Lobe examples per cab design?

[Marzen]

Has anyone run across a web page with examples of lobe plots for different types on enclosure designs? I have a few in my speaker design book (ie: MT& MTM), but I was looking for examples of line arrays, bessels, etc.
While pondering what to do for a center channel to go with the Modula MTM's I noticed PE's recent Cynosure design. I'm not thrilled with the idea of a WMTW for a CC and was looking for some other options to explore.

Thanks,
Ward

[cjd]

looking for some other options to explore.

Sure. Vertical MTM that matches your mains. Vertical TM.

Um...

How much vertical room do you have available?

But, keeping things in the family (so to speak) and building a slimmer center, a WTMW with RS125 and RS180's is probably about as good as it's gonna get as far as voice-matching goes.

C

[Marzen]

Sure. Vertical MTM that matches your mains.

This one's in the works already, with the eventual upgrade to the WTMW below

But, keeping things in the family (so to speak) and building a slimmer center, a WTMW with RS125 and RS180's is probably about as good as it's gonna get as far as voice-matching goes.

I'm not really sure if I'm concerned with voice matching the center, at least not at this point in the process. That could change drastically after I finish the matching MTM.

How much vertical room do you have available?

Only a 7 ft ceiling in the basement of this 1930 tudor.

I'm still interested in building an inline multi-driver speaker. If for no other reason than to learn something during the design and then listen to it. Perhaps it will morph into a L/R pair instead of a CC. It looks like a fun project & I haven't had any success in finding anything local to listen to that's outside the typical big box offerings. Certainly no exotics.

Thanks,
Ward

[cjd]

Voice matching is, IMO, underrated even by people that suggest the front three need to be voice matched. Of course, there aren't that many films that truly use surround, but those that do it can be good to have voice matched all around. I was surprised the difference it made in my setup, and I have dirt cheap speaks in the HT still.

It will probably get upgraded to RS125mid RS180 woofer pair and something tweeter-ish (Seas is up there simply because a 5.1 setup = ~$100 saved over RS28A, 7.1 = ~$140...) one of these days. We'll see.

But, I think you're really asking for information far beyond what we're even pretending to address here. For your space though, I think the WTMW (or, anything that keeps the core TM vertically aligned, and woofers wherever - MTM or TMM vertically fits this model just fine) is going to be the key to good center sound though.

C

[Marzen]

But, I think you're really asking for information far beyond what we're even pretending to address here. For your space though, I think the WTMW (or, anything that keeps the core TM vertically aligned, and woofers wherever - MTM or TMM vertically fits this model just fine) is going to be the key to good center sound though.
C

Chris, I get the impression you're trying to tell me I'm forcing a square peg in a round hole w/o using a stacked TM? Sorry, my subtle detection skills appear to have eroded or I would've picked up on that sooner.

Thanks,
Ward

[JonMarsh]

Ward, I understand another side to your issues- this is going to be looked on as slightly heretical, but prior to launching in ernest a WMTW design, I intend to look at the difference in launch behavior for horizontal dispersion vs frequency for both the conventional configuration (horizontal W -MT- W), and something more like a squat tower that would have all drivers vertical, but still fit under my FP screen. For those with an RPTV, for example, that wouldn't be practical. I suspect their might be some advantages to the latter approach because there won't be any diffraction off the woofer drivers, and their won't be such a wide launch baffle in the mids.

Just gut level speculation at this point, I intend to simulate in whatever tools I have that might work best, whether it's the new baffle modeler in LspCAD, or SPEAK from Gedlee. Still sorting that out.

OTOH, I just may be making this all more complicated than it needs to be. But sometimes I have to go through that process to assure myself I'm not overlooking something.

~Jon

[cjd]

Dangit Jon, either you're looking at my notes or I'm looking at yours. :P

Since I have a FP it is my intention to experiment with NOT mounting the woofers to the sides of the TM as I work up my next HT speaker setup. Of course, this won't work for everyone as you pointed out, but... In fact, I think for a FP theater it makes far more sense because otherwise you need a stand for the CC but nothing else (assuming you have 3-ways all around, which are likely floor-standers, and if they're not, WHY not?)

I do think it will change things, but I suspect it will be an order of magnitude LESS important to overall results than going from a simple MTM to anything that allows the TM to be vertically aligned (though a single TM on its side won't have the issues of an MTM).

Ward, have you seen the Java ripple tank tool? I wonder if that might provide some insight into things for you.

Of course, I am wondering how a WTMW might work for surrounds at the moment. My situation is such that they may have to be tucked into the corner between wall and ceiling also (7' ceiling and barely enough width to fit the couch will do that). Lotsa fun stuff to ponder. And the budget (within reason)! Just not the time.

C

[JonMarsh]

Synchronisity?


You didn't notice that little web cam I have above and behind your PC, so I can cadge your best ideas, did you?


~Jon

[cjd]

You didn't notice that little web cam I have above and behind your PC, so I can cadge your best ideas, did you?

Um... I have my best ideas in the shower and, um... yeah. You know, places where I'm just letting my mind wander without paying it any attention at all. Web cam eh? Enjoy the show

C

[Marzen]

'...no, No, NO!! 7 MINUTE ABS, nobody wants 6 minute abs...'*
I'm nicknaming you two the distraction twins. :W
Here I am, focused on an objective & you two are flashing shiny bits of interesting info in my peripheral vision. Here's the rub:
1) Will a L/R mains vertical line array work with low ceilings?
2) Why won't a horizontal center array work with low ceilings?
3) CC placement needs to be above or below a RP.
4) I think I ran across the ripple tank a while back when researching optical density meters for liquid media. I'll revisit that.
5) I can't remember where I was heading with this, I seem to have come down with a bad case of CRS. I have some Xmas ale on tap; I'm going to pour one & figure out where I was headed with this originally. :rofl:

* crazy hitchhiker from 'Something about Mary'
PS - send me some shower stills.

[Paul W]

Chris,
What are your thoughts on your wall/ceiling WMTW? Mid on top or bottom? xo order? I'm in the planning stages of doing the WMTW thing with a new set of surrounds and am currently thinking a relatively large mid with a low 3rd order xo...not cast in stone...or even wood.

Ward,
Vertical L/R line arrays should work well with low ceilings (might even try them as a phantom center). Horizontal can be a can of worms for lobing, regardless of high/low ceilings.
Paul

[Steve Goff]

Ward, I understand another side to your issues- this is going to be looked on as slightly heretical, but prior to launching in ernest a WMTW design, I intend to look at the difference in launch behavior for horizontal dispersion vs frequency for both the conventional configuration (horizontal W -MT- W), and something more like a squat tower that would have all drivers vertical, but still fit under my FP screen. For those with an RPTV, for example, that wouldn't be practical. I suspect their might be some advantages to the latter approach because there won't be any diffraction off the woofer drivers, and their won't be such a wide launch baffle in the mids.

Just gut level speculation at this point, I intend to simulate in whatever tools I have that might work best, whether it's the new baffle modeler in LspCAD, or SPEAK from Gedlee. Still sorting that out.

OTOH, I just may be making this all more complicated than it needs to be. But sometimes I have to go through that process to assure myself I'm not overlooking something.

~Jon

Hey, that is the same idea I had, for my front projector. Wish I had time to actual make some speakers.

[Paul H]

... prior to launching in ernest a WMTW design, I intend to look at the difference in launch behavior for horizontal dispersion vs frequency for both the conventional configuration (horizontal W -MT- W), and something more like a squat tower that would have all drivers vertical, but still fit under my FP screen. For those with an RPTV, for example, that wouldn't be practical. I suspect their might be some advantages to the latter approach because there won't be any diffraction off the woofer drivers, and their won't be such a wide launch baffle in the mids. ...
....
~Jon

It seems there's a few of us that have wondered about this, including me. Were you thinking of a straightforward tmww layout Jon?

Paul

[cjd]

Ward: the trick is keeping any horizontal speaker arrangement such that no two drivers are *next* to each-other that are particularly close to having a wavelength they cover that's close to the distance between them - i.e. comb filter avoidance. That's why the vertical TM is so good - the W's don't roll in till below the point where they would have comb filter troubles, but a straight-up MTM, the mids *would*.

While the measurements have some issues, this still shows what happens with an MTM horizontally placed. On-Axis (yellow), 15° off-axis (red), 30° off-axis (green), 45° off-axis (pink), and 60° off-axis (blue).



Nice nulls in there as you move off-axis, eh?

The best solution to all this is, of course, an acoustically transparent screen and a front-projector setup. FP will *always* help the cause in a big way, especially in a room that is already small - a big box makes it feel even more cramped. We won't talk about how horrible it is to have a big glass/plastic mass between your mains. The next best option for a CC would actually be to make the center speaker your TV stand, and have the added height to work with, not just a tiny shelf space below (or above).

Paul: I am not sure TM or MT - that's one of the things I want to check. There will be interesting loading what with the surfaces so near. It may be that it does not work well at all, or it may be really good, or... who knows.

And, re: CC TMWW, my thinking was that it would have to be short, such that the woofers might be placed side by side but still under the midrange. Probably some baffle tilt as well. This should lend itself well to integration in a TV stand as well.

C

[Marzen]

Ward: the trick is keeping any horizontal speaker arrangement such that no two drivers are *next* to each-other that are particularly close to having a wavelength they cover that's close to the distance between them - i.e. comb filter avoidance. That's why the vertical TM is so good - the W's don't roll in till below the point where they would have comb filter troubles, but a straight-up MTM, the mids *would*.

If by cover you mean share - like where the filter center is; what if the mids are not xo'd into groups, but rather run as a single entity, all sharing the same frequency range?

While the measurements have some issues, this still shows what happens with an MTM horizontally placed. Nice nulls in there as you move off-axis, eh?

I remember this from your web page on the mtm cc design. I have one of these now, an HTD Level 3. I can vouch for the nulls in the mtm cc. What sparked my interest in a different approach was from reading about ribbon tweeter polar plots - wide horizontal and narrow vertical dispersion. Which in turn led back here to search for options beyond the mtm. (the Xmas ale worked)

The next best option for a CC would actually be to make the center speaker your TV stand, and have the added height to work with, not just a tiny shelf space below (or above).

Now were cookin' with gas!

Paul: I am not sure TM or MT - that's one of the things I want to check. There will be interesting loading what with the surfaces so near. It may be that it does not work well at all, or it may be really good, or... who knows.

Modeling this was on my short list after reading the Arvo thread (ie: box beneath a panel). I haven't tried using SoundEasy to model anything beyond a box cab. I wonder if I can indicate the type of reflective surface above the speaker? I believe it supports this in the car modeling module, room modeling too perhaps.
And thanks Paul for summing up the mains array. I can't believe I wasn't able to work the phrase 'launch behavior' into the above ;x(

[cjd]

Ward: By cover I mean share. But, that's any time ANY two drivers are both contributing output at any given frequency. Not just the passband.

So, a long line of mids horizontally is no different than two mids. In fact, that's one of the issues you have to contend with and consider any time you do more than one driver - vertical can be as much an issue as horizontal - the difference is you can design a smaller speaker (MTM, WWMTM< WMTMW) so that the vertical comb filtering doesn't occur in the relatively narrow average vertical listening window.

A center channel has a potentially *wide* listening window over the axis where comb filtering exists.

A line array, of course, is almost guaranteed to have comb filter issue potential at the listening spot because of how the drivers are laid out.

Check out the ripple tank. It really does do a great job of visually illustrating some of this stuff.

C

[Marzen]

...I intend to look at the difference in launch behavior for horizontal dispersion vs frequency for both the conventional configuration (horizontal W -MT- W), and something more like a squat tower that would have all drivers vertical, but still fit under my FP screen.

Doesn't this data already exist in the public domain? I feel like a caveman sometimes compared to my day job where I can source info fairly easy when working a new design. It's odd to me that so much in this field is proprietary.

OTOH, I just may be making this all more complicated than it needs to be. But sometimes I have to go through that process to assure myself I'm not overlooking something.

Well c'mon, it's a hobby. If your workplace is like mine you'd be hanged for putting out a 'perfect' product. Which, by definition is obsolete :W and way past due. Hence the attraction to REALLY getting blood from a turnip.
PS - I guess I really DO want 6 minute abs...and I'm all wrinkly from being in the ripple tank to long...

[JonMarsh]

It seems there's a few of us that have wondered about this, including me. Were you thinking of a straightforward tmww layout Jon?

Paul

Yep. :T But a little more "squatty" than I would normally do. Maybe optimized for right up against the wall under the screen.