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Unity horn build

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_djk_ View Drop Down
Old Croc
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Joined: 23 November 2004
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2013 at 10:39am
"Danleys box is 100db."

He has many models,
SH50=100dB
SH64=103dB
SH46=106dB
SH25=110dB
djk
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snowflake View Drop Down
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Joined: 29 December 2004
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 02 July 2013 at 1:31pm
done some high power testing - was still indoors so not ideal but found some interesting stuff.

first off i fitted a protection bulb and polyswitch in series as protection for the beyma cd1014fe HF driver. also fitted an 80uF cap as HP for the mids. still waiting for the coils to finish the passive network. filter settings are posted above.

bulb is a 24V 50W osram halogen. cold resistance is 1.5R and calculated full power resistance is 12R - so ratio of cold to hot resistance is only 1:8 which is lower than usual. polyswitch is one of these:

played around turning the volume up quickly and the polyswitch seemed to cut out at moderate volumes before the bulb started glowing as planned.

played a few tracks at full volume with earplugs in as it was insanely loud. was putting 3*800W amp channel into 1.4",4*6", and 2*10". at higher volumes there was a lot of colouration of the upper treble and severe chuffing from the reflex ports. examining with the mic and signal generator confirmed this. frequencies above 5kHZ showed high levels of distortion up to 20kHz at a level approaching -10dB of the signal at high volumes. the chuffing distortion was coming from the ports from the rear of the bass drivers. the output from 120Hz to 260Hz from  the other ports did not have significant distortion even at full volume. the mids seemed relatively clean but might try making the shorts shallower to increase HF extension.

the beyma cd1014Fe was the cheapest 1.4" I found so have ordered a Paudio BM2-D740 for comparison. going to try some flared 2" port tubes rather than the current 36mm holes to reduce the chuffing.

will have it out at St Pauls carnival in Bristol if anyone is interested.


Edited by snowflake - 02 July 2013 at 1:57pm
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snowflake View Drop Down
Old Croc
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Joined: 29 December 2004
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2013 at 12:21pm
got the new compression driver and ports fitted for carnival. didn't get set up early enough to do very much fiddling but got it eqd flat. by the end of the day had it near full volume with the protection bulb lighting up pretty constantly and it didn't sound distorted as with the cheaper driver.

old compression driver shown for comparision:




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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 23 December 2013 at 11:26pm
just finished new prototype (apart from the crossover)





those aren't quite the finished article as I have since added flying point brackets and handles.
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bee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bee Quote  Post ReplyReply Direct Link To This Post Posted: 23 December 2013 at 11:28pm
nice work....
https://www.elements-audio.com
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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 23 December 2013 at 11:34pm
about 75% of the box is made from laminated ply and mdf hence the different woods showing inside the horn. it seems to ring a lot less when you hit it - will see how it sounds when I do listening tests.

I have abandoned using tee-nuts. a coach bolt with a couple of normal nuts and a washer works fine and if it does start to spin the nuts and end of the bolt are always on the driver side and accessible to pliers.

this was the most complex build I have ever done but seems to have turned out well thanks to my new festool saw and guide rails. I just used PVA on most of it as the joints were so close polyurethane didn't seem necessary.


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Lee In Montreal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lee In Montreal Quote  Post ReplyReply Direct Link To This Post Posted: 23 December 2013 at 11:38pm
I definitely want to hear from you how well the "point source" works on that cabinet.
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grec View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote grec Quote  Post ReplyReply Direct Link To This Post Posted: 24 December 2013 at 11:37pm
Originally posted by bee bee wrote:

nice work....
Beautiful!Clap
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Phil B View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil B Quote  Post ReplyReply Direct Link To This Post Posted: 25 December 2013 at 10:51pm
Nice work.....!

How did the rear port of the woofer end up? I see you have extended the path by going to the edge of the outside box with the woofer baffle ?

.p.
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tv00 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tv00 Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2013 at 12:06pm
WHOW! Good work!
Is there any difference in the new prototype from the old one?
This year I've been digging top builds, amazing what people are doing!
-It is good to see a unity horn build!
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all bass View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote all bass Quote  Post ReplyReply Direct Link To This Post Posted: 26 December 2013 at 12:48pm
Looks good!

Good to see that people are still building and experimenting different stuff!
https://www.instagram.com/my_modular_journey/
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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 31 December 2013 at 12:57pm
Originally posted by Phil B Phil B wrote:

Nice work.....!

How did the rear port of the woofer end up? I see you have extended the path by going to the edge of the outside box with the woofer baffle ?

.p.

at the moment the rear woofer ports are the same size as the front woofer ports. the response is falling off at about 100Hz and then there is a shelf that extends down to 40Hz. I think if I make the ports about 50% bigger should raise the tuning and the output of the port to make it -3dB at about 65Hz.

major differences from the first prototype are that there is no wasted volume inside making the rear volume of the woofers much bigger. have used 12" rather than 10" woofers. changed the throat geometry a bit so that it is an exponential expansion which matches the compression driver throat angle at one end and the angle of the conical horn at the other.

response of the new compression driver is very different to the BM-D740 which means re-design of the crossover. a compression driver that rolls off a 6dB per octave from 1kHz can easily be made flat with the right capacitor but the new driver is fairly flat to 7kHz anyway.
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