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drboar

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Posts posted by drboar


  1. 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 brandūü§Ē.¬†


  2. 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.

    • Like 1

  3. 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?


  4. 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.

    • Thanks 1

  5. 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.


  6. 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.


  7. 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 ;)


  8. 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.


  9. As I recall radiation angle affect the needed mouth area not horn length. There is some effect of the end correction that extend the accoustical lenght a bit in a corner compared  free field.

    Very nice video and a very nice kit where all the parts snaps together. As I live in Europe shipping a kit would be way to expensive so I will  do my own interpretation if I build the horn, but that does not diminish the joy of looking at the video.

    • Like 1

  10. Looking at the horns makes me wish that I had not reduced my collection of 12" drivers:rolleyes:

    On the other hand I have modeled the LaScala and other in HornResponse, there horn lenght is critical for where the high pass occurs. The JWC looks really short something like 50cm or so (thats 20" in imperial units) Then the horn should start dropping at 140 Hz or so??

     

    The scientist in me wants to how the horn work to get down to 60 Hz!

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