My hybrid MTM project

[johnaec]

Wow! Are those sides made of oak?

John

[pangea]

Thank you guys!

-lfh
Actually it isn't that difficult, as long as you double check every measurement and always go back and check with your drawing and most importantly as long as you dont rush things.
I must admit, I've spent many slepless hours in bed trying to figure out the best way to do it. Needless to say, I loved every one of them.

-Johnaec

Yes, the outer side panels are made out of 27mm (>1") solid oak.


Hmm... I wonder why the pic's got so blown up this time?

BR
Roland

[Zilch]

Will it have a whirlpool bath, or just a shower?

Nice work!

[Earl K]

Hi Roland

Glad to see that you're moving forward on your project .

Yes, the outer side panels are made out of 27mm (>1") solid oak.

Nice !

- Did you glue the oak strips together and then plane this assembled panel down to its' final 27mm measurement - or - did it all start out at 27 mm with just a bit of sanding applied to smoothe any prominent ridges ?

- The reason I ask , I've had thoughts that a "cheap & cheerful" approach to something very similar to what you've done - would be to make an internal box shell of 12mm that is then clad with 19mm thick "pine shelving". This pine shelving is available from either Ikea or stores like "Home-Depot" in various sizes. Like I said, "cheap & cheerful" . And of course pine is quite easy to work with and will accept colored stains quite handily .

Earl K

( PS; I hope those front panels are removable on your top box to facilitate some different component spacings )

[pangea]

Will it have a whirlpool bath, or just a shower?

Nice work!

Neither, I'm afraid, the only option would be the "Sauna".

BR
Roland

[pangea]

Hi Roland

Glad to see that you're moving forward on your project .



Nice !

- Did you glue the oak strips together and then plane this assembled panel down to its' final 27mm measurement - or - did it all start out at 27 mm with just a bit of sanding applied to smoothe any prominent ridges ?

- The reason I ask , I've had thoughts that a "cheap & cheerful" approach to something very similar to what you've done - would be to make an internal box shell of 12mm that is then clad with 19mm thick "pine shelving". This pine shelving is available from either Ikea or stores like "Home-Depot" in various sizes. Like I said, "cheap & cheerful" . And of course pine is quite easy to work with and will accept colored stains quite handily .

Earl K

( PS; I hope those front panels are removable on your top box to facilitate some different component spacings )

No, the panels are ready made "kitchen benches", which already are sanded and smooth. I think IKEA would be a good place to start.

There is some room for movement of the drivers, but if it requires greater movements, I will have to make new top boxes all together, but that's no problem really.

BR
Roland

[Earl K]

No, the panels are ready made "kitchen benches", which already are sanded and smooth.

Bravo !

I love a clever implementation of the axiom, "economy of effort" .

[pangea]

Hi all!

Finally the day has come where I got to listen to these hybrid MTM speakers for the first time.

At first I forgot to adjust x-over frequencies and therefore I could see that they were connected alright, but no holographic soundstage of course.

But then I tried to sum up all the info I got from all of you guys. I can't even begin to describe how grateful I am and how much I appreciate all the help I've received from you all!!!

I began to give the 2215H a + 3dB gain and an extra slight boost below 40Hz. (fb 23,3Hz) x-over point 330Hz/18dB/oct.
The 2123H is crossed over between 98-897Hz, 0dB gain, also 18dB/oct.
The 2441J then takes over from 897Hz up to 9,06kHz, - 7dB gain, 18dB/oct.
Finally the 075 at -4dB gain, takes care of the rest, also 18dB/oct.

Then I placed the microphone 114cm in front of each speaker and let the Behringer UltraDrive do it's thing and after that I let the UltraCurve do it's thing and guess what, there were only very small adjustments made by the UltraCurve, unlike before, where the adjustments sometimes went outside the measuring range.

As you can imagine I then sat down in my listening chair, somewhat nervous and pushed the play button....

I'm not kidding, after only a few seconds I was so moved, my eyes got moist.

Maybe it's just beginner's luck that I got it right, already at the first attempt, but I know for sure, that the outcome wouldn't have been such a success without your kind help and without the Behringers.

If you think the baffles look strange, it's because the 4mm "Masonite" baffle with the artificial leather is still missing.

Also, any suggestions or ideas that might improve things, are most welcome.



BR
Roland

[Earl K]

Congratulations Roland !

I'm glad your project is working out nicely - especially with you having to construct in a kitchen. I admire your fortitude .

Sometime when you can , please tell me what you hear ( and measure ) if you move the 2215h crossover point upwards to somewhere in between 600 and 900 hz . Thanks !

[pangea]

Congratulations Roland !

I'm glad your project is working out nicely - especially with you having to construct in a kitchen. I admire your fortitude .

Sometime when you can , please tell me what you hear ( and measure ) if you move the 2215h crossover point upwards to somewhere in between 600 and 900 hz . Thanks !

Funny you should mention that. That was exactly what I just was thinking of trying out, to see what happens if I let the 2215H go parallel with the 2123H up to where the 2441J takes over.
I should think the UltraCurve will have to make even fever and smaller adjustments to the frequency curve.
I was also thinking earlier during the building process and I think I even wrote about it, if it would be possible to hook the 2215/2123 up in parallel, i.e. making the system a three way, instead of a four way system.

Next time though I think I will have to get me a proper workshop before starting on a new project. There's MDF dust absolutely everywhere right now. It'll take me a week at least, to clean the place up again. So, perhaps fortitude isn't the right word. In hindsight, lack of common sense and stubbornness, is what comes to mind right now.

EDIT:
OK, I would say the soundstage became much more solid and homogenous. It also had the effect that it drew me in and it felt as if I became a part of the music. That really surprised me!
This I have never experienced before in my entire life!
I like!
Wan't more!!!

If I was addicted to JBL before, WHAT THEN, AM I NOW???

EDIT2: I almost forgot. As expected, the adjustments made by the UltraCurve, became smaller in that region!

BR
Roland

[Earl K]

Hi Roland,

EDIT:
OK, I would say the soundstage became much more solid and homogenous. It also had the effect that it drew me in and it felt as if I became a part of the music. That really surprised me!

- What frequency did you take the 2215 up to ? ( Try 600 or 700 hz )
- What slope ? ( Try all these; 6 / 12 / 18 db per octave )
- What filter type ? ( Try ButterWorth & Bessel ) I'm especially curious about Bessel at 600 or 700hz at 6 db per octave .

This I have never experienced before in my entire life!

- Well, that's what one should get with MTM when using a horn that has good to great imaging qualities all on its own .

I like!
Wan't more!!!

Yeh , it's pretty addictive .

Without hearing your system , it's hard to know how much "more" is available .

I have more ideas for you - I'll post in the next week ( maybe this weekend ).

I just was thinking of trying out, to see what happens if I let the 2215H go parallel with the 2123H up to where the 2441J takes over.
I should think the UltraCurve will have to make even fever and smaller adjustments to the frequency curve.

- Yes maybe intime the adjustments will be so small that you could take the UltraCurve out of the circuit and just use the "UltraDrive" for any frequency adjustments.

I was also thinking earlier during the building process and I think I even wrote about it, if it would be possible to hook the 2215/2123 up in parallel, i.e. making the system a three way, instead of a four way system.

- Don't do it. The 2123h needs some protection from lowfrequencies (LF) below 100hz ,,, so it's best to keep going 4-way so that you can filter out everything below 100hz . If you were using a different 10" with a deeper coil winding ( say 75mm deep ) - then my advice would likely be different .

[pangea]

Hi Roland,

- What frequency did you take the 2215 up to ? ( Try 600 or 700 hz )
- What slope ? ( Try all these; 6 / 12 / 18 db per octave )
- What filter type ? ( Try ButterWorth & Bessel ) I'm especially curious about Bessel at 600 or 700hz at 6 db per octave .



- Well that's what one should get with MTM and a horn that has good imaging on its own .


Yeh , it's pretty addictive .

Without hearing your system , it's hard to know how much "more" is available .

I have more ideas for you - I'll post in the next week ( maybe this weekend ).






- Yes maybe intime the adjustments will be so small that you could take the UltraCurve out of the circuit and just use the "UltraDrive" for any frequency adjustments.



- Don't do it. The 2123h needs some protection from lowfrequencies (LF) ,,, so it's best to keep going 4-way so that you can filter out 100hz ( & below ) from the 2123 .

I let the 2215 go to 897Hz, the same as the 2123 and I'm using 18dB/oct. BW on all x-over points.

Could you elaborate on the "Bessel at 600 or 700hz at 6 db per octave" .
I'm not sure where, but I know I read somewhere that the third order characteristics would yield the best phase alignment in an MTM configuration. Something with lobing or comb filter, I think, or something like that.
I'm sure "lfh"/Fredrik knows a lot about that. BTW Fredrik, you need to come and listen to this!!!!!

I've said it a thousand times at least, that with this hobby, you'll never be finished, but right now it feels like I'm being VERY close.

But still, I'm looking forward to your other suggestions.

It would be nice to be able to take out the UltraCurve from the equation and perhaps also make a passive filter for each driver, but unfortunately I don't have a clue as to how to translate milliseconds in to R/C circuits. Math's has never been my strong suit.

OK, I'll stay away from the 3-way thing. I only thought there would be a natural roll-off at the low end of the 2123.

BR
Roland

[Earl K]

Hi Roland

I need to read the operators manual for your UltraDrive before I make any more suggestions . ( I thought/assumed that each filter/output could have completely different filter characteristics assigned to it - that was just an assumption/hope on my part )

I'll get back to you this weekend . I've got to dash now .

[pangea]

Hi Roland

I need to read the operators manual for your UltraDrive before I make any more suggestions . ( I thought/assumed that each filter/output could have completely different filter characteristics assigned to it - that was just an assumption/hope on my part )

I'll get back to you this weekend . I've got to dash now .

You are absolutely right! Each and every output can be assigned, just about anything you like. Normally the x-over points are linked, but it's possible to even set them "free" and then you can overlap the frequencies anyway you want.

When you want me to use the 1st. order Bessel at 600-700Hz, do you mean that I should do that only at the overlapping points between the 2123 and the 2215 and keep the rest at 3rd. order BW?

BR
Roland

[Earl K]

Yes, I am leaving shortly but ,,,

When you want me to use the 1st. order Bessel at 600-700Hz, do you mean that I should do that only at the overlapping points between the 2123 and the 2215 and keep the rest at 3rd. order BW?

(a) I'm suggesting that you play around with just the one crossover point ( try 450 hz even ) and slopes of ( 6 to 18 db ) the "low-pass filter" from the UltraDrive output driving just the 2215. ( leave everything else at 18db Butterworth for the 2123s, 2441, 2405 ).

(b) Also try lowering your horns' overall crossover point to 800hz or 750hz, from the @ 900 hz you are now using . Do this adjustment for both the 2441 / 2123 sections. Then again, try different points of ( say 375 hz up to 750 on just the 2215 lowpass output - again with the 3 different slopes and two filter types ) .

This should occupy you for a while ( unless some of them just sound plain bad and measure awful )