New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[roadrune]

Quick question; i have never made crossovers before, is this layout correct? minus input/output goes on the same place?

 

[Swerd]

Quick question; i have never made crossovers before, is this layout correct? minus input/output goes on the same place?

I think it may be correct. But I am not sure where in the layout you connect to the plus (+) and negative (–) terminals on the drivers and the + and – terminals on the back of the cabinets.

 

[roadrune]

Its not all that easy to see, but its written on the boards in norwegian "inn" is input "ut" is output.

 

[Swerd]

Its not all that easy to see, but its written on the boards in norwegian "inn" is input "ut" is output.

Now I see. Yes, that looks correct to me.

 

[roadrune]

Thanks Swerd. Always quick and good answers from you

Would it make sense to make all the internal cables the same length?

 

[Swerd]

Thanks Swerd. Always quick and good answers from you

Would it make sense to make all the internal cables the same length?

There is no reason to make the internal cables all the same length. Make them long enough to easily reach, without being too taught, where you must connect them .

 

[roadrune]

Being a plumber i know how hard it can be to cut a pipe straight on freehand, so i made a small tool to cut the ports:

And used the router to get the Connectors fit:

Not Perfect, but Close enough

 

[Swerd]

Nice work! I'm enjoying all your work-in-progress photos.

 

[roadrune]

Nice work! I'm enjoying all your work-in-progress photos.

Thank you, then here's one for ya!

One 0.1mH coil and one 0.06mH, had to remove aprox 180cm (70") of wire to get the right value:

Improvised fumes "extractor"

Really difficult to get all these thick and stiff wires soldered together without overheating the components, but i managed it somehow...

All done with the crossovers, they may not look nice, but i doubt the sound cares
I covered the back with McGyvertape to keep things in place, coils placed like this to avoid interference and altered impedance, after the Troels Gravesen method

First glued joint is setting

 

[FingerlessHackWoodworker]

Hey guys! I've been fascinated with this thread! I'd love to sink my teeth into building a pair of these gems. I have questions about the baffle. I noticed the upper portion of the baffle stands proud by 3/4" (upper piece made of 3/4"-thick plywood) with its bottom trimmed to a radius shape.

1) Is it critical to have the upper baffle piece standing proud by 3/4"?
2) Is the radius shape critical?

I am hoping to get away with a design where the upper baffle piece only stands proud by 1/8" and replacing the radius-shaped bottom as a square shape.

Hopefully, the two images (hardwood layer glued onto the MDF cabinet front) communicate/ illustrate how I plan, if viable, to alter the original design:

THANKS!

 

[roadrune]

As long as you keep the internal dimensions this will be no problem.

My speakers will have a clean front from 2 layers of 3/4" mdf when they are finished.

 

[Swerd]

FingerlessHackWoodworker – welcome to this thread! Love the monniker, hope it's not completely true .

I have questions about the baffle. I noticed the upper portion of the baffle stands proud by 3/4" (upper piece made of 3/4"-thick plywood) with its bottom trimmed to a radius shape.

1) Is it critical to have the upper baffle piece standing proud by 3/4"?
2) Is the radius shape critical?

I am hoping to get away with a design where the upper baffle piece only stands proud by 1/8" and replacing the radius-shaped bottom as a square shape.

The answer to both your questions is, no neither of these features are critical. Roadrune has it correct, the critical cabinet details are the correct internal dimensions, the external cabinet width of 9", and the speaker & port locations. The rest is up to you.

I do worry about the thickness of your front baffle. Your drawing shows the upper front baffle as 3/8" thick and the lower part as ¼" thick. I think it should be at least ¾" thick overall for two reasons. (How thick are the other sides of the cabinet?)

1. The ER18 woofers are heavy (4.73 lbs each) and their mounting frame flange is 0.2" (5.2 mm) thick. When you cut the recess to flush mount them, the remaining wood may not be enough to hold them securely.
2. A front baffle that thin will probably will vibrate audibly, even if the screws do hold the woofers.

When I made the drawings, I was imitating the look of these cabinets:

The photo shows Salk Veracity HT2-TL speakers https://www.salksound.com/ht2-TL - images.htm. They are the same dimensions and shape as the ER18 MTM cabinet. In fact, when Dennis Murphy designed the ER18s, he used an unfinished "test mule" cabinet for the HT2-TLs that he had in his basement.

 

[FingerlessHackWoodworker]

As long as you keep the internal dimensions this will be no problem.

My speakers will have a clean front from 2 layers of 3/4" mdf when they are finished.

Thank you kindly sir! I wait eagerly to see pictures of the final product.

 

[FingerlessHackWoodworker]

FingerlessHackWoodworker – welcome to this thread! Love the monniker, hope it's not completely true .
The answer to both your questions is, no neither of these features are critical. Roadrune has it correct, the critical cabinet details are the correct internal dimensions, the external cabinet width of 9", and the speaker & port locations. The rest is up to you.

I do worry about the thickness of your front baffle. Your drawing shows the upper front baffle as 3/8" thick and the lower part as ¼" thick. I think it should be at least ¾" thick overall for two reasons. (How thick are the other sides of the cabinet?)

1. The ER18 woofers are heavy (4.73 lbs each) and their mounting frame flange is 0.2" (5.2 mm) thick. When you cut the recess to flush mount them, the remaining wood may not be enough to hold them securely.
2. A front baffle that thin will probably will vibrate audibly, even if the screws do hold the woofers.

When I made the drawings, I was imitating the look of these cabinets:

The photo shows Salk Veracity HT2-TL speakers https://www.salksound.com/ht2-TL - images.htm. They are the same dimensions and shape as the ER18 MTM cabinet. In fact, when Dennis Murphy designed the ER18s, he used an unfinished "test mule" cabinet for the HT2-TLs that he had in his basement.

Swerd, thank you kindly sir.

The moniker is humor with some truth. I am a hack woodworker. I would like to change that, the hack part that is, while remembering to do everything possible to hold onto my 10 digits. It serves as a humorous warning to myself. Your thumb-nail pic, I remember that add (Maxell tape I think). I believe the speaker, blasting away at his tie, is a JBL 3-way. I have a pair of those puppies.

You are correct. I was not clear. The 3/8" thick upper front baffle and ¼" thick lower, will be glued onto a 3/4" piece of MDF. In total, the front upper baffle will be 1 1/8" thick and the lower baffle will be 1" thick. All other cabinet sides will be 3/4" thick (1/2" MDF + 1/4" Quarter Sawn White Oak).... with my new found knowledge (from you and roadrune) I am planning on changing it up. Maybe using 3/8" Leopard wood as the bottom and the 1/4" QtrSwn White Oak as the upper. I suppose my eyes want to agree with nature (more weighted things tend to settle at the bottom).

 

[Swerd]

The moniker is humor with some truth. I am a hack woodworker. I would like to change that, the hack part that is, while remembering to do everything possible to hold onto my 10 digits. It serves as a humorous warning to myself. Your thumb-nail pic, I remember that add (Maxell tape I think). I believe the speaker, blasting away at his tie, is a JBL 3-way. I have a pair of those puppies.

I also have a pair of JBL L-100s. My first effort in DIY speaker modification was building redesigned crossovers for them. See this thread.

The 3/8" thick upper front baffle and ¼" thick lower, will be glued onto a 3/4" piece of MDF. In total, the front upper baffle will be 1 1/8" thick and the lower baffle will be 1" thick. All other cabinet sides will be 3/4" thick (1/2" MDF + 1/4" Quarter Sawn White Oak)…

Good. I've never worked with 'veneer' that thick but it ought to work.

 

[FingerlessHackWoodworker]

I also have a pair of JBL L-100s. My first effort in DIY speaker modification was building redesigned crossovers for them. See this thread.
Good. I've never worked with 'veneer' that thick but it ought to work.

Sweet, I am excited to hear there is a thread on the redesign of JBL crossovers. Thank you so much for mentioning it!

My L-100 cabinets got real scratched up. Not my doing. Long ago, someone did me a favor of transporting the JBLs from my college dorm to the West Coast (Illinois to So. Cal.). I was livid when I saw how much damage the cabinets and foam front-grills had sustained, but bit my tongue and thanked him for the help. I suppose that is why I want thicker hardwood on this build. In case something bizarre should happen again, better chance of repairing the cosmetics.

 

[Swerd]

My L-100 cabinets got real scratched up. Not my doing. Long ago, someone did me a favor of transporting the JBLs from my college dorm to the West Coast (Illinois to So. Cal.). I was livid when I saw how much damage the cabinets and foam front-grills had sustained, but bit my tongue and thanked him for the help. I suppose that is why I want thicker hardwood on this build. In case something bizarre should happen again, better chance of repairing the cosmetics.

Try rubbing out the scratches with 0000 steel wool and clear untinted Watco Danish Oil. It may not remove all of the scratches, but it will improve things.

The danger with solid hardwood on a closed six-sided cabinet is cracking. The wood will expand and shrink as the humidity changes. MDF has no grain and doesn't expand or shrink, and veneer is more flexible. I don't know what will happen with ¼" hardwood glued over MDF.

Those polyurethane foam grills on mine crumbled and turned to dust a long time ago. That happened to everyone.

 

[roadrune]

Not much happening theese days, but i got both the boxes glued With sides, back and braces, ready for insulation crossovers and terminals.

I do not have enough clamps, so i use everything available to help...

All the driver holes are cut, hope they fit....

 

[Researcher]

Hi roadrune, your build it's looking great!!!, & nice working place BTW.

I'm curious about what amp you're planning to use with the ER18s?

 

[roadrune]

Hi Researcher, and thanks, i am lukcy enough to live a place where i could build a decent garage

They are built for a cinema, however i dont have anything else than the amp yet, so obviously i will test them in my livingroom once they are finished, and then on a Hegel H80. Do they sell Hegel in the US? Fantastic amps, made in Norway.
Once the HT is finished they will be driven by a Denon AVR2313. The plan is to build a 7-channel poweramp, and use the Denon as a pre, but i will like to hear them together first. It seems the er18's might not need anything else