Upscale MTM?

[zieglj01]

What about the XTZ Divine 100.33 speakers ? This speaker has been reviewed on this site and others, most recently on Home Theater Shack.....

Here is your link - expensive, however they do look nice and some heavy cabinets.
http://www.hometheatershack.com/forums/speaker-subwoofer-reviews/120970-xtz-sound-divine-100-33-speaker-review.html

 

[TheWarrior]

Here is your link - expensive, however they do look nice and some heavy cabinets.
http://www.hometheatershack.com/forums/speaker-subwoofer-reviews/120970-xtz-sound-divine-100-33-speaker-review.html

Those XTZ's have always looked good to me, more than aesthetics, I like their design. And I am happy to see more reviews on those Accuton Ceramics. In seeking out DIY options, their drivers often seem to have much flexibility and incredibly high efficiency. I just always feared them sounding harsh on top of their high price point.

Thanks for sharing!

 

[KEW]

I am conflicted!

Last week, at TheWarrior's house, I listened to his RBH WM-30 wall mounted speakers against RBH 61LSE or Paradigm Signature S-2's. As you would expect, the 61LSE and S-2's beat the WM-30's in many respects, but the spatial component of the WM-30 was pretty impressive!

http://www.audioholics.com/tower-speaker-reviews/rbh-sound-wm-24-wm-30-fm-45-m-series-loudspeaker-system-review/wm-24-wm-30-fm-45-m-first-impressions-and-setup.html

It was near the end of my visit when we tried this, and I did not get adequate time to listen to different types of music, but for Tori Amos it had a great appeal.

Trying to figure out what the WM-30 might have over the 61LSE and the S-2's, the MTM configuration is the most obvious candidate.

I think the difference I heard would appeal to the vast majority of people. If it is truly an artifact of the MTM configuration, it begs the question of why designers like Jim Salk, Dave Fabricant (sp?) of Ascend, and Dennis Murphy; who are all very familiar with MTM designs would opt for non-MTM designs for their premium products.

What experiences have you had with MTM vs non-MTM?

I'm hoping for any discussion of what might have caused the dramatic effect I heard or what type of musical content would cause that effect to be a liability (if that is the case).
When I ask the question that way, I am thinking of my Mirage Omnidirectional OM-5 speakers . For orchestral strings (which project sound radially) they offer a brilliant soundstage; however, if you are listening to a trumpet solo (which is directional), the imaging suffers greatly.

 

[TheWarrior]

I am conflicted!

Last week, at TheWarrior's house, I listened to his RBH WM-30 wall mounted speakers against RBH 61LSE or Paradigm Signature S-2's. As you would expect, the 61LSE and S-2's beat the WM-30's in many respects, but the spatial component of the WM-30 was pretty impressive!

Trying to figure out what the WM-30 might have over the 61LSE and the S-2's, the MTM configuration is the most obvious candidate.

The spatial component is easy, the extra driver in an MTM accounts for that. And even the sealed nature of the WM-30's is augmented by the use of passive radiators. Making it a 'virtual' MMTMM. But especially with my high ceilings, the better vertical axis response of MTM's is what sealed the deal for you.

We'll have to do another review...

 

[KEW]

The spatial component is easy, the extra driver in an MTM accounts for that. And even the sealed nature of the WM-30's is augmented by the use of passive radiators. Making it a 'virtual' MMTMM. But especially with my high ceilings, the better vertical axis response of MTM's is what sealed the deal for you.

We'll have to do another review...

The deal is not sealed yet! I'm not that easy!!!

 

[Dennis Murphy]

The spatial component is easy, the extra driver in an MTM accounts for that. And even the sealed nature of the WM-30's is augmented by the use of passive radiators. Making it a 'virtual' MMTMM. But especially with my high ceilings, the better vertical axis response of MTM's is what sealed the deal for you.

We'll have to do another review...

I'm not really following this. Why does adding a second midwoofer increase spatial information when the two midwoofers focus their output midway between their centers? And in what sense is the vertical axis response of an MTM "better"? The main difference in the vertical response is that an MTM will have a huge suckout in the vertical plane around 1500 Hz. An MT will just have a suckout at the crossover frequency. Less vertical dispersion might be a plus with low ceilings, but I'm not seeing the advantage with high ceilings. And the alleged advantage of an MTM's vertical dispersion pattern is very controversial. I have nothing against MTM's--the most popular crossover design I've done was for an MTM (the Salk Song Tower). But I don't think they have any inherent advantage over an MT or an MMT or a WMT.

 

[TheWarrior]

I'm not really following this. Why does adding a second midwoofer increase spatial information when the two midwoofers focus their output midway between their centers? And in what sense is the vertical axis response of an MTM "better"? The main difference in the vertical response is that an MTM will have a huge suckout in the vertical plane around 1500 Hz. An MT will just have a suckout at the crossover frequency. Less vertical dispersion might be a plus with low ceilings, but I'm not seeing the advantage with high ceilings. And the alleged advantage of an MTM's vertical dispersion pattern is very controversial. I have nothing against MTM's--the most popular crossover design I've done was for an MTM (the Salk Song Tower). But I don't think they have any inherent advantage over an MT or an MMT or a WMT.

Thank you, Dennis!

Adding a woofer to make an MT, a MTM, increases the perceived 'spatial' information as a result of the extra radiating cone surface. I think we agree on that?

As for the vertical dispersion, please help me explain this better: Because of the dual woofers in an MTM, and their vertical arrangement, the perceived benefit is a 'taller' sound stage, that when combined with a good tweeter and crossover frequency that is low enough to avoid 'beaming' yet provide wide dispersion, creates a speaker with an enormous sound stage that is audibly superior to an MT design.

Granted everyones preference, and ears, are different. But that is what both Kurt and I heard. Was this a better explanation of that fact? I need constructive criticism of my choice of verbage to describe this situation.

 

[Dennis Murphy]

Thank you, Dennis!

Adding a woofer to make an MT, a MTM, increases the perceived 'spatial' information as a result of the extra radiating cone surface. I think we agree on that?

As for the vertical dispersion, please help me explain this better: Because of the dual woofers in an MTM, and their vertical arrangement, the perceived benefit is a 'taller' sound stage, that when combined with a good tweeter and crossover frequency that is low enough to avoid 'beaming' yet provide wide dispersion, creates a speaker with an enormous sound stage that is audibly superior to an MT design.

Granted everyones preference, and ears, are different. But that is what both Kurt and I heard. Was this a better explanation of that fact? I need constructive criticism of my choice of verbage to describe this situation.

I'm not convinced that the larger radiating surface will do much for spatial information=--it just produces more sound. Suppose you place two speakers in a normal stereo position Left and Right, and a single speaker in the middle, and adjust the gain so that the center speaker can be played as loudly as the two L and R speakers when switching back and forth. Then suppose we feed the speakers a mono signal. The L and R speakers will image in the center (if they're hooked up in phase), so that the apparent sound source is the same as the single speaker in the middle. Now switch back and forth between the two setups. I've actually done this, and I had a very hard time telling which setup was which. It's an interesting issue, however. My guess is that you and Kurt were hearing something not related to the size of the radiating surface per se. But you've got my curiosity piqued. The next time I have two of my Affordable Accuracy MTM center channels running, and two of my MT monitors, I'll switch back and forth in stereo mode. They have the same drivers and are voiced the same, so it's as good a test as I can think of.

 

[TheWarrior]

But you've got my curiosity piqued. The next time I have two of my Affordable Accuracy MTM center channels running, and two of my MT monitors, I'll switch back and forth in stereo mode. They have the same drivers and are voiced the same, so it's as good a test as I can think of.

Oh great, I stumped Dennis Murphy! Lol. Not really, but yes, 'more sound' we all agree on. I might also add that I spent a great deal of time positioning the WM-30's, where as our bookshelves are given 12" off the wall, and arranged for ease of rotation, not optimal listening. So I would think that could account for some of the difference.

Is there a more precise adjective for 'more sound?' That much is obvious given the extra driver, the spatial aspect is debatable of course.

And then I need to find a good driving day to go hear Kurt's Philharmonics!

 

[monkish54]

Speaking of crossovers, Dennis, how would you describe your approach?

I obviously own your Phils, and I have heard the SS8, Veracity ST, and the Salk Silk at CAS in 2013. While they have their differences (mostly in the bass), the overall tonality is quite similar. 4 speakers with very different drivers, and you seem to bring out the best in all of them. What's your secret Dennis?

 

[Dennis Murphy]

"What's your secret?"


I follow da rules.

 

[monkish54]

"What's your secret?"


I follow da rules.

You do not talk about fight club?

 

[zieglj01]

You do not talk about fight club?

You see, you finally got him to open up and speak.

 

[TheWarrior]

"What's your secret?"

I follow da rules.

This gives me hope. More studying and reading could turn me into an effective DIY builder. Oh, and building...

 

[Swerd]

This gives me hope. More studying and reading could turn me into an effective DIY builder. Oh, and building...

The single best thing I learned in DIY speaker building is:

Build a Dennis Murphy design. Do not fool yourself into thinking you can design something better .

 

[KEW]

The single best thing I learned in DIY speaker building is:

Build a Dennis Murphy design. Do not fool yourself into thinking you can design something better .

Dennis is undoubtedly excellent at what he does, but I don't think anyone (including Murphy) wants DIY innovation to end with him. We want the person who will design something better in the game!

 

[slipperybidness]

Dennis is undoubtedly excellent at what he does, but I don't think anyone (including Murphy) wants DIY innovation to end with him. We want the person who can design something better in the game!

That's one of the things I've always appreciated about DM. He has countless commercial speakers to his name, and countless DIY designs to! I like that he gives back to the audio community and doesn't just chase the $.

 

[KEW]

I am conflicted!
... the spatial component of the WM-30 was pretty impressive!

It was near the end of my visit when we tried this, and I did not get adequate time to listen to different types of music, but for Tori Amos it had a great appeal.

Yesterday, thanks to Alex's (TheWarrior) hospitality, I had the chance to revisit this. I brought an audition CD with a variety of familiar music.

We had noticed this enhanced spatial component as compared to all of the bookshelf speakers, so I reconfigured to compare the RBH (MTM wall mount) WM-30 to the RBH-61LSE bookshelf. My thinking was:
1) both being RBH products they may have more of their sound character in common so I could focus better on the spatial component.
2) The sound character of the Be tweeter of the Paradigm S-2 often called attention away from the spatial component. In retrospect, I'm not sure the LSE's were better - their bass runs deeper than the S-2's and I think I just robbed Peter to pay Paul (Peter being treble and Paul being bass).
3) If the spatial component was as strong and good as I remembered, the WM-30's would be a giant-killer of a sort whether against the LSE or the S-2's. The added accuracy of the LSE and S-2 is clear, but the spatial component gives a major "wow" factor.

The "spatial" sound experience. Ethereal and immersive - a bit like headphones. It has a very nice affect, giving a close intimacy to the music. As I listened to music I was familiar with, I realized the imaging I was used to was largely missing. In other words, instead of hearing a voice coming from a specific location, it was as if it radiated from all around. Intellectually, that makes me suspect it as an inaccuracy, but as a human enjoying music, it is very nice!

Listening session:
Yes - "Heart of the Sunrise" has been on my audition CD from the start. This song goes from fast driving rock to very open bass/piano/vocal, providing nice diversity. For the most part, it favored the WM-30, but there were rare occasions where the LSE took over the spatial effect. I am not saying the spatial effect disappeared, I am saying it flip-flopped so the LSE had it and the WM-30 sounded comparatively flat. Isolating and trying to identify the common element of these occasions proved difficult.
At the end of this song, there is a segue into a clip of "We Have Heaven". This segment lasts maybe 90 seconds and is all vocal (male, though Jon Anderson's voice overlaps many females). The LSE exclusively kept the spatial effect for this passage.

Lyle Lovette - "Here I Am" is a good audition song because it has Lyle's rich and nuanced voice paired with Francine Reed's rich and nuanced voice, covering a wider range. Instrumentation is not too busy, so you can keep track of the nuances of both of their voices at all times. The LSE's dominated the spatial element for this number.

Norah Jones - "Don't know why" this content split the speakers. There were places where the LSE's, but there were places where the WM-30's took over. It seems like whenever she had deeper resonance, the LSE's took the prize and when she sang higher or with a thinner voice, the WM-30's took over. Don't know why!

I am citing those instances where the LSE's took over, but the WM-30 actually captured the spatial effect for the majority of the time. Instrumental passages, Rikki Lee Jones, and Tori Amos favored WM-30's spatial presence at least 90% of the time.

Ed Palermo - "RNDZL" is a big band cover of Zappa's RNDZL. I use this because it is a big band and I play in a big band, so I am very familiar with the sounds. It includes Alto Sax and Trombone solos. What really stood out in this song was listening to the A. Sax solo. The WM-30's offered their spatial magic and I could experience it, however, the tonal balance (harmonics) of the sax was off. It was thinner and less resonant than it should be. For me the balance of the sax over-rode the spatial improvement. I doubt that would be the case for someone who did not listen often to the sax. It did sound like an Alto Sax, and an Alto Sax can certainly be played to sound that way, but not by a pro "playing large" - a strong solo in front of a big band.
I don't know if the tonal balance relates to the spatial presence, but because of the way the LSE took over at lower midrange, I might guess something about the upper mid, low treble of the WM-30 creates this effect. Could a reduction in low-mid and increase in mid-high cause this?

Note: bottom end of Alto Sax is ~120Hz

If anyone has ideas on this I would love to hear them. I believe it is probably an "enhancement" of the actual recording, but it is undeniably pleasant. If this effect is available in a reference class speaker with out the loss in accuracy and tonal balance, I want one. "Mama don't take my Kodachrome away!"

 

[TLS Guy]

I'm not convinced that the larger radiating surface will do much for spatial information=--it just produces more sound. Suppose you place two speakers in a normal stereo position Left and Right, and a single speaker in the middle, and adjust the gain so that the center speaker can be played as loudly as the two L and R speakers when switching back and forth. Then suppose we feed the speakers a mono signal. The L and R speakers will image in the center (if they're hooked up in phase), so that the apparent sound source is the same as the single speaker in the middle. Now switch back and forth between the two setups. I've actually done this, and I had a very hard time telling which setup was which. It's an interesting issue, however. My guess is that you and Kurt were hearing something not related to the size of the radiating surface per se. But you've got my curiosity piqued. The next time I have two of my Affordable Accuracy MTM center channels running, and two of my MT monitors, I'll switch back and forth in stereo mode. They have the same drivers and are voiced the same, so it's as good a test as I can think of.

Dennis, I've been thinking about this.

In my time I have designed two MTM, and I have to say I really like them. They are little different to TM speakers. The sound stage is very solid and deep and imaging is precise. I think they are closer to full rangers and coax designs. Not that the TM is bad it isn't.

Joe D'Appolito published is paper on MTM in October 1983. He presented in New York October 9 1983.

I have to say this is a paper that caught my eye.

Joe's main aim was to bring some order, into the lobing problem and not have to use even order crossovers which in TM have a better lobing pattern than odd order crossovers.

He was trying to come as close as possible to a coaxial or full ranger and get a symmetrical lobing pattern, as well as to try and create a pin point source.

The downside was limiting the choice of crossover point. With the usual size of drivers, it works best with the crossover in the 2.5 to 2.8 KHz range. The axis of the crossover should be a little down for the upper driver/tweeter and a little up for the lower/tweeter.

This does result in symmetrical lobing.

In all of this one has to consider the lobing error and dopler distortion of reflections from the tweeter response from the mid/woofer cones.

In coaxial speakers, this distortion of the tweeter reflections was investigated by Paul Klipsch. Of course it is measurable as the woofer cones is moving and the tweeter is not.

This of course occurs in all speakers as higher frequencies are radiated from a moving cone.

However in a TM, these reflections are below the tweeter. In a an MTM this reflection pattern is also symmetrical.

The upshot of it is I believe a more stable sound stage. This effect is exists across solo instrumental recordings and large forces. To me this arrangement does sound much more like my good full rangers and good coaxial designs.

The we get a big advantage of increased power handling and very much reduced thermal compression.

If we have one 8 ohm driver with and then add another is parallel then the amps voltage will remain constant and power output from the amp will be doubled, then since the drivers are in close proximity total increased output will be 6db, so the amp power from the amp can be reduced 6db. This results in a significant reduction in VC heating and a useful reduction in thermal compression.

Now I know a 2.5 way has a driver to offload the BSC, but the top driver is on its own from the step to crossover. There is a lot of power all the way out to 2.5 KHz.

This undoubtedly increases the effortlessness of MTM designs in my view.

After digesting what Joe had to say I designed this speaker.

It won the audiophile sound off that year. My two sons both have a pair and I get to hear them often. One pair is in a small space and the other a large space. The latter pair fill the space effortlessly from an old Sony receiver.

With my reference set I really enjoy the sound stage and in good recordings, height information seems to be reproduced. I think human speech is more coherent and realistic. They blend very well with my coaxial center.

Would I design MT again, certainly. However, if I were designing another all out reference speaker, then I think I would have to have a good reason not to make it MTM.

In closing, I would say, that there are designers around that think MTM is just the driver layout. It is not. You have to take everything on board that Joe had to say in his paper, and design according to his well researched precepts. I have a feeling that this frequently does not occur.

 

[Dennis Murphy]

You raise a very good point. An MTM is not an MTM is not an MTM. Very few, if any, current MTM's conform to the design parameters that Joe specified in his 1983 paper. My takes on the MTM configuration certainly don't meet the 1983 specs. What I find interesting is that Joe himself abandoned that design. For example, his Thor TL MTM used a 4th order acoustic slope. So I'm not sure where that leaves us in the current discussion. As promised, I did compare a couple of my monitor designs with an MTM that used the same drivers as one of the MT's, using a volume-compensated A-B switching preamp. The two speakers with the same drivers sounded almost identical. The only real difference was a slightly heavier bass on the MTM due to a cabinet that wasn't twice as large as the MT--the cabinet tuning was a little higher and a bit humped up. The other MT, which used more expensive drivers, including a ribbon tweeter and a larger woofer, sounded more spacious and cleaner over all. So I remain unconvinced that simply mounting drivers in an MTM configuration and optimizing a crossover for flat response will yield any particular sonic benefits other than increased sensitivity and lower harmonic distortion in the bass.