M8N based designs, which one?

[Jam_Master_J]

HI guys
I'm really intriqued by some the M8N/A designs I've seen floating around here. I'm looking for something good for a college dorm room where my full 5.1 rig is too large(and isn't the best for 2 channel music). Up to this point I was fully ready to build a 75 L Sealed DPL 12/ Adire HE 10.1 combo. However, these m8n designs look great.

I'm not sure, however, which m8 design to go with. I do like a fair serving of bass(not a basshead, I like clean, tight and extended though) so I was wondering what set I should build. Basically I've got a few options I was thinking about:

1)M8 single woofer, sealed design + sealed DPL12. The key benefit I see here is a relatively low cost and a small, bookshelf type speaker.

2) MTM -sealed. Medium sized and more expensive. Should have a bit more punch though. I'd probably get a DPL 12 with it too once budget permits, but not sure how well it does without a sub.

3) MTM - ported. Medium-large size, most expensive. Plenty 'o bass I'm sure. Probably wouldn't bother with a sub.

4) The last option was my original plan, DPL 12 and Adire HE 10.1s.


I'm not really sure which of these options are best. I listen to alot of female vocalists(which I hear sound great on the m8 designs). But I also hear that the HEs are good for metal(which I also like) because of the lively, efficient design. The HE 10.1s would be cheapest and simplest since it is a kit too.

If the only benefit to the MTM designs is the bass, I'll probably just get the small sealed design and pair it with a sub, but if other benefits are realized with the MTMs I may consider the extra cost.

Thanks,
JMJ

[ThomasW]

It's an apples vs oranges comparison between the M8 designs and the Adire HE10.1.

The MTM designs were created primarily for larger rooms and people using them for HT. IOW, they are a higher output system. They have pretty good bass but do benefit from a sub.

In a smaller room, and augmented by a sub, the TM version should be fine.

But with a moniker like yours, I suggest the ported MTM version..... :wink:

[JonMarsh]

Either the MT or the MTM can be tuned for extended bass output in the rise size ported enclosure. The MTM is usually recommended for HT use or those wanting louder playback with still reasonably low distortion. The straight MT can be built in various ways, from a small sealed box, a moderate size (48L) ported box (as published in the AudioXpress articles in 2003)

http://audioworx.virtualave.net/M8Stand2SS.jpg

or in a larger ported box with bass down to the mid 20's (the M8ta).





The M8a driver is available again also, from PE, and the price is a bit lower than previously, so it may be even a better value if you prefer cast frames than the M8n.

Since there's no getting around Hoffman's iron law, bass extension comes at the price of enclosure size or power. The optimum bass extension, such as with the M8ta, requires about 68 liter per driver. The "wide range" MTM's have been built with 120-130 liter internal volume cabinets.

There are several threads here detailing different aproaches to doing MTMs, and the MTM crossover is linked from the Klone-Audio site. Take the link to the AudioWorx site, then check the projects list.

The original design was done around the Vifa XT and SS9800, which have very similar impedance curves, sensitivity, and FR between 1 kHz and 20 kHz; enough that you can drop in one or the other. It looks like their may be a third candidate with higher spl capability in the upcoming Dayton RS28a 28 mm aluminum dome tweeter made by Usher for Parts Express. This tweeter is very low distortion, quite flat and smooth in FR, and again has an impedance curve (net Fs and noiminal 3-1/2 to 4 ohm impedance) which looks quite compatible with the original design at a very modest price increase over the Vifa XT. In a few weeks I hope to try a set out in one pair of the original M8 bookshelfs; it's mechanically compatible, too, as regards faceplate diameter and holes.





Occasionally we get lucky...


Regarding your subwoofer choice, the DPL12 is a very good driver for a sealed box sub; very good distortion performance from 50 Hz on down. The TC Sounds TC2+, available from OAudio, priced similarly, has similarly good LF non-linear distortion, but less distortion in the range from 60 Hz to 200 Hz. You should check it out, too, before making your final purchase decsion.

~Jon

[Captain Cojo]

M8a MTM or Modula

Jon,
Given that the RS drivers weren't around at the time your M8a design came out, what are your impressions comparing the 2 designs now (for a large room). Perhaps you could compare them to the Arvo as well? Some questions I would have:
1. Does the M8a have more "punch" than the Arvo, because of the open baffle?

[Captain Cojo]

continued..

2. I would assume that the Arvos would be much more "enveloping"-but how would they integrate with side,rear and center boxes using the same drivers (M8a) for HT, or would a dipole setup be better?
3. Same question , pairing the Modula designs with the Arvo-timbre problems?

Thank you so much for all the time, effort, and patience that you and your compadres bring to this site. I've lurked for 18 months, and have been accused of being addicted to this site.....

[ThomasW]

The Arvo with it's 2-12" woofers has more 'punch' than either the TM or MTM box designs. As with any dipole, one gets the illusion of the room disappearing.

Closed box 'effects' speakers using the same drivers, will integrate fine with the dipole mains. Open baffle effects will sound good too, but are a bit difficult to place unless the room is big. By changing the baffle step compensation, one can wall mount either the box TM or MTM designs. I have a small box M8a-MKIII (different tweeter) wall mounted in my bedroom, they sound very good.

In the late spring or early summer there will be a dipole center that matches the Arvo mains.

If you stay with metal cone woofers, identical tweeters and similar XO topology, it's pretty easy to 'timbre' match systems using different brands of woofers.

[JonMarsh]

The Arvo project was intended for music playback, at a high quality sound level with relatively minimal room interaction when properly setup. There's things that dipole speakers do in that configuration that even well designed box speakers like Avalons, with placement such as they or Geroge Cardas recommend, can't seem to replicate.

I have listened to the Arvo's a couple of times with HT material, and I really like the way they sound- works quite well with a processor that supports phantom center- a great deal of depth and presense, and a larger sound stage than it seems is easy to achieve with box speakers for HT.

BUT, the size and positioning requiements make them relatively impractical for a lot of folks HT setups. That's part of why I split what used to be a single setup in two, because I'd rather have the music part optimized for that, and I can live with some shortcomings (if they're minor) in the sound department for HT, considering the space issues (I have NEC CRT front projection setup). If I had a much larger room, I'd use something like the Arvo's instead for HT.

OTOH, dipoles have a disadvantage as regards sheer output in the low frequency registers, and realistically it takes two long throw dipole 12s to roughly equal the bass output of a good long throw sealed 10. So, there's definitely a cost premium for going dipole.

Regarding your questions, ideally, two equally flat speakers with similar transient response should have the same characteristic quality in the mid to low bass (punch?). The reality is that most box speakers are placed too close to the wall, giving them some extra bass lift, and many listeners find that euphonic, espeically for the way a lot of rock albums are mixed. I have many friends that prefer their bass to depart from strict reality in a somewhat rubenesque manner.

Now, if by "punch" you meant the ability to reproduce the LF impact with all the upper harmonics intact and in proportion to the original sound, IMO the Arvo has a clear advantage, especially as the mids from 200 Hz on up are reproduced by seperate transducers than the lower bass, and the IM is dramatically reduced compared with a conventional two way. ThomasW experimented with a set of what we called "Arvo Ultras" when he didnt' have an IB subwoofer in his familry room, using four 12's per side; in no sense did that system lack "punch", even at fairly loud playback levels. In fact, it's the kind of system that you have to be careful about trying to assess subjectively how loud it is, because the normal cues of rising distortion at 100 dB were pretty much absetn, just like the X1 SLAMM clones (which we during initial testing we kept cranking up and up, enjoying them quite a bit, until realizing we were approaching 110 dB on peaks, and the old ears were staring to ring.

Regarding your second question, I'm not sure enveloping is the right word. As I mention above, they reproduce whatever sound field is on the film sound track very well- if there's depth and ambient recorded, they reproduce that, without having to recreate it by ambience in your own room. I tend to prefer a setup like Widescreen magazine uses, with four speakers of identical signature in quadrature; and a phantom center. One speaker I'd consider for rears if using dioples in the front (and I had the room) was Magnepan MMG's. Very compatible sonic signture, and works pretty well at ThomasW's, even though his space is a little limited for setting them up optimally.

3. The modula's, like the Arvo, have been designed for a very uniform power response with regards to frequency- unlike a lot of commercial speakers. Even 7" midwoofers have dispersion issues above 1500 Hz, so the typical 2.5 kHz to 3 kHz crossover in commercial speakers is at fault for a significant part of the signature issues- signature is NOT just the on axis response, but the total power response summed from on axis, 10, 15, 25, 30, and even 45 degrees off axis. The Arvo's are derived from the original M8 bookshelf design, having a roughly 1200 Hz crossover using 48 dB/octave slopes, so the response even measured to 45 degrees off axis is almost dead flat thorugh the crossover region. That's very unusual for a 6-1/2" two way, and unheard of for an 8" two way. But it's a key factor in having a "neutral" signature and one which can be readily matched by other speakers. Otherwise, you're just trying to match different types of coloration.

Look at these response plots taken on the M8 bookshelf at up to 45 degrees off axis. You can't hardly detect the crossover point from these sweeps; this is not the case with most conventional designs; just look at the speaker tests in Sterephile.



The Modula IV-1 uses a very similar design, but dual 7" drivers in a narrow cabinet, not quite as much low end, but very similar crossover concept and crossover frequency. As a result, the power response will be quite similar, and hence, the overall "signature".

The upper end of the Arvo is literally just an MTM M8, but with the LF demands taken off the midwoofers. This does open up the sound at higher playback levels. Additionally, the dipole construction means that there isn't stuff radiated in the lower frequencies at 90 off axis, so the tonal balance of the power response is even more consistent with the front axial response. Obviously, it comes at at cost in size, complexity, and cost.

I designed the Modula MTM's because of requests from several friends, and also to use in my own HT area. The performance target was speakers like the BESL Series 5 MTM. The cost target was as low as coudl be achieved without sacrificing the performance target significantly. This narrowed things down to a very small range of drivers to consder- the number two choice for the midwoofer, for example, costs twice as much as the RS180, for similar SPL and nonlinear distortion, but slightly better linear distortion up to 1800 Hz. Since I planned a 1200-1400 Hz crossover, the advantage of the Peerless 850439 was a moot point, against it's 2X higher price. Likewise, the 27TDFC was selected because of it's excellent distortion performance, (compared even with the Millenium Excel), and acceptable frequency response that could be voiced with a little effort to the desired characteristic.

They won't pull the same kind of disappearing act that the dipoles do, but then nothing but a dipole will. But they're very good performers relative to what they cost to build. One could do much, much worse.

Bottom line, it's all about tradeoffs, and I do different projects because no one set of tradeoffs is the right one for all circumstances.

~Jon

[Paul H]

Justin,

I've built the ported M8n's and have a sealed M8n for a centre, all with Vifa XT25 tweeters. My net volumes are 125l for the ported and 70l for the sealed.
I'm very happy with these speakers, particularly for female vocals and guitar, as the clarity of the M8's is excellent.

The ported full size version is worth building (versus the sealed) if you have the space, don't mind the weight (think ~180 lbs each) and want full bass extension at moderate volumes (think Sunday morning levels at the dorm rather than Saturday night ).

If you want full bass extension at loud volumes these speakers definitely benefit from a sub - and if you always run a sub, the smaller sealed version of the M8 MTM may be fine. I run my ported speakers full-range for typical music listening but always kick on the sub for movies, or brief intervals of too-loud music.

If you decide to go ahead with these, hold off until Jon has experimented with the new tweeter from Dayton - it may be a worthwhile improvement.

Paul

[Captain Cojo]

Perhaps "punch" is the wrong descripter. Pop, snap, resonance, richness,guttoral are more appropriate terms related to my minds eye examples-pop and snap of a snare drum or timbales,the resonance of a string bass, or the richness and plain ol" guttoral sound that a Hammond B-3 and a good leslie can produce in the hands of the right artist. It drives me nuts to hear systems that "muddle" or "mute" these defining sounds to mere background greys,loosing the wonderful dynamics that would be heard in a live performance.
I presently have a pair of highly modded Dahlquist DQ-10s that are going to be replaced with the Arvo as soon as you are finished optimizing. The 10s strong point has always been imaging due to the open-baffel 5-way design. The mid-bass driver is backed with 1/2" felt to control the xmax-if removed the driver will distort badly at volume. The problem was never sound quality in the mids and highs-it had a .92 cuft. box for the 10" Advent woofer that was anemic for most of us 70s rockers.I probably went through 100+ 3a. fuses in my youth trying to get some decent SPL out of em.Bought some cerwin-vegas to give me all I wanted-except the mids sounded sooo muffled.Now, in my old age, Im hoping that these Arvos of yours will do the trick.

[JonMarsh]

As an ex musician that used to own a B3 Hammond, I certainly understand part of what you're getting at there- part of the problem is the difficulty of capturing some instruments in recordings adequately- then there is the micro and macro dynamics of the speakers and the reproduction of the original sound space.

For me, what drives me to dipoles for my main music listening is that they're the closest thing to sounding like good headphones- a very difficult feat for speakers to pull off or even get close to. It's the inherent dipole radiation characteristic which is behind a lot of the classic appeal of electrostatics like the Quads and Acoustats, the Levinson HQD system with stacked Quad 57's and Decca ribbon tweeters, Magneplanars, etc.

It was reverse engineering the Legacy Whispers with ThomasW that really put me on the path to dipole dynamic systems using "traditional" drivers.

Funny you should mention the DQ 10's; I can remember driving a pair of them with a Luman 6000 (300 watts per channel) in order to get the SPL I wanted... too much midband distortion that way, though.


~Jon

[Jam_Master_J]

Thanks for all the responses guys.

Thomas,
You mentioned the HE 10.1s and M8 designs being very different. Do you mean this in regards to quality(The HE 10.1s are only $400 CAD for the kit) while the m8 designs going to be about double that I think, or do you mean sonic signature?

One of the key benefits I see to the HE 10.1s was that they are well suited for near-field listening, which is most of what I do. Plus, I'd imagine that lively type sound would sound awesome with some of the guitar music I listen to(like Joe Satriani).

Just as a reference I really like the sound of Grado headphones, I own SR-325s. I realize that speakers and headphones are very different but I figured that would help with a reference to my general sound preferences. I really like the forward, but sweet sounding mid-range on Grados, it really sounds great with female vocals and guitars.

If I decide to go all out and build the M8 MTM set, I'll probably go ported. I can always plug the port if I don't like it.

[Jam_Master_J]

Regarding your subwoofer choice, the DPL12 is a very good driver for a sealed box sub; very good distortion performance from 50 Hz on down. The TC Sounds TC2+, available from OAudio, priced similarly, has similarly good LF non-linear distortion, but less distortion in the range from 60 Hz to 200 Hz. You should check it out, too, before making your final purchase decsion.

Thanks,
I've been looking at the DPL 12 for a while now. I'd imagine the sub 50Hz performance is most important since I could get away with crossing over to any of the mentioned designs near that range I think. Maybe like a 65 Hz crossover for the sealed designs and perhaps a 50Hz crossover ported?

[ThomasW]

do you mean sonic signature?

Yes.

The metal coned drivers used in the MTM and Arvo designs are extremely transparent.

As Jon recommended it would be worth your time to take a serious look at the TC-Sound TC2+ from www.oaudio.com. My Arvo prototypes originally contained the DPL12's, they now contain TC2+, hint, hint, hint .....

[Jam_Master_J]

Thanks, those TC2+ look nice. I really like the look of no protuding dust cap.

I think I'm gonna go ahead and build the MTM ported M8 design. Should cost me about $1000 CAD total, which is a bit pricey but I'm sure they'll serve me nicely. I think I'll order the stuff for the crossovers and build the cabinet first, then I'll order the drivers when I get a bit more cash flow.

By the way, would it be a bad choice to make the MTM design front porting? I haven't seen any done like that, and I've seen mentions of port noise to explain that. Front porting is more aesthetically pleasing(to me anyway) but if the noise will be too much, I'll port to the back.

As well, in Circuit Analysis class(I'm a second year electrical engineer) today we just started filters. Hopefully these crossovers will make more sense now.

[Paul H]

As well, in Circuit Analysis class(I'm a second year electrical engineer) today we just started filters. Hopefully these crossovers will make more sense now.

Maybe it'll be the circuit analysis classes that will make more sense

Paul

[ThomasW]

Front porting is fine, just keep the port away from the tweeter...

[Jam_Master_J]

Sounds good, I'll probably put the port in close to the bottom of the baffle.

[JonMarsh]

A port near the bottom of the cabinet would be best, near the floor; exiting from the bottom, with the cabinet on pedastal/spike combo (like the M8ta) would be even better.

[cjd]

Why not a TL then?

Unless I've screwed something up in running the numbers through Martin King's mathcad sheets, a TL for the RS225 would be something like this (F3 ~30Hz).



Rather big for a TM IMHO, but hey.

C

[JonMarsh]

Hey, that's not THAT much bigger than an M8ta, which I found out could sort of be modeled as an MLTQWT or whatever that mix of letters is Martin uses to describe a quarter wave box with a port at one end...

'Course, this guy wants to do an MTM... TWO 8" drivers. That would be a bit bigger....

[cjd]

Well, some folks disagree with my numbers (and very possibly with good reason). I really need to use his "Sections" worksheet instead of the "offset driver" sheet.

MTM would indeed be big - twice as big. Since all measurements are a factor of Sd. Nice and simple that way though!

I don't know if the M8 versions would work in a smaller TL or not - haven't run that through.

C

[Jam_Master_J]

Well, i guess to get a start I'll order about 100 of those 10uF caps from Madisound. For some of the values such as 68uF would it be ok to use 7 10uF caps, especcially since the caps will more often be below the rating than above?

[JonMarsh]

Well, i guess to get a start I'll order about 100 of those 10uF caps from Madisound. For some of the values such as 68uF would it be ok to use 7 10uF caps, especcially since the caps will more often be below the rating than above?

THat's probably reasonable. Maybe you'd consider getting an inexpensive hand held digital meter that includes capacitance measurement- we usually bridge measure caps and combine to get the closest values. For the tweeter cap values, accuracy is important, to a half microfarad. Same for cap across second woofer series inductor, which is the resonant notch.

[Jam_Master_J]

ok,
I'd imagine at least of the many meters in our circuits lab can measure capacitance. I'll see if I can borrow one.

[Jam_Master_J]

And I suppose I'll just buy some assorted smaller caps so I can get the exact values I need, should I just get some more GE ones while I'm getting all the 10uF ones?

[JonMarsh]

That would work, certainly wouldn't be cost prohibitive, though you might want to put together a Bill of Materials for your order that adds up to the current posted values, with a few extra. That would be "safest".

~Jon

[Jam_Master_J]

Thanks, yep that's what I did. Paul H was kind enough to lend me his price list so I went through and added up all the capacitors. I think 100 of the 10uF should ocver me, perhaps I'll get a few extras though.

[Paul H]

Thanks, yep that's what I did. Paul H was kind enough to lend me his price list so I went through and added up all the capacitors. I think 100 of the 10uF should ocver me, perhaps I'll get a few extras though.

I bought 150 + 20 spares for three of these speakers - I'm pretty sure I have 20 spares left over (they'll be used soon).

Paul

[Jam_Master_J]

Nice, so if you needed 150 for 3 speakers then 100 for 2 speakers seems in line.

Couple consruction questions here:

1)How do most people arrange their panels? I'm not sure if I'm wording this correctly but I mean like does your front panel cover the whole front area? ie, does your top piece sit behind the front panel or on top, likewise for the side panel(but behind rather than beside)?

That reads like a mess but hopefully someone knows what I mean, I'm sure any arrangement would work but is there a best way to do it?

2) Regarding ports, the port length I need is 12". Since the port will be visible I won't be using PVC like I did with my Tempest(plus it seems silly to spend about $1000 CAD and cheap out on the port). To set the port I use a center length of 12" correct, while the overall length will be longer since the rounded end pieces don't contribute to the tuning?

Thanks,
JMJ

[awkameraad]

Did anyone try the good old peerless wa10 tweeter together with the m8n/m8a?
I know 1 kHz x-over is a bit low, but I am planning to try anyway with digital and analog active filters.

[Jam_Master_J]

I just planned out all the cuts I need. I also arranged them in terms of how to cut them off sheets of MDF. Maybe, I'm doing something wrong but if I use double layered panels, I'm going to need about 3.5 sheets of MDF total. These things will weigh more than me I'd imagine (I weight 180lbs). Would it be a bad idea to go with only one layer of 3/4" MDF, even then they would still be fairly hefty. But if the difference is noticeable I'll splurge for the extra MDF, plus it'll make a good theft deterrent.

Oh BTW, I actually figured out my questions in the post 2 above this one, just a little digging was required.

[cjd]

Some of us like to work with 13 ply birch over MDF for many reasons, but weight being one of them.

Some folks also like to do a laminate of MDF and 13 ply birch.

The good birch isn't entirely cheap though, and isn't something you can usually pick up at your neighborhood home improvement store. Baltic or Apple ply usually, but sometimes other names I guess.

C

[JonMarsh]

Did anyone try the good old peerless wa10 tweeter together with the m8n/m8a?
I know 1 kHz x-over is a bit low, but I am planning to try anyway with digital and analog active filters.

The original M8a/M8n used a 1200 Hz crossover, but this would likely be too low; are you referring to the controlled directivity DT100 WA Peerless?

You might want to do some non-linear distortion measurements in the lower end to see how it holds up; you could do that with something as simple as TrueRTA in the 1/48th octave mode with a good sound card.

[Paul H]

I just planned out all the cuts I need. I also arranged them in terms of how to cut them off sheets of MDF. Maybe, I'm doing something wrong but if I use double layered panels, I'm going to need about 3.5 sheets of MDF total. These things will weigh more than me I'd imagine (I weight 180lbs). Would it be a bad idea to go with only one layer of 3/4" MDF, even then they would still be fairly hefty. But if the difference is noticeable I'll splurge for the extra MDF, plus it'll make a good theft deterrent.

Oh BTW, I actually figured out my questions in the post 2 above this one, just a little digging was required.

The experts on the forum here recommended to me last year to go with double layers, and I'm glad I did, for the reduced vibration.

Baltic birch is a lighter, stronger but somewhat more expensive alternative. It's available at Robert Bury's (a hardwood and sheet goods supply house in Burnside, Dartmouth).

Paul

[Jam_Master_J]

Sounds like the double MDF will be worth it. I don't know why, but I actually like the idea of having speakers that weigh 200lbs each.

[ThomasW]

3/4" BB ply isn't lightweight material. Grap a 60"X60" piece and go for a walk, see how far you get.... :wink:

[Paul H]

Thomas is very correct. My apologies if I gave anyone the idea that baltic birch is a lightweight material. It certainly feels somewhat lighter than mdf, but heavier than typical plywood - I've never checked actual densities.

Paul