400Hz-20KHz horn for BMS 4595 |
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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A Klipsch K-402 HF horn on top of a LaScala. It's conical in the throat area, with a tractrix mouth.
It's large enough to have good horizontal directivity control to 400hz, and still have good dispersion at 16Khz (without a slot). http://forums.klipsch.com/forums/storage/4/1959035/K402_hor.pdf http://forums.klipsch.com/forums/storage/4/1959037/K402_ver.pdf H=25.5" W=39.5" D=16.25" 2" throat. Edited by _djk_ - 28 April 2013 at 2:03pm |
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djk
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PavelP
Registered User Joined: 25 March 2011 Location: Russia Status: Offline Points: 159 |
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MarjanM, it's very interesting. Is it useful from 500Hz on music signal? And what about efficiency/power when 450-700Hz diapozone is used? I mean 8" single speaker with some horn of the same size (f1-like) could have maximum sensitivity about 108db not 118db as driver, but it has more power so it could be considerably equal in sensitivity but costs much lower and go lower about 200-300Hz.
Edited by PavelP - 28 April 2013 at 2:02pm |
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MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7816 |
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Pavel, the main advantage here is getting a true point source. Meaning one source is always better then two sources.
No phase problems and so on. About the power, BMS coax is 150W, mid range 8 inch drivers are all about 200W, so not much power difference there.
Edited by MarjanM - 28 April 2013 at 2:31pm |
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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PavelP
Registered User Joined: 25 March 2011 Location: Russia Status: Offline Points: 159 |
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I see. But if we place delayed twitter in mf-horn mouth it will be such a point soure as a 2-way driver with crossover.
I like this idea and thought about it, but it looks like very expansive hi-end, because it's very difficult to make effective mid 90-450Hz. To reach good sensitivity in this diapozone over 3-4 cabs needed, but the effective mid will be 90-250. In this way we need additional 3-way system: 20-90, 90-250, 250-450 plus 2-way driver. Wo-wo-wow! |
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TONY.A.S.S.
Old Croc Joined: 21 February 2007 Location: United Kingdom Status: Offline Points: 6878 |
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there was a comment about the sound quality at such a low frequency. I only have experience with the B and C coaxil compression driver, which also has a similar x/o point. These drivers are made to go that low. I'm not sure how the BMS driver sounds at the lower frequencies, because I believe that the larger diaphragm is also metal. But the larger diapragm in the B and C driver is a paper cone, and I guess in part, this also combats any harshness at lower frequencies. I think this gets a better result for upper mids than depending on the high end of a 12" speaker to do the same job.
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MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7816 |
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Tony, BMS is an annular polyester ring. Not a cone or a diaphragm.
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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Steve_B
Old Croc Joined: 29 September 2007 Status: Offline Points: 1587 |
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As I said, the low end response is set by the included
angle. There is not much difference between yours and Timebomb's dispersion
angles so the low end should be similar even though your horn is smaller. The effective length of a horn can be slightly longer than
the physical length. Add to that the additional length in the driver, between
the diaphragm and exit and let’s say it is 34cm long. If we go with 340msec-1
for the speed of sound, to make things easy, the length of your horn is 1
wavelength at 1000Hz. If the mouth area is too small the horn will exhibit
resonant peaks at multiples of ½ wavelength of the horn, so 500Hz, 1KHz, etc.
This can be seen in your measured response. Timebomb’s larger horn does not
exhibit these ripples. This may or may not be a problem. Size versus slight uneven
response it is the designers choice. The thing is, if you don’t know the theory,
how do you decide which way to go if you wish to modify your horn. The other thing that doesn’t show in either response graph
is the off axis response. The larger horn will have a lot better control at
lower frequencies. Again the loss of control (wide dispersion pattern) might
not be a problem depending on what device is being used in the next passband
down. With a compression driver of this size and output, I wouldn’t expect it
to be used above a single 12” cone.
I guess it depends on
what you call good dispersion at 16KHz. At 1.6KHz the coverage is 90˚ whereas
at 16KHz it is down to 50˚, highlighted with red arrows. The horn also exhibits
fingering, highlighted by yellow arrows. I’m not saying that it is a bad design, but a tractrix flare
means that it will have narrowing dispersion at higher frequencies. Assuming
that the designer knew what he/she was doing, it will have been a conscious decision,
and the advantages of the flare curve will have been considered to outweigh the
disadvantages. I think that this all goes to show that Timebomb already has
a horn that can compete with commercial designs. |
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MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7816 |
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Steve, as all the things in life, one must compromise.
The horn i did has to fit in a box of a given size. So i can live with resonant peaks of 1.5db. This horn also has to be used in a DB C4 type of box so the size was chosen before all the other things were involved. Having that on mind i am quite happy with it. And it does not have a strait walls. Ill post some pictures once it is all done. Looks like a Frankenstein right now ;-) And yes this driver is used above a single 12 inch and single 15 inch. Why not?
Edited by MarjanM - 28 April 2013 at 5:06pm |
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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Timebomb
Old Croc Joined: 11 October 2004 Location: Lancaster Status: Offline Points: 2716 |
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Cheers Steve, i chose a linear / conical expansion as it was easy to build and has more consistent directivity compared to exponential, hyperbolic, tractrix etc. I built some tractrix flares for some other drivers and they sounded great on axis but the beaming was too much for me. I knew the large mouth would cause lobing at the top end but i think you need a large horn to get down that low cleanly, its not something you can really get away from. And i thought it was best to make it as big a possible but fit inside the cases that fit inside the low mid horns. I have some smaller OHM horns that the drivers came with and they are not as clean as my big horns, even with a much higher high pass.
I still think its worth trying some mouth correction, i thought of a different way to do it, more like the Klipsch horn DJK posted, i could possibly truncate the existing horns and add a roundover / front baffle. I still have a OSB prototype that i could cut down to test with, and i think i have some 6" plastic pipe somewhere. I will have a dig on my hard drive and see if i took any off axis measurements of this horn, i think ARTA will do polar plots so i recon my next step is to make a scabby prototype with the osb horn and take a load of measurements. |
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James Secker facebook.com/soundgearuk
James@soundgear.co.uk www.soundgear.co.uk |
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TONY.A.S.S.
Old Croc Joined: 21 February 2007 Location: United Kingdom Status: Offline Points: 6878 |
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Nice internal shot there Marj. It's good to know these things. This is a completely different principle to the B and C DCX50.
Edited by TONY.A.S.S. - 28 April 2013 at 6:09pm |
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Timebomb
Old Croc Joined: 11 October 2004 Location: Lancaster Status: Offline Points: 2716 |
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Something like this.
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James Secker facebook.com/soundgearuk
James@soundgear.co.uk www.soundgear.co.uk |
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Steve_B
Old Croc Joined: 29 September 2007 Status: Offline Points: 1587 |
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I’m not saying it won’t
work, but it just seems a very expensive option if the output is limited by a
single 12” driver. Directivity wise and given the size of your horn, I would
think that 800Hz to 1KHz would match up. Olson gives the directivity of both
conical and exponential horns of a similar size the same directivity as a 12”
driver at 1KHz. If the idea of the lower
crossover is to use a more bass orientated drive unit for the 12” then the
sensitivity is likely to be lower, which is even more of a waste of the high
output achievable by the compression driver.
With a square mouth and straight walls a 60 x 40 dispersion
angle is unlikely. Have you got any off axis response plots? They are always
interesting. |
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