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Old 3rd October 2009, 10:36 PM   #1
tresch is offline tresch  United States
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Default Introducing: "Thesis"

I'm referring to this set of speakers as my "Thesis" as I feel as I feel like this was my thesis project for loudspeaker design and building school, and I just graduated.

All of my speakers so far have been entirely of my design and build, and these are no exception, but the couple pair that I've built before are both very simple full-range ported boxes. Not a lot going on. These are a much bigger thing!

This is a 5 channel Home Theater setup. The "front three" are MTM designs, using Dayton DA175s as the woofers (picked these based on Zaph's review of them) and MarkAudio Alpair5s for the tweeters. Technically, these are more of a W-MT-W. I was initially planning on crossing at 400hz, but through R&D I decided to go with a slightly more conservative 800hz crossover for a few reasons. The left and right channels are towers. Center is fairly standard form factor. They are all sealed, well braced, and fairly densly stuffed.

The rear channels are simple little sealed full-range bi-poles using the MarkAudio CHR-70. Such a cute, easy to build, versatile little box!

I've mentioned work on this set of speakers over the last several months in a couple other threads, namely this one: Horizontal MTM Center channel: avoiding off-axis nulls

I've spent hundreds of hours building up to the completion of these speakers, during which time I've delved into DIY microphone assembly (WM-61A), learning many of the intricacies of various softwares like speaker workshop, HOLMimpulse, LspCAD Pro (demo), did all kinds of measurements with different drivers, different mics, enclosures, playing with cabinet damping, stuffing, baffle shapes, room reflections...

And then there's the building.. tinkering with table saws, stick-on vinyl, learning how to better seal MDF end-grain, designing and optimizing crossovers, then actually BUILDING them, etc etc etc.

Anyway, They're finally done and I'm feeling particularly proud. We're having a sort of "unveiling" party on Monday where they're going to be installed in the house of a friend of mine who commissioned me to build them. I can't wait to hear them in a proper home theater with a proper receiver in their surround-sound glory

So far they sound pretty great, but I haven't done a lot of listening in proper rooms. I want to get some final measurements of them and I'll post them in this thread when I do, along with some better pictures of the construction

Anyway, have some pictures! Celebrate with me! I did it WOOOOO!
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File Type: jpg thesis-complete.jpg (248.3 KB, 618 views)
File Type: jpg cross-over.jpg (103.6 KB, 560 views)
File Type: jpg cross-under.jpg (78.3 KB, 518 views)
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Old 4th October 2009, 01:35 AM   #2
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Big Thumbs Up Tresch They look great! I hope I will be posting a completion post sometime in the future.. Well Done!

Tony.
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Old 4th October 2009, 03:06 AM   #3
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They look awesome Tresch Are those inductors wound by you?
I've been looking into winding my own, just need to find/build the tools required.

I hope the unveiling party goes off!

Well done and good luck!

Mick.
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Old 4th October 2009, 03:38 AM   #4
tresch is offline tresch  United States
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Nope, unfortunately not. Maybe some other time. They're just ordered from parts express
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Old 4th October 2009, 01:12 PM   #5
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Thanx,

love your work all the same !

cheers mate,

Mick.
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Old 4th October 2009, 05:23 PM   #6
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They look really great - I think anyone would be proud to own them, even as a bought item, but to make them...

Keep up the good work
Chris
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Old 7th October 2009, 11:33 PM   #7
tresch is offline tresch  United States
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In-room measurement. Total response, including room reflections and all that jaz. One-third octave smoothing (can do less smoothing if you're curious.


Blue line is left channel rotate to fire directly at the mic, so on axis. Red line is left channel facing directly forward (normal position), taken from listening position at the center of the room, so about 30 degrees off axis. The green line is the same as the blue one, but it's the right channel, so it's dealing with different room modes.

Again:
Blue: Left channel on-axis
Red: Left channel off-axis
Green: Right channel off-axis
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File Type: png thesis-inroom.png (50.7 KB, 303 views)
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Old 7th October 2009, 11:37 PM   #8
tresch is offline tresch  United States
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And combined stereo output both with and without the subwoofer, which is his old sub from his Klipsch 5.1 system that the Thesis are replacing. The sub only offers a tiny bit more extension than the towers themselves. Poor thing got put out of a job

Next he's going to have me build him a subwoofer. I'm going to be shooting for solid 20hz response. The klipsch here drops off pretty quick below 35

Again:
Blue: combined stereo output
Red: stereo output + subwoofer
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Old 7th October 2009, 11:46 PM   #9
tresch is offline tresch  United States
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I think it's worthy to note that the off-axis response of the MarkAudio Alpair5 is pretty excellent for a full-range cone. The driver is small enough that off-axis response doesn't really drop steeply until about 15,000hz, which is, well, perfectly acceptable!

The "swell" in response centered around 3,500 is definitely noticeable when listening to sin wave sweeps. I think that might be the result of the enclosure that the Alpair is in. It could also be an indication that I attenuated the +9k peak on the driver a little too much, and the driver as a whole not quite enough? The interesting thing is that the combined stereo output from both speakers measures very flat in that area, which could indicate that the "comb" effect from having both drivers playing the same sound might actually be beneficial in this instance effectively leveling things out in that range.

Last edited by tresch; 7th October 2009 at 11:53 PM.
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Old 8th October 2009, 04:20 PM   #10
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Hi guys,
Just to let you all know I've made a new CHR-70. Here's the thread link with all the details:

New CHR-70

Cheers,

Mark.
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