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Old 4th April 2013, 11:28 PM   #1
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Default What's the Easiest DIY Unity Horn Project?

I've been really tempted to buy some drivers for another Unity horn project. But I already have a pile of drivers from *existing* Unity horn projects.

I wanted to get some feedback from other members who've built Unity horns.

Basically:

1) If you've built a Unity horn, are you happy with the way it turned out?
2) If not, what would you change?


Off the top of my head, I believe there are two or three easy ways to build a Unity horn, and a number of difficult ways.

Let's start with the difficult options:

Option one would be for me to buy some compression drivers, some midranges, and get my measurement rig working. The upside of this option is that I enjoy experimenting with Unity horns, as illustrated by dozens of Unity horn projects that I've messed around with over the past seven years or so. The downside is that 2/3rds of these didn't work so well, and I usually lost enthusiasm to finish them, particularly when it came to cosmetics.

Click the image to open in full size.
Option two would be to build one of the Synergy horn designs from Paul Spencer. Although they're not much more difficult to build than the ones from Bill Waslo or Tom Danley, the Spencer designs require a midrange that isn't readily available, so that makes it tricky. On the plus side, I believe Spencer's choice of midrange has some advantages over the one used by Waslo. (Bill's midrange is two bucks; all drivers have limitations, and at this price point, they get kinda severe.)

Those are the difficult options. Now let's talk easier options.

Click the image to open in full size.
Option three would be to build Bill Waslo's Synergy horn.
Bill's Synergy horn is arguably the best documented one in the whole world. Bill's published the crossover, the dimensions, a spreadsheet that lets you build your own horn, lots of pics, etc.
My main concern about building this one is the midranges. I've uses the $2 buyout midranges in my own projects, and they sound 'grungier' than the Peerless or Tangband 2" woofers. I have a whole case of the Peerless woofers, and I've certainly wondered if it might make a suitable replacement for the two buck mids.

Click the image to open in full size.
Option four would be a Lambda Unity horn.
If I did this, I'd use the Pyle sealed back midranges instead of the Misco mids, and I'd use the Parts Express clone of the B&C DE250 instead of the B&C DE25. The drivers are close enough that the modifications to the crossover would be fairly minor. This option is tempting for a couple reasons. First, I've used the Pyle midranges, and they're by far the best value of all the mids I've tried. In my opinion, they sound as good as the most expensive mids that I've tried in a Unity horn, and they sound better than the two buck specials from Parts Express. Basically you could spend a lot more on midranges and they won't sound much better.
I haven't heard the D250P, but if it's a close knock off of the DE250 than it should work just fine.
About the only downside to cloning the Lambda Unity is that it's a kinda dated design; Danley has evolved the design quite a bit in the 12 years since it went on sale.
Then again, I've heard the Lambda Unity myself, and it sounds better than any of the Unity horn experiments that I've done personally. I had a couple Unity horns that worked a little better in one aspect or another, but none of my Unity horns were better overall.

Click the image to open in full size.
Option five would be to build a front loaded horn for the Kef KHT1005 satellites. For the life of me I can't figure out why more people don't use these for horns, if there's a better 3" driver for under $50 I don't know what it is. You can get a set of five, plus a subwoofer and an amplifier delivered to your door for under $250. Thiele Small on these is similar to the Fostex and Faital 3" woofers. The Kef is a coaxial, so it would looks a bit like these Danley Synergy Horns once it's horn loaded:
Click the image to open in full size.

Downside to the Kefs is that they're not going to get remotely as loud as options one through three.



If I *do* go with option one, I was thinking something like this:

Click the image to open in full size.
Basically a couple of compression drivers in a Paraline and a pair of eights. Sort of similar to the Sound Physics Labs 'Runt':

Click the image to open in full size.

Last edited by Patrick Bateman; 4th April 2013 at 11:36 PM.
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Old 4th April 2013, 11:33 PM   #2
ra7 is offline ra7  United States
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Not much experience building these, but FWIW, I'm going to try build bwaslo's well documented coSynes this summer.
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Old 5th April 2013, 02:19 AM   #3
bwaslo is offline bwaslo  United States
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A problem with my current 'well documented' design is that the woofers are NLA. Someone cleaned them all out of both Parts Express's stock and Madisound's.

I'm working on designing with some replacements. Also replacing the 2"ers (since they're buyouts, too), should make PB happier! Though after testing the ones that looked best on HornResponse modeling, they don't appear to work as well (for smoothness and sensitivity) as the 2 buck specials. One note, I only use the 2" for a fill between the tweeter and woofer, it doesn't cover much range but allows me to get the thing working linear phase. The design can be done with just tweeter and woofer, but then the crossovers have to be a lot sharper, so no linear phase with that.

I still want the system to reach to below 100Hz - hence the woofer (200Hz is too high to jump to a subwoofer and I want to be able to place subwoofers for better room mode handling). The Pyle midranges are too big, I couldn't fit those on along with woofers unless the horn was a lot bigger (which wouldn't fly with my wife).

I have a better/easier way of cutting and assembling now, was in the process of writing it all up when the woofers went bye-bye. So I'm working to get some stock drivers working before coming out with new revised (and even more detailed) plans.

Thanks for the plug, Patrick!
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Old 5th April 2013, 05:12 AM   #4
Pallas is offline Pallas  Pakistan
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Quote:
Originally Posted by Patrick Bateman View Post
Click the image to open in full size.
Option five would be to build a front loaded horn for the Kef KHT1005 satellites. For the life of me I can't figure out why more people don't use these for horns, if there's a better 3" driver for under $50 I don't know what it is. You can get a set of five, plus a subwoofer and an amplifier delivered to your door for under $250. Thiele Small on these is similar to the Fostex and Faital 3" woofers. The Kef is a coaxial, so it would looks a bit like these Danley Synergy Horns once it's horn loaded:
Click the image to open in full size.

Downside to the Kefs is that they're not going to get remotely as loud as options one through three.
I'm not sure the KEFs have the motor strength to take advantage of horn loading. Even the Q100 driver, which has a magnet bigger than some subwoofers - I imagine KEF originally intended to use neo, only to change plans when neo prices skyrocketed - has barely half the motor (BL) of the BMS concentric Danley uses in the SM60.

That said, if you do choose this route, use the Q100 driver or the KHT3005SE driver. The newer Uni-Q's with the radial phase plug are just much much better performers than the older Uni-Qs. Also, that HTS1005.2 has a teeny tiny tweeter that doesn't really do dynamics.
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Old 5th April 2013, 03:15 PM   #5
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Quote:
Originally Posted by bwaslo View Post
A problem with my current 'well documented' design is that the woofers are NLA. Someone cleaned them all out of both Parts Express's stock and Madisound's.

I'm working on designing with some replacements. Also replacing the 2"ers (since they're buyouts, too), should make PB happier! Though after testing the ones that looked best on HornResponse modeling, they don't appear to work as well (for smoothness and sensitivity) as the 2 buck specials. One note, I only use the 2" for a fill between the tweeter and woofer, it doesn't cover much range but allows me to get the thing working linear phase. The design can be done with just tweeter and woofer, but then the crossovers have to be a lot sharper, so no linear phase with that.

I still want the system to reach to below 100Hz - hence the woofer (200Hz is too high to jump to a subwoofer and I want to be able to place subwoofers for better room mode handling). The Pyle midranges are too big, I couldn't fit those on along with woofers unless the horn was a lot bigger (which wouldn't fly with my wife).

I have a better/easier way of cutting and assembling now, was in the process of writing it all up when the woofers went bye-bye. So I'm working to get some stock drivers working before coming out with new revised (and even more detailed) plans.

Thanks for the plug, Patrick!
That's a good point about the buyout drivers. When I used them in my projects, I was running them about 2-3 octaves. (About 300hz to 1500hz.) And I wasn't using a highpass, which would exacerbate distortion.

It sounds like you're only using them for about an octave or so in your design.

What do you think about the Celestion compression driver? The Dayton D250P looks good, but it kinda bugs me that it's such a blatant rip off of the B&C. If the Celestion works well, I can't see a reason not to use it. (IIRC, power handling on the Celestion is lower, but that's of little importance for a home audio situation, where we'll likely give the compression driver little power.)
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Old 5th April 2013, 03:25 PM   #6
tinitus is offline tinitus  Europe
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how do you control the drivers 'overlap', to avoid phase 'suckout' or peaks ?
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Old 7th April 2013, 03:12 PM   #7
bwaslo is offline bwaslo  United States
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Quote:
It sounds like you're only using them for about an octave or so in your design.
That's about right. Really just a 'filler' driver almost, something that can be placed close enough to the throat to reach easily past the crossover frequency. I imagine it would be terrible if driven full range!

Quote:
What do you think about the Celestion compression driver? The Dayton D250P looks good, but it kinda bugs me that it's such a blatant rip off of the B&C. If the Celestion works well, I can't see a reason not to use it. (IIRC, power handling on the Celestion is lower, but that's of little importance for a home audio situation, where we'll likely give the compression driver little power.)
Well, I really like the sound of the CDXi-1445 Celestion driver (extremely natural, does its job without calling attention to itself. Though part of that is the Synergy "sounds like one driver" effect). The 1445 also has a relatively wide throat angle, which helps maintain the beam width at the high end, and it also extends to a little over 20kHz without a sharp drop off. But unfortunately it doesn't go very low - 2kHz is about it, and it appears consistency isn't great. One of the last ones I got has trouble reaching even that. I also tried its big brother, the CDXi-1745, which surprisingly didn't seem to go much, if any, lower! It was a little more sensitive, though.

The 2kHz low end and the difficulty pushing the mids much above 3kHz (and that seems to vary with angle) has me now working with the large DE250 type mylar drivers. I'm using a Denovo DNA-350, since that's what I have available. (I'm not bothered by the DE250 imitations - there are no patent numbers listed in the DE250, and none of the imitators are claiming theirs to be a B&C brand device). I wish these had a wider throat angle and went a little higher (if only for prettier graphs!) but I do know they are good-sounding devices so this isn't a big compromise. I do wish they weren't so heavy, though! All this ferrite hanging on the glue-assembled wood horn has me worried that it wouldn't likely survive much of a drop.
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Old 7th April 2013, 03:19 PM   #8
bwaslo is offline bwaslo  United States
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Quote:
Originally Posted by tinitus View Post
how do you control the drivers 'overlap', to avoid phase 'suckout' or peaks ?
By controlling phase in the crossover, like always. But in a synergy horn, you don't have to worry about combining them in-phase to keep a lobe facing forward. 90 degrees (or whatever gives you flat response) is fine, since the waveguide controls the lobe always in the forward direction. One of the numerous things that manages to inherently go right in a synergy horn.
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Old 9th April 2013, 06:23 PM   #9
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At this point, I'm leaning towards a variation on the VTC Paraline box, but for home use. Here's why I think it would be compelling:

1) In a Unity or Synergy horn, I find that the most difficult part to get 'right' is the midrange. Basically it's hard to get the mids to play up to the xover point of the compression driver. About a week ago it occurred to me that the dual compression drivers in a Paraline would facilitate a lower xover point. After reviewng the DSP settings from VTC, my 'hunch' appears to be correct. The VTC box with the single compression driver has an xover point of about 950hz, but the one with the dual compression drivers has an xover point that's almost an octave lower! (The 'real' xover point is a bit nebulous, because there's a ton of EQ in the DSP settings.)

I think this is very exciting news, because it dramatically simplifies Unity horns. We can *finally* have a two way Unity horn that goes down to 100hz. This makes e-v-e-r-y-t-h-i-n-g so much easier:

a) Instead of a humongous and expensive three way crossover, we have a relatively simple and easy to manage two way crossover, using DSP of course
b) Instead of dedicating the next six months of my life to tweaking inductors and capacitors we just buy a minidsp, measure with the mic, then set the xover and EQ accordingly
c) We can experiment with various xover slopes, for instance we can try transient perfect xover topologies. While you *can* do that with a passive xover, it gets expensive in a hurry due to the number of components involved and the bizarre response shape of compression drivers, not to mention their crazy impedance curves

Probably the most compelling reason to do a 'VTC' style box is that there are numerous drivers that will work with an xover point of 600 or 700hz, but there are very few that will work with an xover point of 1500hz. Paul Spencer had to have his Unity horn midranges special ordered from Celestion, and I had mine special ordered from Misco.

What I'm picturing would look like this:
Click the image to open in full size.
Dual Dayton D250Ps in a Paraline, with an xover point around 700hz or so

Click the image to open in full size.
Woofers are Silver Flute 4ohm eights

Click the image to open in full size.
Crossover is MiniDSP

Cost for each channel is $273. ($99 for minidsp, $100 for dual Daytons, $74 for dual Silver Flutes.)
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Old 9th April 2013, 06:49 PM   #10
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Sorry to hijack the thread but Mr. Bateman's PM box is full.....

Dear Patrick,

I have noticed from some of your posts that you are into car audio. I am desperately trying to find a DVD head unit that encodes Dolby digital, DTS and pro logic II.

I was going to do a MS matrix wiring to use with a center channel but pro logic II seems to be the best solution.

Please PM me!

Thanx Patrick. Now, I have to go....."I have to return some video tapes"
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