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Unity horn build

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_djk_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 26 March 2013 at 8:30pm
I built these double 12 mids in 1980 after reading the manta-ray paper, they sounded much better than the Altec A7, JBL 4560 type enclosures that were popular at the time.

http://i56.photobucket.com/albums/g196/dkleitsch/dual12MantaRay.jpg
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2013 at 8:37pm
I've sanded the horn throat to give a more gradual transition from compression driver throat angle to horn wall angle but it hasn't made any significant difference to the response.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 02 April 2013 at 11:35pm
added more felt strip six inches wide and half an inch thick all the way round the throat. had to readjust the crossover slopes a bit and now seem to have got on axis response pretty flat. moving off axis the response curve pretty much keeps the same shape. response is now -3dB at 180Hz and 17kHz. in band response is +/- 2.5 dB with 1/6 octave resolution. adding felt to the edges is certainly easier than increasing the size and weight of the box by enlarging the mouth flange. the midrange response is damped down slightly by the felt but only about 1dB. would be good if the mids went a bit higher but pretty happy with the response. I did spend a long time designing this but quite surprised it has turned out so well. now for the ten inch bass drivers Confused
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_B Quote  Post ReplyReply Direct Link To This Post Posted: 03 April 2013 at 10:46am
Quote I've sanded the horn throat to give a more gradual transition from compression driver throat angle to horn wall angle but it hasn't made any significant difference to the response.

Quote added more felt strip six inches wide and half an inch thick all the way round the throat. had to readjust the crossover slopes a bit and now seem to have got on axis response pretty flat. moving off axis the response curve pretty much keeps the same shape. response is now -3dB at 180Hz and 17kHz. in band response is +/- 2.5 dB with 1/6 octave resolution. adding felt to the edges is certainly easier than increasing the size and weight of the box by enlarging the mouth flange. the midrange response is damped down slightly by the felt but only about 1dB. would be good if the mids went a bit higher but pretty happy with the response. I did spend a long time designing this but quite surprised it has turned out so well. now for the ten inch bass drivers

Welcome to the world of design and experimentation. Some things work, many don’t. It sounds like you are moving in the right direction though. Thumbs Up

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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 20 June 2013 at 6:20pm
gave up trying to accurately model the bass section of the unity horn so just went for it and drilled some extra holes in the box at the start of the thread. I went for two beyma 10MI100 drivers because of it's strong motor, low Vas, compact size, reasonable power handling. two of them were predicted to be similar in sensitivity to the other two sections.

tapped the front of the driver into the horn just over half way down the horn with two 36mm holes per driver. this seemed reasonable compared to the mid drivers which had a 1" hole per driver. measured the response and found the low section was giving a similar sensitivity to the top section with a bit of a peak at 350Hz and the first cancellation notch at about 450Hz. the low end had a gentle roll off to about 70Hz. the rear volume was about 12L per driver. two 36mm holes per driver through 12mm wood happens to give a predicted tuning of about 100Hz so went with this. response was now -3dB at 80Hz with a bit of a hump at 100Hz at a similar level to the one at 350 Hz. the dip in between was several dB. all these measurements have been done indoors so not that accurate especially for the bass. just using behringer mic and ultracurve.

playing around with the filters I tried to keep them low order to reduce the number of components needed. 6dB per octave at 8kHz made the top section similar in sensitivity to the bass. 12dB per octave at 1kHz protects it from overexcursion and gives the max response at crossover. ended up having no LPF on the mids - they help out filling in a dip around 4.5kHz and it sounds more natural without a filter. HPF on mids is 6dB at 260Hz - the small chamber on the mids means there is no danger of overexcursion and LPF on bass is 12dB at 260 Hz which flattens out the upper bass region. acoustic crossover points are 350Hz and 1.2kHz. the three sections (1.4", 4*6", 2*10") are matched in sensitivity when the filters are set so the entire crossover network will be four caps and two coils with possibly a notch filter on the tweeter if needed.

would be interesting to get some phase and impedance measurements but seem to have done pretty well without. sounds better than any other speaker I have listened to and doesn't need much eq to make it totally flat. bit of chuffing on the rear bass ports which might be solved by rounding the edges and the taps from the front side might work better an inch nearer the throat.

will post a photo when I charge my camera up.


Edited by snowflake - 20 June 2013 at 6:22pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 21 June 2013 at 7:11pm



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Post Options Post Options   Thanks (0) Thanks(0)   Quote grec Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2013 at 11:05am
Nice!Clap
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil B Quote  Post ReplyReply Direct Link To This Post Posted: 26 June 2013 at 11:56am
Originally posted by snowflake snowflake wrote:

gave up trying to accurately model the bass section of the unity horn so just went for it and drilled some extra holes in the box


After all the modelling and predictions we did with our Unity box in the end we did just that...drilled holes and saw what we got!
Getting a decent model seems only practical in Akabak..which I have no knowledge of...

Curious as to why you put the 10" rear ports on the same horn face as it`s front ones? But it seems to work??

Good work !

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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 26 June 2013 at 7:35pm
I was using akabak and wasn't getting anywhere - my model ended up so complicated I'm not sure I hadn't made an error somewhere. anyone know if it is possible to generate a 2D schematic from akabak script like you can in hornresp as a sanity check?

anyway, the side walls of the horn continue to the top and bottom of the box seperating the rear volume of the woofers from some wasted volume that contains the mids and compression driver.  the main reason for doing this was to make contstruction easier as the rear panel and vertical edges at the front of the cab don't need to be airtight. I guess if I had 12" drivers and wanted to go down to 50Hz then I would need the whole volume. think I may need to increase the 1.4" reflex ports up to 2" and put some 5cm tubes in as they seem to be chuffing at moderate levels.

just been estimating the average sensitivity by comparing to some other boxes and would guess it is 104dB/2.83V and the impedance should be over 8R for all but half an octave of the operating range. waiting for the crossover coils to arrive. can't wait to get it outside to do some high power tests.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 27 June 2013 at 12:47am
104db? Danleys box is 100db.
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2013 at 10:08am
danley's SH50 is -3dB at 50Hz whereas mine is currently tuned with -3dB at 80Hz. I am guessing he uses one of the Faitalpro 12" drivers which has considerably more xmax and lower BL than the beyma 10MI100 that I used. so mine should be more sensitive. there are no l-pads to match the levels of the drivers in my box - the crossover filters do it all.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyWave Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2013 at 5:20pm
Very interesting this whole thing. Hats off and Clap
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