I do it in the room and get the "least' amount of relections.......which is what I sent to greg....1.5 meters on and off axis with the horn in the center of the room No matter how I measured the BMS on that horn, there was always a "rise" somewhere in the 3000Hz range.....until you move off axis. I was thinking the polar loss at the high end was effecting the whole top end more than anything.....don't know. I stopped doing curves in the past with the mic up close. That was the only way I was doing it for some time. The results to me were always...."too good". When I started taking bass horns or whatever outside.....the results seem to be more realistic......I'm sure there was more reasons at the time...can't remember... Greg....the horn isn't shortened when on a baffle right...as you incorporated the baffle as the very end of the flare...correct? jc Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 Greg....the horn isn't shortened when on a baffle right...as you incorporated the baffle as the very end of the flare...correct? No. The horn mouth is 23" when the design calls for 24". 24" simply would not fit. I suppose you could say that the front frame on the V-trac extends the mouth of the horn back out to 24". But I'm quite sure the tiny bit of trim that I did to the outside of the flange is not the reason there are any 3Khz peaks. The 3Khz peaks are on the BMS curves too, and even more pronounced than the curves that you or Bob did. Why would we jump to the conclusion that shortening the mouth of the horn that tiny little bit is the reason for ANY of what we see on the curves? The obvious conclusion, when over-thinking these things, is to say that the 3Khz peak we see in the BMS curves are also the same thing we are seeing in our test curves! BTW, I don't see any 3Khz peak on Bob's curve. This is getting over-thought and over-analyzed as do so many things here on the forum. Greg Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 No matter how I measured the BMS on that horn, there was always a "rise" somewhere in the 3000Hz range.....until you move off axis. OK, so I'm going to over-analyze and over-think this some more. The reason you are seeing the 3Khz bump more on axis is because it's coming more directly from the driver and not the horn. Greg Quote Link to comment Share on other sites More sharing options...
jwc Posted April 27, 2009 Share Posted April 27, 2009 This is getting over-thought and over-analyzed as do so many things here on the forum. Yes they do. Agreed. I do believe the hump could be from the driver as we have spoke of before. makes sense. I was just curious on the shortening thing....not to explain a curve result as I don't know how it would effect it anyway. The curves look good to me. I think the proof should be what people hear....and I bet they sound great. jc Edit...you posted as I was. I can't answer that with any confidence. Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 Edit...you posted as I was. I can't answer that with any confidence. Me either, I was just over-ly excited to continue the banter. [] Greg Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 I think the proof should be what people hear....and I bet they sound great. I've got a page started with quotes from people who have heard these horns. www.dcchomes.com/Vtrac4.html All negative comments are translated into Russian and placed in the Russian section of this forum. Greg Quote Link to comment Share on other sites More sharing options...
Deang Posted April 27, 2009 Share Posted April 27, 2009 But I'm quite sure the tiny bit of trim that I did to the outside of the flange is not the reason there are any 3Khz peaks. Did you remove the trim and measure? If not, then you don't know. The 3Khz peaks are on the BMS curves too, and even more pronounced than the curves that you or Bob did. There are no published curves for the 4592ND-Mid. The only curves we have are for the ferrite version (4591). There is no peak at 3kHz. http://bmspro.com/fileadmin/bms-data/curves_compression/ferrite/bms_4591_curves.jpg Why would we jump to the conclusion that shortening the mouth of the horn that tiny little bit is the reason for ANY of what we see on the curves? I'm not jumping to conclusions, I'm curious about the peak and what's causing it. Any deviation from the design either in the throat, transition area, or mouth -- will cause abberations in the frequency response. The obvious conclusion, when over-thinking these things, is to say that the 3Khz peak we see in the BMS curves are also the same thing we are seeing in our test curves! Again, there is no 3kHz peak in the BMS FR curve. Now there is a 3kHz peak in the 2nd Harmonic Distortion curve -- that curve is not a frequency response curve, it's a distortion curve. BTW, I don't see any 3Khz peak on Bob's curve. Aren't you curious why? As a designer and builder of horns you plan on selling to people -- you should be! Bob measured at 1 foot. JC measured at 6 feet. My money is on a reflection at the mouth as the sound launches off the edges -- and though it doesn't seem likely to you -- the trim may be playing a factor. Quote Link to comment Share on other sites More sharing options...
BEC Posted April 27, 2009 Share Posted April 27, 2009 Dean, I think a horn mouth reflection is easier to see up close than at a distance. I know that the 470 hz horn mouth reflection the K-400 has when it is not mounted on a baffle is easier to see up close than it is if the mic is further back. Bob Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 I'm sorry Dean, I see where part of the confusion is. I requested a curve for the BMS4592ND-MID a few months ago. Here it is. THIS is where the 3Khz bump is coming from. It is not the tiny bit of trimming I did to the mouth of the horn. Greg Quote Link to comment Share on other sites More sharing options...
greg928gts Posted April 27, 2009 Author Share Posted April 27, 2009 Did you remove the trim and measure? Again, sorry. I should have said "trimming". There is no trim. I was referring to the little bit that I trimmed off each side of the horn. Which I'm quite sure is having no affect on the sound of the horn, good or bad. Let's set up a double blind test with one 24" wide Fc260 horn and a 23" wide Fc260 horn. Good grief. Greg Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.