DIY mains, MTM vs. MMT

[Eric S]

Hi Folks,

I've become intreagued by some the DIY projects for mains I have been seeing around lately. Specifically, projects involving the Raven R2 look very interesting, like this one.

I'm kind of new to some of the design concepts however. So my question is, what is the practical difference between an MTM and an MMT design? I know is has something to do with the dispersion pattern of the tweeter, but I'm not sure on the specifics. I'm looking for a (relatively cost in-sensitive) system with excellent imaging and soundstaging.

Thanks!

[ThomasW]

Hi, And welcome.

The benefits of the MTM design are as follows.

1) when drivers are "stacked" in a vertical array, this creates a wide horizontal sound field.

2) if in a MTM design the woofers are placed close enough together, they couple acoustically and function as one larger driver. So this will create a speaker that radiates into the room the same pattern as a single woofer with a tweeter mounted in it's center.

MTM, aka. "D'Appolito" design, when done properly with correct cabinet design, speaker spacing, and appropriate crossovers, creates a "quasi-spherical" vertical response pattern.

The geometry for this to work properly requires the distance between the "centers" of the adjacent drivers, be kept close to one wavelength of the crossover's frequency.

The e-speakers design is the classic D'Appolito, and uses drivers of the highest quality.

The only drawback a design is using the Raven in a 2-way requires a very steep crossover slopes. This is necessary to "shutdown" the ribbon very quickly so it doesn't receive any low midrange information. If it does the ribbon melts.

The TMM design also benefits from the woofers "coupling". But the tweeter placement is somewhat more forgiving of XO design and requires less baffle design consideration. So, you get B&W type enclosures with the tweeter free-standing, as the best design compromise.




theAudioWorx
Klone-Audio

[Eric S]

Thomas, Thanks for the quick reply and the welcome! I haven't heard the new B&W series (MMT) to be familiar with them.

I have a set of speakers that has the D'Appolito design (AT351s). When I first got them, I noticed a sharp difference between them (my first purchased pair of speakers) and my earlier POS speakers built with Radio Shack $10 drivers in some randomly designed MDF cabinet. To me, the treble sounded much more restricted (vertically) with MTM design... But then, the older speakers were really junk, and quite harsh, so its possible I was adjusting to more refined treble.

I guess what I am really asking is which design MTM or MMT will give me better soundstaging and imaging? Or are these goals mutually exclusive?

Also, why is a steep roll-off for the R2's a drawback? I understand it is necessary to protect the driver, but why is that a bad thing? Does it affect the blending of the drivers?

[ThomasW]

I guess what I am really asking is which design MTM or MMT will give me better soundstaging and imaging? Or are these goals mutually exclusive?

This is totally subjective. Neither is "best", it's just what you prefer. I prefer MTM.

The rated low frequency use for the Raven 2 is 1.8Khz. Now I tend to be conservative in my use of tweeters, so I use crossover points one octave above the lowest rated frequency of the driver. This would mean 3.6Khz as the XO point

The XO point for the kit is 2Khz. This is cutting it pretty close. Not that it won't work, but if you clip your amp, wave goodbye to the ribbon. Replacement elements are $50ea, I think.

The XO is using second order on the woofers, meaning 12db/octave, and 3rd order on the tweeter, meaning 18db/octave. So they are running the woofers up higher, to compensate for the sharp roll-off on the tweeter. I haven't used these specific woofers. But woofers in general tend to start "beaming" in the high frequencies. These are rated to 4Khz, but I haven't seen any axial plots as to the dispersion at high frequencies. I couldn't find any response plots of the system, so it's hard to tell if there is a significant "hole" between the ribbon and woofers.

My guess is that these speakers sound terrific, but aren't really designed to be flogged, for something like HT use.




theAudioWorx
Klone-Audio

[AndrewM]

I'll add a little to what Thomas said (as he covered everything), I think the choice between going with the MTM or MMT design is going to be a coin toss. You may want to pick the version that puts the Raven closest to ear level, as the Raven is limited in it's vertical dispersion, but probably not enough to make a difference between the MTM or MMT, but every little bit helps.

I was also looking at this kit for a future project, but I've decided to go with something a little more full range. I'm thinking of going with the other 6W focal woofer (extends up to 6khz, 6Ohm..etc) in an MMT or MTM sealed cabinet of maybe a little under a cu/ft with a Raven 1, then sit that on top of a Focal 13W woofer cabinet. I'm thinking of x-over points around 300-400Hz and 3000Hz, or somewhere around there. Of course this could all change between now and when I decided to start this project (like going with a Manger and woofer).

Andrew

[Eric S]

Thomas & Andrew: thanks for your input. After reading your post Thomas, I realized that I was thinking about using these speakers as a stereo pair, and not for HT... Funny things happen when you leave parts of what you want to say inside your head!

I'm pretty happy with the speakers I have now. I was just curious to see how a set that costs more for just the drivers alone would sound. I suspect there will be quite a difference, and just wondering if anyone else has any experience with this or similar kits.

Thanks for your input!

[ThomasW]

Eric

Although I haven't personally used the Ravens, I have corresponded with several people that have, all were pleased with the product.

Something else to consider is that the cabasse' drivers in my opinion are overpriced. I make this statement about much in audio.

There is a diminishing point of return on invesment with regard to drivers. Unless you have absolute state of the art electronics driving then, I doubt that you'd hear much difference between Cabasse', and the best Eton or Scan Speak drivers




theAudioWorx
Klone-Audio

[Eric S]

Thomas,

For Mid/Woofs I've been looking at units from Focal, Scan-Speak, Morel, and Seas. They seem to be somewhat reasonably priced, meaning I can put together a pair for $1000-$1500 plus cabinets. I've been looking to venture into something a little more "high end" than my current speaker set. (It an Atlantic Technology System 350 with a DIY Mass12 Sub which I am very happy with). Its just that every so often, the "Must Build Something" urge hits which seizes control and makes me buy electronic parts and copious amounts of raw lumber...

Having just finshed my Mass subwoofer and feeling pretty proud of the results, I thought a set of mains would be fun to exlore. Where appropriate, I do appreciate warnings about products that seem to be too high on the "price" to "value" ratio. Isn't this the spirit of DIY?!?

[ThomasW]

Eric

Believe me I understand the "need to build" concept.

I see the Cabasse'/Raven system as kind of a "niche" system. Something for people with Rolls-Royce wallets, that have $$$$$$$$ electronics and want the ultimate chamber music speaker.

Now I don't think this type of spending is wrong, but it's not for the average listener.

There are lot's of great kits out there if you don't want to build from scratch.

My thoughts on midwoofer cone materials are:
1)poly, nonlinear,(nonpistonic) old technology
2)kevlar, very linear, very transparent
3)carbon fiber, very linear, quite transparent
4)metal, wierd breakup modes/resonances, needs special XO's to compensate for the cones problems.
5)ceramic, great but too expensive.

Tweeters, your personal choice of soft "silk" dome, or metal. Neither is best.

There are "ribbon/planar/leaf" technologies available other than the Ravens. Here's a link to consider
http://www.newformresearch.com./fact...ct-prices.html




theAudioWorx
Klone-Audio

[AndrewM]

Well, I'm just finishing a set of the Adire audio kit 281's (hope to be able to listen to them this weekend), the cabinets have consumed about 100hrs of time (hate being a perfectionist). But while I'm building them, I'm also thinking in my head about my next project (sanding and polishing is mindless work). Anyways, I have a lot of the same goals as you do Eric, and my budget was set around the same range (I've since upped it a bit), so I can pass on some information from what I've found in the past few months of researching everything. First you are going to need to define what you want out of the system, are you going to want a nice soft/warm sound, or do you like a more analytical very detailed sound? Are your components (reciever, CDPlayer, cables..etc) up to having a very good set of speakers? Do you want to go full range, or to where your bass management takes over?

My design goals right now are for a full range speaker system (full range down to around 30Hz will do). Personally I prefer the very detailed/analytical type sound (the Ravens fall into this area), I love the sound of metal dome tweeters as long as they are of highest quality, reminds me of funny time when the sales guy was showing off his latest speaker system...this came a day after listening to a set of JM Labs Utopia's (I had to know what I was missing), he cranked it and the highs were just nasty ear piercing harshness (granted the speakers cost about 10% of the Utopia's, but still). Anyways, if you like this type of sound then the Focal stuff is a good match for you, then one of the Orca kits would be good, like the Aria 7 or Aria 7 Monster (re-design that ugly cabinet), or some of the E-speakers kits, or just email Andre and tell him what you are looking for and he'll certainly mention a few things, he's very helpful and receptive. Or here's another one from Speakerbuilding.com http://www.speakerbuilding.com/content/1044/
You'll have a fun time sourcing some of the x-over parts like a 4.7mH Inductor with a DCR of .14Ohm (I'm still looking into doing this setup). I'm also thinking of doing simple Focal MTM/W, with the MTM in it's own cabinet and the woofer in it's own cabinet (be almost like a Utopia clone but built better, but probably not prettier), but I may go with the Raven's for a tweeter instead of the Focal's (blowing up $25-50 ribbon is a lot better than $100 tweeters...hehehe). So far I like the looks of the new Focal W-cone stuff, and I certainly like the JM Labs stuff. I'm also considering just going with a Manger driver and some kind of woofer...or maybe go with the Newform kit....I may never get this whole thing decided.

Andrew

[Eric S]

Hi Andrew,

Yeah, I've been giving some thought to sound characteristics, too. I suppose I don't really have enough experience to determine which characteristics I really like and which ones I don't In my previous speakers (homebuilt, RS brand drivers) the tweeter was a softdome, but it really screamed - too shrill. I've heard the Polks, too that use a metal dome - and they sound way too bright for me as well. My AT350's have a fabric (silk?) dome and they sound a little soft, took some getting used to. I think I'd like more treble than the silk provides, but the Polk metal domes are too bright for me.

What I think I really need to do is convince each tweeter manufacturer to loan me one of their drivers for a weekend and line them all up and have a listen, then send back the ones I don't like! How's that for a plan?

[AndrewM]

Eric,

Yea, this is the rough part of picking out the right DIY kit/design, as you can't go out and listen to what you are building first (well, 90% of the time you can't), so you end having to take a gamble. Plus, when you are going to spend $1000-1200 on a DIY kit, you are probably going to be building a speaker system that will compete with a production speaker that would sell for $10,000+ (well it should anyways), and they are going to be in a totally different leauge than what you are used to seeing at the local Circuit City/Best Buy..etc.

It's like what I mentioned in the above responce, I was out on a Saturday and dropped into my local JM Labs dealer and he was demo'ing a pair of Utopia's (about $35,000), he was also using some VERY high end amps...etc. The next day I was in one of the local superstores buying some stuff and stopped into the stereo room and talked to the sales manager there for awhile (he's sold me a few things in the past, friendly guy), and he was showing off the top of the line Infinity's that he had (I think $2000 or so), so he started playing them and I thought my ears were gonna bleed from the harshness/shrill that was coming from them. Now this is certainly no knock on those speakers, as I have a friend who has the same line of speakers except in a bookshelf version and I think they sound very good, but not after listening to something on a much grander scale.

Now before I got into this whole DIY idea I was just going to buy some regular production speakers, I was looking at a few different species of the B&W line the 600 and 800 series (loved the 800 series, but I don't think they are the best value). I absolutly love the sound of the Martin Logans, but I don't like the pinpoint sweet spot (or the fact I had to lug them around to make them sound good, damn dealers!), and the fact they are very big, but it can create a great soundstage, lots of detail. I listened to the Electra line of JM Labs and was very impressed (I would have probably bought one of these). Vanderstein's were great also (a good bargain also). I didn't get a chance to listen to any of the Maggies, Dynaudio's (the non-kit versions), Dunlavy's. I didn't find much else I liked, or liked well enough that I could see myself investing in them. But if you can try and listen to any of the ones I've listened to and this will give you an idea of what a "bright" detailed/analytical speaker will sound like.

What kind of electronics are you going to be driving these speakers with? This was probably the stupidest hobby I've ever gotten into, you see when you upgrade one piece, it automatically means you have to upgrade at least 2-3 more piece's. You get a really nice reciever, wow, now I need some great speakers and a new DVD/CD player. You buy those great speakers, well now I wish I had seperate amps and new mega-$$$ speaker cables. You bought that new DVD/CD player, now I need an external DA converter and new mega-$$$ cables (or more DVD/CD's to watch/listen to). You get that really nice seperate amp, well now you need to ditch the reciever and get a really nice pre-pro...on and on and on....

[Eric S]

Hey Andrew,

The concept of a $10k+ speaker package for $1K + some elbow grease is what appeals to me most about the DIY. I hardly suspect that I am alone in this desire... The rest of my electronics chain is good, but nothing spectacular. I have a pre/pro and amps from Marantz that all of my music goes through. They sound great with movies & music, but I know things can get better.

I'll probably end up making a music only system out of my DIY stuff. I tend to acquire one piece at a time, however. Its easier to afford ;-) and its fun to see what impact individual changes make. I remember at each evolutionary stage of my current system both my wife and I remarked "Wow!". First it was the new speakers - Wow! Then it was the new Amps & Preamp - Wow, Again! Then there was the new CD player - Wow, a third time! Money well spent here. Then I did new cables. The "wow" wasn't quite as big, but still a difference. After these changes, my wife wouldn't let me use the old system anymore! She said it sounded terrible!

So, I'm starting on a new system that is probably more music oriented (oops, guess we're treading on thin ice at the HTG!). I figure high efficiency speakers first. I'm leaning toward smaller sized speakers that won't take over the room. Maybe somthing that sits on a stand, or has a tall but slender appearance. I can easily build a nice sealed sub to pick up the bottom end... if that's necessary. Then, I'll look into an amp. My major choice here is solid state or tubes. There are plenty of cool tube kits out there too!

There just seems to be too many choices available! Who'da thunk that was a bad thing?!?!

[AndrewM]

Well, actually if you buy a $1000 in speaker/x-over parts, you'll probably end up closer to $1500-2000 once you're done with the cabinets (need to build a heavy duty cabinet for the great drivers), finishing (might as well get some rare wood veneer to make them look as good as they sound), oops need some tools...hehe, plus many, many hours of labor. This is part of the enjoyment I suppose.

So you want high efficiency, small size and some bass...shouldn't be to hard Actually this is pretty much what I'm trying to do also, although the efficiency isn't as important to me as I'll just throw some brute force at them. Personally, I'd love to have a small stand mounted speaker, but I have yet to hear good bass out of a 6.5" driver (despite what the Bose dealer says , hence why I'm going to go with a TMW or MTMW setup. I don't like trying to blend a sub into smaller speakers, unless you can cross it over real low like 40-50Hz.

But, you may also want to look at the Northcreek Rhythm kit, it starts at around $1000 (and goes all the way up to $2200 for the Rhythm/Revelator with .25% matched components), you can even buy the cabinets pre-finished. You can't beat the Scan Speak 8545's (one of the best), or the tweeters. But it's a softdome tweeter, so it won't be as "bright" as a Focal/Raven based setup. So if you go the tube route some day you may end with something that sounds to soft (I've never heard the tweeters, just about them, so somebody else may be able to provide a little more help there). But there's lots of choices out there as you said, and I don't think you can go wrong with any of them in terms of quality, just have to narrow it all down.

Andrew

[Eric S]

Andrew,

The Northcreek Relevator set looks pretty interesting, too! Hmmm... too many options :? I've been searching the web for a review of them, it seems the only review is from Speaker Builder from last year - and its not on the web :M Guess I'll have to order a back issue.

I need to go find a high end shop and have a listen to fabric/metal domes and ribbons for a while. I suppose somewere down the line, I'll be looking up new/better amps as well. I hardly suppose that my MA500s would do justice to such a speaker.

On another note, Speaker Builder seems to do lots of reviews of these kits. Is this a decently written magazine that has meaningful conclusions other than "of all of the speakers we've reviewed, this is certainly one of them." ?

The Ariels as also an interesting pair that a lot of people seem to have had success with in the past. It seems that the biggest hurdle is becoming familiar with all of the different drivers and their approx sound characteristics. This would be SOOOOOOO much easier if all of the major speaker manufacturers would reveal who they purchase their drivers from :B

[ThomasW]

This would be SOOOOOOO much easier if all of the major speaker manufacturers would reveal who they purchase their drivers from

Ask and yee shall receive.

http://www.snippets.org/ldsg/sect-14.htm

won't be as "bright" as a Focal/Raven based setup

Raven are not at all "bright". They have one of the flattest frequency responses available.

http://www.e-speakers.com/ravenr2.0.pdf

Guys,

Speaker Builder and other magazines need ad revenue to remain is business. So their reviews on the surface tend to be "bland". This is usually the case if the reader just "skims" the article in a superficial manner. The trick is to read between the lines regarding HOW they talk about the speaker. Quite often there is a lot more info as to what the reviewer really thinks. But it's hidden in analogies, or vague comparisons/references to speakers he does, or doesn't like.




theAudioWorx
Klone-Audio

[AndrewM]

Raven are not at all "bright". They have one of the flattest frequency responses available.
http://www.e-speakers.com/ravenr2.0.pdf

This is true, and I didn't articulate it the right way. They aren't bright, and they aren't warm...maybe a better way of explaining it would be that they lack a lot of the coloration that you have with other drivers. I've heard the same is true of the Accuton tweeters.

And your comments about Speaker Builder are very true, and true of every commercial magazine you are going to read.

As for a review of the Northcreek rhythm's, you can find some at Audio review, but there aren't many.

[ThomasW]

Eric

I've got back issues of SB. Later today I'll dig out the North Creek review, and paraphrase it's salient points.




theAudioWorx
Klone-Audio

[Eric S]

Thomas,

thanks for the link! I remember seeing that one before, but had forgotten about it! Its interesting to see that the same drivers are used in systems that run up into to $20k-$40k range! Heck of a bargain for under $2k.

I suppose you are right about the reviews being somewhat bland on the surface. HomeTheater magazine was the only magazine that would tell you if they didn't like a product, but it seems that this has changed over the past few months with many of their writers leaving and a new editor. Wonder if they were losing ad revenue from disgruntled manufacturers.

[ThomasW]

Ok

Here are the "highlights"

He's a little leary of the claims made by NC for their special XO products,(I'd be too). The kit was complicated due to the cabinet assembly (he bought a kit cabinet). His performance conclusion is that they perform beyond his expectation.

His quotes, my comments ( )
"So how convincing are these speakers in reproducing original musical events?(difficult to tell since they aren't designed for PA use),I heard soundstage, focus, presence, dynamics, detail, naturalness and musicality"
"full-spectrum soundstaging that faithfully reproduces live music"
"The Revelator kit delivers performance beyond expectation. It's an easy kit to deal with if you are patient. For the more seasoned builder, it is a good challange to undertake"

(there are several other performance quotes, but they say virtually the thing.)

My feeling is that he's overly complementary, probably to a fault. This is sometimes diagnotic of the author and his "experience".

Just a aside, his auditioning equipment, Adcom 700 CD transport, Sonic Frontiers Assemblage, Monarch DIP, Sound Valve pre-amp, Sound Valve power amp.




theAudioWorx
Klone-Audio

[Eric S]

Thomas,

Thanks for providing the info! Seems that the reviewer was pleased - although he has a better supply chain than I do. Right now, my music is provided by an Adcom 700 cd and a Marantz av600 pre/pro with the MA500 monoblocks and AT350 speakers. Its a nice entry to the world of separates.

I'm planning on a music only system when we get a house, so I have a few hurdles to clear first. I appreciate you taking the time to dig that one out for me! Thanks!

Returning to my question that started this thread, it appears that the MTM design is more popular and highly regarded than I knew. Interesting that you learn with a little bit of poking around..