M8ta - klone but wait...

[posix]

Ok, so M8ta looks like the Opus. I can't remember hearing them (I think I have but after eidolons you tend to forget other kit). So sonically M8ta probably is a world apart from eidolons but how would one go about creating a klone thereof? At least a visual klone (since etons alone cost in the region of $1.5k and the little accuton items aren't a lot cheaper either).

Also, how about active crossovers? What do people who work for Infineon technologies think of those in this context? Would they bring us close(r) to the 3d walk-through soundstaging of eidolons?

I'm all hung up on eidolons even though I may not have the room large enough for them and opus (or m8ta) would be more appropriate. But once you slapped one with an open palm and heard nothing but a slap akin to slapping the pavement (I picked up the pavement-comparison off here somewhere), not that I ever did slap the pavement but I imagine that's what it'd feel like, you develop feelings for 'em. The "I want this in my living room" kind of feelings. No wait, I did slap a pavement, on numerous occasions, when I was a kid, falling off my bicycle.

I've heard most of the "important" high-end kit out there (never heard those puppy thingies, though) and eidolons just put all of them to shame. Or maybe I was spoilt by listening to a pair hooked up to another pair - of premier 8s? ...which were hooked up to an ART? ...which was h...

[ThomasW]

The Opus is 3-way, the M8ta if anything is sort of a copy of the Classic Eclipse.

The person that works at Infineon choses to use passive XO's for his designs, even though he has ability to make active XO's

[Ten 99]

I haven't heard the Eidolons or anything else from Avalon. I do know that they have a solid reputation preceding them. I think it would be nice to have heard them to compare against some other speakers that I have heard. And trust me when I say I haven't heard many of the upper echelon speakers at all.

I'm going out on a limb here, but I expect that the M8ta speakers are getting you 95% to 98% of the Eidelons. I do know that drivers play a very important role in overall speaker implementation. I think that it's probably second or third on the big three overall contribution to the end product. Certainly the cross-over is the biggest concern, then next would be the drivers, followed third by the cabinet. Having the best drivers in the world won't make a difference at all if the cross-over isn't worth a flip. From what I can tell, this is where Jon's reputation is king. He knows how to make and tweak very good cross-overs. I don't think he overlooks the importance of drivers either. I think he does put a lot of time into the research and measurement of the drivers he would consider. Of course I think the drivers that he initially considers are based aroundt he parameters of the type of cross-overs he likes to write. It seems like he is all about getting the largest bang-for-the-buck quality that he can wring out of the setup. We are truly lucky to have him sharing his creations, and his knowledge with us. Sort of the old addage of Give a man a fish, feed him for a day. Teach a man to fish, you feed him for life.

[TacoD]

I can say that drivers make a difference! But I agree that a x-over is very important part, to get anywhere close to a good sounding loudspeaker.

I've experience with different type of materials (Excel, Eton, AT, Scanspeak, Seas) but every unit has its specific signature.

[posix]

The Opus is 3-way, the M8ta if anything is sort of a copy of the Classic Eclipse.

I was thinking visually - M8ta looks mostly like the Opus. Technically more like the Eclipse.

The person that works at Infineon choses to use passive XO's for his designs, even though he has ability to make active XO's

Which is strange, considering all the oppinions on the subject, don't you think?

[posix]

I may be sounding like a smartass here, but I'm not, I'm clueless, I only want to learn. :T

[ThomasW]

Ten,

If anything the drivers in the M8ta should be better than those in the original Eclipse. The speakers used in the Eclipse aren't terribly state of the art by todays standards. And the woofer in the Eclipse, had some performance issues even when it was a high-end design.

posix,

Which is strange, considering all the oppinions on the subject, don't you think?

Strange? Nope don't think it is....but everyone has their own opinion.

Since Jon was actually involved with the original Avalon designs (he was Charlie Hansens audio mentor), I'm sure that Jon has a pretty good grasp of where active XO's offer an advantage, and where they don't ....

Regarding Linkwitz's designs, frequently it's 'easier' and less of a technical challenge to create the needed circuits with active filters and active EQ. Sometimes however technical challenges are fun.

I think that most people would be hard pressed to tell if the M8ata were biamped or passive just from listening. Also these are designed to be DIY projects. And most DIYers don't have access to the tools and technology to create custom designed active XO's. Nor to they have the funds to buy multiple high-end power amps.

Regarding Rod Elliot, his designs aren't in the same league as those being discussed here. But all things being equal, a proper active XO can certainly make a speaker with a poorly designed passive XO sound better.

[JonMarsh]

Interesting discussion...

Interesting discussion, here- I was heavily involved in some domestic re-arranging and sorting and culling yesterday, never even looked at a PC after about 9 in the AM!


I think the best way to approach this is to provide a little info on my background in audio electronics, then some info regarding my last project for myself with an active crossover, then wrap up with my thoughts at present about active versus passive crossovers, where and when to use each, and what I perceive the tradeoffs to be... that way I'll be able to keep this down to a novella, instead of the audio equivalent of "War and Peace".


Background
First off, it's probably quite justifiable to say I'm more a wires and sparks kind of guy than a speaker designer- though the latter has been a long term hobby and avocation on and off since the late 60's. While I have designed pro audio gear in my day job years ago, and have done consulting design in audio electronics, I can't say the same for loudspeakers- it's just a hobby. Albeit, one seriously out of control.

At one time I was working with another guy on some designs which we intended to build commercially, but he died in an untimely fashion. Some of the ideas and concepts, and one of the prototypes, were passed on to Charles Hansen, one of the co-founders of Avalon Acoustics, and the chief designer and I believe CEO of Ayre Acoustics. (Charles worked for my part time when I had that pro-audio gig as chief designer, while he was a Physics student at CU). Charles has at time in the past introduced me to folks as the grandfather of Avalon, so you could say it's a little bit different situation when I build an Avalon Klone, perhaps, then when some other folks do- though the principle should be the same.

In the 90's I did a little bit of electronic design consulting- the most fun project being a amplifier design for a small company that wanted to break into the studio amplifier market, as well as high end reinforcement. Probably not a wise market choice on their part, but their main guy was driven more by passion and ego than anything else- Their desire was for a high power amplifier using primarily MOSFETs, especially the output stage, and with very low wideband output impedance, and a high level of control over difficult dynamic loudspeaker loads (read, difficult load curves in ported and horn loaded reproducers). By high power, we're talking 400 watts+ at 8 ohms un bridged, 1500 watts at eight ohms bridged, and stable with reactive two ohm loads, and with no loudspeaker decoupling network (the usual RC network used to provide capacitive load stability for amplifiers with feedback).

My approach to solving his request was not really hugely original- but it hit the targets for both measured performance and the sonics he was seeking in comparison to other designs, particularly some high power European monoblocks. The front end has a passiing similar to the front end of Bob Cordells' ultra low distortion MOSFET amplifier design published in an AES journal back in the 80's, but with some improvements to the front end differential gain stage and the output voltage amplifier, as well as throwing away the so called "feed forward error correction" circuitry, which reduced to it's basics was nothing more than a nested feedback loop around the MOSFET output stage (which was a single EF follower made with one pair of IR MOSFETs - fine for a 50 watt amplifier, but not expandable to higher output levels. The output stage which was realized used a class A MOSFET driver and high power MOSFET modules from England in an A/B output stage; the whole output stage was a compound amplifier, which is kind of tricky to stabilize under normal conditions, and without a decoupling network to isolate capacitive loads even more tricky; once I got that sorted out, though, the performance was really quite good, and with very modest levels of feedback achieved a low output impedance to beyond 30 kHz before the output impedance started rising appreciably. Part of what I learned in doing that project was passed on to Charles, who utilized some devices and concepts in first the V1 amplifier, then the V5 and V6.

Since then, I've been working on some of my own ideas for converting my Aragon amplifiers to non-loop feedback designs; I'm at my third generation of design iteration at this point, though since I'm doing so much with speakers lately, work is stopped for now on that. My poor Aragon 8002 has been the test bed for this effort; the only thing left in it from the Mondial factory is the chasis, heatsinks, and power switch.

I'm just providing this info by way of explaining that I do have a little background in audio electronics design, without going into too much detail.


X1-Klone biamped speaker system - an active example

I built my first active electronic crossover from scratch (including etching my own PCB's) in 1972; I've done quite a few designs since then, including a pro audio biquad filter based design, and some focussed more on high end performance issues, like a design I did for Thomas in the late 70's which he used with his Acoustats for years.

The X1 Klone was not a true clone/reverse engineering project, but rather a speaker I wanted to build incorporating the form factor and hopefully most of the performance of the Wilson Audio X1, but based on some drivers I had on hand (Audax Pro series) and some innovations with other driver choices and crossovers- including a partial active crossover.




The Audax 13" and 15" drivers had typical pro-sound sensitivity, but even lower Qts - how many drivers do you know of with a Qts under 0.2?

The LF alignment of the cabinet might not seem that usable at first - tuned to 22 Hz, there was almost a straight line 10 dB drop between 100 Hz and 24 Hz, due to the overdamped alignment. But in practice, with efficiency of 96 - 98 dB, this is easily compensated with a shelving EQ, and allows adjustment for a wide range of room conditions- including ones for which a nearly flat speaker would be over powering in the LF region due to boundary gain. This made the design with it's custom electronic crossover very flexible. LF EQ and BSC were implemented in the crossover, which was built to high standards- OPA627 op amps, AD615 video buffers as cable drivers within the feedback loop of the OPA627, premium Jensen balanced output transformers with bandwidth from the subterranean to AM radio (literally).

Here's a pic of the electronic crossover in development, with the top off...



The midwoofers used were Eton 370's, because they had lighter, stiffer cones than anything else I could find in the late nineties, and were cleaner up to 3 kHz than any other midwoofer I could find at that time- besides, it was kind of like keeping it in the family, ya know? :wink: The Wilson's reportedly (by Stereophile) used a custom Dynaudio (not the 3" voice coil jobbies, though), and were described as being a bit steely on the upper end at time, with material like piano.

The tweeter was the Focal TC120dx2, of course- in that regard, I had no desire at all to deviate from the Wilson approach.


At one time I considered writing a magazine article about this design, but instead, when Audiomatica announced their CLIO Grand Prix contest, I took my fledging write up, added a few bits and very minimal polish, and submitted it to them. That won me an upgrade to the full CLIO WIN standard, from my DOS CLIO Lite, as first place prize. The project is still posted here.

OK, you're probably wondering, if you've keep reading this long, what's the point? The point is, I have some experience doing customized electronic crossovers from scratch (circuitry and PCBs) and building the same to a fairly high construction standard. (completely isolated left and right channel supplies; complete regulation/bypass isolation for EVERY op-amp/buffer gain block; high grade capacitors for bypass, only polypropylene caps in signal path, precision ten turn pots for level set, ultra wideband transformers with high CMRR, etc, etc, yadda yadda gafweeb ad nauseum!


So, why did I ever build another pair of speakers since these?


These speakers did some things well, some things very, VERY well, and other things not at all satisfactorily, IMO. You wouldn't believe what the SACD's of Kenny Loggins greatest hits sounded like, or the soundstage and impact that "Gaia" from James Taylor Hourglass had... to say nothing of Lindsey Buckingham's solo albums, or Eric Johnson, or even (shudder!) the Titanic Soundtrack SACD...


Yep, you got it, I built the world's ultimate party speakers. No question about it! :B Well, apart from not being very small or portable... :rofl:


But, I was shooting for more than that... what went wrong?

Well, if you look at the behavior of the woofers and midwoofers, they're pretty good in terms of what was available in the 90's... but with the 2.2 kHz crossover I was using for the Eton 7's, there was a low level first cone mode about 1.8 kHz (like the Eton 8's have at 1.4 kHz- a dip, not a peak, but also an energy storage ridge). Also, Eton has made very good cones, but continues to this day to make rather indifferent motor assemblies, and this shows up in THD and IMD, at low frequencies, (below 100 Hz, and at frequencies above about 300Hz, where the VC inductance rises.

That's part of the story. But part of the story is that everything has a foot print- and while the electronic signature of my crossover design was fairly benign by standards at that time, it didn't hold up next to my passive preamp, or my experimental active preamps.

So, a point to consider is how the inherent component "signature" of a high quality active crossover compares with a high quality passive crossover. For low frequency crossovers, their can be some clear cost advantages to the former. Active crossovers, in addition to possible "signatures" from the reactive components, also have the active gain path and power supply to consider. Plus, you've got more interconnects, more amplifiers, more speaker cables, etc.

I'm just not sure that's the right approach- for a commercial product, I'm pretty sure it's usually not the right approach- unless highly integrated- and then it will be resisted for the "high end" market because of the lack of flexibility. Linn and Meridian pull that off for some very specialized markets, but few do.

My own experience suggests that particularly for something like a two way speaker, a good passive crossover can be implmentend with less of a signature and at lower cost than an active solution.

Even with a three way, after my experience with hybrid passive/active systems (which we did with Thomas's Arvo Part's, too), I'm still working on a full passive Arvo, excepting possibly an inline passive LF EQ. The current working version of that system (the full passive Arvo) does stuff with regards to imaging and that so called holographic floating in space thingie that the X1's could just hint at, in comparison. So, I think I'm going in the right direction.

Now, the Orion's do that quasi holographic thing, too- but when I think of all those opamps in the signal path, my skin crawls... it's just an emotional reaction, but after the effort I've spent on other parts of the system, it bothers me... (it's that old luddite in me coming out). I don't think it helps the highs or overall transparency. And trouble shooting a system like that when it gets a little flakey can be a major PITA. Just ask Thomas about his travails with this theater room system, which is all electronic crososvers.

The Arvo may be ultimately biamped to an IB sub, but the crossover to it will be a simple high pass buffer - no op amps, absolutely minimal components added above 60 Hz.

Component signatures

We live in an imperfect world; every component in our audio chain has some type of signature and effect; to some extent deltrious. It's just up to us to find the ones we can live with, that do minimum damage to the music. The following info is just provided for reference, to give context to my evaluations, if I say I think I prefer the footprint of a passive crossover (with good components ) over an active one with good components. And I recognize that my current systems have some unusual characteristics.

For instance, one of the arguments for active vs pasive crossover in the bass region is better damping factor, which is important if you put your driver in a box, and want to keep as much control over it as possible, so Qtc doesn't rise- extra series impedance (from inductor) raises the effective resistance and increases Qtc- usually a bad thing in a box type speaker. But what about a dipole? Hmmm, driver is free air, Qtc is quite low, because there's no enclosure air mass or compliance added to the driver, and in many cases you may want to RAISE the Qtc a little... different design rules and goals, huh? Gee, that's not fair, we changed the parameters for evaluation by changing the LF paradigm. But it also coincidentally reduced or removed one of the oft quoted advantages to active crossovers.


The basic standard by which active electronics should be judged is an A/B with straight bypass- and everything else being as clean and neutral as possible. It's very, VERY rare for the synergies due to the presence of electronics in the system to sound better than not having the electronics in the system- one of the rare times I can say I've heard that is comparing my passive preamp against an Ayre K5x preamp- I prefer the latter. So, occasionally, more is better than less- but it's the exception, in my experience.

Associated components- interconnects, speaker cables. This is a real can of worms to discuss, particularly on this board. Let's just say I have evaluated a lot of cables, pretty much price not an object- I have been a proponent of DIY in the past, and I think if you're on a tight budget, you can do well that way-

BUT, if you're gunning for reference quality, as much as I've tried, I haven't been able to avoid the inevitable. The really good stuff makes a difference. A difference you can hear even on things like DIY eight inch two way loudspeakers. Whether it's enough to justify the money is every person's decision. Ideally, interconnects and speaker cables should just get out of the way and let all the music through. They shouldn't be tonal equalizers, but in practice, they often are subtle ones. My current choice it what works best with my solid state amplifiication- Ayre signature interconnects (balanced), and Cardas Golden Reference speaker cables. The latter aren't strictly neutral (their Neutral Reference series probably are), but have a more resolving and palpable midrange presentation with high end solid state gear than the Neutral Reference series does- they work well with Ayre, Theta Digital, etc, whereas if I had a Sonic Frontiers tube monoblock, I'd probably go with the less expensive Neutral reference series. So sue me, my speaker cables cost more than any of the speakers I'm listening to right now... (OK, now you can cart me off to the funny farm).




Re M8ta and Avalon Klone


Just a few comments to the discussion regarding Avalon speakers and the M8ta.

The M8ta idea came into mind as a way to improve on the Eclipse and Arcus from Avalon. I'm very familiar with the Eclipses and the Ascent, and have heard the Eidolons on a couple of occasions. I haven't heard the Opus, but since it's in many ways a junior brother to the Eidolon, I expect it to be similar, except probably bass extension and definition.

There are three main design "rules" followed at Avalon:

1) Stiff, inert enclosure with minimal enclosure "talk", achieved with unusually thick front panels and careful bracing and sidewall construction

2) Use drivers only in the pistonic region

3) Design for a wide uniform power response, with as uniform off axis frequency response as possible.

Regulars here will find these concepts familiar... :W

There's a fairly well done review online at Sterephile which sums up the strengths and the weakness of the Eclipse. I've worked with similar 8/9" woofers from Eton; the 8-800 is typical, having a very stiff cone, but the first mode (impedance bobble and slight farfield dip) is at 1400 Hz, like other 8" Eton drivers. This necessitates Avalon's use of a 1 kHz crossover point with conventional crossover technologies; a 4th order L-R was used, which with the MB Quart tweeter roll off, results in a tweeter electrical roll off of about 12 dB/octave. This is pushing the MB quart a bit hard, and this shows up in the measured distortion.

Another problematic area for the Eclipse if you push it is the LF response. It's a nicely damped sealed box with Q of 0.5, which with correct room placement can make for a moderately extended smooth in room response. But, the 8"/9" Eton midwoofers only have about 3.5 mm of Xmax, so they're a little more limited in LF output level than drivers like the ScanSpeak 8's, the HiVi M8a, the Seas W22, and especially the Dayton RS225 (7 mm). Also, the Eton woofers cones are great, and motor is so-so at best- LF distortion is not their strong point, and distortion above the impedance minima at 200-300 Hz rises more than I would like to see. Avalon is still using a lot of Eton woofers- I hope they've improved the motor designs for the parts they're using.

So, keeping the simplicity of a two way (with regards to crossover design), the M8ta uses a much longer throw woofer with lower nonlinear distortion and lower distortion in the midrange. In addition to that, the LF design is a carefully optimized ported system, which, if you look at it from another angle, rather strongly resemble's Martin King's MLTQWT quarter wave tube ported transmission line. My first tests show this design capable of levels of low bass output in the mid 20's which one usually only associates with 12" subwoofers (~100 dB per cabinet before room gain), while not losing any definition or smoothness in the mid and upper bass. This driver choice and cabinet design extends the output capabiltiy and lowers distortion compared with any of the two way Avalons, and may put it in competition with the Opus at least.

In the upper range, the Hales Transcendence or the big Seas tweeter is more linear and capable of higher output level than the MB or Focal tweeters used in Avalon two way designs. The cauer elliptic crossover allows a much steeper roll off, which helps lower IM distortion, while still controlling the Q and smoothly and providing a larger vertical disperion window than the Avalon crossover does - as implmented, even the M8 bookshelf has uniform response to 30 degrees above the midwoofer/tweeter axis, which is very unusual in a two way system.

I have a lot of respect for the capabilities of the Accuton midrange and tweeters used in the Opus, so it wouldn't surprise me at all if in this range the Opus excels, as there should be reduced IM compared with a two way. The Opus sell for about $14K per pair; the Ascendent, their new two way model with dual 7" Eton midwoofers sells for ~ $9K per pair. The Ascendent I wouldn't worry about putting the M8ta up against (other than veneering- they've got a really experienced team building the cabinets!).

So, in a nutshell, that was the goal- lower distortion across the band, greater LF output, and better power response. And DIY. Excluding exotic veneers, one could build a set of these for ~$1K in materials with walnut veneer.

[posix]

Thanks for the wonderfull writeup Jon.

It's a shame that, except for your explanation on active vs. passive, it, too, manages to miss the point.

I was asking about creating an Eidolon klone :rofl:

And that's where I tacked my question about active vs. passive - it was only meant as a simple enquiry as to a possible way of improving sound if one were to undertake building eidolon klones but without accutons. But it was a tangent, anyway.


So, I love both music as well as appearance of eidolons. Do I want them, or will I do fine with "only" M8ta? :T

[posix]

Also, Jon, any new photos of your M8ta's? Avalons are really well veneered. Veneers are matched too so you have symmetrical speakers. But the best thing about them is the texture - silky smooth, not shiny, not matt and you can't feel the grain of wood and it doesn't appear to have been lacquered at all. They've somehow managed to POLISH wood veneer. How?

[ThomasW]

I was asking about creating an Eidolon klone......Do I want them, or will I do fine with "only" M8ta?

One of these designs you can probably build if you copy Jon's project. For the other design you're on your own....

[AndrewM]

Can't help you in regards to how they sound, value for the $$ spent, etc...

http://home.hetnet.nl/~geenius/Soup.html

[JonMarsh]

If you have the resources to tackle an Eidolon klone, I'd say by all means, go for it! OTOH, I don't think that an active crossover setup will make it any easier or better in the long run- unless, for example, you want to prototype the crossover design acoustically, and evaluate different approaches. The best way to do that would be with LspCAD Pro, in the emulator mode- then, you'd have the passive design with an accurate transfer function emulation to listen to. The other possibility would be to work on the acoustic targets using something like a one of the programmable digital crossovers (which LspCAD supports emulation for several) and then use a tool like LspCAD or SoundEasy to design the equivalent passive crossover. Or not, and stay with your active design- this is where the ease of development and initial implementation for an active may outweigh the disadvantages (at least in the short term) of the extra components in the signal path.

How loud do you want to listen to music? What kinds of music? I'm sure the three way like the Eidelon, with at least using the same mids and tweeters, would work quite well- but that mid takes some effort to tame. I've had a pair of C44's, and other than their low end limitations, they're relatively very easy to work with. And low distortion, too. But maybe you wouldn't get the same advatanges crossing over at 800 for the mid as for 300-400.

If someone held a gun to my head and said, "Jon, you must design something quickly to rival an Eidolon, AND at much lower cost", I'd probably look at some other drivers and possibly different crossover points. Things I'd consider are other 5" to 6" class midrange or midwoofers, and considering the upper crossover point based on the disperion of the mid- where it starts narrowing.

Imagine, for example, Dayton RS270- after baffle step comp, about 84-85 dB efficiency, so don't need any more efficiency than that in midrange. Very good distortion and energy storage behavior up to 600 Hz.

Love the Accuton mids, but they're pricey and not easy to work with. Considering driver spacing and wavelength issues, with a CT-CT distance of 6", I'd rather not see a crossver frequency higher than 2.3 kHz. So, the mid should span a region of 300 Hz to 3 kHz comforably, with low distortion, and a reference sensitivity of ~84-85 dB. Many possible candidates, but I expect only a few with very low distortion in this range -figuring that out is the harder part, short of buying one of every one promising and measuring. Probably cheaper in that case just to buy the Accuton's. I would check out a few, though, like the HiVi M5a, and the Seas W and L series, with a focus on distortion measurements in the range of 250Hz to 2 kHz.

Tweeter? Well, for a 2.2 kHz crossover, there's a lot of units to consider; I'm partial to hard dome units, but that's just me. If it was my project, it would come down to cost issues- under $100, probably the new unreleased RS tweeter, or one of the smaller Excels, though the XT19 has nice distortion numbers above 3 kHz as long as you don't mind the mediocre off axis dispersion above 10 kHz. I'm planning on some distortion measurements of the Focal Tc120's we've got on hand, and I"ve liked how that tweeter sounds in the past, though it's not paritcularly forgiving of mediocre upstream electronics or digital sources (an understantement if I've ever made one!) I'd probably take the 27TDFC over some of those, and put the money into better crossover caps. Above $100 each, the Accuton C12-6 is an "obvious" choice, as might be the Millenium Excel and the SS98000 (one of my personal favorites- very natural sounding with good source and electronics). While ribbons are getting available and popular again, I don't know of a moderage cost ribbon that's clean enough down to 2K that I'd be inclined to go that way- obviously, Rick Craig and some others would disagree, that's what makes this hobby interesting.

Oh, maybe I should change that last sentence, for me it's a hobby, for Rick Craig, it's a business.

Bottom line, as a short term tool, an active might allow prototyping a working design faster- (though not in my personal case). Doing an analog crossover for an Eidolon clone would be just as complicated as a good passive, and would have many tradeoffs, I'd recommend passive. But I'm old fashioned.

[posix]

Thanks, again!

Here something to drool over...