Why wouldn't a ribbon based MTM be ideal for home theater

[indygreg]

been reading a number of posts and was curious why an MTM using a ribbon like a raven would not be ideal for home theater? the downside to the ribbons is their lack of vertical dispersion but that is a big plus for home theater.

greg

[Dennis H]

been reading a number of posts and was curious why an MTM using a ribbon like a raven would not be ideal for home theater? the downside to the ribbons is their lack of vertical dispersion but that is a big plus for home theater.

greg

Ribbons need to be crossed quite high to keep them from breaking. MTMs like to be crossed low because the center-center distance of the M-M should be, at the absolute most, one wavelength at the XO frequency. Hard to reconcile those two requirements.

[indygreg]

can you point me to something or perhaps do a brief laymans description of the principles of an MTM? i kind of get that two mids helps control vertical dispersion of the midrange. is this the related to the way a line array does this? i kind of get that. if so, would a small line array of mids (like maybe 5") and a ribbon be a good match?

greg

[Jim Holtz]

Ribbons need to be crossed quite high to keep them from breaking. MTMs like to be crossed low because the center-center distance of the M-M should be, at the absolute most, one wavelength at the XO frequency. Hard to reconcile those two requirements.

Hi Dennis,

This subject has been discussed numerous times in the past on MAD. It's my understanding, it's M-T on both sides for CTC spacing rather than M-M. Also, ribbons emit sound from their full length so the CTC measure starts at the edge of a ribbon vs the center as a dome. One more thing. Many of the current ribbons (short for good dispersion) cross comfortably at 2.5K. Lower is better for MTM's but that is most certainly not unreasonable from my understanding.

Jim

[thylantyr]

like a raven would not be ideal for home theater?

The word home theater is broad. Does it mean one or two
people listening or a crowd in the room? Any critical listening? Single small planars and ribbons yield the best sound when
they are aimed at the listener due to the weak vertical dispersion. As you aim the tweeter you will notice an
SQ improvement. Domes on the other hand will sound sweet
even when not aimed exactly.

If the HT is for you and another, then it shouldn't be a problem. If the HT has many seats with an audience, you
might want to examine the design in more detail and
weigh the pros/cons.

The only way to really know is to buy one tweeter and
mess around with it and do some listening tests to
see if it's satisfactory under the conditions you present it.

There is an interesting solution if you want a true ribbon,
check into LCY ribbons, word on the street says the sound
quality is just as good as the best domes, maybe better
while keep wide dispersion.

https://web.archive.org/web/20070312110959/http://www.e-speakers.com/products/lcy-components.html

[peterS]

i found the lcy110s sounded better than the rs28
if the distortion is lower depends on who you ask but it does sound better

lcys also are more compact so a mtm may still be feasable
of course a tmm is always doable too- thou id have to do some reading up on what the trade offs are- id suggest "loudspeaker design cookbook" by vance dickenson if you are shacky on the basics (parts express has it)

fyi ribbons can handle as low of an x/o point as any 1" dome tweet
there mechanical durrablity is by most peoples accounts surprisingly resiliant (i know some have them in spl comp cars)

[indygreg]

what do i mean by theater

i didn't want my original post to go on for days. here is a little more detail.

the LCR are in question here. the theater will seat 12 in 3 rows. the room is 21' x 28'. the closest seat is 12' from the speakers. will be used 80% theater/20% music but i really like music and would like to have it sound good for that use. i am not an audiophile but i like a smooth but airy sound. music taste is kind of contemporary/old fart (stephanie mills, al jarreau, eagles, etc). i like to hear a female voice be breathy or a high hat have attack.

room layout is here. seating has been replaced by 2 rows of 5 seats (center is the old fart's chair) and bar stools in back.

Image not available

greg

[Landroval]

The big Fountek NeoPro5 can be x-o'd quite low, 1-1,5kHz should be no problem:
http://www.madisound.com/cgi-bin/ind...10290&pid=1891

[Jim Holtz]

[b]Single small planars and ribbons yield the best sound when
they are aimed at the listener due to the weak vertical dispersion. As you aim the tweeter you will notice an
SQ improvement. Domes on the other hand will sound sweet
even when not aimed exactly.]

Short ribbons such as the the Fountek NeoCD3.0, AC G2 etc do not suffer from lack of vertical dispersion. This length ribbon comes extremely close to any one inch dome for vertical dispersion and easily exceeds the horizontal dispersion of any dome.

I've listened to Fountek, AC and LCY and can verify this to be fact not opinion.

Also, I found the sound quality to be very, very similar. I'd go with the Fountek NeoCD3.0 personally. These are extremely nice sounding tweeters and more durable than the others due to the ribbon construction. BTW, durability is not an issue if you use common sense in their application. They are not designed to be crossed super low, however they also don't require extremely high crossovers to sound excellent either. Listen to a Salk Sound Veracity or HT3 design for an excellent example of a 2.5K crossover. That's crossing to a W18 too.


Jim

[cjd]

How deep is that front stage?

It doens't look deep enough to support an AT screen properly without on/in-wall speakers behind it but scale can be slightly deceiving...

Beyond that, budget will control to a large extent just how good a ribbon you work with, and that will often dictate how low it can go before self-destructing. On most the more commonly used ribbons, crossing below 3.5k means more distortion than you would get with any number of quality domes, and above, no better.

You WILL need to avoid any horizontal MTM arrangement in that room of you'll get big suck-out through the upper midrange in the front row of seats.

And finally... I think that vertical dispersion is waaay toward the bottom of things to consider when putting together a speaker design, even for a HT where some folks like THX recommend limiting vertical dispersion.

C

[indygreg]

the stage is not build yet but i was planning 20" behind the screen. for budget i was considering the klipsch thx ultra which would be about $3000 for the LCR setup. i live in indy and klipsch was kind enough to let me visit the factory yesterday and hear them. they were VERY intelligable for dialog but seemed a little harsh in the upper midrange for me. if i could do something for 1500 in drivers i might be inclined to try that. i already have the amp channels to biamp (or triamp if needed) and a behringer crossover.

i would think that controlling vertical dispersion would be a plus for home theater and since i like that airy ribbon sound that seemed like something worth pursuing.

i wondered if something like this http://www.orcadesign.com/systems/sy...R1_6w4311b.htm

might be good for me since i am a little sensitive to harshness in the upper mids and this would have a cone extended up higher than the rs180 can practically go.

greg

[JonMarsh]

The LCY 130 was interesting to me; it's curious that it seems to have a bit of a waveguide built in. With the recess of the ribbon, there does appear to be some cavity resonance as shown in John Krutke's plots. Note the higher levels of high order harmonics compared to the other designs he tested.

Considering the Q of the Fs at 1 kHz, I'd use a crossover that's well down in level by that point- no lower than 2.5 kHz.

I'd say that claiming that these can be crossed as low as any 1" dome is not borne by the facts of the driver performance, as many 1" dome tweeters are availble with essentially flat FR to 600-700 Hz, and in a steep crossover are usable to 1200 Hz or so.

The most interesting tests John did were the multi-tone spectrum tests...

One of these is the D26CN55, which is not meant to be used below ~2.5- 3 kHz, the other is the LCY130 ribbon. The ribbon costs six times was the D26CN55 costs. As you move further from the fundamental, the audibiliy of distortion increases. Subharmonic generation is also a matter for concern; it increases the "grunge" factor, below the fundamental.








Which is which, and which do you think would sound cleaner and more faithful to the program material?

Of course, it's really not fair to compare the $199 LCY130 ribbon to a $30 dome. A more appropriate comparison might be to a dome tweeter like the $220 ScanSpeak D3004/66000.



Very extended operating range, very smooth response without a tip-up in the top end, and low distortion. Who says you can't have it all?


Now, it's a free world, and if we want to build colorations into our system, go for it- some of the most popular speakers built in the last 30 years were successes on that basis. Let's be up front about it, too.

[cjd]

The Klipsch stuff is quite respectable.

You have to understand that many people would look at the RS180 and say it's fine crossing at 2.5k 2nd order. Around here folks tend to take a far pickier approach to choosing crossover frequency. And upper mid harshness sensitivity suggests you would be happier with some of our work than with about anything else because we actually pay attention to driver problems and deal with them, rather than leaving them in and maybe using drivers that, when measured at distance and played nicely, seem to inherently deal with those problems (but don't really). You don't really often know just how far down breakup issues are pushed. ANd it's normally not far, but they still don't show up.

If you want ribbons, by all means spend some time, look around, see what's out there. Dollar for dollar, you probably won't find any that really compete with what's out there using domes, particularly when you consider that domes that surpass the ribbons out their in SQ are less than half the cost.

In that room and your stated "driver only" budget the RS TMWW 3-ways [go with a variant using a Seas tweeter and you'll get some of that "airy" sound you like] and go with a tower for your center) would be my recommendation across the front stage. Natalie P's or Modula MT for surround duty.

Give yourself about eight inches between the screen and the FRONT of your speakers. That means you can have speakers no deeper than 12 inches if they're smack on the wall. Which may be just what you're working with, and therefore fine.

Have you seen the SMX screen stuff by the way?

C

[indygreg]

yes i have and i figured to use the smx for a 12' wide CH screen. also, counting the thickness of the screen wall and the fact that the screen is mounted at the front face i actually have 24" from wall to screen. i can noodle that a little if it makes a difference.

i have 3 other questions since you are being so kind to a noob:

- do i need to do something special since it is against the wall? the other option is that i could build a solid wall (the way theaters do) and have the RS RMWW's flush in the surface of it.

- since i don't care how wide or tall they are, should i do a sealed box? it would seem that sound would be in better phase than it would with a port which would be good for dialog but i could be missing something.

- could i do the rsTMWW 3 way active? in pro audio we just set up the drivers, ran a program like EASE and calibrated it but in this world there seem to be a lot of things i don't know about like baffle step calibration etc. maybe i am underestimating the difficulty of setting up the crossover when it is active but i have done it hundreds of time for pro gear and always liked that we could easily noodle changes and hear the results.

greg

[Jim Holtz]

If you want ribbons, by all means spend some time, look around, see what's out there. Dollar for dollar, you probably won't find any that really compete with what's out there using domes, particularly when you consider that domes that surpass the ribbons out their in SQ are less than half the cost.
C

That is a very bold statement Chris. One I don't agree with of course.

Measurements are only one of the tools most experienced designers use. They're essential and give a lot of indicators of what you can expect for accurate reproduction of the source but most certainly not the only one that's relevant.

If you use the measure of as closely as possible recreating the original performance as each person perceives it, ribbons always sound closer to me. I've heard most of the budget and several of the top dollar low distortion "kings" and I still think ribbons offer a more accurate presentation.

It isn't whether I "like" a particular sound, it's about what I hear that sounds accurate to me.

My opinion only. YMMV

Jim

[Dennis H]

Hi Dennis,

This subject has been discussed numerous times in the past on MAD. It's my understanding, it's M-T on both sides for CTC spacing rather than M-M. Also, ribbons emit sound from their full length so the CTC measure starts at the edge of a ribbon vs the center as a dome. One more thing. Many of the current ribbons (short for good dispersion) cross comfortably at 2.5K. Lower is better for MTM's but that is most certainly not unreasonable from my understanding.

Jim

Yes, you can find a variety of opinions on MAD. Mine agrees with this article that what counts is the W-W distance. It's easy to simulate with some of the FRD tools so you can see what's going on.

http://www.birotechnology.com/articles/VSTWLA.html

Edit: also see Jim Griffins paper for woofer C-C recommendations.

[cjd]

That is a very bold statement Chris. One I don't agree with of course.

Probably. While I like the distortion characteristic of a ribbon tweeter as much as the next guy (really, I do - I keep coming back to them for my next big project) they DO have more non-linear distortion low and start out being twice or more the cost of a RS28A or Seas 27TDFC/TBFC. They would be a great match-up with a nice dome mid like the Dayton if the center-center issues of that mid and the available ribbons don't get in the way.

A 2-way with a ribbon is, IMHO, an exercise in compromises beyond what I find reasonable or acceptable without a few hundred bucks per ribbon (i.e. the bigger ribbons). On the other hand, in a 3-way it may cost less than some of the other options when I consider what kind(s) of drivers would need to be used and relative crossover points likely, components for a crossover would likely be less.

This is also an observation on the state of available designs, not on what is possible. So I'm not saying the value can't be found, just that it is less commonly found. Harder to find stuff to fit any given situation. So far the price of entry has kept me away from messing with ribbons. And the price of screwing up. Some day.

Greg, active is a possibility but for home use, that's a significant increase in the electronics you would require (more amps, the electronics for the crossovers, lotsa cabling, etc.). On a more subtle scale, I've always found good passives to have that edge in some ethereal quality scale, where they're just more appealing when it comes to the sound. That could have been many things as I've never heard exact transfer function duplication active vs passive. Same cabinet/drivers but different crossover topology.

You would want a low baffle-step compensation (low-BSC) crossover variant, and I think some nicely sized sealed boxes would be the way to go if you've also got yourself high quality sub(s) crossing in all around. You still should try to keep the baffle dimensions and layout to plan (or close - small variation is ok in baffle dimension) since that changes diffraction as well as step frequencies. If you've got the stuff to measure and noodle, go for it. We won't tell you not to. It may open up options for you, in that you could pick drivers and put together a system that no one else has built before (so you CAN go ribbons and pick out other drivers). Heck, just being able to get accurate measurements in the right format would mean a few of us might be happy to grab 'em and whip up a passive crossover option for you. And with an AT screen in the picture, there are other advantages to getting measurements in-situ to work with.

DO allow at least eight inches screen to speaker face. But if you know about SMX you probably already know exactly why.

Oh yeah. Don't build 'em into the wall. You want to treat the wall, and you want the speakers (at least the faces) out in front of that at least a little. Front wall should be full absorbtion floor to ceiling. Floor to ear-level on the side walls absorb, ear up diffuse. Back wall diffuse usually, sometimes a bit of absorb down low and in the corners.

C

[indygreg]

i'm curious why not to build them into the wall. that is what theaters do to meet the thx spec.

when you say use the seas tweeter version is that a millenium exel or the 27TBFC? the exel seems to have the same high end extension of a ribbon.

greg

[Jim Holtz]

Yes, you can find a variety of opinions on MAD. Mine agrees with this article that what counts is the W-W distance. It's easy to simulate with some of the FRD tools so you can see what's going on.

http://www.birotechnology.com/articles/VSTWLA.html

Edit: also see Jim Griffins paper for woofer C-C recommendations.

Hi Dennis,

That was an interesting read. If I understood it correctly, the major benefit of reduced M-M spacing vs. typical MTM would be increased vertical dispersion thus bringing it closer to a typical 2-way radiation pattern. Is that correct?

It certainly merits consideration. However, putting it in perspecive, there have and are many fine sounding MTM systems using the old fashioned methods of calculating MTM spacing. Closer seems to always be better however and I agree with your philosophy, just in practice other methods seem to work quite well too.

BTW, opinions at MAD. I was referring to John K., Jeff B., Rick Craig, Dennis Murphy, Jim Griffin, Phil Bramberg and others that I hold in very high esteem. ;x(

Thanks again for sharing the link.

Edit: Dennis, I'll also add an edit here. I built my line arrays based on Jim Griffins work and adhere stringently to his guidlines when I build point source speakers. I have the utmost respect for Jim's thoughts. Besides that, he's a heck of a nice guy if you've ever spent any time with him. Very gracious.

Jim

[cjd]

TBFC - the TDFC and TBFC are surprisingly similar to the Millenium in many respects sound-wise, distortion-wise... clearly very near siblings.

You can go in-wall if that suits your fancy. THX spec isn't specifically put together to be the best possible result, but to be a set of consistent compromises that allows them to have a relatively controlled theater environment from place to place. It eliminates any baffle step loss from the equation. If you can build boxes into the wall (i.e. control box volume and keep mids/woofers/etc in separate enclosures) it's particularly reasonable.

If you say, "hey guys, I'm building a theater and will be doing the crossover actively/digitally the way I do commercial sound rigs, these're going to be built into the wall, and I want to use ribbon tweeters - give me some thoughts on what else to use" we'll point you one way.

Without knowing what you know, can do, want to do, we kinda have to feel it out, point out some things that should do well and are known quantities, etc.

If you want to discuss the merits of different approaches, can do that too.

I think one thing you'll find is that most of the folks around here that do design have their preferences, their philosophies, and their reasons for both, and will end up making suggestions that fit with those thoughts, and that they're not necessarily going to be the prevailing attitude among any in the industry.

C

[peterS]

hmmm

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-700

[cjd]

Well, yes... when you set your budget beyond what I've done, ribbons start to get quite interesting. Quite interesting indeed.

[Dennis H]

i'm curious why not to build them into the wall.

Like Chris said, it's nice to do some bass trapping behind the screen. Room modes aren't an issue in a big theater or auditorium but very much an issue in a small room. A foot or two of fluffy fiberglass will absorb pretty low and eliminate most of the longitudinal room modes and help smooth out your bass. So, with unlimited space, you could soffit-mount the speakers and do your room treatments in front of that. But with only a small space behind the screen, it's better to pack it with fiberglass. One thing, with all that bass trapping around the speakers, you may want to go with a 'standard' BSC design because the speaker will act like it's farther from the wall.

[Jim Holtz]

Yes, you can find a variety of opinions on MAD. Mine agrees with this article that what counts is the W-W distance. It's easy to simulate with some of the FRD tools so you can see what's going on.

http://www.birotechnology.com/articles/VSTWLA.html

Edit: also see Jim Griffins paper for woofer C-C recommendations.

Hi Dennis,

This is all your fault! You made me rethink the driver spacing on a project I'm cutting MDF for today. I can make your recommendations work. Thank you for the very interesting discussion and making me think outside the box so to speak. :T

Best regards,

Jim

[JonMarsh]

hmmm
http://www.partsexpress.com/pe/showd...number=264-700

This isn't really a full range mid to tweeter driver, but it is a good midrange driver, in the range of 600 Hz to 5-6 kHz.

This is the implementation we worked out in ThomasW's home system crossed at 600 Hz and 6 kHz. The Panasonic leaf tweeter really won't go any lower, or we'd have gone with about 4 kHz to be below the cavity resonance on the front side radiation.



The black panels are Acoustat 1+1, electrostatic speakers which run from 100 Hz to 600 Hz in this system. It's a nice range from them- no beaming.

I've got a pair of RD50's I keep saying I'm going to build into a system someday, but I keep getting side tracked with other pursuits.

Do a search for RD75 on this forum if you want to see some of the past discussion.

[indygreg]

peter - i have looked at the rd75's before but they seem to be light on high end (not the airy sound i mentioned).

greg

[indygreg]

cjd - i kind of walk the line here between telling and asking since i am learning my way. in another thread i tried to tell what i thought i would do and thomas indicated that "it would take writing a book to explain all the problems the proposed modifications would create". i decided i would read and fish a little before i dumped a potentially hair brained proposal out there.

My Background - i am a woodworker and have a shop with a x10 table saw, etc. and since these are all hidden it would take me no time to put together some boxes. i have driven a soldering iron doing pro audio so i can assemble a crossover (but it does not sound like fun). i have calculated box sizes and ports for pro audio using a unibox. i have a friend with all the measurement equipment including EASE and more experience than i have setting up electronic crossovers although i have done it for pro gear many times.

what i want to do surrounds - i want to do inwalls for surround and put an array of them like theater does rather than try to simulate that effect with a dipole. since my theater has 3 rows i feel that this would work better and i don't like the look of fabric wrapped columns. based on some suggestions in another thread i propose that i will build 12 modula MTM's (4 in back and 4 on each side) into boxes that are 5.5" deep (i have 3.5" of wall plus 1" of drywall plus 1.5" of acoustic treatment behind my GOM fabric) and set them in the wall. i propose to drive them with 4 channels each of 2 7 channel amps and use a behringer electronic crossover. this avoids building 12 crossovers and lets me tweek a bit. maybe i should use the seas tweeter here.

what i want to do for LCR - i was thinking klipsch but when i heard them i was not blown away. if i am building boxes anyway and i have 6 amplifier channels left over (plus 5 more in a carver amp if i need them) i am not thinking that i might just make a run at doing the fronts also rather than buying the klipsch. from a few past experiences i have an image that ribbons have a really unique, airy sound but you know how this stuff is - you can get it in your head that a speaker sounds a certain way before you even hear it. i guess i did that with the raven to be honest. so many have raved over it that i was kind of heading that way. when i hear that ribbons have more controlled vertical dispersion i decided this was meant to be

i appreciate peoples thoughts on these things even though i know everyone has different taste. i think a reasonable first step for me might be to order components to make 2 modula mtm's (maybe with seas tweets?) and build two cabinets (a wall mounted surround and a full sized behind the screen box) and do some listening. then i will be better prepared to have discussions like this.

greg

[Habs4life]

Edit: also see Jim Griffins paper for woofer C-C recommendations.

Were might I find this paper?
Thanks

[Dennis H]

Were might I find this paper?
Thanks

Jim Griffin's line array paper:

https://web.archive.org/web/20070221101021/http://www.audiodiycentral.com/resource/pdf/nflawp.pdf

[Lindahl]

Give yourself about eight inches between the screen and the FRONT of your speakers.

FYI, that guideline is for microperfs like Stewart's. Woven screens, like Dazian CCC, SMX and SR ClearPix2, have very minimal difference (see: inaudible) in measured response anywhere from 1"-18" distance between screen and driver.

[Dennis H]

FYI, that guideline is for microperfs like Stewart's. Woven screens, like SMX and SR ClearPix2, have virtually no difference in measured response anywhere from 1"-18" distance between screen and driver. To add to that, the audible difference just isn't there.

Yeah, I think Lindahl is correct. I can't find them now on Screen Research's page but I remember graphs showing what Lindahl says. The performance is a bit better (less combing) if you move the tweeter back but it's not a big deal compared to a perf screen.

[Habs4life]

Jim Griffin's line array paper:

http://www.audiodiycentral.com/resource/pdf/nflawp.pdf

Dennis,Thanks for the link ,thats a good read.

[cjd]

FYI, that guideline is for microperfs like Stewart's. Woven screens, like Dazian CCC, SMX and SR ClearPix2, have very minimal difference (see: inaudible) in measured response anywhere from 1"-18" distance between screen and driver.

Sorry, but that's simply not true. You can see it clearly in their measurements.

I think you're misunderstanding the difference in these screens - Stewarts need significant EQ to fix things no matter what. Significant drop in SPL in the top octave or two. The SMX, etc. don't but you DO get bad comb filtering if you place the speakers too close to the screen.

I'll try to respond with more thoughts when I'm not about to fall asleep.

C

[Lindahl]

Sorry, but that's simply not true. You can see it clearly in their measurements.

You're a bit confused here and wrong on some accounts, although slightly. Let me correct.

First of all, no matter what you put in front of the screen, no matter the distance, grill cloth, anything, will cause comb filtering and high-end roll-off. The good part about this, is that the human ear (or brain, not sure which) will filter out dense comb filtering, providing the peaking is moderate. The filtering is roughly equivalent to 1/3rd octave smoothing.

Woven screens tend to have tightly packed comb filtering with limited peaking, making it pretty much inaudible - roughly equivalent to +/- 0.5db combing, stretched pretty wide after human filtering. The comb filtering will change, as the distance between the screen and the driver changes. However, the changes are so minimal, it really doesn't get any worse or better, just different. The woven screens also will roll off the highs, about -1.5 db at 20khz in an exponential curve starting around 4khz, hitting -.5 db around 16khz.

Microperf screens have both problems, as well, but to a much greater degree. This is because the woven screens openness has a much greater density. I haven't looked at measurements of microperf screens in a while, but I believe they're around 6 db down at 20khz, starting at around 4khz, as well. The comb filtering is less dense and more peaky, and therefore audible. Shifts in distance will change the comb filtering, just like woven screens. However, the changes in distance will change the comb filtering much more dramatically due to the significant comb filtering already present.

That said, both screens harm audio quality. And both screens DO change frequency response based on distance between the drivers and the screen (I never claimed otherwise). However, since the effects of woven screens are minimal the measurement differences when changing distance of driver to screen are more-so minimal, and most definitely not audible.

As for references, I've seen the graphs generated by a well-respected acoustician in a room designed for such measurements (anechoic chamber). However, the link has succumbed to link rot.

[TacoD]

The LCY 130 was interesting to me; it's curious that it seems to have a bit of a waveguide built in. With the recess of the ribbon, there does appear to be some cavity resonance as shown in John Krutke's plots. Note the higher levels of high order harmonics compared to the other designs he tested.

Considering the Q of the Fs at 1 kHz, I'd use a crossover that's well down in level by that point- no lower than 2.5 kHz.

Now, it's a free world, and if we want to build colorations into our system, go for it- some of the most popular speakers built in the last 30 years were successes on that basis. Let's be up front about it, too.

The LCY is a true distortion generator, the German magazine HobbyHifi measured the distortion and it was very high. I forgot the details, but the performance was so bad that I would not recommend the tweeter. If you want to use a low distortion tweeter you can look at the Mundorf AMT (the lowest distortion measured by HobbyHifi). It's one of the best tweeters I have heard.

[cotdt]

The LCY has less than 1% distortion in a range that the ears are not sensitive toward. I wouldn't call that high distortion. It's higher than the domes, but having heard the LCY's myself, I question the meaningfulness of the distortion tests. Subjectively it sounds wonderful and has amazing dispersion. one might say that it sounds good because of its higher distortion, but i know how real instruments sound like and when i hear the cymbals from a ribbon that don't sound quite right from even the best domes, then that's a cymbal not a distortion!

[Piotr]

About vertical dispersion in mtm's..

Why would you want to keep a tight center to center distance and a low cross?

In a MT design you want that to keep a smooth dispersion. A MTM will have reduced output from the mids aproaching 20-30degrees or thereabout. If you choose a ribbon and cross it low, the dispersion will suddenly take a jump up again and after a while the dispersion will get narrow again due to the height of the ribbon (edit)..


Look at Dynaudio's top designs how they use a solution to extend the "controled" vertical dispersion from the mids up to the tweet's. They use two dome tweeters in the low tweeter range to REDUCE vertical dispersion and only the upper range is coming from a single tweeter.

What you want to do is match the dispersion i the 1.5k - 5k range or so to the limited vertical dispersion that you have in the midrange and the upper range from the ribbon.

Well, that's what I would do if I would design such speaker.

And yes, ribbons usually have higher distortion than the good domes and limited vertical dispersion is a fact in the upper range.

edit: a typo, was dome now is ribbon! ops:

/Peter

[Paul H]

About vertical dispersion in mtm's..

Why would you want to keep a tight center to center distance and a low cross?

...

One reason would be to keep the driver spacing below the distances at which the location of individual drivers are discernible by the listener.

Just another trade-off in a long list ..

[Piotr]

Paul,

I don't think a large radiating surface maeks it easier to locate the sound source. You don't locate the sound as coming from the speaker in a decent design. Also we allready talk about separated drivers playing the same range. A couple of inches won't make a difference in that regard. Power response on the other hand are pretty important. You don't want (I don't want at least ) sudden changes in the dispersion in the midrange of a speaker. That's common sence in speaker design but are often overlooked when it comes to the driver interaction in MTM's... at least at an amateur level.

/Peter

[Jed]

The LCY is a true distortion generator, the German magazine HobbyHifi measured the distortion and it was very high. I forgot the details, but the performance was so bad that I would not recommend the tweeter. If you want to use a low distortion tweeter you can look at the Mundorf AMT (the lowest distortion measured by HobbyHifi). It's one of the best tweeters I have heard.

Taco,

How does Mundorf compare to ER4? On paper, the ER4 has a flatter FR, and pretty close in low distortion. I'm using ER4 right now in a 3-way, and it does some magical things. I still need to play with it more to experiment with different absorption of the rear wave. Right now, I have it set up in a small enclosure stuffed with thick foam, probably not small enough to get the region of 2-4K flat with the rest of the response. Suggestions?
Jed

[cjd]

http://www.bobgolds.com/SmX720/20060708/home.htm

Amazing how different people can look at the same data and get different results. I maintain that eight inches is probably ideal, 4 inches would work. I wouldn't go closer than 4 inches between screen and speaker face. Am I splitting hairs? Probably. I tend to get carried away with that some days. But I don't disagree with the specific facts being stated, just with the drawn conclusions.

I wanted to comment on the difficulties using multiple surround speakers is going to pose as well - namely that getting the level set well at all seats. You can do it I think but will need to have output level control at each speaker. I think you will.

You won't achieve the same results with the Modula and the behringer crossover as with the passive, though you'll definitely get something that works. If you're going that route, by all means go for it all around. You can then say "I want to go with ribbons, help me pick a good driver complement" and we'll dive in.

You're going to have a LOT of hardware, and you're going to have some looong wire runs to your speakers after your crossovers. You'll need to make sure the impedance they impart are included in any box design decisions. The depth you have to work with will *just* get by if you manage internal back-wall reflections well.

One last comment - I'm not sure, but sometimes I wonder if ribbons sound airy simply because they lack breakup issues up top. This one is purely conjecture on my part at this point.

C

[Dennis H]

Why would you want to keep a tight center to center distance and a low cross?

Because if you don't, you get a vertical polar response that looks like this.

[Piotr]

Because if you don't, you get a vertical polar response that looks like this.

Yea, and what do you think the vertical polar response look like in a typical separated pair of mids in the MTM layout?And what do you think the vertical polar repsonse look like in a typical ribbon tweeter?

Read and digest my earlier posts in this thread..



/Peter

[Lindahl]

Amazing how different people can look at the same data and get different results. But I don't disagree with the specific facts being stated, just with the drawn conclusions.

Fair enough. Let me just get this straight, though... you're saying that you believe the differences between tests 5-11 should be audible? I would have let this go, but, to me, that's so unbelievable that I want to make sure I understood you correctly. Keep in mind, too, that those tests are only applicable to someone who puts absorptive material on the baffle of the speaker which has its own problems, as the tester recognized (completely threw off everything below the high mids). The tests I had seen were a little different in that regard.

[Piotr]

cjd

I've seen measurements of ribbons showing strange things going on in the upper range. Energy storage and distortion may be the explanation for the airyness that some people like about ribbons. The better domes typically performs better than ribbons in this regard.

Also the metal foil in ribbons go thru structural changes, I think I've seen reports of decreased performance after some playing time... or was it the other way around :roll:

/Peter