DIY Mid-Hi: BMS Coax + 2x 12" B&C - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 123 Old 10-01-2018, 01:20 PM - Thread Starter
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DIY Mid-Hi: BMS Coax + 2x 12" B&C

Project time again! Looking to build the ultimate mains that go with two SKhorns.

The DIY Mid-Hi 90 Degree Version:

This design has been around for a couple of years and has gotten solid reviews. Original Post (90 degree horn) -- Second Thread (60 Degree Version)

Why build this? Well, 145db sustained anywhere above 100hz AND exceptional sound quality in a reasonable size box. That's what 112dB w/m hi's (with 1300w peak handling!) and 105 db w/m mids gets you!

I've only heard good things about the BMS 4594HE and can't wait to try it for myself.

I will be using:

Coax: BMS 4594HE (4594 with shorting ring, and full fruition phase plug)
Horn: RCF HF950 (90-degree horn)
Mids: B&C 12NDL76 x 2 per speaker
Processing: Minidsp DDRC-88A + BM

The design looks like this:


The 12" drivers fire towards the back of the box through slits into a folded ported horn that is ~2ft long.

The BMS 4594HE is crossed quite low at approximately 650hz on the excellent HF 950 horn. The horn is placed in-between the horns, allowing for excellent pattern control. Read the threads on soundforums.net for more details. Some audio gems in there.

Design feedback from others:

"Without a doubt this speaker exceeds the sonic performances of any speaker I have ever owned. It sounds better and measures better; its impulse response is as good as I have ever seen and there are very few speakers in the world that can reproduce a square wave both on and off axis (horizontal and vertical)."

My Build:

Done:
  • Research
  • 3D Modeled Box in Solidworks
  • Purchased Parts: Horn - Drivers - Handles - Baltic Birch
  • Purchased: Minidsp DDRC-88A and Amps
  • Posted on the internet about it
  • Built my subs

To Do:
  • Make sawdust
  • Assemble
  • Active EQ
  • Listen to stuff

Side note:

One fun item this made me think about. In AVS land we often lean towards the "no replacement for displacement" way of life. There is a replacement and it's called sensitivity. Combine sensitivity with high power handling and win?

________________________________________
DIY Mid Hi Speakers Build - SKHorn Build - Gjallarhorn Build SOLD - Othorn Build SOLD - SEOS 12 Build - Other Gear: JVC NX5 - Seymour Matinee Black - QSC CX4.5Q amps x 5 - QSC Q-sys 110f - Speakerpower 6000 x2

Last edited by dsl1; 10-26-2018 at 10:05 AM.
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post #2 of 123 Old 10-01-2018, 02:15 PM
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Following, want to eventually do something similar.


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post #3 of 123 Old 10-01-2018, 02:15 PM
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Yay, I haven't seen anyone build these yet. Is there a reason why you didn't choose to build the slightly wider version with the XT 1464 horn instead?

Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, implusivity, uncontrolled or repeated movements.
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post #4 of 123 Old 10-01-2018, 02:27 PM
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Guy lives down the road to me who designed these and must say they do sound fantastic and have lots of dynamic capabilities. Look forward to seeing yours built.
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post #5 of 123 Old 10-01-2018, 02:59 PM - Thread Starter
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Quote:
Originally Posted by michael hurd View Post
Yay, I haven't seen anyone build these yet. Is there a reason why you didn't choose to build the slightly wider version with the XT 1464 horn instead?
For my uses, the 90-degree horn seems more versatile with just a pair. If I had a ton of extra $$$, I'd probably build 4 of these and go 2 per side if I wanted to do any live sound. I honestly cannot say if I am making the right decision. Feel like I'll be pretty happy either way though.

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Guy lives down the road to me who designed these and must say they do sound fantastic and have lots of dynamic capabilities. Look forward to seeing yours built.
Peter seems like a really smart guy. You need to finish your skhorns and take them over to him!

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post #6 of 123 Old 10-01-2018, 04:04 PM
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This looks interesting. I think I heard the 4594 in a JTR setup and it was as good as I could imagine anything sounding. Not sure if it was that exact driver though.

Question, why does the bottom horn section not have the window brace and the brace in front of the driver? Appears symmetrical otherwise.
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post #7 of 123 Old 10-01-2018, 04:48 PM
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What are the dimensions on this?


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post #8 of 123 Old 10-01-2018, 05:14 PM - Thread Starter
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Quote:
Originally Posted by Samps View Post
This looks interesting. I think I heard the 4594 in a JTR setup and it was as good as I could imagine anything sounding. Not sure if it was that exact driver though.

Question, why does the bottom horn section not have the window brace and the brace in front of the driver? Appears symmetrical otherwise.
Yes, believe the 212's use the 4593ND. Assuming some of the other JTR designs do as well.

Good eye @Samps ! I must have hidden it by mistake. That isn't just a brace, it is part of the horn. The rear section is actually open with some handles and inset Speakon connectors.

Here are some more images. Should make it more clear.






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What are the dimensions on this?
15.6" wide x 36" tall x 18" deep (16.5" from the front of the horn to rear)
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post #9 of 123 Old 10-01-2018, 05:17 PM
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Wow! That’s pretty awesome build. I forget, where are you located again?

Hopefully close enough for me to get a listen once they are done.....


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post #10 of 123 Old 10-01-2018, 05:20 PM
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dsl1 what is the biggest panel size you need for your CNC to build this?

I ask because my friend who is helping me with some other builds with his CNC is limited on size of panels used. Looks like I may have to build this in the future possibly middle next year. Still have Skhorn and a bunch of TPL design speakers to finish.
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post #11 of 123 Old 10-01-2018, 05:27 PM
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I love dissecting these.

That's a crazy design. No chance of trying to build one of those. Even with a CNC it looks tough. One wrong angle someplace and it might be crap.

I actually heard a trio of 215rt's. Best thing I've ever heard.

Gonna look badass on top of those skhorns.
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post #12 of 123 Old 10-01-2018, 06:36 PM - Thread Starter
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Quote:
Originally Posted by chrapladm View Post
dsl1 what is the biggest panel size you need for your CNC to build this?
If you could do 36" you'd be able to cut everything.

Quote:
Originally Posted by EndersShadow View Post
Wow! That’s pretty awesome build. I forget, where are you located again?

Hopefully close enough for me to get a listen once they are done.....
Southeast Iowa

Quote:
Originally Posted by Samps View Post
I love dissecting these.

That's a crazy design. No chance of trying to build one of those. Even with a CNC it looks tough. One wrong angle someplace and it might be crap.

I actually heard a trio of 215rt's. Best thing I've ever heard.

Gonna look badass on top of those skhorns.
Complicated, just the way I like it :P

3 x 215rt's would be quite the system. These should be pretty comparable, hopefully even better if I can hit a home run on the active processing.

________________________________________
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post #13 of 123 Old 10-01-2018, 06:58 PM
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Quote:
Originally Posted by Samps View Post
I love dissecting these.

That's a crazy design. No chance of trying to build one of those. Even with a CNC it looks tough. One wrong angle someplace and it might be crap.

I actually heard a trio of 215rt's. Best thing I've ever heard.

Gonna look badass on top of those skhorns.

If you can use a pencil and measuring tools, it shouldn't be too hard to lay these out and cut them if you have all of the dimensions, angles and pictures to go by.
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Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, implusivity, uncontrolled or repeated movements.
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post #14 of 123 Old 10-01-2018, 07:33 PM
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Every single panel on the inside has an angled edge except a couple of the braces. I'm sure I could build it, but it would need a case of PL. Unless all of those angles are somehow the same degree.

Are the ports only the thickness of the wood, or are tubes going in there?
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post #15 of 123 Old 10-01-2018, 07:39 PM - Thread Starter
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Quote:
Originally Posted by Samps View Post
Every single panel on the inside has an angled edge except a couple of the braces. I'm sure I could build it, but it would need a case of PL. Unless all of those angles are somehow the same degree.

Are the ports only the thickness of the wood, or are tubes going in there?
Ports are only the thickness of the wood.

It's a mix of angles, but nothing too crazy. Can provide a parts list with dimensions / angles easily enough.
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post #16 of 123 Old 10-01-2018, 07:48 PM
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Lol, I can't afford the drivers.

I'll just watch from the bleachers and enjoy the show.

I imagine they'll be done in a few days.
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post #17 of 123 Old 10-01-2018, 11:01 PM
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This design can be used with a lot of different budget 12's. BUT The BMS model is expensive either way. A cd was used before but the results weren't as good. But still an option.
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post #18 of 123 Old 10-03-2018, 08:04 AM - Thread Starter
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This design can be used with a lot of different budget 12's. BUT The BMS model is expensive either way. A cd was used before but the results weren't as good. But still an option.
The BMS is what makes the design feasible since it can go down to 650hz.

In terms of the 12's, technically I am using the "budget" 12.

The "ideal" driver is the RCF MB12N351 but $390 x 4 vs. $180 x 4 for the B&C 12NDL76 seemed worth the "downgrade" to me. Seems the performance will be pretty close.

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Got my horns! Look great. Excited to get my coax's and start playing around. Sounds like end of the week on those
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Quote:
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The BMS is what makes the design feasible since it can go down to 650hz.

In terms of the 12's, technically I am using the "budget" 12.

The "ideal" driver is the RCF MB12N351 but $390 x 4 vs. $180 x 4 for the B&C 12NDL76 seemed worth the "downgrade" to me. Seems the performance will be pretty close.
Would the AE TD12’s work in this enclosure? Do you think they would beat out the RCF’s?
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post #21 of 123 Old 10-04-2018, 03:54 AM
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Would the AE TD12’s work in this enclosure? Do you think they would beat out the RCF’s?
You have to simulate to see if they would work. But I am almost certain that nothing from AE works in a tiny horn alignment such as this. So no they would not beat out the RCF's. Most of Peters design use what ever the best driver is available. So the RCF is top of the line. AE's are not on the list at all because the design. (horn)
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post #22 of 123 Old 10-04-2018, 07:13 PM - Thread Starter
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Got some goodies today:






It's a beautiful driver in person. Can't wait to get them fired up.
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post #23 of 123 Old 10-04-2018, 08:24 PM
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Originally Posted by dsl1 View Post
In AVS land we often lean towards the "no replacement for displacement" way of life. There is a replacement and it's called sensitivity. Combine sensitivity with high power handling and win?
Well, those are two different things really. Unless you're referring to how horn loading can get a lot more output from a given diaphragm displacement. Funny thing, someone wrote an Audio Engineering Society paper purporting to show that an array of ported boxes outperformed horn loaded designs...and their test data chart showed the opposite!

The thing you're making is very cool, reminds me of the crazy Turbosound stuff back in the day-126 dB at about 50 meters on Iron Maiden's World Slavery Tour! Yee-ha! Nobody plays that loud any more, at least in big arenas.

Definitely tricky woodworking-you should take orders! (Not totally kidding, do like a Massdrop kinda thing...)
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Following so i can try to understand any of this lol
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How would this setup work with a radian 745 or faital HF144?
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post #26 of 123 Old 10-05-2018, 02:31 AM
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Quote:
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How would this setup work with a radian 745 or faital HF144?

Radian 745:


Recommended minimum crossover point 800 hz.

10 degree exit angle, 3 inch coil, 100w AES power handling, 111dB sensitivity on their specified horn. If crossing the driver lower than 800 hz, maximum power must be reduced and crossover slope increased. 1w>100 watt = 20 dB. I'd expect to shave 6 dB minimum off it's maximum output when crossing it at 650 hz as in this design. 111+14 dB= 125 dB. One diaphragm to cover 650 hz to 20 khz. The BMS driver has two diaphragms and two coils to cover the same range. Magnetic gap flux density not specified. No mention if the phase plug is annular or tangerine style.





HF144:


Recommended minimum crossover point 900 hz. 29 degree exit angle, 2.56 inch coil, 80w AES power handling above 900 hz. Dropping the crossover point to 650 hz, Faital recommends cutting the power handling in half to 40w. 108dB + 40w ( 16dB ) = 124 dB. I would expect to cut that by a further 3 dB, for 121 dB maximum.

One diaphragm to cover 650 hz to 20 khz. BMS has two diaphragms driven by two coils for the same range. 1.7T flux density in the magnetic gap. Annular phase plug.



BMS 4594HE:


Midrange diaphragm 3.5 inch coil. HF diaphragm 1.75 coil. 300 hz recommended crossover frequency for midrange diaphragm. 150w AES power handling above 400 hz for the midrange diaphragm. 80w AES power handling for HF diaphragm. Flux density of 1.95T in the gap for the midrange. 2.2T for the HF.





From the original post: "Why build this? Well, 135db sustained anywhere above 100hz AND exceptional sound quality in a reasonable size box. That's what 112dB w/m hi's (with 1300w peak handling!) and 105 db w/m mids gets you!"


The Radian narrow exit angle of 10 degrees may not the best match for a 90 degree horn. At some frequency at high ka values, the driver will be beaming into a 10 degree angle, and only the side lobes "illuminate" or will be loaded by the horn. Just a speculation on my part, but I would bet the Radian would be a better match for the 60 degree horn version of this box with the 18 Sound XT1464. Polar response curves on the horn would be the best indication if it is suitable.



If you are fine with lower output, you could use a different driver, but there are trade-offs. A driver optimized for HF output will necessarily have tight clearances ( around a half mm or so ) from the diaphragm to the phase plug. This is less useful if you want low frequencies from the compression driver which requires more diaphragm excursion.

Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, implusivity, uncontrolled or repeated movements.
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post #27 of 123 Old 10-05-2018, 02:40 AM
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Quote:
Originally Posted by michael hurd View Post
Radian 745:


Recommended minimum crossover point 800 hz.

10 degree exit angle, 3 inch coil, 100w AES power handling, 111dB sensitivity on their specified horn. If crossing the driver lower than 800 hz, maximum power must be reduced and crossover slope increased. 1w>100 watt = 20 dB. I'd expect to shave 6 dB minimum off it's maximum output when crossing it at 650 hz as in this design. 111+14 dB= 125 dB. One diaphragm to cover 650 hz to 20 khz. The BMS driver has two diaphragms and two coils to cover the same range. Magnetic gap flux density not specified. No mention if the phase plug is annular or tangerine style.





HF144:


Recommended minimum crossover point 900 hz. 29 degree exit angle, 2.56 inch coil, 80w AES power handling above 900 hz. Dropping the crossover point to 650 hz, Faital recommends cutting the power handling in half to 40w. 108dB + 40w ( 16dB ) = 124 dB. I would expect to cut that by a further 3 dB, for 121 dB maximum.

One diaphragm to cover 650 hz to 20 khz. BMS has two diaphragms driven by two coils for the same range. 1.7T flux density in the magnetic gap. Annular phase plug.



BMS 4594HE:


Midrange diaphragm 3.5 inch coil. HF diaphragm 1.75 coil. 300 hz recommended crossover frequency for midrange diaphragm. 150w AES power handling above 400 hz for the midrange diaphragm. 80w AES power handling for HF diaphragm. Flux density of 1.95T in the gap for the midrange. 2.2T for the HF.





From the original post: "Why build this? Well, 135db sustained anywhere above 100hz AND exceptional sound quality in a reasonable size box. That's what 112dB w/m hi's (with 1300w peak handling!) and 105 db w/m mids gets you!"


The Radian narrow exit angle of 10 degrees may not the best match for a 90 degree horn. At some frequency at high ka values, the driver will be beaming into a 10 degree angle, and only the side lobes "illuminate" or will be loaded by the horn. Just a speculation on my part, but I would bet the Radian would be a better match for the 60 degree horn version of this box with the 18 Sound XT1464. Polar response curves on the horn would be the best indication if it is suitable.



If you are fine with lower output, you could use a different driver, but there are trade-offs. A driver optimized for HF output will necessarily have tight clearances ( around a half mm or so ) from the diaphragm to the phase plug. This is less useful if you want low frequencies from the compression driver which requires more diaphragm excursion.


Trust me I get the reason the coaxial is used, I’m NOT asking because I think these are simply “drop in” replacements but more of poor mans version to drop the cross over as low as possible. I mainly looked at CD’s under $300 (vs $800 for 4595HE), they look like they can work but won’t get nearly as loud so wide, open venues probably not .

Thank you for the response you were very helpful.


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post #29 of 123 Old 10-09-2018, 02:30 PM - Thread Starter
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Been working on another project so failing to do anything productive on these this weekend.



Ready to cut everything though. Entire speaker fits on a single 15mm sheet (except the driver panels - those are out of 18mm baltic birch). Unless I forgot some parts, which I may have :P



This project is already looking to be more fun than the 6 sheets it takes to build a SKhorn...

My minidsp experiment can begin tomorrow. I bought a DDRC-88A with Dirac. Going to try to go full active with these speakers, then use Dirac for correction.

The concerns are:
1. Is there going to be too much hiss? Sounds like people have had issues with the 10x10 being noisy on the super sensitive BMS.
2. Will it sound better than doing manual FIR filters?
chrapladm and Trimlock like this.

________________________________________
DIY Mid Hi Speakers Build - SKHorn Build - Gjallarhorn Build SOLD - Othorn Build SOLD - SEOS 12 Build - Other Gear: JVC NX5 - Seymour Matinee Black - QSC CX4.5Q amps x 5 - QSC Q-sys 110f - Speakerpower 6000 x2

Last edited by dsl1; 10-09-2018 at 02:38 PM.
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post #30 of 123 Old 10-09-2018, 04:00 PM
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Quote:
Originally Posted by dsl1 View Post
Been working on another project so failing to do anything productive on these this weekend.



Ready to cut everything though. Entire speaker fits on a single 15mm sheet (except the driver panels - those are out of 18mm baltic birch). Unless I forgot some parts, which I may have :P



This project is already looking to be more fun than the 6 sheets it takes to build a SKhorn...

My minidsp experiment can begin tomorrow. I bought a DDRC-88A with Dirac. Going to try to go full active with these speakers, then use Dirac for correction.

The concerns are:
1. Is there going to be too much hiss? Sounds like people have had issues with the 10x10 being noisy on the super sensitive BMS.
2. Will it sound better than doing manual FIR filters?
Is that a factory five of some sort? I just finished my ff cobra and love it. For some reason, it reminds me slightly of mine in the build stages (aluminium panels, etc)
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