Ported M8n MTM designs.....

[Paul H]

The final cabinet finish (unless I change my mind in the next couple of weeks) will be gloss black lacquer.

This will require some serious prep time, as while this finish looks fantastic on a really well prepared surface, it also tends to show the tiniest of faults.

Paul

[Ten 99]

Painting black...

Paul,

You are absolutely right about that. Preparation is everything, and you do have to have good painting skills to boot. Are you painting them yourself, or having them done by a pro painter (maybe a car painter)?

Also, have you modeled that design in some sort of 3D image software to mimic the glossy black with lighting to see what it will look like at all angles. I know that an enclose with hardlines and angles would look great in glossy black, but I'm curious about those sexy curves on your enclosers? I've seen similar shapes with my speakers (Rockets by the folks at AV123) done in veneer, but I'm curious about the gloss black.

BTW, they do look very well made. I'm impressed by your cabinet skills.

[Paul H]

Thanks Chris.

I am painting them myself. I've been making furniture off and on for 7-8 years (for myself or friends) , and always finish it myself.

I like using lacquer, but it's comparable to using a router - you can do really nice work very quickly, or make a mess of your project in minutes!

Good suggestion on the 3-D modelling. I've got a 3-D autocad model of the speaker but haven't yet taken the time to check gloss black under various lighting.

Paul

[Daryl Furkalo]

Paul, they look amazing! Great work! :T

[JonMarsh]

Thanks Chris.

I like using lacquer, but it's comparable to using a router - you can do really nice work very quickly, or make a mess of your project in minutes!


Paul

Man, isn't that God's own truth! I'll have to remember that...


~Jon

[Paul H]

Dual M8n closed box centre channel

I started thinking about the centre channel to go with the ported M8n's.

I'm looking at a 65-70 litre closed box, as I don't want the very large ported box, or need the very low end frequencies, for the centre.

Most centres seem to be "laid on their side" as it were, I assume because they usually sit on top of or beneath a television. I would think better horizontal dispersion would be had with a "stand-up" speaker. In my room I can fit either option.

If I do a vertical speaker it would be fairly low, maybe 30-32" tall. I would think the baffle should be tilted back slightly (speakers pointing slightly upwards) to put the tweeter in line with our listening position ear heights.

Thoughts and comments anyone?

Paul

ps If this should be another thread please move.

[ThomasW]

Tibor used a smaller sealed version of the original MTM design as a center. We used the same driver layout and XO as his MTM mini-towers. It works quite well.

The best dispersion is obtained with a vertical MTM or a horizontal center, built as a 3-way with a dome mid mounted under a tweeter centered between the woofers.

[Paul H]

Thanks Thomas.

I assume Tibor's cabinet was fully filled (stuffed) with insulation/polyfill or whatever?

Paul

ps Hooked up an XT25 tweeter through one of the crossovers yesterday - it works so I guess I've built the tweeter xover and zobel network correctly - so far so good..

Paul

[ThomasW]

Paul,

Yeap, we stuffed it with poly. Adding increasing amounts an ounce or so at time. With each addition the bass output should tighten. When the bass stops changing and the only effect is a overall decrease in output, remove the last amount added.

[Paul H]

Before I start making more sawdust..

I thought I'd ask for any opinions and comments on the centre speaker in the attached sketch.

The cabinet is 32" high x 18" deep (at the bottom) x 12" wide. The tilted front puts the tweeter aiming at ear level approx 12' away.

The net volume of around 54L with this configuration is less than the apparent optimum of around 70L, but seems to give up only a very minor amount of low end, which would go to the sub through the LFE during movies anyway.




Paul

[JonMarsh]

Should be a very reasonable tradeoff; especially considering room gain will have some added lift below 100 Hz. I imagine any LFE crossover from about 60 Hz up should blend well.

Regards,

Jon

[Paul H]

Thanks Jon. I think I'll go ahead with that cabinet the way I've shown it.



Picked up a package tonight - six M8n's :T


Paul

[JonMarsh]

Congratulations! Glad they finally arrived!

~Jon

[Paul H]

Thank You

Thomas & Jon,

The ported M8n's were completed and hooked up this morning. They sound fantastic.

The bass is tight, mids & highs are crystal clear. I love the sound of a pick hitting a guitar string

I may run some audio tests in the next week or two just for curiosity's sake.

I may do some tweaking of cabinet fill, etc - or maybe not.

I'll post some pics when I get a chance - the cabinets are still unfinished of course.

In the meantime, I'm going to listen ...

Thanks for all your help, support, answers to good questions, and patience with silly ones. I appreciate it.

Paul

[JonMarsh]

Congratulations, Paul! We really enjoy seeing more sets and variations on a theme built, and yours is a very classy one! :T

I'm even thinking now about doing a "shorty" version of the M8ta tower, something like Tek from Norway was contemplating a year and half ago. But there's a lot of other things to finish first.

The nice thing about the basic M8 two way design is that it has lent itself well to many variations on a theme meeting specific user or application requirements - the basic tonality remains the same. Good candidate for an HT setup, when you think about it. I've just been so focused on the music side, that hasn't really been my concern.

Have a great weekend!

~Jon

[Paul H]

Now that I've had them running for a week ..

I'm very impressed and happy. After running the speakers hard and long all last weekend they loosened up and the bass filled in just a little more.

I found the lower end still a little light though, and last night removed a little stuffing from behind the mids - voila!

My goals were
1) to build a two main ported speakers that were full range for music. I don't usually listen at really loud levels, and I didn't want to have to dial in the sub for music listenening - I never seem to be able to get it just the way I want it.
2) to add a sealed centre with the same drivers and use all three as the front channels for home theatre, with a sub. The crossover frequencies and volume matching of the sub is not nearly as critical to me for HT.

The ported mains achieve their goals nicely. The bass is strong and tight, imaging and sound field is terrific, vocals, piano, guitar - all sound superb.

I pick up a Yamaha RX-V3300 receiver a 5-6 months ago - between these speakers and this receiver I think the receiver's the weak link. Maybe Santa's bringing Bryston gear this year

One thing these speakers shouldn't do - play real loud HT LFE. I had LOTR on yesterday playing the opening part of the first movie loud (right around reference volume) and I had accidentally left the sub off and the speakers on main. They actually sounded OK, but when I looked up and noticed them they looked ready to fly across the room - which probably isn't good for a speaker with a 1/4" Xmax. ops:

Paul

[JonMarsh]

which probably isn't good for a speaker with a 1/4" Xmax. ops:

Paul

Uh, well, yeah, those suckers tuned that low will really TRY to do LFE at high levels, but there's just so much an 8" woofer with 5 mm Xmax has to give...

But I'd imagine theyr'e pretty nice on music!

These tend to break in the same way as Avalons, IME; expect their best after about 200 hours. My "lowly" single driver two ways didn't seem to reach their final level for a few months. That's more an indication of how much time I don't have to listen to music; OTOH, I do that a lot more than video- don't even have cable. Just DVD.

Happy listening, Paul!

~Jon

[Al Garay]

Congrats Paul,

Instead of Bryston, why don't you consider building AKSA amps? They are excellent sounding kits from: http://www.aksaonline.com/welcome.htm

Bryston are well made and have excellent warranty. If you like Naim and Linn amps, you will like AKSA. Check their forum in audiocircle.com and see if there is someone near you that you can audition.

Here is a testimonial from the AKSA website:

John Banas, North Carolina, USA - January 2004

Both AKSA amps are now up and running! So far they sound fantastic after just a few minutes of running in. I have used a lot of high end gear like ARC 100MKII, BATVK200 & VK60, Conrad, Hybrids, ASL, and the list goes on. I must say that the AKSA is one of the best I have heard. Smooth and detailed without any solid state glare. Soundstage to die for. My next project will be to build either two more 55 W stereo amps or one 100 W stereo amp to run the base of the Orion dual bass drivers.


Al

[Paul H]

I just noticed Bing asking about MTM's and thought this thread might be useful. Also I remembered that I intended to post a pic or two on my completed speakers. I still haven't applied a finish for the best of all reasons -because I'm enjoying them and don't want to unhook them.

Speakers shown are MTM M8n's/Vifa XT25's ported mains and sealed centre. There is also a new 214 litre (also unfinished) tempest sub in the corner.










Paul

[JonMarsh]

Looks mighty nice, Paul. Still, when/if you do get around to finishing them up, I'll be curious to see them!

Of course, given my unfinished M8ta's, I know where you're coming from. If all goes according to plan (famous last words), I'll be doing the veneering on them the 2nd week of December (full week, that is- first full week I'm "on the road again", to quote Willie Nelson).

Do enjoy!

~Jon

[Bing Fung]

Hey Paul,

Thanks for bringing this thread back :yesnod: I had read it the other day actually and was going to post in it asking how they were working out....

They look very nice, and you certainly have build yourself a customized set. How are they sounding for you?

[Paul H]

I've posted a few comments above on how they sound, but in a word - sweet.

Also as I believe I've previously noted, these don't and won't do pounding bass, due to excursion limitations of the M8n. They do a fine job with music by themselves (without a sub) at my normal listening levels.

If you're looking for extremely loud rock speakers, these aren't the ones. For HT (with a sub), and various rock or jazz music running full-range speakers at eighty-something decibels these speakers are wonderful.

I've been visiting several audio shops this past year and have heard only one set of speakers that I would undoubtedly prefer over mine - I forget the brand/name but they were selling the pair for $25K Can.

I imagine if I built the Arvos .. hmmm ... do you think I could use the tower MTM's as surrounds? Would that be overkill, and would my wife not speak to me for a month for even thinking of building another set of mains? :wink:

Paul

[JonMarsh]

I imagine if I built the Arvos .. hmmm ... do you think I could use the tower MTM's as surrounds? Would that be overkill, and would my wife not speak to me for a month for even thinking of building another set of mains? :wink:

Paul

Well, I think they'd make great surrounds, as I'm one of those guys that thinks surrounds should be close to as capable as mains. Now, would it help if I wrote you a letter of reference to your wife and said it was all my fault, but that once she heard the results on her favorite music and movies, it would be worth while? I supply references from other women....


~Jon

[Paul H]

I dunno, do you think comments from the "irascible but efficacious" back-to-the-future mad scientist would help?

Paul

[JonMarsh]

Uh, yeah, Paul, you probably have a good point there.... :wink:

Maybe we could work on reverse psychology- I told you NOT to do it, so it must be a good idea? :B

~Jon

[Paul H]

OK, that might do it .. try it on myself first .. will NOT build more speakers .. will NOT build more speakers .. will NOT build more speakers ...

Paul

[Hank]

Paul: Looking good! When you veneer/finish them, please post.
As for the note from Jon, let's give Paul a note from the world's premier speaker VALUE forum for people with the skill to build speakers that outperform commercial rivals for 1/10th the cost (that should impress the Ms.). We'll all sign the note, with no accompanying sigs or pics. Surely the weight of all this knowledge will sway Paul's wife

[Bing Fung]

Paul, I can't get over the dominating presence those speakers of yours have :T

I'm really warming up to the HiVi drivers..

So how much cross over work/changes are required to use the M8A in a MTM config with the S9800 Scan speak tweeters? Is that still a viable option?

Would the Swan 6.1's sound simular to these? I ask as they look to be the same drivers, and Pauls cabinents look simular, with exception to the mid driver and the tweeter on top.

[Daryl Furkalo]

So how much cross over work/changes are required to use the M8A in a MTM config with the S9800 Scan speak tweeters? Is that still a viable option?

The LCR LF zobel with the D2904 is 68uF + 2.0 mH (can be high DCR) + 5 ohms net. By 5 ohms net, I mean that the DCR of the 1.8 MH inductor plus the resistor should equal 5 ohms. Most likely you can buy a 1.8 MH air core inductor with about a 1 ohm DCR, and add 4 ohms in series. For example, the 2.0 MH "standard Inductor" line at PE is 1.07 ohms.

Bing, the above is the information Jon gave me for substituting the SS9800 for the Xt25 in the MTM crossover. I am going start building my crossovers soon.

[ThomasW]

So how much cross over work/changes are required to use the M8A in a MTM config with the S9800 Scan speak tweeters? Is that still a viable option?

Not a big deal, just use the existing XO design for the tweeter section of the Arvo ........ :T

[Bing Fung]

The LCR LF zobel with the D2904 is 68uF + 2.0 mH (can be high DCR) + 5 ohms net. By 5 ohms net, I mean that the DCR of the 1.8 MH inductor plus the resistor should equal 5 ohms. Most likely you can buy a 1.8 MH air core inductor with about a 1 ohm DCR, and add 4 ohms in series. For example, the 2.0 MH "standard Inductor" line at PE is 1.07 ohms.

Uhhm, OK... :scratchhead: :??


Thanks on the cross overs guys :T

So where can I find a parts list for the XO's?

What is the advantages of the off axis tweeter in the MTM array? What would happen if it was placed on axis? Or is that not possible due to the speaker distance/placement requirements?

How would the speaker sound in a TMM arrangement?

[Paul H]

Bing,

I'll PM you some files when I get home. There are some pictures of completed crossovers posted above by me in this thread. Note that I chose to build low and high pass together on one board with a 'common ground'; the schematics illustrate separate boards.

The tweeter is offset to allow the M8's to have an 11 1/2 inch centre-centre spacing, maximum suggested for the 1250 hz crossover.

The 'masters' can jump in here and let me know if I've learned something in the last few months or not, but I believe using a TMM would push the tweeter-to-lower-woofer distance beyond the above maximum recommended spacing and introduce comb filtering.

Paul

[JonMarsh]

Paul's on the money, here; an inline TMM would skew the radiation pattern, because of the center to center difference between the tweeter and the further woofer. IDEALLY, one would prefer that the outer edge of the midwoofer to the tweeter not be outside the distance boundary.

As you notice, we don't recommend a conventional MTM with the tweeter in the middle, because it would move the LF sources even further apart and narrow the radiation pattern in the crossover region.

To do an MMT at 1200 Hz would require using a modified crossover design, a 2.5 way, in which the farther woofer is rolled off in the baffle step pattern plus, and the response on the nearer woofer would be fairly close to flat, with out BSC, up to the crossover point, Bing.

Now, if you really want this, it can be designed, but it would increase the component count and cost in the crossover by about 40%. Just so you're warned....


~Jon

[Dotay]

Assuming the crossover is designed correctly would there be any difference in sound between an MTM and a TMM configuration? If there is a sound difference how would it be characterized?

[Andrew Pratt]

Would the Swan 6.1's sound simular to these? I ask as they look to be the same drivers, and Pauls cabinents look simular, with exception to the mid driver and the tweeter on top.

Bing a guy local to me owns the Swans and his comments were that my M8a's sound very similar to his Swans as far as over all tone etc. If you wanted to go full HT buying the swan surrounds might be one way to go if time becomes an issue etc.

How much of a change is there in the XO if I were to add another pair of M8a's to my current 2 way design? I'm considering buying two M8n's to put in the two centre speakers and using the M8a's from those in the mains as an MTM. It would mean a rebuild again for the fronts though which I'm not ready to commit to.

[Daryl Furkalo]

How much of a change is there in the XO if I were to add another pair of M8a's to my current 2 way design? I'm considering buying two M8n's to put in the two centre speakers and using the M8a's from those in the mains as an MTM. It would mean a rebuild again for the fronts though which I'm not ready to commit to.

The XO block diagrams are in the first post of this thread. The change to the MTM also needs a 4" port.

[ThomasW]

between an MTM and a TMM configuration? If there is a sound difference how would it be characterized?

They have different dispersion (lobing) patterns. MTM's give a more even spread on the horizontal axis.

There's a raging debate as to which is "better". A google search will plug you into the debate.

How much of a change is there in the XO if I were to add another pair of M8a's to my current 2 way design?

Basically doing that means doubling the values of all the caps and cutting the inductor values in 1/2.

[JonMarsh]

They have different dispersion (lobing) patterns. MTM's give a more even spread on the horizontal axis.

There's a raging debate as to which is "better". A google search will plug you into the debate.

Basically doing that means doubling the values of all the caps and cutting the inductor values in 1/2.

But that's just for the LF crossover. Another way to look at it, realistically, is you need to completely replace the LF portio of the crossover.

Part of the debate on MMT versus MTM stems, IMO, from the fact that most MTM designs are significantly flawed, as regards the driver array spacing versus crossover frequency. I think if you do that part right, then the things which the MMT guys don't like about MTM's go away. Let's face it, the MTM crossover IS much simpler, and easier to optimize. But for conventional approaches and crossover frequencies, it's a problem- especially when used in the classic center channel lay down mode. Then it's really messed up.

The only network types to use (IMO, based on polar dispersion) for a laydown MTM is either a 3rd order butterworth, if the drivers can handle it at a sufficienctly low frequency (unlikely) or a six order cauer-elliptical. Guess which one I use....


~Jon

[Bing Fung]

Thanks Paul, looking forward to the info..

Man, it's amazing what a guy can learn around here..... 8O

I was planning on building the centre as a MTM laydown (if I was to go this route), with a smaller overall size. So because the dispersion pattern is different once the speaker is layed horizontial, does that mean I have to build a different cross over for the centre speaker?

I would really prefer the mains to be a TMM config as a 2.5 way, for no other reason other than "wanting". I have always wanted to own a true 3 way speaker, but it seems 2 ways or 2.5 (my current speakers) are all I ever end up with :scratchhead:

Jon when you say 40% increase in costs of the XO's in a TMM array, how much are we talking about here? I have not calculated the XO component cost yet as I don't know what is required. The driver costs I have :T


Andrew, thats good to hear about the Swans, which model does he have? The 6.1 are nice looking units for a reasonable cost. Not as reasonable as a DIY, but they replicate closely to what I would like in a speaker design, now if only I could build them myself.

[ThomasW]

The XO for the horizontal center is the same as the vertical orientation.

It's was designed that way LONG ago, when Tibor built his set.

[Dennis H]

We talked about those Swans 6.1s in a thread ages ago. They are worth the price just for the HiVi woofers and the beautiful cabinets, especially if you buy them used. The midrange and tweeter aren't so great but you could replace them with higher quality components, rework the crossovers, and have a world-class speaker.

[JonMarsh]

I was planning on building the centre as a MTM laydown (if I was to go this route), with a smaller overall size. So because the dispersion pattern is different once the speaker is layed horizontial, does that mean I have to build a different cross over for the centre speaker?

I would really prefer the mains to be a TMM config as a 2.5 way, for no other reason other than "wanting". I have always wanted to own a true 3 way speaker, but it seems 2 ways or 2.5 (my current speakers) are all I ever end up with :scratchhead:

Jon when you say 40% increase in costs of the XO's in a TMM array, how much are we talking about here? I have not calculated the XO component cost yet as I don't know what is required. The driver costs I have :T


Andrew, thats good to hear about the Swans, which model does he have? The 6.1 are nice looking units for a reasonable cost. Not as reasonable as a DIY, but they replicate closely to what I would like in a speaker design, now if only I could build them myself.

Only with the right crossover should you consider a laydowm MTM. The "Standard" M8 series crossover is an 8th order transfer function, but that's not hard to modify. That's what they make good ole LspCAD for.

The reason the crossover costs go up so much for an 1.5 way MMT is that you're basically doing two different low frequency crossovers- they share nothing in common, if you want to be able to optimize each driver accurately. I've seena few folks try to combine parts fo the network, but that usually winds up a bit of a mess. So, instead of two inductors, and three caps, plus R-C zobel, you have four inductors, three caps in one crossover, two in the other, and two R-C zobels. Since you're feeding the woofers individually, in order to make different transfer functions, they're seeing an 8 ohm load, which means you have higher value inductors than for a 4 ohm MTM; this increases cost compared with the MTM. I'm not saying that's bad or not doable, but it has to be taken into account.

To price out the crossover, you can get most of the standard parts at PE (solen caps, solen inductors), and you can save some money on caps by using the surplus GE polypropylene caps which Madisound carries, though it's a little more work, because you have to parallel values to make up the larger ones. The standard two way or MTM crossovers have close to $200 of parts.

Regards,

Jon

[AndrewM]

Jon when you say 40% increase in costs of the XO's in a TMM array, how much are we talking about here? I have not calculated the XO component cost yet as I don't know what is required.

I've priced it all out, and here's the breakdown for a single speaker x-over;
X-overs using all Solen parts with Mills resistors priced from PE = $186.82
X-overs using Solen parts with Mills resistors but using the 10uF GE caps to get the big values = $84.69 + $33 in GE caps (assuming you are buying 110 GE caps for 3 speakers) total of = $117.69

I have a better spreadsheet at home that compares buying the x-over components from various vendors (madisound, Northcreek-YIKES!!!, Solen, etc), but basically going straight to PE would probably be easiest, except perhaps to make use of the discounted GE caps (but note the extra shipping charges will eat into the savings, so to you it may or may not be worth the extra hassle). I've also priced out going with "cheaper" components such as Dayton caps, Jantzen coils, no-name resistors, which does knock the price down some, but I think you'll compromise a bit to much on the specs (for instance a .68mH instead of a .7mH inductor all with their own +/-10% range, all 15ga instead of 14ga, the DCR is all out of whack as well), and as mentioned I priced it out with ULTRA high end components (8uF cap goes from $4 to $40!!), but ruled that out pretty quickly.

Just in x-over parts and drivers for 3 speakers here is the price breakdown;
PE-solen/GE Mix = $836.24
PE-solen Only = $1032.63

You'll need to add things like binding posts, internal cabling, wood, tools, etc all to that as well.

[JonMarsh]

Thanks for tossing the details out, Andrew!

Now, for an MMT, just take it up about another $80.

Oh, and if you use the Scanspeak tweeters, and want to tweak up the crossover a bit, the film and foil crossover caps mods for the tweeter are about $160.

Yeah, it does seem to get carried away after a point.

~Jon

[AndrewM]

Here's a question I had, what would you say the pluses and minuses of the M8ta vs the M8n MTM would be?

Basically as noted in another thread I'm looking to make another upgrade, now I'm about 50/50 with HT and Music (although I'm much more critical of music), the MTM version looks good (and I've spent quite a lot of time researching the various costs), but the enclosure for it is rather large, even a sealed system with a low(er) Q can easily push into the 85-100l range, a vented MTM system just isn't that feasible.

So for me I'm not interested in ear bleeding SPL levels, I'm much more of a quality over quantity kind of guy. I'm not very good at describing what I hear at a very fine detail, but there is just a "difference" when I listen to a good high end speaker system, even at low/moderate volumes. Everything is just there (from say 80Hz on up).

So are there any pro's/con's between the two pair?

I'll shoot you a PM with my email address as I believe you mentioned having some information lined up with the M8ta.

Andrew