Tony Reed Posted August 9, 2000 Share Posted August 9, 2000 I'm thinking of running vertical "strips" cut on a 45 degree angle in the back corners of my LaScala's. These "strips" would run top to bottom filling in the last 90 degree corner somewhat. This would help round out the last turn in the bass section. How would this affect the sound? I thought it might reduce standing waves by helping the air flow. Thanks, Tony Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted August 9, 2000 Share Posted August 9, 2000 Tony, I don't completely understand what you are describing, but I would NOT do anything to change the rate of area expansion inside the horn! Cross bracing is another natter. That would help. Al K. Quote Link to comment Share on other sites More sharing options...
Tony Reed Posted August 9, 2000 Author Share Posted August 9, 2000 This is a view looking from the top. The mod in question is shaded in red. I talked to Trey at Klipsch, he seemed to think it might be worth a go. Thanks, Tony Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted August 9, 2000 Share Posted August 9, 2000 Tony, Ok... Now that I see it on the drawing I tend to think it might be an improvement. I don't think it will do any harm. In fact, the Belle has a wedge like that right at the throat of the horn, right in front of the woffer driver. The La Scala may have that too. You would have to pull the woffer out to see it though. Al K. Quote Link to comment Share on other sites More sharing options...
Tony Reed Posted August 9, 2000 Author Share Posted August 9, 2000 Al: Yes, there is a wedge at the throat of the horn in the LaScala. I thought I would use a wedge of similar size and shape for the mod. Thanks, Tony Quote Link to comment Share on other sites More sharing options...
Klewless Posted August 9, 2000 Share Posted August 9, 2000 Looks like a good mod to me. It would tend to help the high freqs negotiate the turn. I might even try that myself. ------------------ John P St Paul, MN Quote Link to comment Share on other sites More sharing options...
WMcD Posted August 9, 2000 Share Posted August 9, 2000 Dr. Bruce Edgar published something in Speaker Builder on how such structures were necessary to prevent the area in the turn from being too great and thus effectively widening the duct. I.e. a departure from the approximation of an exponential expansion. The Speaker Lab near copy of the K-Horn has such pieces at the first turn, i.e. the turn which is actually at the top and bottom just behind the front surface. This is analogous to what you're talking about. The duct there in the Speaker Lab version, like in in your drawing, is about three inches wide. The diagonal piece is solid. The short sides of the cross section of the piece are 1.5 inches long. Therefore the hypotenuse is 1.414 time that. I mention this as suggested dimension to work with. I've seen one explanation from Speaker Lab that this is a matter of "reflecting" treble frequencies. I think that is not quite accurate in view of the wavelengths involved. 400 Hz is about the upper limit and has a wavelengths of over two feet. The other way of explaining it is that the wave has to go a relative long way around the outside of the curve, and a short way around the inside of the curve. You don't want that difference to be anywhere near a half wavelength, because there would be cancellation. My understanding of the design of the K-Horn, Belle, and LaScala is to keep the width of the duct in the turn to a minimum width. The path is split into two symmetrical structures. Otherwise, one path could have a duct width of six inches. The radius of the outside of the turn would then be greater and thus would be closer to half a wavelength. The split path may well reduce the purported problem. Especially since there is only one bend in the LaScala. So, that may be a reason for the piece's omission. However, putting the brace in is probably, IMHO, a good idea and can't hurt. It would be interesting to see how the turns in the Jubilee are designed. It seems the bass horn is being used up to 800 Hz where such considerations have a larger role. Gil 1 Quote Link to comment Share on other sites More sharing options...
Tom Brennan Posted August 9, 2000 Share Posted August 9, 2000 Originally posted by Klewless: My Peavey FH-1 basshorns (similar to the LaScala horn) have such reflectors in the corners, they help the highend response of the horn. Supposedly the LS horn runs out of gas at 400 cycles, my Peaveys (with K-33E woofers installed) run flat up to 500 cycles. So the reflectors might help the top response of the basshorn but since the LS crossesover at 400 cycles the mod may be of no practical use. However if you CAN get the basshorn to respond to 500 cycles then lots of other mods become possible such as substituting aluminum diaphragm Altec or JBl drivers for the stock mid drivers. Then you could junk the tweeters and go 2-way and play with 511B or Edgar saladbowl horns and on and on, it never ends. :-) Quote Link to comment Share on other sites More sharing options...
WMcD Posted August 10, 2000 Share Posted August 10, 2000 Tony, Thanks for the very nice drawing. To complete the picture, can you tell us the interior dimension of the height of the bass horn. Regards, Gil 1 Quote Link to comment Share on other sites More sharing options...
Tony Reed Posted August 11, 2000 Author Share Posted August 11, 2000 Gil: 22 1/4 in. There's a little more to the bass horn, but it must be viewed from a different "angle". Such as the 3 x 13 slot the woofer fires through, the wedge on the back wall across from the slot and the 4 deflectors that expand from the slot. Tony Quote Link to comment Share on other sites More sharing options...
KGeist Posted August 11, 2000 Share Posted August 11, 2000 Tony, I've tested prototype La Scala's with wedges positioned as you suggest. It does increase the bandwidth of the speaker by a couple of hundred Hertz, but the amplitude response above 400 Hz was pretty choppy (very narrow 6-10 dB dips if I remember correctly). I believe we tried more than one size wedge, but I don't remember the difference it made. We abandoned the idea after we realized the response wasn't as smooth as we would like. However, we were also concerned about the bass-horns dispersion characteristics above 400 Hz. At these frequencies, the horn is beginning to get fairly narrow. I suspect some of this is due to the bifurcated horn section. I don't want to discourage you from trying this because we probably didn't explore it as thoroughly as we should have. Extending the bandwidth of the bass-horn in order to relieve some of the burden on the midrange may more than offset some of the problems I describe above. Quote Link to comment Share on other sites More sharing options...
pzannucci Posted August 12, 2000 Share Posted August 12, 2000 Anything that keeps the horn more in a continuous curve would be good but the effect will likely only be at higher frequencies (as suggested) of the bass driver. Don't know how this would affect response of the system as a whole since it was not designed in the crossovers to handle that change in response. You might like it. Peter Z. Quote Link to comment Share on other sites More sharing options...
dtximages Posted August 13, 2000 Share Posted August 13, 2000 This sounds like a good mod but in my experience with the LS I would rather take more of the high frequencies out of the bass horn. It makes some lower vocals sound fat and muddy I think. Wouldn't this mod aid in the hollow upper mids? Just a random though. Ill probably try it anyway though. Quote Link to comment Share on other sites More sharing options...
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