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Unity horn build
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pappdani7 View Drop Down
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    Posted: 26 October 2022 at 8:36pm
Hello! Perfect work! 

Could you share the plans of the speaker? 
I would like to build my own so i would gladly pay for it as well. 
My email address:  mailto:pappdani7@gmail.com - pappdani7@gmail.com 
Thank you very much!
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snowflake View Drop Down
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Points: 3122 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2021 at 12:32am
Originally posted by fatfreddiescat fatfreddiescat wrote:

With a blocking cap the comp driver is partially decoupled from the amplifier due to the series impedance. This could be a problem due to the comp sharing a waveguide with the mid drivers as the SPL is very high at the throat of the waveguide, the pressure from the mids can cause the comp diaphragm to modulate excessively potentially damaging it. By coupling it directly to the amp or having a low impedance path across it's terminals, the diaphragm will be better damped and should help to reduce the modulation.


the compression drivers have an inductor across them so they will be damped at low frequencies. It is the mids I was worried about as cap was between them and the amp.

Unless you are using amps that are clipping badly and putting out DC, the DC blocking caps will not help and possibly make things worse. My amps have clip limiters and enough headroom that they never clip anyway.
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Points: 1083 		Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 06 April 2021 at 4:18pm
With a blocking cap the comp driver is partially decoupled from the amplifier due to the series impedance. This could be a problem due to the comp sharing a waveguide with the mid drivers as the SPL is very high at the throat of the waveguide, the pressure from the mids can cause the comp diaphragm to modulate excessively potentially damaging it. By coupling it directly to the amp or having a low impedance path across it's terminals, the diaphragm will be better damped and should help to reduce the modulation.
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Teunos View Drop Down
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This one you need to explain to me; why would electrical damping at low frequencies be a problem if you insert a DC blocking cap?
Off course presuming that it is really meant as "last resort HPF protection in case i insert the wrong speakon" or "my amp crapped the bed and really put out DC on the speaker output", or maybe "I wrongly configured the output matrix mixer of my DSP and sent bass to the tweeters". (which are the 3 primary reasons i use them on all HF drivers).

DC blocking cap HPF corner frequency should be chosen well below the intended passband of the speaker.
As long as you maintain that rule (I suggest at least an octave below the intended passband), there is absolutely no noticeable impact on damping factor whatsoever. 


Edited by Teunos - 06 April 2021 at 3:24pm
Best regards,
Teun.
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Points: 3122 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 05 April 2021 at 2:29pm
Originally posted by snowflake snowflake wrote:

old crossover left, new version right (designed with more accurate REW data). HPF shifted up to 1.5kHz and changed to second order rather than third (plus polarity reversal on tweeter). got rid of bulb and high-shelf bypass cap - rather implement these in LMS. series resistor and PTC moved to amp-side of filter inductor to protect whole circuit from over-powering. large cap is DC blocking and signal for both 6" and 1.4" now goes through it. same resistor network used as previously posted.




I now realise that using a DC blocking cap is a really bad idea because it removes all electrical damping at low frequencies. fortunately the HF and mid drivers are also protected by the cutoff frequency of the conical horn which increases the nearer to the throat you get, and by the rear chambers of the drivers.

so with that removed the crossover is just a second order filter on the compression driver, an L-pad to match the levels and a protection fuse. Everything else is done by the horn geometry, front chambers, and tap sizes. In this case the midrange roll-off turned out very close to target without any electrical components, if not a series inductor can be used to modify the response of a FLH as explained in Kolbrek (though it is probably as quick to find the optimal value by trial and error than go through the theory). The acoustic LPF of the unity mid is one order higher than a FLH because of the cancellation of the reflection to the horn throat - so fourth order which matches the 2nd order acoustic and 2nd order electrical high pass filters applied to the compression driver.


Edited by snowflake - 05 April 2021 at 2:42pm
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Points: 5482 		Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2019 at 10:10pm
Originally posted by snowflake snowflake wrote:

if you can 3d print the tweeter and mid mountings it will save a lot of woodwork and allow you to play around with chamber volumes and port shapes that just weren't practical with a router and rail saw.

PM me if you want the CAD drawings of what I built as a starting point.


That was my thinking, good for prototyping. I was also wondering if extending the port length to the mid chambers such that they were time aligned to the HF diaphragm could be of any practical value.

Cheers for the CAD offer, maybe sometime in the future. I've already spent a while trying to flatten 3D CAD models of Unity horns into sheets for cutting - it's surprisingly non trivial. Not a typical use of CAD but there are ways.

The plan in the meantime is to upgrade the CNC to a 4x2 ft bed and then I can just run the sheets off and finish them with a table saw to give near perfect results with minimum effort. It's not strictly needed but I'm going to do it anyway so why not use it.

No obvious discontinuities in the phase with either xover but the newer does appear to have a more linear slope up to 2k so hopefully that leads to better mid-tweeter integration
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Points: 3122 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2019 at 2:03pm
forgot to switch on the active filter - 3rd order LP and HP @350Hz. mid/top output inverted and delayed 33cm



phase (old green, new red)



group delay



Edited by snowflake - 19 August 2019 at 2:34pm
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Points: 3122 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2019 at 1:54pm
if you can 3d print the tweeter and mid mountings it will save a lot of woodwork and allow you to play around with chamber volumes and port shapes that just weren't practical with a router and rail saw.

PM me if you want the CAD drawings of what I built as a starting point.
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Points: 5482 		Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2019 at 12:46pm
Yep, nicely damped the peak at 1KHz, much smoother roll off now and aintegrates well with the top. Hows' the phase looking?

I'm still extremely keen to build a pair of Unitys but being realistic it's going to be years before I get to the final and finished items. But I can start with the mid/high portion of the design. I'm considering 3D printing the horn/mid assembly and then integrating that with a wooden cabinet with the low mids.
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Points: 3122 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2019 at 11:39am
measurements of old vs new crossover. on axis and 25 degrees off axis. old: green and blue, new: red and orange. smoothed 1/3 octave. ignore below 400Hz as measured in small room due to rain.

much improved. mid-range lobbing isn't too extreme and expected high-frequency fingering above 3kHz is acceptable. I was having to do quite a lot of corrective eq with the old crossover (obviously too much vocal). with the new crossover it sounds pretty nice with no eq at all.

next will try and play around with splay angles.

see below for response plot


Edited by snowflake - 19 August 2019 at 6:31pm
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Points: 5482 		Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2019 at 1:13pm
Yup I agree with that assessment.

I usually model xovers in Spice as well as Akabak if I'm trying to integrate them fully into a design. Spice is so much better for estimates of power dissipation as a function of frequency etc and I find helps when sanity checking.

Peak current through the coil is going to depend on a few factors including musical content and the crossover design. Hard to say.
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studio45 View Drop Down
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 As I see it, with the two components in the orientation shown, the tweeter's external field lines will be parallel to the mounting board, while the coil's will be perpendicular. So they are not particularly well set up to couple. 
There may be a very small modulation of the tweeter's magnetic field, and the coil will experience some mechanical forces as current passes through it - this will probably introduce a minor amount of distortion, but likely at a level far below other sources of distortion.
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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