New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[skyline_123]

Most of the wood working is done. Drivers are here. Waiting on parts from Erse. just ordered figured Madrone. It will take a bit more but its getting closer-

Good going Jeff! I'm glad someone else besides me will be enjoying these. I look forward to your opinions (and your pictures).

I have to agree about those curved Statements, they look amazing. The craftsmanship appears to be top notch. I think it would be difficult to convert all those dimensions to fit the original design though. They definitely give me inspiration for how I would do my future build. You know, the one speaker to rule them all; that DREAM build that you can't stop thinking about about while you're supposed to be paying attention at meetings; the one build that puts the rest to shame; the one you fantasize about when you and lady friend are..........wait, what?

Sorry, I got off track there. Anyway, I'll be following your progress closely. God speed Jeff!

 

[Ed H]

Wow! These are VERY tempting. And I look forward to a matching center (hint, hint)!

Can someone who has heard both give a comparison to the Nat-P towers? And/or Mini-Statements?

VERY well documented build. Many people will benefit from this thread!

 

[Jeff G]

Hey guys,
A couple of questions-

1) Any foam, Blackhole kinda stuff in the bottom cavity (not a euphemism for the backside). My has nothing in it. A big ringing chasm-

2) My cabinet (without the front baffle) is pretty live. there is a minor 3rd (or so) tuning between the top and bottom sections. I kinda want to shove some dowels in the there to add some more rigidity. I am concerned that it would screw up the quarter wave groove. Thoughts?? It sounds like a nicely tuned conga now....

3) I think I am going to mount the xover behind the driver for easy access. If I screw something up I'll never get to it in the bottom section.

4) I added some screen door material to the top section to hold the stuffing in place. i don't think it will alter the airflow significantly. let me know if I am wrong.


Can't wait to hear this beast. I have next week off!!!!
thanks!! Pics to follow-

 

[Swerd]

1) Any foam, Blackhole kinda stuff in the bottom cavity (not a euphemism for the backside). My has nothing in it. A big ringing chasm-

Leave the lower portion of the cabinet empty. No filling or lining is needed.

2) My cabinet (without the front baffle) is pretty live. there is a minor 3rd (or so) tuning between the top and bottom sections. I kinda want to shove some dowels in the there to add some more rigidity. I am concerned that it would screw up the quarter wave groove. Thoughts?? It sounds like a nicely tuned conga now....

Some extra dowels may help. As long as they don't impede air flow between the woofers and the port it can't hurt. Once the front baffle is attached it should be more solid.

3) I think I am going to mount the xover behind the driver for easy access. If I screw something up I'll never get to it in the bottom section.

No problem with that.

4) I added some screen door material to the top section to hold the stuffing in place. i don't think it will alter the airflow significantly. let me know if I am wrong.

Screen or netting should keep the fiberfill from falling. Good idea.

We eagerly await your pictures .

 

[braves]

Hi Skyline! First I have to say "nice job". But somehow I have two questions
1. Did the internal brace really need to be this complicated??
2. If it have to this complicated, could u post the detail drawing of the brace?

 

[Swerd]

Hi Skyline! First I have to say "nice job". But somehow I have two questions
1. Did the internal brace really need to be this complicated??
2. If it have to this complicated, could u post the detail drawing of the brace?

I'm not skyline, but I did put together the written plans for these speakers that skyline posted early in this thread. If you would like a copy of the plans as a pdf file, send me a PM with your email address and I'll send it to you.

No the internal braces do not need to be exactly as skyline did them, although all the circles with rounded edges do look impressive. When I scheched them, I imaginined them to look something like this:

They can be roughly cut with a hand-held sabre saw. The important features are:

1. The braces add stiffness to the overall structure, especially by stiffening the large panel walls
   
   
2. The braces should not impede the air flow inside the cabinet between the woofers and the port tube.

Other than that, cut them out as you wish. Skyline might be too busy listening to music now, but because he built them he may have something to add about the bracing.

 

[jinjuku]

I would love to hear these and my Statements side by side when I have them finished.

How close is anyone with this MTM Louisville / Cincinnati?

 

[braves]

Hi Swerd!
Sorry I haven't qualified to send message yet.
I am really interested in this DIY plan.
Can u send the detail plan to my mail box "m8832669@gmail.com "?
Besides that, I have some more question about the plan
1.since the inner bracing is asymmetrical,what is the real dim of the two proportion ?
2.I have built the "SR71" which Zaph designed with the same midrange of er18. Will this plan get real improvement in sound stage or quality from Sr71?
Thanks for your kindly reply.

 

[jinjuku]

Hi Swerd!
Sorry I haven't qualified to send message yet.
I am really interested in this DIY plan.
Can u send the detail plan to my mail box "m8832669@gmail.com "?
Besides that, I have some more question about the plan
1.since the inner bracing is asymmetrical,what is the real dim of the two proportion ?
2.I have built the "SR71" which Zaph designed with the same midrange of er18. Will this plan get real improvement in sound stage or quality from Sr71?
Thanks for your kindly reply.

The MTM will have more output hands down with better bottom end extension with lower distortion. The TDFC tweeter Zaph chose is real smooth with good dispersion. Same goes for the RS28a on the MTM. I can't speak for the ribbon alternate.

 

[skyline_123]

Skyline might be too busy listening to music now, but because he built them he may have something to add about the bracing.

Sorry, I don't have much to add other than I was kind of excited about how neat the braces turned out. They just felt nice in your hand, but at the end of the day, they just sit inside the enclosures, never to see the light of day. I will say, they do a good job of keeping the stuffing from falling through to the bottom, but that's it.

I would love to hear these and my Statements side by side when I have them finished.

How close is anyone with this MTM Louisville / Cincinnati?

Roughly 850 miles How bout it?

 

[Swerd]

Hi Swerd!
Sorry I haven't qualified to send message yet.
I am really interested in this DIY plan.
Can u send the detail plan to my mail box "m8832669@gmail.com "?
Besides that, I have some more question about the plan
1.since the inner bracing is asymmetrical,what is the real dim of the two proportion ?
2.I have built the "SR71" which Zaph designed with the same midrange of er18. Will this plan get real improvement in sound stage or quality from Sr71?
Thanks for your kindly reply.

I emailed you the plans earlier today, but I've been away from a computer until now.

You second question is a good one, and I haven't heard the SR71 so I can't really say anything for sure. But I can always speculate .

I haven't heard any DIY speakers designed by Zaph, so I really don't know how he "voices" them. By "voicing", I mean all the small choices made by a crossover designer that have a big effect on the final sound, especially in the all important midrange. I am very familiar with Dennis Murphy's "voicing" and I know I like it a lot.

Both designers have a very good reputation, and I don't doubt that they both can do an excellent job.

Two woofers will certainly be louder than one. I can guess that the bass in the SR71 won't go as deep as in the ER18 MTM. The ER18 tansmission line tower cabinet is larger too. I also like the sound you get from a transmission line bass cabinet better than from a typical bass reflex cabinet (as in the SR71). TL cabinets also allow more flexibility when you choose where to place the cabinet with respect to the wall behind them.

I think the tweeter in the SR71 is excellent, as are the two tweeters you can choose from in the ER18 MTM. As a guess, I'd say the crossover frequencies Dennis used with the Dayton dome tweeter is close to the crossover frequency John Krutke used in the SR71. I do know the crossover frequency for the Fountek ribbon tweeter is higher, but that seems to have little effect that I could hear.

Both speakers seem to have 4th order Linkwitz-Riley type crossovers. So if both John Krutke and Dennis Murphy make similar voicing choices in the crossover range, they might sound similar - except for the bass.

If you have a pair of SR71s and want to know if they will blend well the ER18 MTMs, I'd guess that they will blend well. Actually, I'd be more surprised if they didn't blend well.

I hope that helps.

 

[Jeff G]

Sloooow going

Here's my progress on the ER-18s. it has been a slow process. Two kids (2,5 and 10mos) and the younger one has been in the hospital a bit. Doing better now

My shop is usually messy this is a new low. Embarrassed to make it public.

My wife is sick so i was home to look after the stinkers today. Stole away a few minutes whilst they were locked in a closet. Just glued the baffle and base on the second speaker. Need to attach the binding posts, add the stuffing and mount the drivers. I have some floor spikes coming (back ordered until 6/15 or so). Might be listening to new speakers soon. Hopefully the xover is correct!! If anyone can make heads of tails let me know.

Soon....very soon...now for a new preamp-
Jeff

 

[darien87]

Here's my progress on the ER-18s. it has been a slow process. Two kids (2,5 and 10mos)[/QUOTE]

Uuummmm.... isn't that 3 kids? Hope your better at building speakers than you are at counting.

Sorry just had to give you crap for that.

 

[Swerd]

Jeff - Your cabinets look great. I like the veneer. Which tweeter did you get, ribbon or dome? It's hard to see the wiring in your XO photos, but they look like you've done this before .

Working around the house with little ankle-biters is tough. They either cry and demand attention, or they scatter and loose the parts that you need for the next step in your work.

Keep up the good work

 

[Jeff G]

The tweeter is the ribbon. Had it on hand for the Statements. The veneer is Makore. I did the heat application method. The veneer is book-matched. had difficulty keeping the joint together. Finish is 2 coats of Tung oil, lots of oats of Blond shellac and some wax. Looking forward ti hearing them.

 

[Jeff G]

I just realized my 3" port tube is 2.75" ID!! yes, another counting error...

I looked at WinISD to see what happens with a smaller tube. Looks like length gets shorter. Mine is flared on both ends. The port center is 3" above the bottom floor.

If Paul is viewing this, can I make it OK with this port? If so, any thoughts about how long the overall port should be?

Sorry for the poor planning and groveling for assist-
JG

 

[jinjuku]

The tweeter is the ribbon. Had it on hand for the Statements. The veneer is Makore. I did the heat application method. The veneer is book-matched. had difficulty keeping the joint together. Finish is 2 coats of Tung oil, lots of oats of Blond shellac and some wax. Looking forward ti hearing them.

Why didn't you build the Statements?

 

[TLS Guy]

I just realized my 3" port tube is 2.75" ID!! yes, another counting error...

I looked at WinISD to see what happens with a smaller tube. Looks like length gets shorter. Mine is flared on both ends. The port center is 3" above the bottom floor.

If Paul is viewing this, can I make it OK with this port? If so, any thoughts about how long the overall port should be?

Sorry for the poor planning and groveling for assist-
JG

What is the internal volume of your box?

Yes, the port will be shorter, bu air speed will be up. You should try and correct this, so you use the correct vent if you can.

 

[Swerd]

The tweeter is the ribbon. Had it on hand for the Statements. The veneer is Makore. I did the heat application method. The veneer is book-matched. had difficulty keeping the joint together. Finish is 2 coats of Tung oil, lots of oats of Blond shellac and some wax. Looking forward ti hearing them.

The Makore really looks good. Finishing with tung oil, blond shellac and wax all make sense, but I can't picture just how you apply lots of oats .

I just realized my 3" port tube is 2.75" ID!! yes, another counting error...

I looked at WinISD to see what happens with a smaller tube. Looks like length gets shorter. Mine is flared on both ends. The port center is 3" above the bottom floor.

If Paul is viewing this, can I make it OK with this port? If so, any thoughts about how long the overall port should be?

Paul's original design predicts air velocity of just over 3% the speed of sound using 3" ID tubes. If I remember, the rule of thumb says anything under 5% will not be audible, so I think you have some leeway. If its easy to enlarge your hole and mount 3" tubes, do it. If not, use the 2¾" tubes made a little shorter and don't worry about it. Tuning cabinets for bass seems to have plenty of room for error in it.

 

[Jeff G]

I will use spell check from this point forward (unless I'm in a hurry)

I'm going to roll with the 2.75" ID port for now. Don't won't to risk hosing up the veneer/ finish, etc. I did a sim in WinISD just to try and get an idea how much to reduce the length by. Had to tune the cabinet to 57hz to get the port length to 2.75. I'm sure that's off the mark. The whole funky TL thing changes things I'm sure. Anyway, looks like the length of the port with no flare goes from 2.75" to 2.14" (about 78%of the original length). Applying the same guesstimate to the flared port I go from 3.75" to 2.92"

Hopefully no port noise. Only 1/4" smaller The port is on the rear as well. Anyway, I hope to finish them (except for the spikes) this weekend-
JG