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Old 16th January 2013, 09:27 PM   #11
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Quote:
Originally Posted by Scottmoose View Post

Indeed I have. My usual response though is 'what would you like them to look like?' This is the issue with in-room response curves; within certain broad trends, it's possible to make them look pretty much however you want them to look by changing the measurement / simulation conditions. FWIW though, here's an example. Box angled 45 degrees into the room; 1m distance, on-axis, carpeted floor, 8ft ceiling, edges of the front baffle 2ft from the front & side walls. As you can see, it's a high-gain design to allow greater placement fexibility since you can get rid of what you don't require. Once damped to ~flat, F10 will be similar to Bob's MLTL, but the overall sound will be very different on the bottom end given the respective radiating areas etc.

FWIW, I still suspect your friend will be better off with Bob's MLTL.
Clear as mud But at least you leave no doubt about the fact that you are not trying to sell your design

Now all we need is for Bob to log in and say that he thinks the Silbury is better for my friends' needs.

Honestly, I am tempted to go with the Silburys simply because it sounds like Scott owns the only pair. My friend might not even be able to tell the difference between the two...
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Old 16th January 2013, 09:30 PM   #12
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Scott, with a horn, can you nearfield mic the driver and the horn mouth and combine them like a ported speaker, or how do you do that? I've got no experience with horns. I worked on a horn with the alpair10BW but wasn't sure what to do with that. I wasn't so concerned with bass anyways, just the >300hz frequency response which wasn't affected by my farfield measurement.

Edit - I did measure impedance which was crazy in the bass region. This wasn't a surprise really though, I expected that. I wasn't sure how to determine tuning from it though. 2 or 3 troughs in the impedance iirc.

Last edited by tuxedocivic; 16th January 2013 at 09:32 PM.
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Old 16th January 2013, 10:03 PM   #13
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You can, assuming quasi-anechoic is required. If you've got a design that employs boundary loading, i.e. the room boundaries actualy form a part of the horn expansion, it gets a bit more complicated, since removing that means the final part of the horn has gone AWOL, which throws the results.

The impedance measurements you mention you took sounds about par for the course, since the cabinet presumably wasn't impedance matched down to the 1/4 wave cutoff frequency (F0). Ergo, below Fc (the frequency to which it's impedance matched) you've got pipe harmonic resonances. Here you go; a series of impedance values arranged in two columns, top to bottom. This is a pipe of fixed axial length, throat area, and driver location, expanding in a linear fashion (i.e. a conical horn). The driver is generic, the actual dimensions of the pipe were fairly arbitary, although I set length to approximately 1/2 wave at 100Hz. Top left has the smallest terminus area. Bottom right the largest. You can see the harmonics gradually vanish as terminus area increases until its finally getting near to being impedance matched at F0, leaving just the single large peak at tuning.

Quote:
Honestly, I am tempted to go with the Silburys simply because it sounds like Scott owns the only pair. My friend might not even be able to tell the difference between the two...
I don't have a pair myself; I don't have the space. There are a couple out in the wild though.

He would. Back horns don't often sound like a regular box speaker; if he hasn't heard any & is considering these, I'd strongly advise he listens to a pair with a similar terminus configuration if possible (FH3 or something like that) & thinks long & hard before making a decision.
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File Type: png Horn impedance matching example.png (70.4 KB, 164 views)

Last edited by Scottmoose; 16th January 2013 at 10:33 PM.
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Old 16th January 2013, 10:32 PM   #14
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May I say the following:

I don't do back-horns because they are too big to ship by FedEx and WAF will not permit very tall speakers.I don't do corner-horns because my home doesn't have any suitable symmetrical corners. A MLTL for the A10.2 is a no-brainer. The A10.2 works very well in a remarkably small BR, but that's another story.

When I was doing the the design for the M10-A10, I needed something to break in the the drivers, so I built a pair of Pensil's. Six boards and some polyfil. Done! They sound pretty darn good too. I have a problem, though, with stuffing out unwanted harmonics. So I went about designing out the majority of the bad harmonics, and rather that stuff the cabinet, I line the cabinet with 1" fiberglass. The result is a cabinet with much less volume and somewhat better bass response. I am told that the M10-A10 can be a bit boomy, and if yours is, a bit of port damping will fix it.

I am quite happy with the M10-A10. It is one of my better designs, up there with my FT-1600 and the TT-2000. But then, the choice is yours.

Bob
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Old 16th January 2013, 10:46 PM   #15
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And on current evidence my opinion hasn't changed: the M10-A10 is likely to be the better option in this case.

Out of interest Bob, and briefly OT, what happened to those BRs you were doing?
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Old 16th January 2013, 10:50 PM   #16
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I have a thread that talks to my MLTL design for the Alpair 10.1 and later for compatibility with the 10.2. You might read that thread:

Mark Audio Alpair 10 MLTL Design

I also did an open back 10.2 version in 2011 with an active DSP crossover from an Eminence 3015LF Neo Kappalite 15" woofer. The latter is one of my best speakers from a sound viewpoint but it is too much machinery and spacing into the room for your friend's needs.

My MLTL performs similar to Bob Brines but his design has more maturity and data points at this time. If the cost of Bob's plans choke the horse, get back with me and I'll help work the details of my design with you. Otherwise, I have confidence that Bob's design will fill your needs.
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Old 16th January 2013, 10:57 PM   #17
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+1

Perhaps this thread would be best removed to the commercial area?

Open back design, Jim? I must have missed that one somewhere along the line. Sounds interesting though.
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Old 16th January 2013, 11:16 PM   #18
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Scottmoose,

This is the open baffle thread:

Openminded--A Mark Audio Alpair 10.2 Open Baffle Project

Jim
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Old 17th January 2013, 02:16 AM   #19
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Quote:
Originally Posted by Scottmoose View Post
Out of interest Bob, and briefly OT, what happened to those BRs you were doing?
Oh, they're doing fine. I finished the prototypes and they are the current speakers in my 2-ch. I have offered they for beta testing through my personal forum. The boxes I will use for demo's are in cherry with a high gloss finish. Pictures attached. The bass that comes out of those little boxes is crazy. F10 just below 40Hz, and at an 80dB listening level, there is room for some bass boost. For those going to Dallas for LSAF, I will have these there.

A note on the high gloss finish: I did it just to prove to myself that I could do it. But it anyone wants to buy a set, add $200 just for the finish. It is a mother bear.

Bob
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File Type: jpg B10-A10 Prototype.jpg (78.9 KB, 133 views)
File Type: jpg Demo Boxes.jpg (82.1 KB, 129 views)
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Old 17th January 2013, 03:39 AM   #20
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Quote:
Originally Posted by Jim Griffin View Post
I have a thread that talks to my MLTL design for the Alpair 10.1 and later for compatibility with the 10.2. You might read that thread:

Mark Audio Alpair 10 MLTL Design

I also did an open back 10.2 version in 2011 with an active DSP crossover from an Eminence 3015LF Neo Kappalite 15" woofer. The latter is one of my best speakers from a sound viewpoint but it is too much machinery and spacing into the room for your friend's needs.

My MLTL performs similar to Bob Brines but his design has more maturity and data points at this time. If the cost of Bob's plans choke the horse, get back with me and I'll help work the details of my design with you. Otherwise, I have confidence that Bob's design will fill your needs.
Jim,

Thanks for the link to your MLTL thread. I like the design, but I'll have to see if my friend feels the same way.

Yes, I had seen that OB + H frame system thread before. Very cool setup. I can just imagine the sound. Low WAF, lots of space usage, extra gear... as you say.

The cost of plans is quite small, all things considered, so this is really about what design my friend will like the best. I do appreciate you putting your design out there for us DIYers and I think if it was me I might chose your design. I like the fact that they are tall.

Last edited by cogitech; 17th January 2013 at 03:44 AM.
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