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drboar

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Posts posted by drboar


  1. 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.

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  2. 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!


  3. Regarding reflectors

    I had a horn similar to LS Kuben.jpg

    Using a Beyma G320 driver adding corner reflectors did not to much in the 250-500 Hz range

    KubenBeymacornerBlue.png

     

    Adding a reflector at the horn split did nothing at all

    KubenBeymaBisectBlue.png

     

    The effect of having both a splitter and corner reflectors was less than corner relectors alone!

    KubenBeymabisectCornerBlue.png

     

    Using an other driver adding splitter did do a difference

    KubenFaneBisectBlue.png

     

    And having both splitter and corner reflectors added som dB from 250 to 800 Hz.

    KubenFaneBisCornerBlue.png

     

    These findings suggest that adding corner reflectors does not mean that you can take frequency response improvements for granted. At the time I did not have equipment to measure time domain response, now I would have done that if I had the horns still in my possesion.

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  4. With such short horns and rellatively low upper cutoff horn flare really does not matter that much. I have been playing around with LS in Hornresponse and with set mouth, throat and length the horn is mosty set response wise. Flare, driver and backchamber do change it a bit but not much.


  5. I did some measurements on adding reflectors on "Kuben" a vintage horn similar to the La Scala.

    1. Bisecting reflector= minor changes

    2. Reflectors at the corners= +12 dB above 1500 Hz.

    3: Both bisecting reflector and corner reflectors =Back to minor changes.

     

    I also discovered that the results were inconsistent between different drivers. So the result you get with your corners and driver may not be the same as other drivers or corners. Some mesurements would be nice...


  6. I built the corner horns with the boards as straight 90 degree cuts. All compound angles with hand saw and file. Some angles not so pretty but out of sight! Used a Phyle MHC600 15" woofer. I really liked the slam and effortlessness of the horns but they really need proper corners. Concrete walls works well flimsy plaster board walls does not.


  7. If corner reflectors improve the high end response has to be tried by trial and error. Cone breakup causes the upper range to be hard to model.

    Below is a measurement of 3 different drivers (gamma LA1232 30 Hz Q about 0.4 and Vas 300 L and a proper PA Horn driver from Beyma. They still both work to about 1000 Hz even if he gamma should have a mass rolloff above 150 Hz...

     

    Kuben is similar but not indentical to the LS, even the 150 Hz peak is there

     

     

    BeymaGammaEminence.jpg


  8. I measured the response of a driver with a theoretical mass roll off in the 150 Hz range in horn "kuben" quite similar to LS. It worked well up to 1200 Hz at least level vise! I assume that the mass roll off stipulates that the cone works as a rigid piston and cone breakup alters the response.

    One way to get the LS to go a bit deeper would be to have an additional horn section extending 20-30 cm into the doghouse. Byusing two 10" driver per cabinet as drivers they would fit in a narrower part of the doghouse.

    • Like 1

  9. The basic frequency response of the LS is determined by horn lenght (bass depth ) and mouth size (evenness). Driver chamber and throat size/flare makes minor changes. The LS will at most go down to 55-60 Hz. Depending on driver and chamber you can get the LS to start to slope below 100 Hz gently towards the cutoff or be flatter in that last octave. Download HornResponse and fiddle around with different options to simulate.


  10. 1. Unplug all drivers from both crossovers (remember to take note on polarity)

    2.turn on the music and connect any widerange driver, old car speaker or what you have, to one crossover driver connection one by one.

    My guess is that one of the serial components such as the paper in oil caps has failed.

    You can find out wich one by simply bypassing each cap with a short cable. That also seriously afffect the working of he crossover so it is no cure for failing components!

     

    If I was you  I would keep the old crossover as is (for resale value of orignial state for vintage nuts) I would also invest in a modern crossover


  11. The shortcoming of the LS is the horn length. In the Ciare B1 design the horn can be extended into the chamber by perhaps 150 mm, not much but for such a short horn everything helps. With the LS there really is not much space to do this but most of the section of the doghouse with no flare this can be done. How this section is made can affect the upper working range as well due to differences in path lengths and shape of the throat.

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  12. Agree about the walls.

    The measurements was on Klipsch clones and the annotation is the other way around. In a proper corner with both walls concrete the horn kept going to 40-50 Hz. With the outer wall still concrete but the backwall in flimsy plaster the response below 80 Hz or so lost 5 dB. Mesurements were made 30 years ago using a Technics SH-8000.

     

    615aaa01-778b-4c50-98f0-5c10f4d1fe22.jpg


  13. The curves below are from "Kuben" a horn similar to the La Scala horn but in this case using 12" drivers. The measurements was with the horn on a table and on axis on about one meters distance. Upper trace is Beyma PA driver Fr about 60 Hz and Qes of 0.2 a typical good horn driver. The lower trace is a Bulgarian Gamma Gamma 1231 driver, light cone very soft suspension and quite high Q (25 Hz 0.42 Qts and 340 L Vas) so the mass corner frequency is about 100 Hz.

    Gamma1231-80cmTable.png

     

    For PA use the beyma is far better more output by far for the same voltage and greater powerhandling as well. For domestic use a trade off between relative bass output and sensitivity might be scewed in the oposite direction. I am not claiming that frequency responses are everything, they have to sound good as well.

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