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Mid-bass Horn Design help
Mid-bass Horn Design help
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Old 8th February 2019, 08:44 AM   #21
Rob Dingen is offline Rob Dingen  Netherlands
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The questions I still have are, should I build a round or square horn?
What drivers are best for midbas design 8" 12" 15".
I wil keep the total lengt max at 1 meter but shorter is nice and mouth height below 85cm.
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Old 8th February 2019, 07:05 PM   #22
chromenuts is offline chromenuts  United States
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I think your questions can only be answered through further reading and research and your own experimentation.

There may actually be people that would give you a definitive answer of “This is the best mid bass horn and driver combination.”...I doubt it would be a universal truth.

My research so far has led me to the conclusion that there is no one answer because there are just too many variables. It seems that building acoustic horns is very much like any other complex design problem in that it is all about trade-offs.

I recently re-read this interview article with Bruce Edgar. Take it for what it is. Many people are critical of his horn systems. He does discuss issues facing the use of square versus round horns about half way through the article.

edgarinterview
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Old 8th February 2019, 07:19 PM   #23
Rob Dingen is offline Rob Dingen  Netherlands
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I think it's true wat you say. It' difficult to com to a design that fits all. What I know is that I like the sound of the Uchi horn with a CD. So I think to use that design to the midbas horn. It must have a CD en not be to long because I wat align the speakers and not working with digital filters and delay. I'm gonna build a square one and a round one. The square in combination with the Uchi horn and the round Tractrix with the round Tractrix mid. And then decide which direction I wil go. It wil take some time before the build is finished before I report back.

Rob
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Old 8th February 2019, 09:36 PM   #24
GM is offline GM  United States
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Quote:
Originally Posted by Rob Dingen View Post
The questions I still have are, should I build a round or square horn?
What drivers are best for midbas design 8" 12" 15".
I wil keep the total lengt max at 1 meter but shorter is nice and mouth height below 85cm.
Sound is round, but the pioneers did extensive testing as to how much a square or rectangular horn 'colored' the telephone BW [250-2500 Hz] enough to affect high speech intelligibility over long distances and concluded that if the square or rectangular horn had the same mouth area [Sm] as round it could be 'stretched' up to a 1:1.273 aspect ratio.

Depends on the desired HF response and peak power handling capability.

OK, then optimal rectangular is largest = ~95 Hz Sm, ~67 Hz if a true 2pi, so 100 cm may be too short once the driver is included.

To the first approximation then based on modest power handling, 5-600 Hz limit, a single 8" horn driver suffices, but to shorten axial length [bigger throat], a 15" horn driver, which will perform near enough like Edgar's 100 Hz horn posted earlier if specs are same/similar to the JBL2220.

As you can see, mouth area is your limiting factor for going low and not obvious is the driver's mass corner that sets it HF gain BW = [2*Fs/Qes' or Qts'] depending on who you ask.

Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design

GM
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Last edited by GM; 8th February 2019 at 09:39 PM.
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Old 8th February 2019, 10:12 PM   #25
djn is offline djn  United States
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I can only talk to my mid horns. They run from 700hz to 7khz and I absolutely love them, however the sweet spot is only 6 inches one side or the other from center. Otherwise the imaging and depth of field and soundstage falls apart.

This is ok by me as I have a dedicated room with only one in it.
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Old 9th February 2019, 12:46 PM   #26
Rob Dingen is offline Rob Dingen  Netherlands
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Originally Posted by djn View Post
I can only talk to my mid horns. They run from 700hz to 7khz and I absolutely love them, however the sweet spot is only 6 inches one side or the other from center. Otherwise the imaging and depth of field and soundstage falls apart.

This is ok by me as I have a dedicated room with only one in it.
What midrange horn and CD do you use?

Rob
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Old 9th February 2019, 12:56 PM   #27
Rob Dingen is offline Rob Dingen  Netherlands
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Here are some pictures of my A-290 Uchi horn I build.
And the measurement with a JBL 2445 and passive EQ.
For SPL you have to ad 20dB because my measurement mic cannot deal with that high SPL

Rob
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File Type: jpg IMG_6211.jpg (588.9 KB, 119 views)
File Type: jpg IMG_6214.jpg (302.1 KB, 117 views)
File Type: jpg IMG_6242.jpg (341.3 KB, 118 views)
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Old 10th February 2019, 10:49 PM   #28
RobWells is offline RobWells  United Kingdom
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That uchi horn looks great, the measurements look really smooth too.. It looks like it should sit above a pair of boutique pro 15's in vented boxes..

I've been going through my old files and found this measurement of the evm horn vs the jbl horn I built so I can say that the plot I posted earlier of the evm horn would have been at 1m groundplane outside.

Cheers,
Rob.
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Old 11th February 2019, 09:33 AM   #29
Rob Dingen is offline Rob Dingen  Netherlands
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15" in vented boxes sound ok but how do you resolve the time alignment?
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Old 11th February 2019, 12:43 PM   #30
marco_gea is offline marco_gea  Italy
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Quote:
Originally Posted by Rob Dingen View Post
15" in vented boxes sound ok but how do you resolve the time alignment?
It can be done passively by using asymmetrical slopes on the LF and HF sections.
Typically, you'll need a 6th order electrical LP on the Woofer, and a 2nd order electrical HP on the horn - plus lots of simulation and measuring, of course!

Marco
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