Ported M8n MTM designs.....

[Paul H]

Someone asked if I had photos of these "ported M8n" speakers, which reminded me that I intended to post some pictures way back when. These roughly follow the order of construction:











(more next post)

Paul

[Paul H]

More photos ..











(1 more post w/photos below)

Paul

[Paul H]

Last picture post ..







Paul

[GrahamT]

Thanks Paul. Beautiful work. If I'm ever out east I'll have to drop in and steal...err.. I mean listen to them.

How did you make those corner pieces in the first photo? The ones that run vertically in the corners.

Once again, those are stunning. I think I'm in love

[Paul H]

Thanks.

The corner pieces are solid maple, cut on a table saw to sizes and angles to fit with the rounded edges of the plywood pieces. They fit into notches cut into the rounded plywood pieces with a dado blade on the table saw.

I drew the speaker in autocad, and pulled dimensions and angles from it - autocad saves an incredible amount of time and provides for very accurate layout, particularly on curved/angled interfaces like these corner pieces.

Stealing the completed speakers would be challenging - at 180 lbs each you can't tuck them under your arm and sneak out.


Paul

[GrahamT]

Great work, you are a master. I hope to be able to build something like that one day, for now I'll stick with the cement. :lol:

You must be very proud of them.

[JonMarsh]

Great looking work, Paul- thanks for sharing the additional pictures! :T

Even if I was helping Grahm, I don't think we'd be able to sneak them out at 180 lb. each!

~Jon

[JoshK]

Great work! I really like the curved touch, makes them different than the average DIY speaker.

[taz13]

Jon Graham, come on carry out Pauls babies, bad boys.
You use padded dollies with a stake truck that has a power lift gate on it. Pull the heist and run for one of the ferries to get out of there. I'll be waiting to take those beauties off your hands.
Just beautiful work Paul. ;x( ;x(

[Lex]

I really like the curved touch, makes them different than the average DIY speaker.

Actually, what it makes them is a patent violation for Sonus faber's fluted design. lol. Don't worry, I won't tell.

Beautiful work.

Lex

[Paul H]

Actually, what it makes them is a patent violation for Sonus faber's fluted design. lol. Don't worry, I won't tell.

Lex

You mean I've got a patent violation in my basement 8O Jon, Graham - come get 'em.


Paul

[GrahamT]

Jon, Graham - come get 'em.


Paul

Already got my plane ticket. See you tomorrow. arty: :^x

[PMazz]

Bout time you posted pics. And I thought I was slow to finish a project....

Very nice! And I know they sound incredible.

Pete

[TacoD]

I like the curved sides, a lot of woodworking skills on this board (it seems I am the only guy here lacking of these skills ... ).

[AndrewM]

You're not the only one lacking in the woodworking skills department, although I have gone from having speakers that looked like they were put together by a blind drunk guy with no arms to something that actually requires very little prep work for finishing (joints actually line up and I don't need to squeeze 3 tubes of caulk to make them air-tight).

Andrew

[morbo]

Those are shockingly good looking speakers. Congratulations!

[Paul H]

Thanks for the kind words guys.

...although I have gone from having speakers that looked like they were put together by a blind drunk guy with no arms ...
Andrew

That's terribly politically incorrect Andrew - and I almost spewed tea through my nose when I read it :twisted:



They do indeed sound extremely good, thanks to the J & T guru team. They would of course be completely done if Jon would stop making comments about the RS28 being an excellent almost-drop-in replacement for the XT25 tweeter - is it really true Jon? Is it worth doing?

Paul

[AndrewM]

That's terribly politically incorrect Andrew - and I almost spewed tea through my nose when I read it :twisted:

My first DIY speaker was a mess, they were towers and the long-side panels were just a tad wavy (by about a good .25" or so), I had to use 2 of the smaller tubs and 2 tubes of Bondo just to get them semi-straight, the last set I only needed about 1/3 of a tube.

Or as another member of another forum stated;

My fabrication skills makes Sanford and Son look like Scaled Composites.

I believe you went over it earlier in this thread, but how did you do the curved panels? The "normal" methods (wetting, bending and drying)? I really like the look and would love to try it, but..uhhhh...see above I was thinking of trying it with something like 1/4" masonite and then just pop on about 6'ish layers on the sides, but I don't think it would make a good panel material.

Andrew

[Paul H]

... I believe you went over it earlier in this thread, but how did you do the curved panels? The "normal" methods (wetting, bending and drying)? I really like the look and would love to try it, but..uhhhh...see above I was thinking of trying it with something like 1/4" masonite and then just pop on about 6'ish layers on the sides, but I don't think it would make a good panel material.

Andrew

I tried a few methods, including 1/4" mdf and masonite, but didn't have any real success. (I just used small pieces to test some ideas).

What worked very well and what's in the finished product is bendable plywood - sometimes referred to as luan board. This plywood is fabricated with all the grains running in one direction, with a single plastic (?) core at the centre. This provides a product that is extremely flexible in one direction and rigid in the other.

I used 1/4" layers, but 3/8" would have worked also (thicker is less flexible, and a higher number of glued layers is stiffer). The initial layer went on over the "boat frame" and was screwed to the plywood bracing. Subsequent layers were glued only to the previous layer. The hideous number of clamps shown in photos above are required to achieve a tight fit using yellow glue.

The layers went on at the correct height, but intentionally wider then required (overhung at the front and back). I then trimmed off all layers of the overhung material flush to the front face of the braces using a router and jig.

The front and back 2 x 3/4" baltic birch pieces went on after the sides were completely done and trimmed. They were cut very carefully with angled edges to tie in to the end of the curved sides. A hand plane was used to make the "perfect fit" between the pieces prior to final sanding.

Luan board should generally be covered with a veneer. It is relatively soft, and I suspect impossible to coat with a brush as small particles would tend to get pulled loose by the brush - I sprayed the finishes and it worked okay.

Paul

[blue934]

i may have missed it somwhere, but i went thru all 7 pages and didn't see the xover point for the m8 mtm's. anybody know what it is? also what is the xover order?
response charts? i would like to try a set of these since i have been eyeing up the m8's for awhile.
blue934

[ThomasW]

This is an MTM version of Jon's original M8a MT design. The M8a MT design was published as a 3 part article in AudioXpress.

https://www.htguide.com/forum/showthread.php?t=22862

None of the 3 people building the MTM version were/are equipped to make measurements, so there aren't any.....

[Paul H]

...
None of the 3 people building the MTM version were/are equipped to make measurements, so there aren't any.....

Not quite true, but you're right in that I wasn't equipped to do measurements when I built these speakers. I may have done some tests while I had test equipment set up for other speakers since then.

I'll see what I have on file when I get a chance in the next few days.

[---k---]

Hi Paul

The baffle width is 12" total. You can round over the edges if you want to, but there's very little sonic benefit to doing that.

Thomas,

These old threads make great reading for use that haven't been around quite as long. Gives a lot of perspective. Maybe a good post would contain links to some of the better old threads - if you don't have anything better to do with your time.

BTW, you and Jon still think round overs don't matter? Or is it just small ones don't?

[blue934]

thanks thomas/paul, i appreciate the responses. look forward to any measurements you can dig up paul.

blue934

[Paul H]

Sorry, I looked but couldn't find any M8n speaker measurements in my files.

[blue934]

Thanks for trying paul. by the way what is the O/B pic on your profile? any details available?

blue934

[ThomasW]

Paul's build thread...

https://www.htguide.com/forum/showthread.php?t=11889&page=1&pp=35

[blue934]

WOW, paul those are freakin' monsters! hope the sound like they look.

blue934

[Paul H]

I haven't had them hooked up for almost two years, but by a strange coincidence started assembling them tonight in preparation for setting up a home theater system in the new home we moved into a few months ago.

They are incredibly detailed and clear. As they're a 4-way active speaker they do require major cabling and 8 channels of amplification, and a very strong back

[PMazz]

I'm building a set for my nephew. MTMs across the front and the single M8as for surrounds. I built a set of MTMs for my brother
years ago and, while having measurement gear, never thought to measure them after hearing how good they sounded.
Pete

[---k---]

Those look great Paul. Boy, I'm really feeling like I missed out on some great times.

[blue934]

thomas, what are the dimensions or even the internal volume for the sealed tibor version? what was the box alignment and f3 on that model?

pmazz, you have some great looking builds there1 thanks for the links.

blue934

[ThomasW]

thomas, what are the dimensions or even the internal volume for the sealed tibor version? what was the box alignment and f3 on that model?

There's a reason this design is not posted in the Missions Accomplished section....and that's because the design and the build weren't documented..

Tibor's build took place some 6yrs ago. It was custom for his needs/wants. It was drawn up on some scratch paper that was long ago lost..

Besides the 12" wide baffle the info below is what people used to build their boxes....height and depth were adjusted to needs/wants.

The woofers are offset 1.75" to the left of the front baffle centerline. The woofer centers are 11.5" apart, that's center to center spacing between them.

The tweeter is centered top to bottom between the woofers (so it's 5.75" below the top woofer and 5.75" above the bottom woofer). From the far right side of the baffle, the tweeter centerline is inset 3.5".

Since the plan all along was to use a sub, we weren't concerned about Fb/F3 given the use of a standard 80Hz XO point.

The T/S parameters for the M8a drivers are available so it shouldn't be to hard to run a sim looking at the performance characteristics you want...

In the second post in this thread Jon posted specific recommendations about vented box size and tuning..

https://www.htguide.com/forum/showpost.php?p=71037&postcount=2