Ported M8n MTM designs.....

[JonMarsh]

If I was to boil it down to the essence, the M8ta is about finesse and extension in a two way- I tried to distill all the things I liked about the Avalon Eclipse and Arcus, and fix or improve some of the things I didn't like.

Compared with the M8 booskshelf design as publisehd in AudioXpress, the M8ta goes almost an octave deeper in the bass, while maintaining the ability to hit maximum output levels of about 100 dB. There are limits to what you can expect for a two way, of course, and when you push it, IMD and THD will suffer compared with a no holds barred large system. The intent was to come up with a modest footprint speaker with with reasonably low cabinet and driver coloration, and hit a numer of targets with regards to consistency of power response throghout the frequency range, very uniform off axis response, and a wide vertical window, with good playback at 90-96 dB levels from the low 20's up. Without a sub. I'm expecting that the Dayton RS225 will allow expanding the envelope slightly, and reduce distortion 5-6 dB. Not a breakthrough, but a worthwhile incremental improvement.

They aren't high output speakers- certainly, the MTMs setup properly can do better. To achieve comparable bandwidth, the MTM's would need a cabinet of about 120 liters. Not small at all, but that's life, folks. Hoffman's iron law is Hoffman's iron law. A 120 liter MTM tower will extend the dynamic range, or put things more at ease in lower SPL areas. The smaller sealed version, when used with a sub, has a pretty reasonable dynamic range overall. The midrange is more at ease, if you get the low frequencies out of the midwoofer. No surprise there.

Now, one could do a version of the M8ta without the fancy cabinet work- just a straight ahead tower, and it wouldn't be that hard to build, nor the cost all that high, depending on the tweeter choice. But the more expensive tweeters really do buy you something in the top end.

Another variant that would be fun to do would be an MTM version with the 7" Daytons, and then a single TC2+ in it's own cabinet. Or two, if you really want to shake the walls down. The 7's would have to be wired in series if it was only a single TC2+. With the 7's, the crossover could be moved up to ~2 kHz. The midwoofer crossover could be around 125 or so. Of course, what you've got there, is basically an X1 SLAMM, but not as high efficiency, but possibly with better distortion numbers, as the Focal woofers used in the X1 didn't have much Xmax. That system would play loud. Quite loud. Tuning the driver balance without an active crossover might be a little tricky. In fact, I have played with the MkIII and MkIV two way on the X1 bass cabinets, with the electronic crossover system I built for my X1 Klones; that combo worked pretty nicely. The Vifa tweeter was getting stressed before anything else.

It's an interesting idea, but one I'm not likely to build in the near future- got too many other things going on, like the Arvo's and Saint-Saens. The funny thing is that, excepting the Saint-Saen, all of these other system ideas are just variations on a theme, descended from the original Mk IV bookshelf two way published in AudioXpress. I'm not being very orginal, am I?


The "data dump" is on it's way to you, Andrew.

Best regards,

Jon

[Bing Fung]

OK, I'm about as confused as 10 ways from Sunday now regarding the MTM in a Horizontial position... :scratchhead: Thomas said it will work, Jon states it will not.

Maybe this whole speaker building isn't my bagg... There is too much design work that I just don't know how to compensate or calculate for and I don't have the expertise to sort or figure it out myself.

I know what I want, however trying to make what I want based on somebody else's established design, just isn't getting me anywhere closer to understanding what it is I need to do.

Andrew, thanks for costing that XO's for me. Are those prices US? Could I not buy directly from Solen In Canada? When you say "Big Values" are you refering to using many more smaller caps to equal the same value of 1 big cap?

Dennis, Thanks for your comments about the Swans. It maybe a viable option. I do like the looks of them and the design as well, except for the B&W style tweeter on top (too blatent ), however by the time the Swans are upgraded, the money into them maybe more than I should have spent (or not if they are closer to my ideal design), again, I would not know what to do to make them better. Is there a stabdard upgrade that people have been performing to them?

[AndrewM]

Maybe this whole speaker building isn't my bagg... There is too much design work that I just don't know how to compensate or calculate for and I don't have the expertise to sort or figure it out myself.

I thought a lot like that before I started turning perfectly good wood into sawdust. Granted I started a little easier with a pre-designed kit, which included everything down to detailed drawings of the cabinet, x-over layout, etc. But making that first step though was still a HUGE leap of faith.

But the best I can say is just do it, especially if you enjoy the creation part of it all.

I know what I want, however trying to make what I want based on somebody else's established design, just isn't getting me anywhere closer to understanding what it is I need to do.

Well you're going to have mixed results taking an existing design and trying to modify it in a radical sense (ie going from an MTM to a TMM or 2-way to 3-way). In those cases I'd say it would be best to find a design that matches up to what you want to do as close as possible, then sweat the details.

Past that, something that has helped me was to redefine what I wanted, or what I thought I wanted. Or maybe to be more specific, I knew what I wanted but I had misconceptions on how to get what I wanted. Instead of locking myself into specifics on designs and/or brands, etc, I locked more into specifics of performance. I want a fairly full-range speaker (at least in the typical music band), I want all the detail resolution I can throw at the speakers, I want crisp clear high's, I want great mid-bass, I want "no" distortion. I don't care about being able to fill a stadium with reference level volume, I have to be semi-concsious of enclosure size....and on it goes. I don't care how I achieve that, wether it's a 2-way, 3-way, single driver, mini-monitor, tower, soft-domes, metal-domes, ribbons, etc it doesn't matter, I just want to hit or get as close as possible to my "wants". But that's just my own opinion on the matter as a relative newbie, everybody is different.

Andrew, thanks for costing that XO's for me. Are those prices US?

Yes, sorry I forgot we have quite a few Canadians here. I'm not sure how custom's handles order going into Ca from the US, but I'd certainly check out Solen as well for pricing.

The "data dump" is on it's way to you, Andrew.

Got it and I'm still absorbing, I'm sure there will be some questions coming.

Andrew

[Bing Fung]

Hey Andrew, thanks for picking me up off the ground

I think I have evaluated what it is I want in a speaker, however a lot of it is based on asthetics a well. Fundimentally, my B&W's satisfiy me, however I just want to partake in the pride of building something I can be proud of, and if I get increased performance from it, all the better

I just wish I had the knowledge to just wipp them up to my hearts content.

Maybe in the end the I'll have to go preassembled kit... Actually that was my original intent. We'll see as I have some time.

Thanks again~

[JonMarsh]

OK, I'm about as confused as 10 ways from Sunday now regarding the MTM in a Horizontial position... :scratchhead: Thomas said it will work, Jon states it will not.

Standard laydown MTM's for center channel don't work correctly, in that they have dispersion/lobing problems. What this means, is that if you're dead on in front of it, they're OK; if you're off to the side a bit, the frequency response near the crossover region, or even lower (due to driver size and spacing) get's rough due to phase differences between drivers. This is because most of these standard designs use crossover frequecies in the 2.5-3 kHz range, and they can't possibly hit the required driver spacing targest to get wider dispersion in the crossover.

Also, if you look at the most typical acoustic transfer function used for these crossovers in an MTM, the Linkwitz-Riley 4th order, looking at it as a normal vertical MTM, it has a narrow vertical lobe in the crossover region. For a conventional vertical speaker, that's not so bad, as you'll usually be sitting with your ears around tweeter height, and one could argue that reflections from the floor and ceiling (in the crossover region, typically in the presence region) are reduced.

A third order Butterworth network has MUCH better polar dispersion in the crossover region, but places slightly higher demands on the driver. This is especially the case if one has chosen midwoofers and tweeters that are going into their own natural roll-off near the crossover point; then, to get an acoustic transfer function of 18 dB/octave, you may only be able to use a net electrical roll off of 6-9 dB /octave.

Both the 8th order LR and 6th order LR have much wider vertical dipsersion windows than the 4th order- based on my measurements, as you'll probably not find any published ones. For that reason, they would work better in a horizontal MTM, especially the 6th order one. The 8th order is used in the standard M8 two way, the Arvo, and the M8ta. Component values would have to be modified slightly to create a 6th order and more optimum format for an MTM. Should you be interested in a specific configuration like that, I can tweak up a crossover for you, Bing. Dual 8" would be a little large for a center, but if you can handle the space, that's cool. I'm looking at doing a design with dual 7" Dayton's for an inexpensive center in MTM configuration.

Most of the center's we've done to date for folks have been three ways- two flanking midwoofers, with a midrange and tweeter stacked. This is an even more optimum approach, but much more expensive, considering crossover costs. (a three way of comparable complexity is about twice as expensive as a comparable 2 way- because you've got two LP sections and two HP sections, instead of just one of each.

Now, a lot of commercial speakers use simpler crossovers, leave out zobel impedance control parts, etc, but various aspsects of performance suffer when you do this. That's why the designs I do have more expensive crossovers than average, but they wring a higher level of performance out of the systems. It's why upgrading from a Vifa XT to the SS98000 tweeter is feasible and worthwhile in most of these systems, once you have the extra bucks for the drivers.

Since this is strictly a hobby (plans and ideas are given away, not sold, as most of the semi-pro DIY guys do), I admit I'm selfish and focus and doing designs that I want to do, at the performance level I'm looking for. I'll tweak and modify these (within limits) for others, to help them achieve their goals, too. But, for example, there's no way to do the original M8 MkIV crossover in a $100 version unless you wind the coils yourself, and find an inexpensive source of decent capacitors. I won't try to design a low performance version of it- it will mess up too much in the speaker design.

Understand where I'm coming from- it's about finesse and clarity, at it's most basic, and then building on that with greater SPL capabilities in the larger system. Even the standard M8 MkIV is good enough to hear the difference between zip cord speaker wire, Kimber 8TC, and Cardas Golden Reference speaker cables. You don't need $2000 speaker cables to get a nice sounding system, but they're good enough that you can hear differences with a $2000 speaker cable.

Andrew has the right idea Bing- it will probably easier for you if you focus on what you want to achieve in more genearl terms, your general system configuration (HT, music, sub), whether the speakers would run full range or always with a sub, the crossover frequency you use/want (lower is generally better), etc. Space and size being important factors, too.

Then let's put a dialog together about how to address those needs.


The discussion here at Mission Possible is at all kinds of levels- guys who've yet to do their first construction or kit project, to those just learning the in's and outs of SoundEasy or LspCAD or Unibox, to those who'd been tweaking or twiddling with their own designs for some time, but would like to see or discuss some other approaches, and model and play with them, too. It's hard sometimes to gauge the right level for the discussion to occur at- ThomasW tells me that sometimes I just overwhelm a bit with a full data dump- as opposed to taking a more "sales like" process where I find out more about what a person is ready for or looking for. But I'm not here for sales, I'm just here to share my love of quality sound reproduction for music and HT.

So, tell us a bit more about your system, and what you're looking to improve specifically, and let's see if there's anything in our bag of tricks that's relevent. 8)

~Jon

Act

[ThomasW]

OK, I'm about as confused as 10 ways from Sunday now regarding the MTM in a Horizontial position... Thomas said it will work, Jon states it will not.

I think you misunderstood, Jon designed the MTM crossover when we built Tibor's speakers knowing the center was going to be placed horizontally.

The off-set tweeter and the cauer/elliptical XO works the for either vertical or horizontal MTM.

Also I think people tend to get confused when we talk about one design not being as 'good' as another, with regard to our designs, or what we consider 'optimal'

We're not talking orders of magnitude of difference. We're talking degrees of difference.

Bing, I'm pretty sure that you would be quite satisfied with the current MTM as a horizontal center, particularily in comparison to your existing center.

I set up Tibor's speakers in his house. He's using the same MTM XO design for mains and a horizontal center, they sound very good.

Now the reality is that even an optimized horizontal MTM will always be a bit of a compromise. The "best" horizontal center is a 3 way. TM in the middle, with woofers on either side. That however is a completely different speaker design, and there's not a plan in the works for one of those.

[Bing Fung]

So, tell us a bit more about your system, and what you're looking to improve specifically, and let's see if there's anything in our bag of tricks that's relevent. 8)

~Jon

I want "A NAD T770 digital decoder with 70 watt amps and Burr Brown DAC's... It's a big Stereo, speakers so loud they blow women's clothes off..."

Sorry, I couldn't resist :rofl:

Jon, as an audio designer, you are highly revered by me, even though I have to read your comments 4-5 times so I can extract the wealth of information in your posts Most times I have to come back a day or so later and reread, after I have had time to absorb it, and have done a google research on some of the issues you have presented, (IE Baffle step diffraction, and compensation) You are just at a very different level than most enthusiasts :T That's not your fault, it's up to me to get to speed and undestand the information you are presenting. It's not your fault you don't give me the sales approch, your just giving us your wealth or knowledge to our questions, and it's very much appreciated :T

What I have learned thus far is proper speaker design isn't by chance... Its a forged conglomeration of science, knowlege, testing, redesigning, retesting..etc, that yields the end results. This is typical of the work you have made with the M8A. I guess what is happening to me is I have always known Speakers are complex animals to design (properly) and are not simple. I'm realizing I will never have the full understanding it takes to design from scratch, or even slightly modify an exisiting design, and unless I use an existing kit design, thats as close as I will get to building my own speakers. It's frustrating as I'm enthusiastic about it, but man there is a lot to learn, and on that front I'm a bit impatient. Typically I like to understand all aspects of what I'm doing on a project, however I always knew that when it came to speakers, I would have to build a Kit for the required knowledge of raw design is beyound me at the moment.

There are days when I'm thinking boxed commercial speakers look very appealing after all :wink:

The M8A MTM is a nice speaker design that I'm sure I would be more than happy with, however I suppose, understanding it nature and design principles has really eluded me as as I still don't know alot about it and how to go about constructing it... IE recommended box dimensions, guideline etc.. I suppose though that I'm learning more about it the more I ask and read, so thats good.

In it's simplist form, I'm looking for a set of Main speakers that are primaraly Music material driven. Ones that image well, have great bass extension, super crisp highs and play loud with out sounding boxy flat or strained at high volume levels. Ones that will realy reveal new details to old lifeless albums.. Possible?

I would like to be able to build a family of these for the HT environment, however I suppose thats not entirely neccessary as I have a set of speakers now that do a good enough job of HT duty (except my centre, I could use a better centre). So really I'm looking for a set of mains that are more music orientated, where a centre speaker can also be built to match it, and over time surrounds as well.

Ideally I would like to build a set of mains, move my 603 mains to the back surround duties, move my current 601 Surrounds as the centre back surrounds, and then later build a Centre channel, or build it at the same time as the mains depending on what is decided to be built. I would then build and replace speakers at my leasure.

Cost is some what of an issue, as I don't want to spend as much buying materials that places me in the should have just bought the Nautilus speaker and be done with it camp. However I'm hoping to beat the 800 Nautilus with a DIY home built design. I have listened extensively to the 804's 803's, frankly, I wasn't totally impressed audio wise, Sure they sound nice, nicer than my 600's, however I find they are hardley worth all that money more nicer. Thats what I find appealing with your designs. They seem to maximze performance in the right areas placing the money where it counts. I have learned enough from reading the posts here that its the XO network design and marrage of the componets that will make or break a speaker... So I'm starting to understand these are higly tweeked designs where something as seemingly simple as changing speaker palcements really creates a new animal.. Please be patient with me. I don't know any better :wink:

At the end of the day if it comes down to "Bing, stop messing around and just build the MTM with S9800 tweeters, you'll be more than happy" I can accept that, however I will have to be spoon fed with almost step by step instructions.

Thanks, sorry I have to get to a Basket ball game, but will be back later

[ThomasW]

At the end of the day if it comes down to "Bing, stop messing around and just build the MTM with S9800 tweeters, you'll be more than happy" I can accept that, however I will have to be spoon fed with almost step by step instructions.

Yeap, that's a GOOD idea ...... :T

[JonMarsh]

Yeap, that's a GOOD idea ...... :T

I second that, quite strongly. We have all the stuff lying around regarding these issues, and can easily tweak a center channel crossover for MTM. We just haven't put it all together in one place, not super detailed like the AudioXpress article, for example, because that's a LOT of work. But collecting it all into a reasonable guide without making a "publication ready" article wouldn't be at all difficult.

Just a few questions, Bing;

What's you timetable? Are you ready to roll, or six months away from getting in gear?


What's your wood working experience? Are the more complex but cosmetically attractive approaches like Paul's interesting, or is a straight forward tower more to your liking?

Do you use the sub with your mains even for music?

Understand that I usually spend up to 18 months on one project- this isn't usually about "instant gratification", due to the amount of detail work involved... but there are exceptions, and that might be a route for you...


An example would be the speakers I built May 2003 for my daughter. This was a 2 way system, put together including design, in just a couple of weeks, for the Northern CA DIY meet. Sort of the AudioWorx equivalent of the Manhattan project. They used HiVi D6.8 and Vifa XT25 tweeter.





Thes used pre-built lacquered wood finish cabinets from PE; the one's shown cost $85 each. The front panels are removable, until you glue them in. You can buy extra front panels, in case you make a gaffe on cutting/rabbeting the ones that come with the box. They are internally braced, and pretty strong- available in piano black, cherry finish, and beech. They look very nice, as those who have seen them in persona will testify- like expensive European built speakers.


The only reason I mention this, is that I'm doing an MTM design with the 7" Dayton RS180s, which I'll use for center channel, and may also use for surrounds, and may apply to a three way concept- combining the MTM cabinet with a seperate base cabinet. Might be RS225 8", or RS270 10" in the bass cabinet, or even TC2+ 12".

I have the aluminum cone Dayton RS180 7" already, as well as the other models. The 7's have 6 mm Xmax, and unusually low linear and non-linear distortion. Good motor design, from what I can tell.



I'm going to use them with these 1 cu. ft PE enclosures, which are $99.97 each:




These aren't full range speakers; think 45 Hz on up.

Several tweeters under evaluation for this project, may stay with the SS9800, though I'm considering other Seas and SS models (especially the SS D2904/6000, which is a small format tweeter with Neodymium magnet), as well as Northcreek D28.

With a 100 Hz or so crossover to a woofer cabinet, these would make a pretty dynamic box speaker system. And pretty compact, and pretty easy to build. I'm a little embarrassed that the tweeter will probably cost 2X the midwoofers, but finding really good tweeters is something of a problem. With the D2904/SS6000, a CTR to CTR spacing of 8" is possible, indicating an upper crossover frequency limit of 1700. Let's say, pull it down to an even 1500 Hz, with the cauer-elliptical 6th order.

You see my problem? I have the Arvo's to finish, which I really like what I've heard so far, but an intriguing opportunity like this pops up, a "What if?", because of new drivers, and I get all distracted... like seeing an attractive woman walking down the street. :B


Anyway, if you're not in a hurry, I'll probably have a set of these done by mid to late December, and have some opinion of them. Target efficiency, given they're 4 ohms, is 90 dB net after baffle step; only plan to use 3 dB of baffle step, since they'll probably be used closer to wall boundaries than I normally place speakers.

Regards,

Jon

[Paul H]

Hear, Hear! Thomas

Bing, the M8 designs are not the easiest of speaker projects, but much help is available. Our experts here have the complete design, and I've got info on actual crossover layouts and box sizes for ported and sealed.

The crossovers are complex, but no one's going to have a stopwatch on you while you're assembling them.

Any speaker box requires some carpentry skills, but given that, these speaker boxes can be simple or complicated, as you wish.

Paul

[Steve Goff]

Jon,
I love the design idea with the RS180's in an MTM with the 9800, on top of a bass box with RS225's or RS270's or a TC2+. That sounds like a great conbination that many could attempt. I'd even consider putting a plate amp in the woofer box, one with parametric equalizers built in, and maybe try to build a divider network to run the plate amp off of the speaker outputs of the main amp. This combination could work very well as front left, right, and center speakers. And the upper module would be great as surround speakers, though the crossover might need to be adjusted for those speakers that need to be up against the wall.

[Bing Fung]

I second that, quite strongly. We have all the stuff lying around regarding these issues, and can easily tweak a center channel crossover for MTM. We just haven't put it all together in one place, not super detailed like the AudioXpress article, for example, because that's a LOT of work. But collecting it all into a reasonable guide without making a "publication ready" article wouldn't be at all difficult.

Can a person still obtain this AudioExpress article, or was it spanned across many articles?

What's you timetable? Are you ready to roll, or six months away from getting in gear?

Nothing set. I though once I found something I liked, I would start collecting the parts and designing the cabinents. Once thats done, start building. I'm not in any type of rush or Need Now situation, I just thought I would chip away at it.

What's your wood working experience? Are the more complex but cosmetically attractive approaches like Paul's interesting, or is a straight forward tower more to your liking?

Pretty basic, I know my way around a wood shop, however if I was to rate my real experience I would say "can build a decent rectangular box" I don't have near Paul's experience to build like his. However I do have a friend with a wood shop that can probably come close.

At first I was thinking straight forward tower if I was to do it, However I have always wanted to model a cabinent based on this speakers dimensions, maybe not the finish, maybe .... however more the shape of it. Hence the reason I was wanting a TMM so I could more "Klone" the Wilson Benesch Curve, less the Carbon fiber finish.



I don't have the skill, but I have a friend who does. He has a nice wood working shop with all the toys. He also told me he has access to a CNC wood cutter that could be used as well to make complex shapes.

So while I aspire to the Curves, it may be Straight Box in the end, unless I find a design that is esoteric enough where a straight box doesn't matter

Do you use the sub with your mains even for music?

Most definately, unless I really don't have too

Understand that I usually spend up to 18 months on one project- this isn't usually about "instant gratification", due to the amount of detail work involved...

Understood, I was not looking for instant gratification either, but I didn;t want to have to think too hard

An example would be the speakers I built May 2003 for my daughter.....

The only reason I mention this, is that I'm doing an MTM design with the 7" Dayton RS180s, which I'll use for center channel, and may also use for surrounds, and may apply to a three way concept- combining the MTM cabinet with a seperate base cabinet. Might be RS225 8", or RS270 10" in the bass cabinet, or even TC2+ 12"......

Anyway, if you're not in a hurry, I'll probably have a set of these done by mid to late December, and have some opinion of them. Target efficiency, given they're 4 ohms, is 90 dB net after baffle step; only plan to use 3 dB of baffle step, since they'll probably be used closer to wall boundaries than I normally place speakers.

Sounds interesting Jon, so it would be an MTM in a separate cabinent with lower woofer? Sound just esoteric enough for me 8) I'm in no real hurry, nothing is pressing aother than desire and want. I suppose and could wait and learn more...
I do like the look of the Dayton drivers very much!

You see my problem? I have the Arvo's to finish, which I really like what I've heard so far, but an intriguing opportunity like this pops up, a "What if?", because of new drivers, and I get all distracted... like seeing an attractive woman walking down the street. :B

I know, thats what I was eluding to about yours and Thomas's speaker driver collection, you guys collect them like others collect basball cards :lol:


Can the M8A MTM be built with a smaller horizontial centre such as the M6A in a MTM array to go with the M8A MTM's?

Did I hear you say 3 way centre? Two flanking midwoofers, with a midrange and tweeter stacked...? I would love something like that :yesnod:


Thomas, I had posted that last long post not knowing you had psoted. Funny you mention my centre speaker, and I was also talking about it.

Thanks for clearing up the order of differences... It's this exactitude you and Jon express that lets me know the same preciseness and attention to detail has been poured over in your speaker design's :T


Paul, thanks for sending ou tthe XO parts list and pricing guide. I like how you have accessed each vendor for pricing ..etc :T
I may need those XO Diagrams form you yet, depending on what shape the project takes.

[JonMarsh]

Jon,
I love the design idea with the RS180's in an MTM with the 9800, on top of a bass box with RS225's or RS270's or a TC2+. That sounds like a great conbination that many could attempt. I'd even consider putting a plate amp in the woofer box, one with parametric equalizers built in, and maybe try to build a divider network to run the plate amp off of the speaker outputs of the main amp. This combination could work very well as front left, right, and center speakers. And the upper module would be great as surround speakers, though the crossover might need to be adjusted for those speakers that need to be up against the wall.

Well, stay tuned, Geoff, because that is in the works. The only issue I see with moding the crossover is tweeter sentivity- I figure a "partial" BSC compensation of about 3 dB maybe flexible enough for most locations, and the tweeter could run full tilt - 90 dB; paralleled mid woofers of 87 dB each would hit 93 nominal, less 3 dB baffle step.

I may cut a simple test baffle soon to measure the 180's in, but they appear to have enough headroom on the top that I just may go straight to the PE enclsoure. I need a center for the bedroom and one for the living room; this could work both places; and since the drivers are sheilded, just might be the ticket.


Bing,

I'll address your commnts and thoughts further tomorrow- got some stuff to do now, including a workout.

Did get RS225 measurements in M8ta boxes done today. That will post tomorrow.

~Jon

[Bing Fung]

You know the more I think about this the more I feel I should apply the KISS principle to my first set of DIY mains. I think I confuse my dream speakers with wanting to build them in my first real Hi-fi audio grade DIY speakers.

If I build these MTMs I should concentrate on just getting them to sound right first, and as long as I employ soild, proven construction techniques, using Jon and Thomas's plan, how can I go wrong?

I think a standard box shape tower with a nice veneer also has a nice elegant appeal as well. Kinda like the Totem lines of speakers... Nothing esoteric, just great looking boxes :T (minus the rocket feet)



I think 4 of the Tibor Style MTMs would be awesome for the Multi channel audio I seem so into these days (LR Mains, LR Surround). I could then build 2 way M8As for the centre surrounds.

So what can be done for a matching centre channel? 8" MTM may be slightly too big as you mentioned Jon.

Whats expected frequency range of the M8A MTM design?
It's nominal impedance?
Power handling nominal and max?
Typical max SPL level?

Are there any new drivers coming in the not so distant horizon I should wait for, like the Adire Extremas, Daytons...etc?

[JonMarsh]

I think 4 of the Tibor Style MTMs would be awesome for the Multi channel audio I seem so into these days (LR Mains, LR Surround). I could then build 2 way M8As for the centre surrounds.

So what can be done for a matching centre channel? 8" MTM may be slightly too big as you mentioned Jon.

Well, as I've indicated above, I plan to do an MTM design optimized for polar dispersion, which would work well as a lay down center channel. This could use the Extremis 6 (7"), but considering bucks, I'm more inclined to go with the Dayton RS180s (as described above), most likely with a SS D2904/60000 tweeter, crossed at 1250 Hz, because of the space and layout considerations, and it's compact size. With the Extremis midwoofers, you could push these really hard, given the Xmax, but voice coil thermal limitations would still be an issue. Still, might be an interesting way to go.

This will probably be in the 1 cu ft PE enclosure, since for this kind of money, it's not worth my time to build a box, and they look really good. I plan to order some boxes while out at ThomasW's, so they'll be on the way in after I get back. May have to delay that a week, cause I'll be in Chicago most of the following week.

Do you like Beech, Cherry, or satin piano black? If so, you may like these. Or you could build your own.

BTW, the speakers I built for my daughter use the same woofers as one of the Totem models, the HiVi D6.8. Totem uses the LPG 26T tweeter (titanium) in many of their designs. It goes low enough to use with the Dayton 7, but not the M8a or the Dayton RS225. LPG makes some small format tweeters, too, but they don't go low enough.

Whats expected frequency range of the M8A MTM design?
It's nominal impedance?
Power handling nominal and max?
Typical max SPL level?

The M8a MTM design is a four ohm speaker- four ohm tweeter (whether Vifa XT25 or SS 98000), and with two woofers, a four ohm bottom end. Not for SET's, or wimpy receivers. The bottom end extension depends on the enclosure size and tuning. Tibor's were sealed, setup to use with a sub, Q of about 0.6. If you wanted a ported design, similar tuning to the bookshelf version, that's about 80 liters for two drivers, tuned to 32 Hz, response overall down about 5 dB at 32 Hz (anechoic, before room gain). This would be a reasonable "tall" tower size. Full bass extension would require something like 120 liters ported- then, you could expect ~104 dB down to 23 Hz, response gently sloping from 100 Hz to 23 Hz. See the posted Unibox plots in the Dayton Driver thread - M8a in MTM would only be slightly less than Dayton- about 1 -2 dB. The top end is a function of the tweeter- both I've used go beyond 30 kHz, but the 98000 has better dispersion.

Are there any new drivers coming in the not so distant horizon I should wait for, like the Adire Extremas, Daytons...etc?

For the MTM's for CT, I plan to use the 7" Dayton's. For an 8" woofer system, the Dayton requires too low a crossover for most tweeters. The M8a goes higher, is easier to design for. For the MTM center, the Extremis
is a possiblity, but costs 3X the Dayton. It has excellent linearity, lower sensitivity, and twice the Xmax - 12 mm vs. 6mm. The Dayton RS180 has Xmax on a par with the $150 Scanspeak midwoofers, so it's no slouch- especially not at 1/5 the cost. It's a clear value leader, IMO, especially for an MTM. I've got a few friends at work also interested in this configuration- if I was interested in cranking these out, I bet I could sell quite a few.

I'm not aware of anything else concrete coming out besides the Dayton and Extremis. Could always be surprised, but at a 4 piece price of under $31, it's hard to see how the Dayton can be topped. Unless they pay me to take them...

Does that cover all the bases for now?

Until I get my own measurements on the RS180 done, I won't have any more hard facts.

Regards,

Jon

[Brian Bunge]

Jon,

I vote for the 7's in an MTM with dual 225's in the bottom cabinet. That way it might also be feasible to build these as a single large tower should someone (ME!) so desire.

If you use the SS 9800 tweet, those of us on a budget could use the Vifa initially w/o modifiying the XO, correct?

[JonMarsh]

Jon,

I vote for the 7's in an MTM with dual 225's in the bottom cabinet. That way it might also be feasible to build these as a single large tower should someone (ME!) so desire.

If you use the SS 9800 tweet, those of us on a budget could use the Vifa initially w/o modifiying the XO, correct?

This is a very reasonable idea, just some thoughts on it.

First, we could do a design pass for the Vifa XT25/SS9800 alternatives; main crossover could be the same, with just a sawp out of zobel components if you want it fully optimized. For an MTM in a relatively narrow cabinet, this wouldn't be my first choice, mainly because it would require spacing the midwoofers further apart. Still, it would work. I still suspect for center channel applications, or best vertical polar dispersion in convnetional MTM, that the cute little SS D2904/6000 would be the cat's meow. We'll see.

The other issue is matching up efficiency and baffle step. I'm not sure that we'd wind up with the quite the same crossovers, depending on whether the MTM was designed as "stand alone", with normal baffle step, or designed to work with dual RS225. The reason is combined efficiency and total baffle step comp.

If I was doing the system design from the get go as a three way, in one or two cabinets, then I probably wouldn't put hardly any BSC on the 7's, and I'd roll the RS225's gently from 200 to 700, then more steeply above that. The RS225's are about 88 dB /2.83V each, two would give you a net of 94 dB/2.83VRMS. The RS180's are 87 dB; two giving you ~ 93 dB. I'd size the box with the RS180's to give a 0.56 to 0.66 Q, put a LF zobel to kill the Fb impedance rise, and put a series cap on to convert the LF acoustic high pass to 3rd order, 18 dB/octave. Fb would probably be around 85-90 Hz. In the range of 80 Hz to 350 Hz or so, you'd literally have a tall line source, with all drivers radiating- this helps prevent floor bounce dips. The Wilson X1 works this way. The lower driver set provides the extra output to effect BSC on the transfer function of the higher drivers. Might require a little juggling of the transfer function on the MTM midwoofers, but should be straight forward. Allowing for insertion loss of a dB or so with low DCR inductors on the bass bin, it should be possible to wind up with 92-93 dB sensitivity.

Now, on the surface, that looks like it would slightly over power a tweeter with 90 to 91 dB sensitivty, but in practice I find that having the level down just a skosh above 1 kHz is usually more listenable with a lot of electronics than having it dead flat. That's how the standard M8 booksheld design is voiced.

So, it probably could work pretty cool. But to get really deep bass extension on the bottom end, you'll need a fairly good size internal volume for the 2 8" woofers. Hoffman's iron law. Think 80 liters for 32 Hz, 100 liters plus for 25 Hz. But it should be pretty killer, and have great transient response- "fast" bass, as some people call it, while still going low.

And wouldn't cost all that much in drivers.... kinda funny, if you go for the premium grade tweeters (say, $150 each), then the two RS225 plus two RS180 would cost in total about the same. Which is about the price of a single Scan Speak 7" or 8" woofer. :E

As the Who said,

"I call that a bargain, the best I ever had...." :T



~Jon

[Steve Goff]

Jon,

The SS D2904/6000 is cute, but I'd prefer to go for the performance of the 9800, even if it means that the front baffle has to be a bit wider. Your other ideas about this combo sound ideal to me.

[Hank]

But it should be pretty killer, and have great transient response- "fast" bass, as some people call it, while still going low.

Lord Vader is talking directly to me. Brian, don't worry about switchable tweeters, just go ahead and order a pair of D2904 6000's, OR, drop the hint that they'd make a great Christmas present for you.
Can you imagine - this could be the killer value tower speaker. I'm going to get some speaker cabinet quotes from Juarez, Mexico in the near future, for a startup speaker co. - I wonder...what if I quit my day job...NO, MUST FACE REALITY - can't make money selling speakers. Damn, I have to remind myself of that once a quarter.

back to reality

[JonMarsh]

Lord Vader is talking directly to me. Brian, don't worry about switchable tweeters, just go ahead and order a pair of D2904 6000's, OR, drop the hint that they'd make a great Christmas present for you.
Can you imagine - this could be the killer value tower speaker. I'm going to get some speaker cabinet quotes from Juarez, Mexico in the near future, for a startup speaker co. - I wonder...what if I quit my day job...NO, MUST FACE REALITY - can't make money selling speakers. Damn, I have to remind myself of that once a quarter.

back to reality

You know, that's what the problem is with all these new, cute, inexpensive, relatively high performance drivers- I have many more ideas than time, but somehow or another, we're going to crank a few of these designs out in the next few months. For me, my X1 klone tops will be the upper end, though I'm building a pair with the PE cabinets for center channels, too.

Now I've got to figure out where I'll put a set of new bass cabinets just to try out and debug this design. I could debug it with just a smaller sealed version on the bottom end, maybe a Q of 0.566 (Bessel). It's just irresistable... where's my 12 step program for Speaker Builders Anonymous? :rofl:

~Jon

[Bing Fung]

Jon, just when I think I'm going MTM M8A, you dangle a nicer carrot :T

Thats what I talking about wanting, lots of speakers, lots of SPL, yet still able to be delicate and detailed.. :B


The Dayton RS180S 7" s in an MTM with dual RS 225S's 8" in one complete cabinet would be too cool. The savings on the drivers alone would allow a person to spend more on the tweeter, which I would be willing to do.

Alright, I'll be waiting with baited breath to the developments of this project..

I'm even intriuged with the extremas and seeing what application you will fit those into. However I'm more intriged with the top senario. ;x(

Brian, one you have a plan in place. please do let me know :T

[Brian Bunge]

Hank,

Here's my official "hint". Those tweets would make for a great Christmas gift!

Jon,

Couple more questions:

The first is, what would the baffle width need to be in order to use the XT25/SS9800 tweets? Your PE 1ft^3 enlcosures are already 9" wide. I've currently got 10" wide towers here using a single 8" woofer so anything from 10"-12" wide works fine for me since I'd like to use the Dayton 8's on the low end and I like using 3/4"-1" rounded vertical corners on my cabinets. This may not be an issue though since I've dropped the hint to Hank for those SS 6000 tweets.

Second, are those recommended enclosure volumes for the 8's sealed or ported? I'd assume sealed since I know no self-respecting "audiophile" would use the term fast bass when describing a ported enclosure.

[JonMarsh]

Hank,

Here's my official "hint". Those tweets would make for a great Christmas gift!

Jon,

Couple more questions:

The first is, what would the baffle width need to be in order to use the XT25/SS9800 tweets? Your PE 1ft^3 enlcosures are already 9" wide. I've currently got 10" wide towers here using a single 8" woofer so anything from 10"-12" wide works fine for me since I'd like to use the Dayton 8's on the low end and I like using 3/4"-1" rounded vertical corners on my cabinets. This may not be an issue though since I've dropped the hint to Hank for those SS 6000 tweets.

Second, are those recommended enclosure volumes for the 8's sealed or ported? I'd assume sealed since I know no self-respecting "audiophile" would use the term fast bass when describing a ported enclosure.

Yes, that's why being something of a mad scientist, instead of a self-respecting audiophile, does me in such good stead- I don't have to be bound by conventional stereotypes!

There's porting, then there's porting. A lot depends on the overall alignment and damping. What I REALLY can't stand personally, is PR's- time domain resopnse is just terrible.

Let you in on a not very well known secret- most of the current Avalong models are ported, though they don't call them bass reflex per se. They're more like Martin King's TQWT, as is my M8ta.

See the alignments further up in this thread? Response is down ~ 6 dB at the Fb, and there's obviously no peaking in the design - unlike so called "boom" boxes. For the rest, you'd just have to listen.

Why port? Well, an Avalon Eclipse has some response down to about 30 Hz, but it's not capable of putting out much SPL- combination of low Xmax driver and sealed box. The M8ta will put out about 10 dB more at 30 Hz than an Eclipse. That's not a typo....

Anyway, back to our regularly scheduled programing.

The MTM concept can be done with greater driver spacing, but it tends to mess up the radiation pattern a bit - with that little D2904/6000, the 7's can be just about right up against each other (and because the baffle is removable in the PE enclosure, it's possible to install an oak brace across that section, for example), and then the tweeter can be nestled in to one side, like the way I do the Arvo's.

Though I haven't checked the layout with AutoCAD, I don't think I can put the 7's together and squeeze the tweeter in if it's 4" in diameter. Maybe I'm wrong; that's just a gut feeling.

Using a Vifa XT25 or SS98000 dead in the center, the midwoofer center to center spacing will be about 12". Overal radiating size ~ 19". With a 1250 Hz crossover I'd really rather see that in the neighborhood of 11". Ctr-Ctr with little tweeter is ~8", overall 14". That works better for dispersion an minimizing polar lobing in crossover region- results in speaker having more consistent power response into the room, not just flat axial response.

Hey, it's not religion, I'm flexible and will help you do whatever floats your boat. I'm just trying to be sure you have info re the tradeoffs.

BTW, 12" wide is a nice size with regards to BSC; need comp from 200Hz to ~800 Hz. Smaller baffle, you need comp to higher frequency. Note, with 1250 Hz crossover, you're well above the Baffle step region.

I'll be measuring the 7" on the PE box baffle, which is about the same as my X1 cabinets. If you plan a tower or two piece from the get go, then the crossver design will be a bit different, as I mentioned earlier.

BTW, another option on the woofer, slightly smaller than 2 8's, is one of the 10" Dayton's. I've got them coming in; wil be interesting to see how they work. I think for what you're talking about 2 8's is cooler; may handle a bit more power; Xmax about the same. I did some WMTMW speakers using SS 8" kevlar drivers, dome mids, and MB quart tweeter, in Woodstyle tower box years ago (early 90's); they would kick some you know what, and play pretty loud and moderately deep (a virtue of the SS which the RS225 seems to emulate). I only got rid of those last year; was running out of room. They're being replaced eventually by the M8ta's. For now, the M8 MkII's are sitting in.

~Jon

[Steve Goff]

Jon,

If you use the same center to center mid/woofer spacing as the M8 MTM, and at the same crossover frequency, wouldn't you have more room for the tweeter, since the RS180s are smaller? So you could also keep the tweeter at the same offset and move the RS180s closer together than the M8's.

[JonMarsh]

For a center channel speaker laid down, I'd rather have a little tighter spacing than I used in the Arvo. For a stand up MTM, it's probably fine.

I'll have to look at the front panel dimensions and see what fit's where- I'm going to try to do that on the plane this afternoon.

Regards,

Jon

[Dotay]

I'm really anxious to see the RS180 project with the PE cabinets continue to progress. This looks like it could be almost exactly what I am looking for because I have always planned on running a sub anyway. But having said that, would it be possible to add a port to the enclosure to extend the low frequency a bit lower than 45 Hz?

[Brian Bunge]

Jon,

If I'm correct, the dual 8's would have almost 2x the Vd of the single 10. If so, That's the way I'd personally rather go. Sounds like Bing is on board too. I'll really have to think about the 6000 tweeter. A few years ago I'd go with it in a heartbeat, but at the moment my yearly income is roughly half what it used to be. So I really have to watch what I spend and where. Hopefully that'll change soon as I've got something sort of in the works. Dammit, where's the speaker fairly when I need him/her?

[Bing Fung]

Brian, you know it :T 2 x 8" woofers with a Dayton 7" MTM (SS9800 for me) is like a dream come true... I'm salivating just thinking about it :drool:

Jon, please give this speaker life, at your earliest convienence ;x( :wink:

I'm still inspired with 4 of the Tower MTM's (ported), however.... :tennis: If that 2x8xMTM becomes a reality, I think thats for me :B

[JonMarsh]

Well, it sounds like fun to me, too, so let's just do it! :T 8)


Now we have to come up with a name for it. Suggestions?


Back in Houston again today... Hello David Meek!!!!! Can you hear me????


~Jon

[Bing Fung]

Building up those frequent flyer miles Jon?

I don't know how you manange all these project, but I'm glad you can :T

Names.. how about:

Helios, God of the Sun

Asherons, one of five rivers (5 drivers)

Apollo, god of music

Argonauts, for the many drivers representing the 55 sailors that sailed with Jason.

Merlins, because of the magic

Allegros, Lively brisk rapid

Cadence, timing

Da Capos, from the begining, repeat

Legato, smooth flowing

Staccato, separate short detached

[Steve Goff]

What is the diameter of the RS180? Parts Express gives dimension A as 7 1/8 inches, but I'm not sure what dimension A is. Dimension A for the 6-inch RS150 is 5 15/16 inches, which might allow a straight-line MTM with a 4-inch tweeter in the center.

[ThomasW]

Parts Express gives dimension A as 7 1/8 inches, but I'm not sure what dimension A is.

It's the outside diameter of the frame

[Steve Goff]

Thanks, Thomas, that is what I expected, but didn't know.

[Bing Fung]

Is the design done yet? :B

[JonMarsh]

Is the design done yet? :B

Yeah, I finished it completely on the trip, then accidently it from my laptop because I forgot to save when our boarding group was called on the way back.

Sigh.....




~Jon

[JonMarsh]

I'm really anxious to see the RS180 project with the PE cabinets continue to progress. This looks like it could be almost exactly what I am looking for because I have always planned on running a sub anyway. But having said that, would it be possible to add a port to the enclosure to extend the low frequency a bit lower than 45 Hz?

The problem is good old Hoffman's Iron law, and the T/S parameters of the drivers.

A fairly ideal ported alignment (IMO) for these drivers would be a 44 L box (same as the single 8" two way bookshelf design in AudioXpress) with a 7.5 CM, 27 CM long port, tuning the enclosure to ~30 Hz; response at 30 Hz would be smoothly rolled off from 100 Hz by about 6 dB, so with typical room boundary gain, could be fairly flat to 30 Hz.

However, the PE box is only 28-30 liters, and a practical ported tuning wouldn't get you much bass extension, just more power handling above 40 Hz. Practially speaking, a sealed alignment with 2 RS-180 would get you a Q of about 0.566, a Bessel alignment, which is a very nice compromise between a critically damped alignment (Q of 0.5), and a maximally flat Butterworth alignment (Q of 0.707). I never have liked the sound of Butterworth alignements in room, because with the increasing room gain, they usually have too much output near the box FB. The exception might be for flush boundary loaded speakers designed from scratch for that location. But then you still have a bit faster roll off- immediately at 12 dB/octave, while the critically damped and Bessel are around 9 dB/octave for the first octave.

Guess I just like lower Q alignments...

Regards,

Jon

[Steve Goff]

Am I correct in thinking that surround speakers with two RS180s in an MTM could use much the same crossover between woofers and tweeter as the three way, since the three way would use the RS225s for boundary step compensation, whereas the surrounds would be boundary loaded?

[JonMarsh]

Am I correct in thinking that surround speakers with two RS180s in an MTM could use much the same crossover between woofers and tweeter as the three way, since the three way would use the RS225s for boundary step compensation, whereas the surrounds would be boundary loaded?

Steve,

I'm thinkin' that your thinkin' is pretty much on the money. Substitute phrase "MTM Center" for surrounds, and that's my initial application in primary and secondary system.


Have a good weekend - Colorado is calling to me!

~Jon

[Steve Goff]

Ah, yes, and a center channel too, though I would likely place mine horizontally, since I have enough room under my screen. An interesting comparison to my Revel M20s and C30.

[JonMarsh]

Mine will be horizontal, too, in both systems (under a Carada screen in living room, on top of an NEC presentation monitor in bedroom). That's why I'm sweating the details with regards to the driver spacing and Xover frequency.

I've been playing with the demo for LspCAD 6 the last two weeks; it's a little pricey, but will be a lot more pricey if I dither and don't get it soon, so maybe these will be the first project I do with it. It has some very nice tools for polar response simulation and analysis. Got a lot of other neat capabilities, in how it can mix active, passive, box modeling, and measured data all in one development file. It's a whole lot more flexible and totally revamped in the netlist entry. Actually, it's a brand new product, looks like Ingemar started nearly from scratch except for the basic calculation and plotting code. The more I play with it, the more I like.

~Jon

[Paul H]

I told Jon I'd post a photo when I finished these speakers.

I was going to paint them black but thought I'd try a stain first and paint over it if I didn't like it - I like them as is.

The stained wood in the picture is baltic birch on the front, back and top, and luan (bendable) ply on the sides. The bottom pedastal base which houses the crossover is black painted mdf.

They sound great - thanks again Thomas & Jon.

Next up - dipoles. I've ordered four stryke 15" woofers, and am ordering some peerless hds mids and scanspeak 9500 tweeters.



Paul

[Andrew Pratt]

Nice work Paul :T

[JonMarsh]

I told Jon I'd post a photo when I finished these speakers.

I was going to paint them black but thought I'd try a stain first and paint over it if I didn't like it - I like them as is.

The stained wood in the picture is baltic birch on the front, back and top, and luan (bendable) ply on the sides. The bottom pedastal base which houses the crossover is black painted mdf.

They sound great - thanks again Thomas & Jon.

Next up - dipoles. I've ordered four stryke 15" woofers, and am ordering some peerless hds mids and scanspeak 9500 tweeters.

Paul

Great looking work, Paul!

Dipoles.... ooh la la! It's going to be an interesting year!

~Jon

[Paul H]

Thanks guys.

This is a hobby for strong backs - between these towers and the tempest 214litre sub box that I also painted on the weekend I was working hard wrestling heavy woodwork around.

Paul

[JonMarsh]

Believe, me, I know, Paul. This is coming from the guy that had back surgery in 2003, and switched from considering a 375 lb table saw to buying a 125 lb. one!

I've got some pretty nice sub drivers around here which I've been putting off doing anything with, because of the weight involved.

I know, so why did I do the M8ta's, one of the worlds heaviest 8" two ways?

Keep up the good work... :T