Marvel Posted September 9, 2016 Share Posted September 9, 2016 I have a beautiful pair of K-400 horns for the LaScalas I am rebuilding, but found the both horns have a casting mark about 10" straight back into the horn. I've attached a pic showing the little ridge that is on the top/bottom and both sides. Would this be enough to cause some distortion/anomaly in the higher freq. of the midrange? I am making the assumption that it would be better if it were smooth. I've been filing one of the horns smooth, and putting on some primer and will post a newer pic of the results, I am figuring that, other than the time it takes to do it, it can't hurt. Thanks, Bruce Quote Link to comment Share on other sites More sharing options...
Klipsch Employees Chief bonehead Posted September 9, 2016 Klipsch Employees Share Posted September 9, 2016 I would smooth the transition. Looks like the tool was wearing out and the two parts did not mate up well. 1 Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 9, 2016 Author Share Posted September 9, 2016 Thanks Roy. It's rather tedious, but I have the Heresy IIs to listen to. Bruce 1 Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 9, 2016 Share Posted September 9, 2016 I found that the little junction on the TAD 4002 drivers to the K-402 horn is also important to smooth using modeling clay (i.e., originally a Roy D. suggestion, BTW). I once saw a difference in HF output between the left and right drivers at ~10 kHz on a REW SPL and phase plot, then I investigated and found the one driver was radially misaligned by less than 1/16 in (~1.5 mm). Once I used a masking-tape-wrapped 1 7/16" socket to center the driver on the horn, and used the same socket to smooth/flatten the modeling clay filling the gaps in the transition, the issues disappeared. In general, if you measure along the throat central axis centerline to the point of horn/waveguide discontinuity from the center of the driver's voice coil windings (or the flare to the main portion of the horn), that corresponds to about a 1/4 wavelength at the affected frequencies on the output. One further insight to this is that any frequencies above about 7-10 kHz are a driver problem and not a horn problem. If you want better performance above that frequency, look at getting a better driver (the best option), or sticking on an additional tweeter and hope that the crossover problems aren't too intrusive on the overall polar discontinuities and SPL/phase performance. Chris 1 Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 9, 2016 Author Share Posted September 9, 2016 3 minutes ago, Chris A said: One further insight to this is that any frequencies above about 7-10 kHz are a driver problem and not a horn problem. Since this is on the K-400, using the phenolic diaphragm EV1828 I haven't picked up some K55 or equivalent drivers yet, but someone had these in this pair of LS when I picked them up. I tried them on my previous pair of LS and they sounded fine, although I didn't make any measurements with them. 6 minutes ago, Chris A said: In general, if you measure along the throat central axis centerline to the point of horn/waveguide discontinuity from the center of the driver's voice coil windings, that corresponds to about a 1/4 wavelength at the affected frequencies on the output. This means I can calculate approx. what freq. might be getting affected. Thanks for that info as well, Chris. Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 9, 2016 Share Posted September 9, 2016 That little insight (1/4 wavelength along the centerline) also works with finding the right place to start the off-axis ports on a multiple entry horn. Unfortunately, it doesn't tell you how long or how large to make the ports. Chris Quote Link to comment Share on other sites More sharing options...
babadono Posted September 9, 2016 Share Posted September 9, 2016 25 minutes ago, Chris A said: I once saw a difference in HF output between the left and right drivers at ~10 kHz on a REW SPL and phase plot, Just curious...did you HEAR a difference? Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 9, 2016 Share Posted September 9, 2016 Perhaps. I could certainly tell that there was better symmetry of coverage when playing a sine tone. Does that count? Since I'm no longer a "spring chicken" I sometimes have to rely on the ears of others when making adjustments at these frequencies. So I let my wife tell me, and offspring tell me when they visit (yes--empty nesting!). I can certainly hear these frequencies and even higher--but the issue is that no one else is around to share it when it occurs...because it drives them away. Chris Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 9, 2016 Share Posted September 9, 2016 BTW: I can hear the 13.9 kHz "chatter" of the K-69-A quite clearly during cymbal transients. That's why I used a tri-amped 3-way for my center JuBelle when it was there (since replaced by the full-range K-402-MEH). When I get things under control with the other K-402-MEHs that are planned in my 5.2 setup, I'll switch to a 2" Be diaphragm driver in the center, or a tri-amped dual-diaphragm 2" driver like the BMS 4592ND. Chris Quote Link to comment Share on other sites More sharing options...
JohnA Posted September 9, 2016 Share Posted September 9, 2016 18 hours ago, Marvel said: I have a beautiful pair of K-400 horns for the LaScalas I am rebuilding, but found the both horns have a casting mark about 10" straight back into the horn. I've attached a pic showing the little ridge that is on the top/bottom and both sides. Would this be enough to cause some distortion/anomaly in the higher freq. of the midrange? I am making the assumption that it would be better if it were smooth. I've been filing one of the horns smooth, and putting on some primer and will post a newer pic of the results, I am figuring that, other than the time it takes to do it, it can't hurt. Thanks, Bruce Well, mine do too! One is about like yours and the other not as severe. On the worst one the throat mold shifted to the left a little. The question is, if I remove the edge and leave a smooth discontinuity, have I bettered the horn's performance? 1 Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 9, 2016 Share Posted September 9, 2016 Likely. Acoustics are not like mechanical fit tolerances. Discontinuities in the form of slots and ridges on the inside surface of horns isn't good karma. Sometimes, even small depressions are much desirable in terms of performance than ridges and slots. Bear in mind that there are higher order modes that are looking for a reason to be generated and transmitted out the mouth of the horn at some frequency cut-on point. Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 9, 2016 Author Share Posted September 9, 2016 Although mine looks like a ridge, is is more like taking a piece of cardboard (thin, like the back of a notepad) and laying it over another piece, instead of having them butt together edge to edge. Unfortunately, the high side is on the mouth side of the horn. I have used a flat file to work down all the extra, but have spent more than an hour, hour and a half and there is still a lot of aluminum to go.It's far enough in that the vertical height there is only 1.5 inches. It's slow going when you can only put pressure on one end of the file. So, .75 inch would be a quarter wavelength. What would be the freq. this could be messing up? btw, if I can get enough removed, I'll get enough primer/filler to get it smoothed out more in the curve. Bruce Quote Link to comment Share on other sites More sharing options...
JohnA Posted September 9, 2016 Share Posted September 9, 2016 speed of sound = 1130 ft/sec 1130 ft/s * 12 in/ft = 13560 in/s 13560 in/s = 4520 cycles/s 0.75 in * 4 But shouldn't the distance be more like 5" from the ridge to the voicecoil down the centerline? That calculates 678 Hz. 1 Quote Link to comment Share on other sites More sharing options...
Deang Posted September 9, 2016 Share Posted September 9, 2016 Klipsch should be selling K-401s so we don't have to deal with this nonsense. 1 Quote Link to comment Share on other sites More sharing options...
JohnA Posted September 9, 2016 Share Posted September 9, 2016 Well, when did they quit? Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 9, 2016 Author Share Posted September 9, 2016 3 hours ago, John Albright said: speed of sound = 1130 ft/sec 1130 ft/s * 12 in/ft = 13560 in/s 13560 in/s = 4520 cycles/s 0.75 in * 4 But shouldn't the distance be more like 5" from the ridge to the voicecoil down the centerline? That calculates 678 Hz. Duh, boy did I figure that wrong... I just re-read it... yes, but I think it's longer than that. Bruce Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 11, 2016 Author Share Posted September 11, 2016 Ok, the distance from the deformity to the back of the horn is right at 11 inches, as shown in the attached pic. I've also got another pic after some filing (over an hour...) and with some primer sprayed back in the horn to show a little more smoothness. It's better but I'm not done yet. Bruce 1 Quote Link to comment Share on other sites More sharing options...
JohnA Posted September 14, 2016 Share Posted September 14, 2016 Lets add a little for the distance to the voice coil. 13560 in/s = 295 cycles/s 11.5 in * 4 The 1/4 wave point for 295 Hz IS within the operating range of the K-400, but just. 13560 in/s = 1180 cycles/s 11.5 in The full wave point is more concerning. So, I'd say, smooth it with a burr or sandpaper roll on a Dremel and call it good. BTW, I have an air powered die grinder and some burrs, if you want more speed. Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 14, 2016 Author Share Posted September 14, 2016 There's barely enough room to get a flat file in there, much less a powered tool Maybe with the dremel I have, using the flex cable... But it's not a simple ridge. I'll make a drawing showing what I mean. Bruce Quote Link to comment Share on other sites More sharing options...
Karsoncookie Posted September 14, 2016 Share Posted September 14, 2016 Is it possible, after the basic filing anyway, that I would do w a pneumatic 1/4" die grinder, lacking that, graduated coarseness flat files, and then some hand sandpaper on appropriate sized blocks smoothing while watching TV, this is being overfocused on?? You may need to be starting with a coarser cut file. Yes, I understand it's not just a ridge burr, but a "step" Hey just my thinking, what do I know. Lars Quote Link to comment Share on other sites More sharing options...
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