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drboar

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Everything posted by drboar

  1. Plywood for sure is far more sturdy than MDF for mobile use, bumps and scratches and the occational rain shower. For a stationary indoor loudspeaker however, it appears that bracing and damping/lamination to be more important. There are differences but they are not that huge. Here is a test conducted by the German magazine Hobby & HiFi. The setup is a dual chamber box with a driver in bisecting wall. A board to be tested was placed in front of the driver and both soundpressure in front of the box (compared to no board) as well vibrations of the board was measured Vibrations to the left and reduction in sound level to the right. The referense was the 19 mm MDF at the bottom. That result is inserted in the other graphs for comparison. Not much difference between 16 mm MDF, 19 MDF and 18mm Plywood. Fire retarding concrete chipboard 20mm is better but hard to come by. 28 mm MDF is better but not by that much, 20mm stone is way better, 19mm chipboard is slightly worse than MDF and 19mm blockwood a bit worse than chipboard. These measurements were made in the frequency -amplitude domain, I have seen measurement in the time domain and they show most effect of bracing and lamination more than the instrinsic qualities of the board.
  2. At resonable temperatures the speed of sound is lineary proportional to temperature, in Kelvin that is. If we imagine the air above the fire as a hot cylinder, hotter in the center. If a wavefront hits this cylinder the wave in the middle will accelerate more than the wave hitting the cylinder off center as the path lenght is longer and the air hotter through the center. So the wave will become more circular in the horizonal plane and less sound energy will reach the listener in front of the speaker. So the heat cyliner will work as a lens. The lens action works when the pathlenght through the hot cylinder is a sizable fraction of the sound wavelenths. If the rising air is to deflect sound the soundwaves has to be lifted a significiant amount during the less of 1/100 of a second it passes through the heat cylinder. As there is a vertical heat gradient in the air column that gradient will deflect the soundwaves upwards in a similar to the previous description.
  3. I built (long time ago) a Klipsch Horn Clone. I built it in 19mm chipboard, keeping the horn flare as original and then slightly smaller chamber. So the sturderier the better.
  4. bis.se I have several of their records, no compression what so ever. They have mostly classical music but if you like that, the audio quality is really good.
  5. You could also extend the horn throat into the doghouse, that would also extend the length.
  6. LTH-142 with a good driver would work as a two way system. Try that first with maximal baffle loadning of the horn, if needed add a tweeter.
  7. FaitalPRO LTH142 and a driver that you like. Realy good horns, I have the slightly smaller 1" variant.
  8. With a 12" woofer you can extend the hornpath with a short straight stub into the doghouse, extending the bass some few Hz. I would rather look into that then scaling down the basshorn and getting the midrange horn even lower.
  9. I am quite sceptic to the value of very expensive cables. However, good long time quality is important. in 1988 I bought two loudspeaker cables. Some booring looking Supra 2.5mm2 cables and some Monster cable copies shiny and fat. 2-3 years later the latter had the copper turning green, probably due to reactive components in the plastic. If I peal of the plastic of the supra 30 years later it is still coppery and shining! So head for Madisound and Supra! There are many other brands that I am sure ar good as well, but as a Swede and a happy customer I want to push Supra a Swedish brand🤔.
  10. I bought some vintage Ortophon speakers (In Sweden).They contained Scan-Speak drivers. A site in Japan offered to buy them at a very good price. However, I had to pay for the shipping (expensive !) and they would give me their final price after inspecting the drivers. All in all at maximum price a would make a small profit otherwise I would make a loss at the sale... So the point is value depend on were you have someting. So the vintage Dalies would probably go for less than 500 USD here. If you can fill a container with similar goods you could make a profit selling to Japan but not with single speakers.
  11. The Eminence Kappa-15C i supposed to be a really good alternative. 129 € at Thomann
  12. The LS have a peak that seem hard to get rid of. If one used a HH chamber or a pipe resonator to reduce that peak things would be better for home use of the LS. In PA use I can imagine that any contraption that reduce effiency is a bad thing but at home were the LS hardly goes on at full blast hours on endThe LS has that midbass?
  13. How about a socket in one part and a short rod sticking out from the other part? That would attach them in a similar way to that ball and socket corner thing.
  14. Per pound fiberglass is the most cost effective if you need a lot of it. However for a small box polyfill from cheap pillows from IKEA, a DIY store or what is nearby is cheaper as you can get a smaller amount than fiberglass. I newer use fiberglass ( and I have spare insulation in the attic for "free") as polyfill and the like is so much nicer to handle. Avoid covering the crossover with insulation, even if the losses is only a watt or two if well insultated the components can get really hot. My guess is that the horn is padded down with resistors and if they get really hot they can overheat, they can also heat up the capacitors. For electrolytic caps you can estimate that for every 10 degrees C (roughly 22 F) increase in temperature the lifespan of the cap is halved. There is recycled denim and biodynamic hemp fiber and what not, but dont overdo it.
  15. If you are using just caps then you have first order high pass filters. With no filtering in lowpass mode for the woofer and midrange. A cap will give you 6 db/octave for a resistive load only. say 8 Ohms, If the impedance deviate substantially from a constant load so will the filter slope! To get a resonable 6db filter crossover at 600 Hz the bassdriver has to have a flat impedance to at least 2400 Hz (doable with a Zobel) and a flat response to 2400 Hz as well otherwise the slope will shift around for the lowpass. The same hold true for the midrange horn that should be flat down to 150 Hz! So adding a cap in series with the midrange and a coil in series with the woofer, is low slope crossover, and first order in one sense of the word but still not a "true" 6dB filter with that phase and frequency response of a theoretical filter. IRL it will be a hybrid filter with various slopes and orders where it counts, in the accoustic domain.
  16. How have you made your crossover that is picked the values of caps and coils? A textbook coil will not work as the inductance of the bassdriver will change the actual slope. A Zobel network will rectify this
  17. There is no need to get 13 micro, adding caps in paralell is the right thing to do. Go for plastic film caps what ever you can find and do not bother with audiophile grade stuff,
  18. There are many that use aircore coils for woofers. They just become larger and more expensive than iron core for a given inductance and resistance. 2.5 mH is not that large either so a breif look at parts express going from 18 and 16 AWG what ever that is in mm2 air ( 0.9 ohm and 0.45 ohm) drops to 0.3 and 0.15 ohm). Try to measure the losses... I have a pile of woofers and various 2.5mH coils, if I just could find my Dayton Woofer tester I could try measure the accoustic changes,. Going from 1 ohm to close to 0 should be possible to measure.
  19. At some frequency drivers go from wide beam/omnidirectional to beaming. In most cases for any crossover point the low range driver beam more than the high range driver. With a overlapping crossover this change is blurred. With steep slope xovers the frequency dependent beamwith is less blurred. Could that affect center image?
  20. Regarding a cone driver Faital Pro M5N12-80. In my experience the lowpass functions of the horn may or may not follow the calculated curve.so you could try crossing over higher than 400 Hz and then things like Faital Pro LTH142 crossed over at 500 Hz or so (in a domestic setting) is possible. The fact that the basshorn may have output to 1 kHz does not have to equal good sound up to 1 kHz so, test! An old analog active crossover where you can slide the crossover point around with a twist of a knob is handy
  21. As far as smoothness goes it is strongly impacted by curves "in the nude" or smoothed curves. In my setup I can diplay cuves au naturel warts and all. smoothing over 1/12 octave all the way to smoothing to running averages over octave windows. The overall response is then dependent on which horn that is used with the driver.
  22. Up to 80 Hz or so speed is not an issue. Volume displacment is a 6.5" cone van move at 20 Hz but Will have a hard time generating audiable output.
  23. With blue tooth headphones lossy compression is needed, but otherwise? My iPhone has 256 GB thats a lot of music even with just lossless compression.
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