Magnesium Limited

[davewantsmoore]

Very interesting - so exotic drivers

 

Perhaps semantics, but I wouldn't call this an "exotic" driver .... it's only very roughly double the price of the previously used drivers.

 

 

NB - I'm not trying to cast any doubt on the claim it sounds better.

Edited June 1, 2016 by davewantsmoore

[bhobba]

I forgot to ask: did Mike successfully implement the bass reflex ports into the speaker stands? If so I've got to see photos!

 

He decided on a different port that is, as usual, in the speaker.

 

He hasn't built the stands yet.

 

Thanks

Bill

[Lenehan Audio]

Given that you're still using the same drivers, I take it you aren't as seduced by the Morel magnesium drivers as Bill?

 

I must say i'd be surprised if they are a better *all round* solution than your existing drivers - speed and detail isn't everything, and the Peerless HDS are very well behaved, producing exceptional tonal neutrality and accuracy in your designs (and let's face it - plenty of speed and detail anyway).

Hi Lee. Ok I've transferred this from the new ML1 thread

The Seas Magnesium is in a fact a phenomenal bass driver ! The problems with using it though are manifold. Allow me to explain with a parable . The seas range of Magnesium drivers are like Catherine Zeta Jones in Intolerable Cruelty >>> want one ! Want one .

But ! And it's a big Flammin BUT > Just like Catherine maintenance is huge , the Xover for the Magnesium we are currently fooling with in Bills Magnesium two way is complex and a bit edgy .

What I mean by this is that for it to be stable my son Andrew has to sit there and hand tune a shunting series LCR filter for each driver . This entails actually hand winding an inductor on or off a couple of turns at a time ! Likewise tuning the cap up and down by very small amounts and using a 3 watt trim pot for resistance tuning .

I know your going to say ! Hey Mike you can use a computer modelling program to do that , it only takes minutes !! WRONG > using computer modelling for Xover design is like saying that Call of Duty is perfect training for a soldier then sending him to Into actual battle.

Seas Magnesium has a horrifying oil can breakup mode just above the Xover frequency and this must be very carefully and individually dealt with or while your listening to your favourite Beethoven Symphony it sounds like someone is playing Jingle Bells on a bloody Tambourine in the background.

We intend to hold a GTG as soon as Bills Magnesiums are up to a listenable state but suffice to say there is tremendous potential so far .Regards Mike Lenehan

[fell off the boat]

...using computer modelling for Xover design is like saying that Call of Duty is perfect training for a soldier then sending him to Into actual battle.

Like! Simulation is just a simulation, it's helpful but the real test is always in the listening

[bhobba]

Hi Guys And Of Course Gal's

 

Mike has been doing more work on the mag limited's and now has the crossover topology, although final values are not set yet.  It's third order on the bass and third order quasi on the treble drivers which is a slight departure on what Mike usually does which is third order on the bass and second order quasi on the treble.  He has to investigate whether using a trap on the woofer sounds better or not.

 

In practical terms this means there are two critical capacitors in the signal path instead of just one.  This makes a capacitor comparison a lot more difficult unfortunately so will probably will not go ahead.  It also meant if I used the Cast the price would blowout ridiculously - nearly 2.5 times the price of the VSF or Jupiter.

 

Personally I prefer the Jupiter copper so will be getting that.  I heard what they did with my upgraded Leak - very impressive - they seemed to make a bigger difference than Duelund RS.  I haven't done a comparison with the Cast but those that have are pretty impressed:

http://www.enjoythemusic.com/diy/0514/jupiter_copper_foil_paper_wax_capacitor.htm

 

However I am very excited about using some Duelund silver bypass with them:

http://www.humblehomemadehifi.com/Cap.html

Duelund Silver Bypass Capacitor 0,01uF / 100VDC - 2% tolerance

Technical specifications (according to manufacturer): "Precision Speaker Capacitor; Pure Silver Foil; handmade in Denmark".

Sound: In one word: amazing! I have used these 0,01uF pure silver foil capacitors as bypass capacitors in many different systems. In just about every case there was an improvement in overall coherency and realism of tone. With realism of tone I mean that acoustic instruments and vocalists seemed much more tangible, more intimate. The Duelund Silver Bypass Capacitor brings out a certain harmonic richness in overtones, for example with brass wind instruments the tone gets a sort of "glow" making them so much more realistic. Big-band music is bright and warm at the same time if you know what I mean, just like in real-life. And now for a cliché: the Duelund Silver Bypass Capacitor really does remove a curtain from the sound, creating more depth, insight and it generally does a very good job in cleaning things up. It does this without getting harsh nor adding artificial emphasis on any part of the spectrum, something that can happen with certain types of bypass caps. They even scared me once: my personal reference system uses a 1-inch beryllium compression driver connected to a tractrix horn that flares out to 29 inches. This "tweeter" has no resistors in the signal-path and is driven by a first order network, so only one capacitor in the direct signal-path. It works like an acoustic magnifying glass. I was fiddeling around as usual, tuning the value of this capacitor in steps of 0,10uF but the sound didn't quite seem to fall into place how I wanted it to. Then I decided to listen if the 0,01uF Duelund Silver Bypass Capacitor could help out here. Bingo! Makiko Hirabayashi's recording "Surely" (that I know very well) has some small bells that are used on several of the tracks. I thought I knew how they sounded but with the bypass capacitor in the network the bells were so realistic, it scared me :-) I am so pleased with these universal bypass capacitors that I have decided to keep them in stock.

Verdict: add about 2 points to whatever capacitor you are bypassing

 

A comparison with and without them may indeed be possible.

 

Mike has taken some measurements of the new crossover - see attached. 

 

First one is 15% off axis.  The second one is 45% off axis. Notice the very steep anti-phase null indicating coherent phase through the crossover.

 

Thanks 

Bill

Edited July 27, 2016 by bhobba

[davewantsmoore]

Excellent.

[acg]

@@bhobba

Hey Bill, what size Cast do you need? I have 2.2uf sitting up here doing nothing. Could we be so lucky?

Cheers Anthony

[Willco]

Hi Bill, trust your feeling better--nothing like some exciting Audio upcoming to stir the Loins!---well you get my drift !

 

Nice to see the enthusiasm still burns bright--missed ya happy posts ole soulmate!

 

Willco

[bhobba]

I have 2.2uf sitting up here doing nothing.

 

No.  Bigger values than that and I need 4.  It would add something like an extra $3K in part cost alone.  I would do it, but having heard the Cast, and Jupiter (not side by side), and from those that have had them side by side, there is not much in it.  Humble Home Hi Fi gives the Jupiter 13 and Cast 14.  However the silver bypass lifts it and I am hopeful by at least that one point difference - it may even be better - it is estimated it adds 2 points..  Fingers crossed, I can get cast performance (or better) for much less.  Of course Mike is really interested in seeing what the silver bypass does.  If he can get cast performance, and maybe even better, that will be a big win for his speakers.

 

Thanks

Bill 

[bhobba]

Was down with a friend listening to the latest incarnation of the crossover.

 

Yes - better again - Mike thinks its nearing the final design.

 

Just one issue - a slight roughness on the lower midrange that Mike thinks is a result of the trashy stands they were on.  The final version will have its own stand with the crossover built into it.  However in the areas of overall clarity, detail and speed its easily better than any other speaker Mike has built.

 

Had a further discussion about the capacitors.  As mentioned before will be using Jupiter copper bypassed by Duland bypass capacitors on the tweeter.  But it was overkill on the bass driver because its not in the signal path.  So I decided to hunt around for some good value but still good capacitors.  I decided on the new Jupiter VT capacitors:

http://www.partsconnexion.com/capacitor_film_jupiter_vt.html

 

Mike mentioned he wanted to do a capacitor comparison on a new ML1.  Thought, great idea, but will do a separate post about that.

 

Thanks

Bill

[niss_man]

@Lenehan Audio Is there a reason for your crossover to be more phase coherant at 45deg off axis than 30deg off axis? ie. larger notch at 45deg. 

    When designing the crossover are you after the notch to be greater off axis rather than on axis?

 

Simon

[davewantsmoore]

2 hours ago, niss_man said:

@Lenehan Audio Is there a reason for your crossover to be more phase coherant at 45deg off axis than 30deg off axis? ie. larger notch at 45deg. 

    When designing the crossover are you after the notch to be greater off axis rather than on axis?

1

 

The difference between the two measurements is only Very small.

[bhobba]

Hi Guys

 

My Magnesium's are nearing completion.

 

Decided on a couple of things that will be in the final version.

 

1.  It will use Jupiter Copper capacitors bypassed with Duelund bypass capacitors.  I actually slightly  prefer VSF Copper but they must be bought in lots of 10.  The VSF is slightly cheaper, a bit more neutral and natural.  The Jupiter has a slight bloom by comparison but in this case may be an advantage because the Magnesium's drawback is a slight coldness this may counter - we will see.

 

2. Will be using Bybees directly bonded to the driver terminals.  Mike is getting in two lots of the internal speaker bullet kits:

http://bybeetech.com/?page_id=2

 

Will also see how they go on the new ML5's Rawl, me, and some others are tweaking, before installing them in the Magnesium's.

 

As soon as they are completed the comparison to the ML5 will be VERY interesting.  I already think they are better than the ML2 Limited - but we will see.   I have a pair of ML2 Limited at Mikes just for that comparison.  The looser will be sold.

 

Thanks

Bill

 

 

Edited March 14, 2017 by bhobba

[bhobba]

Hi All

 

Now that Mike has finished, or nearly finished, the new Kit speakers  he has been able to do some more work on the Magnesium's.

 

Done some more tweaking on the crossover - thinks it is now substantially better than before.  Third order quasi on both tweeter and bass driver - he may or may not use a trap - if he does it will be what he calls a 'light one' because like me he thinks the reason other manufacturers have trouble with the driver is, like guru George Short whose views I think I posted previously (if not I will add it after this) is the trap drifts over time.   George didn't use a trap - Mike thinks he can get away with a 'light one' - but I will leave it up to Mike who these days has guru status in crossover design like George, but George is retired now - at least I think he is - he isn't designing any more to the bet of my knowledge.

 

Thanks

Bill 

Edited July 18, 2017 by bhobba

[bhobba]

Hi Guys

 

Looks like I didn't post Georges observations.  Here they are.  It a long post, but it shows just how hard even a person like George had to work to get these drivers to sound right.   It was no easy task.  Nor was it for Mike.   But the listen I had to an earlier prototype IMHO makes it worthwhile - it revealed detail like nothing I had ever heard before.

 

Start Quote

 

The W18E’s magnesium cone has a single major break up mode centered at 4888 Hz. It is however not a single frequency break up, and in fact when one examines the frequency response curve closely it is apparent that this break up begins over an octave lower, at 2.4kHz, reaches a relative 10.4dB peak at 4800 Hz, and is followed by a continuing series of peaks higher in frequency. It is very difficult to detect these series of break ups with MLS signal, but with a good old fashioned swept sine wave one can clearly hear them.

 

The initial break up is indicated on the frequency response curve where the knee begins to turn into a hump (marker 1 at 2400 Hz) and peaks at 3141 Hz. The major peak at 4800 Hz is the primary cone bell mode, followed by secondary peaks at 6300 Hz, 7265 Hz and 8600 Hz. Designing a low pass network for the W18E is not so straight forward. Because no one had ever developed a mid-woofer with this kind of break up before, it was new ground to try to tame it. From an electrical engineering point of view, designing a filter with a high Q electrical resonance to counteract a high Q mechanical resonance makes perfect sense. From a measurement point of view the method suggested by SEAS (low pass plus trap) works quite well. It was relatively easy to develop a network that provided the proper third order slope and drop the 4888Hz peak to below –20dB, which would normally be considered the threshold of audibility….. and that’s where the problems began.

 

After making any significant enough change to the system warranting a good listen, I could still hear evidence of the break up – from a bit of hardness to a full blown sibilant "ssszing", and in fact it is so obvious on a recordings of female vocalists – notably Lisa Loeb and Susana Baca - that I would put these recordings on first. Any audible evidence of the break up and I would put the system back on the measurement stand. I reached very deeply into my bag of tricks…higher and lower crossover frequencies, steeper slopes, elliptical filters, shallower and deeper notch filters…. eventually I began to think it was just me. With instrumental music, even where the ssszing was not obvious, I found listening for more than a half an hour or so uncomfortable.

 

At about that same time North Creek had become a distributor of the Aurum Cantus family of ribbon drivers, and my development efforts were shared with designing a new full range flagship, the North Manifest loudspeaker system, which was built around the Aurum Cantus G1 and a custom version of the Scan-Speak 18W8545’s. The Manifests - even in the early going - showed no evidence of the upper midrange hardness….so by mid 2003, I had given up on the SEAS W18E.

 

Then, daring the lifeless, brutally desolate landscape of the wind shorn Adirondack Wilderness in early winter, SEAS USA director John Stone arrived at my doorstep. I had known John for a long time, ever since his early days Vifa-Scan Speak, and after a day-long meeting which included a tour of the new North Creek building-in-progress and the first showing of the North Manifests, he convinced me to travel to Las Vegas CES in January and meet with SEAS chief engineer Olav Arntzen.

 

CES 2004 was the usual – good sound, bad sound, small rooms, long bus rides. But the two highlights were spending a morning hiking Red Rocks Canyon (suggested by Madisound's Brian Kane, thanks Brian!) and an afternoon with Olav.

 

Discussing driver design with an expert is a whole lot of fun, and in this case Olav brought along not only extensive measurements but SEAS’ Klippel analyzer. Watching the W18E go though the Klippel testing was impressive to say the least, proving empirically how exceptionally good the motor is. Still searching for the cause of my discomfort with the W18E’s upper midrange, I asked Olav several questions about the cone construction.

 

First, is the cone break up was amplitude dependent? I asked because it occurred to me that while I do most of my crossover design at about one Volt, which is only 1/8 Watt, listening is at considerably higher volume levels. Perhaps my early system designs were unsatisfactory because I was working at too low a level. Olav however had the measurements with him that proved quite clearly that the cone break up was amplitude invariant. Is it temperature dependent? Not very. Does it float from driver to driver? No. Production run to production run? No.

 

I listened to several loudspeakers that were using various versions of the W18E at CES, and while some were quite good on the right material, I could always here the "ssszing". I also discovered that a lot of people could not here it, and in fact some systems that have been lauded for their midrange clarity I found to be completely unlistenable. On a few occasions I had to leave the room.

 

I have always been way more sensitive to unnatural sibilant emphasis than anyone else I know, and as a professional loudspeaker designer am very accustomed to listening for faults in a loudspeaker design. Repeatedly with this driver, I knew exactly what to listen for and had no trouble finding it.

 

I also learned the oddest thing - that on instrumental music, the break up actually changes the character of the sound in such a way that some people who could clearly hear it actually liked it. Violins, for example, are raspier, and saxophones have more "bite". It is not entirely unpleasant on a limited spectrum of music, but definitely not the North Creek kind of sound.

 

Back at the ‘Creek, I un-gave-up on the SEAS W18E’s, but because I had long ago exhausted all of my conventional ideas about the network design, and because the entry level Echo and tube-specific Catamount had become my design priorities, the W18E’s became my "spare time, rainy Saturday afternoon, had a thought at 4 AM, try a new idea" loudspeaker. The Pegasus prototypes still spent most of their time on a stand against the back wall of the listening room.

 

Eventually it came to me that the problem with the W18’s upper midrange is a two edged sword. The mechanical break up of the cone is a high Q mechanical resonance. The "low pass network plus trap" approach creates a second high Q resonance. The problem, then, is that there are two high Q resonances in the electrical/mechanical/acoustic system right in the middle of the range where the ear (at least mine) is most sensitive. My goal, then, became to design a low pass network with the target acoustic response, but without using this type of filter. Finally, some progress was being made.

 

So by early 2005 the Pegasus prototype had come to occupy center stage in the Large listening lab.

My daily routine is pretty simple; I get to the office and spend the first half hour or so writing or making my to-do list, while listening to the current prototype, trying to identify its faults, making notes, and sometimes making minor changes to the crossover network. Occasionally I do a little serious listening. Then I get my email.

 

Music is playing 24/7 here, so I do most of my day-to-day paperwork and spend every break in the large listening lab. This is not serious listening by any means, but one can pick up obvious faults – particularly voicing imbalances – easily when paying only half attention to the loudspeaker. Often this leads to more minor crossover changes.

 

If time allows (usually two or three afternoons a week), I will spend a few hours making measurements and modifying the crossover network; or, if that morning the loudspeaker sounds good enough to listen to for a couple of hours, I will spend the time playing my reference CD’s and making notes. If it’s really good, I put on the fun stuff and sit back and enjoy.

 

If the current prototype is not good enough for long term listening, or fails one of my reference tests, I attempt to precisely objectively quantify the loudspeaker’ faults, then develop a measurement-based correction. This can encompasses a broad spectrum of elements; that the voicing is a bit off, the port tuning is too high or too low, the midrange is hard or forward or too laid back, the speaker sounds right but it’s not fun. It is a purely subjective way of doing objective work.

 

Once I feel that the measurements indicate the problem is corrected, the iteration gets a serial number (like Pegasus SYS34) and the measurement family gets saved (SYS34, SYS34OOP, TWT34, WOF34, WOF34FR ((which is the full range response form 20Hz to 5kHz, ½ octave smoothed)), SYS34Z ((input impedance)), and sometimes SYS34ZT ((input impedance with the twister)), WOF34VOL ((woofer 34 voltage plot)), TWT34VOL (tweeter 34 voltage plot)). The measurements are also printed, comments added, and left for the next opportunity for a good listen.

 

Those familiar with DOS may recall the 8-charater limit on file names. Without developing a new naming nomenclature, this limits the number of iterations to 99. It never occurred to me that 99 may not be enough.

 

After printing the response curve family, the networks get re-wired and the pair of prototypes are re-set up and switched to music for the rest of the day or overnight. At this point I go back to the day-to-day stuff; no serious listening. The reason why is that even though all lab crossover components are broken in for several days before they are used in a crossover prototype, any component that sits for a few weeks looses it "flex", and will always sound a bit hard or constricted the first few hours it is back in a network. This is particularly true of film-foil capacitors, which completely change character after a few hours of playing time. So there is no point in listening to the system when any newly-added crossover components may still be "cold". By the end of the day or the next morning the equipment is properly warmed up and flexed in, so if time allows I will sit down and give the latest version a listen.

 

The Pegasus set a new record – SYS86 to be exact. Almost three times every other loudspeaker I have designed (with the exception of the Okara II, which got into the 40’s). But I don’t mind saying that of the dozen or two loudspeakers I have heard that use the W18E, the Pegasus is the first one that I find fully satisfying for long term listening.

 

End Quote

 

Yes - one hell of a difficult job.   Did Mike succeed - well I am VERY confident - but we will see.  And you understand a bit why this speaker took so long - not only did Mike have to fit it in between his other work but it is a VERY hard driver to get right.

Thanks

Bill

 

Edited July 19, 2017 by bhobba

[Guest scumbag]

Bill, 

 

I assume that the introduction and perhaps the last paragraph are your comments. Some quotation marks would be handy to differentiate what parts are quotes from George and what parts are yours. The last paragraph has me stumped. Is that your comment or George's? 

 

Mark 

[bhobba]

5 hours ago, scumbag said:

The last paragraph has me stumped. Is that your comment or George's? 

 

Its mine.

 

Thanks for pointing out the problem - now fixed.

 

Thanks

Bill

[Guest scumbag]

21 minutes ago, bhobba said:

 

Its mine.

 

Thanks for pointing out the problem - now fixed.

 

Thanks

Bill

Cool. I assume given Mike's very high standards that if he is happy with the result then it will be well received.

 

Mark

 

 

[bhobba]

2 hours ago, scumbag said:

Cool. I assume given Mike's very high standards that if he is happy with the result then it will be well received

 

I heard an earlier prototype and it sounded awesome - but slightly cold.  It wasn't hard or sibilant like George complained about, but Mike wanted to do what he could about it.  Like George it took him a lot of work and I doubt he would have told me unless he is pretty sure its finalized and being happy with it.

 

As a prototype obviously it didn't use the top shelf capacitors etc which will improve it again.

 

Mike has a new driver that is reputed to be better again - the Satori - that is easier to work with and that's what he will be using in he future - this driver, while excellent is hard to work with.

 

Thanks

Bill

Edited July 19, 2017 by bhobba

[livinit73]

Satori is an amazing driver. That's all I will say. Cheers

[bhobba]

Hi Guys

 

I need a new thread for this - you will see why in the thread Title.  Suffice to say I am awe struck.

 

Thanks

Bill