New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[roadrune]

I dont know what causing that peak, but it might be Audyssey dynamic eq which i just realized i did not deactivate (Audyssey room correction was bypassed on all measurements).

The reason for crossing that high is that the subs, or actually more bassmodules, is just for the fronts and the crossover for them are placed after the pre/pro. This is 2 8" in 2 cabs, one beside each er18 and they are perfectly capable of 200hz. The idea was that the er's should be a lot better in the midrange not having to deal with bass, whitch is working fine, but still not perfect.

The LFE is handled by 2 15" tapped horns whitch is lowpassed at 80.

 

[Swerd]

I dont know what causing that peak, but it might be Audyssey dynamic eq which i just realized i did not deactivate (Audyssey room correction was bypassed on all measurements).

The reason for crossing that high is that the subs, or actually more bassmodules, is just for the fronts and the crossover for them are placed after the pre/pro. This is 2 8" in 2 cabs, one beside each er18 and they are perfectly capable of 200hz. The idea was that the er's should be a lot better in the midrange not having to deal with bass, whitch is working fine, but still not perfect.

The LFE is handled by 2 15" tapped horns whitch is lowpassed at 80.

For informative frequency response measurements of your speakers:

• Operate only one speaker at a time.
• Turn off sub woofers and all Audyssey adjustments.
  
• Move the speaker away from walls, out into the room, to minimize interaction from wall reflections.
  
• Keep the microphone at tweeter level, 1 or more meters away from the speaker.
• Operate the software so that the microphone captures sound arriving at 4 msec or sooner. Reflected sound from walls generally arrive after 4 msec. The software may call this a "gate" or "time gate".

If sub woofers or Audyssey are the cause for apparent mid range loss, then there is nothing wrong with your speakers.

What I'm wondering is, what is causing that hill from 300Hz down? And didn't you say you had your subwoofer crossed at 200Hz? Why is that necessary with transmission line towers?

I was under the impression that the elevated response seen between 200-300 Hz was caused by room reflections – same as what caused the narrow dip at 140 Hz. And then I read roadrune's response. Now I am not sure.

 

[roadrune]

For clearification: all meausurements shown here is with the er's and nothing else. The latest with a single speaker, no subs. Mic towards the speaker centered at tweeter height.

The speakers are close to both side and frontwalls, but both walls have absorbants effective down to atleast 100hz.

I have not used gating.

The mid problem is existent in all setups, also on pure stereo amps with no subs, however, all measurements shown here is in my HT, but with all other speakers inactive.

I also have measurements with the subs both with and without Dirac Live roomcorrection active, but neither looks significant better, and they dont regard the er's and therefore they are irrellevant to this thread.

 

[Swerd]

Gating is important. Look into how to do with your software.

 

[roadrune]

I will try with 4ms gating and Audyssey dynamic off later.

That said the waterfalls are pretty decent in the room with an average decay of about 45db/300ms.

 

[roadrune]

Here is one single speaker With every eq off, aprox 1 meter distance:

4m/s:

And 2m/s:

 

[MrBoat]

Hi Swerd, i was hoping you would chime in

Yes, i am shure that i have built the right crossovers, and that the parts vary by no more then 10%.


View attachment 21692 View attachment 21693

I also built two pairs with the same issues at different times.

Starting to think about my measurments... all measurments is both speakers, so the close range might be affected by the other speaker, i will take new measurments when i have the time.

I measure with a umik using rew.

What are these two different crossover boards? One for woofer, one for tweeter or why are they separate? I am likely missing something obvious because I am new at this but am not used to seeing them made like this.

ETA: I now see Swerd's picture of the crossover but what caught my attention is in the kit at meniscus, the photo of the parts shows only 3 inductors for the ER18.

 

[roadrune]

It should be 4 inductors.

The reason for building them apart was space, and inductor spacing. If you put inductors to close to each other their effective value will change.

I guess my mid-problems is what can be seen best at the 2m/s gating, the hill in the 500 region compined withe the drop in the 1000's?

 

[Swerd]

What are these two different crossover boards? One for woofer, one for tweeter or why are they separate? I am likely missing something obvious because I am new at this but am not used to seeing them made like this.

ETA: I now see Swerd's picture of the crossover but what caught my attention is in the kit at meniscus, the photo of the parts shows only 3 inductors for the ER18.

As roadrune already said, the reason for two different crossover boards is space. Inductors can interfere with eachother if they are too close together, or if they are aligned carelessly. See http://www.troelsgravesen.dk/coils.htm for the diagram near the bottom of that page

You have been building speakers with smaller cabinets. If there is space, it makes sense to have all the crossover components on one board. Sometimes, a small 2-way speaker with internal cabinet braces will require splitting the crossover into two separate boards. In larger floor standing cabinets, you have plenty of space available to separate the crossover into two separate boards, one for the woofer circuit and one for the tweeter. This makes each board smaller and lighter in weight. There is no acoustic performance advantage in using two boards instead of one.

I don't know why the Meniscus photo shows only three inductors. It should show four.
It should also show three resistors, not two.

I didn't know you were thinking about building these speakers. Meniscus shortened my write up when they made the ER18 MTM available as a kit. If you want the full write up, including the crossover schematics, send me your email address by PM.

 

[Swerd]

I guess my mid-problems is what can be seen best at the 2m/s gating, the hill in the 500 region compined withe the drop in the 1000's?

Thanks for the frequency response traces. I am waiting for Dennis Murphy's response. I hope he can make sense out of them.

 

[MrBoat]

As roadrune already said, the reason for two different crossover boards is space. Inductors can interfere with eachother if they are too close together, or if they are aligned carelessly. See http://www.troelsgravesen.dk/coils.htm for the diagram near the bottom of that page

You have been building speakers with smaller cabinets. If there is space, it makes sense to have all the crossover components on one board. Sometimes, a small 2-way speaker with internal cabinet braces will require splitting the crossover into two separate boards. In larger floor standing cabinets, you have plenty of space available to separate the crossover into two separate boards, one for the woofer circuit and one for the tweeter. This makes each board smaller and lighter in weight. There is no acoustic performance advantage in using two boards instead of one.

I don't know why the Meniscus photo shows only three inductors. It should show four.
It should also show three resistors, not two.

I didn't know you were thinking about building these speakers. Meniscus shortened my write up when they made the ER18 MTM available as a kit. If you want the full write up, including the crossover schematics, send me your email address by PM.

I saw that you had done the write-up but it took me a second to put the 2&2 together with regard to your screenname and only after reading this thread.

The photo just made me question whether there had been a revision to the drivers, and thus to the crossover that had slipped thru the cracks somehow. I didn't know if roadrune had built these from his own sources or a kit, so is why I mentioned the discrepancies between the meniscus photo and the diagram you posted.

Thank you for the generous offer. It's great to know the level of involvement here in this forum by some of it's members. Especially as how it seems I can fall into this DIY rabbit hole at times and with some of this stuff a bit overwhelming to us non-technical sorts.

 

[Swerd]

The photo just made me question whether there had been a revision to the drivers, and thus to the crossover that had slipped thru the cracks somehow. I didn't know if roadrune had built these from his own sources or a kit, so is why I mentioned the discrepancies between the meniscus photo and the diagram you posted.

If I remember, roadrune, who is in Norway, did not buy the Meniscus kit. He used various other sources available in Europe. I had to learn how to change American wire gauges (used in inductors) from AWG to the European standard of cross sectional area, mm².

I'm not aware that SEAS has changed anything about their ER18 drivers.

Thank you for the generous offer. It's great to know the level of involvement here in this forum by some of it's members. Especially as how it seems I can fall into this DIY rabbit hole at times and with some of this stuff a bit overwhelming to us non-technical sorts.

I'm glad you think its generous, but it costs me nothing to email a PDF file to you .

Your other cabinet making and finishing has been inspiring as well as entertaining. We'd all be delighted to see what you would do during construction of these cabinets – especially in their finish.

 

[roadrune]

Swerds right, i did not by a kit, but sourced everything locally, a bit challenging with the crossovers to get the correct values and to find someone with a lcr meter to unwind the smallest inductor to the correct value, but everything is within 10%.

 

[rojo]

Swerds right, i did not by a kit, but sourced everything locally, a bit challenging with the crossovers to get the correct values and to find someone with a lcr meter to unwind the smallest inductor to the correct value, but everything is within 10%.

I hope you remembered to convert all the values for Ohms, microfarads, etc. from imperial to metric, right?

Kidding. I really just wanted an excuse to ping @Dennis Murphy's notifier flag thingy and see whether he has any advice to offer. Dennis, the current topic of discussion starts at this post.

 

[roadrune]

Oh, damn, do you have a convertion chart for mH?

 

[MrBoat]

If I remember, roadrune, who is in Norway, did not buy the Meniscus kit. He used various other sources available in Europe. I had to learn how to change American wire gauges (used in inductors) from AWG to the European standard of cross sectional area, mm².

I'm not aware that SEAS has changed anything about their ER18 drivers.
I'm glad you think its generous, but it costs me nothing to email a PDF file to you .

Your other cabinet making and finishing has been inspiring as well as entertaining. We'd all be delighted to see what you would do during construction of these cabinets – especially in their finish.

Well it was still a nice gesture at any rate.

My problem with my own projects is I find it hard to put away the pace from my piecework days. I caught myself doing it again on the Continuums. I end up with a lot of stock looking results, albeit neatly done. I have skills to do much nicer work but I just don't end up using it for my own stuff for some reason.

I get an idea, make a plan, and before I know it, I have gone too far on the project to implement any of them. lol

 

[roadrune]

Thanks for the frequency response traces. I am waiting for Dennis Murphy's response. I hope he can make sense out of them.

I take it Dennis never came back?

Anyway; today we finally found the time to sit down at my mate's place and do a one on one battle of the ER's and his B&W CDM9NT, and i got to say they are REALLY different timbred, and i really get what he's saying about the ER's being "muffled" in the mids, and much darker voiced, the B&W's are lighter and more detailed, and the ER's deliver more bass.

Our conclusion was something like the B&W being more "audiophile hi-end" while the ER's are more "mainstream hi-end".

Both speakers sound good, but on electronic and rock music the ER's perform better IMO (due to the bass), but in acoustic and classical the B&W's are much more detailed and open.

They where tested on Electrocompaniet AW250's and a EC pre (i think it's a 4,6 but not shure) and a Blusound as source.

But what really puzzled us was the measurements, ER's in red, B&W in blue:
Left speakers:

Right speakers:

Both speakers (played, not summed)

All measurements in MLP and having 1/48 smoothing, no gating.

As you can see there is nothing in theese measurements that tells me that they should sound any different.

The waterfalls was the only thing that differed signifently with the ER's having much worse decay in the lower region.

I was also really impressed of the curves since this is in a normal livingroom with absolutely no acoustic treatments, and the MLP towards the back wall.

 

[MrBoat]

As you can see there is nothing in theese measurements that tells me that they should sound any different.

There is so much I would like to say to this effect with regard to modern audio (I've been listening to a lot of different speakers recently) but perhaps for another day/different thread. What ultimately disqualifies my opinion is I am not a gifted by genetics audiophile, and do not have the will with the smarts it takes to technically make my point other than that from an end user.

Still, great comparison along with the effort to get it done.

 

[seamusmcfadden]

Has anybody built this MTM with NeoCD3 tweeters following the suggested crossover and blown the poop out of their Fountek tweeters?

Following the original document thread I built this MTM and everything was fantastic but the Fountek's lasted a week.

Since the demise of my $300+CAD Neo's I have studied the X-over and it does not simulate well and shows high power delivery to the tweeter.

Just wondering if any real builders have had this problem?

Seamus.

 

[seamusmcfadden]

Deadville...x2