My hybrid MTM project

[pangea]

Yes, I am leaving shortly but ,,,



(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 )

I began by lowering the horn and the woofers x-over point from 897 to 805Hz, but that made it worse. The soundstage almost collapsed, so I went back to 897Hz.

As I was about to change characteristics on the 2215 to 1st. order BW (there is no 6dB Bessel on the UltraDrive), I ran in to some problems with one of the UltraDrives, which suddenly "lost" the fourth output, it somehow got assigned to input B.
Don't know happened there. I Had to reconfigure the whole thing, which kept me busy for qute a while.

I'll give it a new try tomorrow.

BR
Roland

[Steve Gonzales]

Really nice job!!. Dreamy looking blue baffles and driver compliment. I hope you get to keep the vertical arrangement. SWEET!!!!

[Earl K]

Hi Roland

I began by lowering the horn and the woofers x-over point from 897 to 805Hz, but that made it worse. The soundstage almost collapsed, so I went back to 897Hz.

- I think it's wonderful that the system already images so well that the effects produced by the lowering of the crossover point, were immediately evident / ie " the collapsing soundstage" .

BW (there is no 6dB Bessel on the UltraDrive),

- Well,,, there shouldn't be. I should have mentioned that before or chosen my words more carefully . It takes more than one pole ( producing a 6 db slope ) to create a "signature" transform ( ie Bessel, Butterworth, LR ). It's the relative spacing of the poles to each other ( quantity of, 2, 3, 4, & up, all working within the desired crossover area ), as well as the filter poles interaction with each other , that creates the characteristic crossover curve near F3. Group-delay characteristics ( and transient response characteristic ) are also dictated by how the different poles interact with each other. Taken together ( along with some other factors ) these characteristic describe the filters' name along with its unique transform function .
- So a single pole is a lonely fellow - left to interact with no other pole - therefore there is no creation of a unique "transform" ( like Bessel, Butterworth, LR ) .

As I was about to change characteristics on the 2215 to 1st. order I ran in to some problems with one of the UltraDrives, which suddenly "lost" the fourth output, it somehow got assigned to input B.

Static maybe ?

- Anyways, I'm going to put my future suggestions in another posting.

- Don't feel compelled to try them out right away / just file them for later if you prefer / the main thing is to enjoy your new speakers and get used to what they do right now.





BTW : I'm really curious, just how did you manage to create those angled/bevelled decorative cuts, that are on the front edges ( like you put in the drawing ) ?

[pangea]

Hi Roland



- I think it's wonderful that the system already images so well that the effects produced by the lowering of the crossover point, were immediately evident / ie " the collapsing soundstage" .



- Well,,, there shouldn't be. I should have mentioned that before or chosen my words more carefully . It takes more than one pole ( producing a 6 db slope ) to create a "signature" transform ( ie Bessel, Butterworth, LR ). It's the relative spacing of the poles to each other ( quantity of, 2, 3, 4, & up, all working within the desired crossover area ), as well as the filter poles interaction with each other , that creates the characteristic crossover curve near F3. Group-delay characteristics ( and transient response characteristic ) are also dictated by how the different poles interact with each other. Taken together ( along with some other factors ) these characteristic describe the filters' name along with its unique transform function .
- So a single pole is a lonely fellow - left to interact with no other pole - therefore there is no creation of a unique "transform" ( like Bessel, Butterworth, LR ) .





Static maybe ?

- Anyways, I'm going to put my future suggestions in another posting.

- Don't feel compelled to try them out right away / just file them for later if you prefer / the main thing is to enjoy your new speakers and get used to what they do right now.





BTW : I'm really curious, just how did you manage to create those angled/bevelled decorative cuts, that are on the front edges ( like you put in the drawing ) ?

These were the tools I used to chip away and grind the corners.



A pair of steady hands are required though, if you dont have big machines at hand.

I have come down with the flue, so the pace is somewhat slow at the moment. But as soon as I feel better again, I'll give it a new try to experiment with the slopes and x-over points, on the 2215.

EDIT: BTW, so far it sounds extremely good" The soundstage is rock steady and it's very easy to locate the singers and instruments!!!

BR
Roland

[Earl K]

Thanks ! ( for the show of tools )

- Sorry to hear that you've gotten the flu .

- I'll be around when you can chat more,

[pangea]

Hi Earl!
I've followed your advice, while recuperating from the flu I've tried to listen to them as is.

Thus far it's already been an overwhelming experience. The soundstage is firmly placed in the middle and the stereo perspective is excellent, so what else is there to ask for?

Well, if I'm allowed to be EXTREMELY demanding, I would like the less protruding instruments to be somewhat easier to locate and pinpoint as well. But then again, that maybe isn't even possible, on the records I've been listening to.

The singers and the lead instruments however, I can easily pinpoint down to an inch or two!


BR
Roland

[pangea]

Hi Earl!

Do you, or anyone else for that matter, have any rcommendations on "difficult" and revealing recordings, wich might be used to (3-D) fine-tune the speakers?

What else is there to be done to improve the sound?

BTW, yesterday I ordered some artificial leather, wich comes as lose as it possibly could, to the JBL blue and guess what the color is called?
It's called 2402, like my dear 075's.

BR
Roland

[Robh3606]

You could try Peter Gabriel Up or Amused to Death by Roger Walters. Both have some wild effects with Amused taking the cake. Uses Q Source??? I use them to verify phase after the standard phase test on my set-up disk. If one driver is screwed up the effects go all to hell. Also use it to set-up toe in, seated distance and height. When it's right you have things all over the room. To your sides, well past the speakers and what sound like behind you it's really remarkable where some of the images are placed, and how repeatable it is. By repeatable I mean it works with my mains XPL's and 4344's. It's easilly tranferable from system to system so it's a good tool. Once you know where everything goes it's a cinch to hear problems.


Rob

[Zilch]

"Up" is crazy. Got 20 Hz on one track. Startling when the walls and ceiling make creaking noises.

And from the "Amused" liner notes:

If the dog barking at the beginning of the record doesn't sound like he's in the yard next door, then your speakers are out of phase.

"Why do I have to keep reading
These technical manuals?"

[Earl K]

Hi Roland,

Some Questions First;

- How wide/narrow is the overall viewing angle into the sound stage ?

- How far apart are the speakers ( to center of horn ) ?

- How many degrees of "toe-in" ( angle-in ) are you using ?

[pangea]

Hi Roland,

Some Questions First;

- How wide/narrow is the overall viewing angle into the sound stage ?

- How far apart are the speakers ( to center of horn ) ?

- How many degrees of "toe-in" ( angle-in ) are you using ?

Two persons seated next to each other, can just about hear the music coming from somewhere in the middle, but it won't be possible anymore to pinpoint the instruments or the singers voice, as the soundstage becomes fuzzy and inaccurate.
A stable and accurate soundstage is only wide enough for one person seated in the middle.

The distance between the speakers is 225cm (horn-center to horn-center) and the distance between speaker baffle and listener is about 300cm.

The toe-in is around 20 degrees. Both speakers pointing straight towards a single listener.

BR
Roland

[Earl K]

Roland

I'll post a "shopping list" of thoughts on this later this evening .

- In the meantime, I do find that keeping a foam surface around the complete horn area makes a bit of difference to the "sharpness" of the image . I haven't studied all the types; but I use open-cell "road-case" foam. Eventually I'll try out more closed cell stuff such as neoprene. Even those cheap foam "camping mats" could offer the necessary resistive surface. I realize you have "fake leather" coming for that same area - I'd listen to it ( and other alternatives" ) before applying it .

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[pangea]

Roland

I'll post a "shopping list" of thoughts on this later this evening .

- In the meantime, I do find that keeping a foam surface around the complete horn area makes a bit of difference to the "sharpness" of the image . I haven't studied all the types; but I use open-cell "road-case" foam. Eventually I'll try out more closed cell stuff such as neoprene. Even those cheap foam "camping mats" could offer the necessary resistive surface. I realize you have "fake leather" coming for that same area - I'd listen to it ( and other alternatives" ) before applying it .

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THNX for the tip, I'll try it out first, before applying any fake-leather permanently with glue. But then again, perhaps I could apply the fake-leather anyhow, since the 4mm "Masonite" I have mounted with the "rough" side out, needs to be covered with something anyway and perhaps it would be possible to place some neoprene/mouse-mat ore something like that, only around the horn-mouths afterwards, don't you think?
I already have two soft mouse-mats from earlier tests.

It would really be a shame not to use the fake-leather, since the color is soooooo JBL'ishly beautiful.

I think I will have to read your "shopping-list" tomorrow, I feel I need to turn in early tonight.
Once again, many thanks Earl!!!

BR
Roland

[Earl K]

Hi Roland

,,,,, needs to be covered with something anyway and perhaps it would be possible to place some neoprene/mouse-mat ore something like that, only around the horn-mouths afterwards, don't you think?

- Really, the whole baffle will need some treatment of sorts. Maybe the fake leather on it's own will suffice. I don't really know. Surface treatments are something that are quite new to me - so I don't have a lot of experience with all the different types. I just know that I hear a "sharpening" of the imaging when I place foam around my speakers / including all the areas around the horn mouth. I mention neoprene because JBL has used it in the past in the XPL series. The Altec Model 19 had open-cell foam all around the horn face / the full width/height of the top box.

- I also think this type of thing falls into the "final-tweaking" category ( though "final" is such wishfull thinking ).

I already have two soft mouse-mats from earlier tests.

- My advice would be to start with the case foam ( the "worst looking" fix ) and work towards ( best looking ) since IME the best looking usually translates into "least effective" .

[Mr. Widget]

Many of THOSE silly audiophile speaker companies including Wilson have used foam or thick felt for this very purpose. I have too. It seems significantly less useful in the horn designs I have tried it on. On a speaker like the XPLs it seams to make the most difference.

It certainly is worth trying out. Sonus Faber uses real/synthetic leather... I don't think it really does much for diffraction, I think it is mostly for aesthetics.

Widget