[Aether Audio]

Friends,

We’ve just experienced a major Revelation – literally.  Karsten is going to chime in here and tell you all about it.  The upshot is that he has made a major set of discoveries concerning our crossover networks while experimenting with his Revelations and Continuum A.D.s.  Apparently, he's rocking the audio world over there in Denmark.  All of his customers that are hearing the new results are being blown away - and many have heard the speakers before.  I’ll let him tell you all about it but in the meantime, I wanted to make an announcement.

Soon we will be providing our products with crossovers manufactured by Mundorf of Germany.  Karsten is finishing up the component selection process as I write and as soon as he is done, we will be taking delivery of the first units.  As a part of our new promotional campaign we will be offering these fabulous little gems (well, some of the parts aren’t so little) to existing owners of our products at cost + shipping.  That’s right – no mark up.

Why?  Because (according to Karsten – I haven’t heard them yet) we figure that the transformation is so complete and remarkable, it will be like shipping all new products again.  We expect all the customers that do the upgrade will WANT to post new reviews – it’s that dramatic of an improvement. 

First, this new crossover implements our new topology that greatly smoothes out the impedance.  The effect of this on the amplifier/speaker synergy has been quite an educational experience for myself.  At least I can say that I’ve heard that and it has made a tremendous improvement compared to the older designs.  I reference Double Ugly’s comments on a previous post as an example: 

http://www.audiocircle.com/index.php?topic=36716.0

Secondly, the new Mundorf components take this improvement several steps further.  Karsten can tell you as he made the topology change using the original components first, THEN…he started swapping out those with the equivalent value Mundorf parts – so he knows. 

Specifically, the Low Pass inductor (in series with the woofers) has been a primary culprit since day-1.  Even though we had used the largest, highest power laminated core inductor we could source stateside, apparently it has issues I would never have guessed.  The only explanation is that apparently, the core material was of rather poor grade steel.  It was big and heavy, so I was deceived.   

Not having had time to do the somewhat complex testing required to test for saturation, I assumed (makes an ass out of u & me ) its specs were honest and it would virtually never saturate.  They weren’t and it does – and the Mundorfs DON’T.  Adding to the above, according to Karsten their capacitors are fantastic too.  I’ll let him tell you all about it.

So anyway…for the folks that already own SP Tech product, I highly suggest you take the plunge and give this new crossover a try.  The cost will be pretty darn reasonable, considering the transformation you will experience.  I doubt you could add or change another single thing in your rig (or everything for that matter) that could provide as significant of an improvement in your sound.  For those that haven’t yet heard or tried our stuff…well, you’re going to benefit from an extremely mature design.  They just ain’t going to get any better than this.

-Bob

[JoshK]

I've read numerous great posts about Mundorf caps.  They are spse to be the cat's pjs. 

[PeteG]

Bob
When will we see pricing for the upgrade.

[Karsten]

You are right Bob, I’ll chime in here  This discovery has been done more or less by incident. Nevertheless the result has made me claim the title of 1st speaker designer assistant.

It all started with wanting to upgrade the speakers here to newest version crossover. Since I have a background within electronics it was not a big problem for me to build these from the schematics supplied by Bob. So I ordered the components, nothing fancy but still reasonable quality. I knew I was going to experiment with different types and quality components so it is always a good thing to start with the cheaper stuff to establish a real world reference point.

I started with the Continuums and they became pretty good sounding (In modest terms) It did change a lot and it also forced me to re-evaluate all the amplifiers here. No doubt that the speakers were a lot easier load to drive after the upgrade.

Next in line were the Revelations. I decided to use some inductors, which were delivered as samples, for the low pass filters. These were however pushed heavily into saturation with pretty nasty distortion as result, hmmm. Okay I pulled these out and replaced them with the original ones wound down to the correct value. That was better but still I noticed a syndrome sounding like the inductor going into saturation, this was because the first one I tried really made me aware about what this sounds like.

Out came the original inductors and a set of heavier EI core inductors were used. Now we were getting somewhere. People really noticed that something had happened, actually across the band. Better impulse response, better bass, imaging improved etc.

However I still had the feeling that more could gained, so I searched for high quality inductors. One supplier came up with some very interesting inductors, the core material seemed to be right and the construction of the core with a calibrated air gap to avoid saturation also looked right. That is of course beside the massive size of the inductor itself. Well frankly speaking I think this Mundorf n106 inductor is overkill but the intention was also to establish a reference point to work from.

My expectations were to get a cleaner and firmer bass but with a subjective feeling of less bass because of the mere 0.02 ohm series resistance.

The result:

Holy cow, this is the most awesome thing I have ever heard. Right now I’m recovering from a 3 hour adrenalin rush with frequent emotional outbursts, little hairs rising, tears, the works….I don’t recall ever having heard anything giving me this physical effect before in my life. The dynamic head room is of biblical proportions!!!! Raw power combined with delicate refinement. A new standard in sound reproduction? Well judge for yourself, I could spend at least a few pages raving about this, but I can’t wait any longer to get back into the sweet spot 

Current SP owners, get the upgrade, you will not regret it. Future SP owners, prepare for the ride of your life 

Karsten

[TomS]

Bob - Will this change trickle down to the Timepiece 2.1 and Continuum AD also?  Tom

[Karsten]

Just one correction to Bobs statement about the Mundorf evaluation. So far I only got those n106 inductors, so I have not evaluated other Mundorf components so far. I should get a big pile of components from them soon. Everything will be seriously evaluated from a cost/performance point of view. This has been one major issue for SP from the beginning. We want to spend the money where it matters the most in order to offer real value. Those components which add a few percent in performance at a high cost, will be offered as optional upgrades. The capacitors will be held up against two other respected brand names and a cheap but good quality alternative.


Karsten

[Aether Audio]

PeteG,

Karsten is still evaluating parts - particularly the capacitors next.  Now that he has the inductor nailed down, he has to pick the best sounding caps.  Some cost more than others but as we all know, more $$$ doesn't always translate into the best sound.  He's getting more samples next week.  Once he's done, we'll get a quote from Mundorf for all the parts - then we'll know.  I expect he should have everything worked out in 2 to 3 weeks.  Since we're an OEM, we get wholesale pricing and since we're not tacking on any profit, you guys will be getting a killer deal.

Just as a side note, quite some time ago I saw Mundorf parts listed on Madisound's website.  I looked at the prices for about 10 seconds and quickly clicked off that page!  Man, retail prices on some of those caps is nuts!  I guess they're some of the very best but still...I wouldn't have thought we could afford to use them for a minute.  Then Karsten started doing his thing before he even told me where he was getting his parts.  Turns out OEM prices are a lot better than retail.  I guess they definitely want manufacturers using their parts.

The upshot is now that SP Tech product will include some of the best crossover parts in the world!  That's always nice to know but the best part is that with the prices we'll be getting, we shouldn't have to raise our product prices a penny!!!  Stay tuned as I can't swear by that, but we're keeping our fingers crossed.  In any case, if it turns out we have to eventually raise prices a little, it shouldn't be much.  And according to Karsten...it would be well worth it.  Regardless, for until March 1st CORRECTION: April 1st we'll eat the cost whatever it is.  We're on a roll and it's time for SP Tech to take its rightful place amongst the competition.  If we have to take it on the chin for a little while longer, that's just the price we have to pay in order to get there.

-Bob

PS.  TomS,

ABSOLUTELY!!! Every SP Tech product will be using the Mundorf parts.  Depending on Karsten's final determinations, there may be a "Standard" Mundorf crossover and then an "Ultimate" version for upgrading.  Some folks can't stand the thought of not having the VERY BEST of the best - so we'll have to accommodate them.

[Karsten]

I'm just taking a little break from the upgraded Revelations in order to get the blood pressure down 

As examble to get an idea of the magnitude of the impact of this upgrade, I can mention the Belles 350A amplifier. The performance I'm getting now from one stereo amp, is more than twice of what a set in monoblock configuration gave me before (!) Furthermore the highs are now really smooth, where before they could have sort of an edge to them with this amp. Hmm, I sort of blamed the amp but it turned out to be the result of a saturating inductor....

I must however mention that the Revelation bass system is power hungry, much more than the Continuum and TimePiece. They want current to perform optimally. That is probably also why this inductor problem was more pronounced with the Revelations.

Ahhh, life is so good.....

Karsten

[brj]

Sounds like SP Tech has a nice upgrade on their hands - congrats!

For my own education, can you describe more exactly what a saturated inductor "sounds" like?  Thanks!

[Karsten]

Sounds like SP Tech has a nice upgrade on their hands - congrats!

For my own education, can you describe more exactly what a saturated inductor "sounds" like?  Thanks!

The most obvious indication is lost control over the woofer with a distortion product as function. As example: At the Oscar Peterson album "We get requests" the track "You look good to me" is a particular strong bass note at some point, in the past that note always bottomed out the woofers. I took it as a flaw in the recording, which of course it partially is, but now it is under total control.

The real tricky thing about this was that the inductors were almost good enough, so they were only clipping at the peaks, which can be difficult to hear, if you don't know what to listen for. So under normal conditions the real problem was lack of impact, detail and control in the bass area plus smearing of the transients.

One strange thing, which I can't explain (maybe Bob can) is that the upgrade also has a substantial impact even at relatively low listening levels. Maybe because substantial peaks are available even at low levels, enough to get the old inductor into trouble?

Karsten

[Aether Audio]

Brian,

For my own education, can you describe more exactly what a saturated inductor "sounds" like?

I think Karsten now has the most practical experience to answer your question, but I will try and approach it from a somewhat "theoretical" standpoint.

First of all, the magnetic behavior of core materials (other than air) can be quite complex.  In fact, this is often the reason many suggest for sticking with air-core coils.  But...there's always a catch.  In woofer circuits (in particular) we usually don't want to insert any series resistance.  Typically, the rated sensitivity of a speaker is based on the sensitivity of the woofer(s) used.  Any added series resistance in the woofer circuit will have the effect of doing 2 things:

1) It will waste power and consequently lower the woofer's voltage sensitivity.  That's not good as we all like our speakers to be as sensitive as possible - unless we happen to have unlimited amplifier power at our disposal.

2) Added resistance lowers amplifier damping.  That's not good either if you like fast, clean and powerful bass response.  An old trick to get more bass out of a speaker is to intentionally add a small amount of resistance (i.e, as in a small value series resistor).  Typically the values used are 0.5-Ohms or less.  This lowers amplifier damping and allows the woofer to "resonate" more at the box tuning frequency.  It works, as long as you don't mind the transient response getting a little sloppy.

Well...back to the point.  An air-core coil will have considerably more resistance than a iron (or whatever) type core - for a given physical size and inductance value.  This is because without the benefit of a magnetic flux concentrating core, an air-core has to have a lot more turns of wire to achieve the same value.  The only way to reduce the resistance is to use very large gauge wire.  If you do that, the coil can become enormous in size and very expensive.  Have you checked out the price of copper lately?

So, to get a large value inductor with low resistance in anything resembling a reasonable size and cost, we're usually forced to go with some form of magnetic core material.  And that can be fraught with hazards.  Yet, done correctly its actually a superior way to go over all.  A well done design can provide extremely low series resistance in a manageable size and at reasonable cost.

But magnetic materials other than air have "personalities" that can vary widely.  It all has to do with an ugly little property we refer to as "hysteresis."  Think of it as a form of memory.  Once the core has a magnetic flux established, it doesn't want to "let go" once the field tries to change polarity.  Well, audio signals are "AC" and change polarity every half-cycle.  If the hysteresis is significant, distortion results.

Therefore, most core materials chosen for low to mid audio frequencies use a material that has the lowest hysteresis possible.  That material is usually  a form of "silicon steel" (steel with silicon alloyed in it - duh).  The problem is that the good stuff ain't cheap and the cheap stuff "saturates" easily (and has inferior hysteresis performance).

What's saturation?  It's when the core material is so full of magnetic flux lines that it can't permit any more to form in it.  The more current flow to the woofer, the more flux lines are needed inside the core.  Once it hits it's limit - that's it - distortion.  It's a lot like when an amplifier clips.  There just ain't no more signal going through.  But a saturated inductor core can be even more insidious.

Once the core saturates the inductor can looses virtually all of its "inductance."  In a bad case all that remains s what we call "leakage inductance."  That ain't much either.  The result is as if the inductor was removed from the circuit or bypassed with a straight piece of wire.  Now your "Low Pass" circuit ain't "Low Passing" anymore - it's "All Passing."  That means high frequencies can get to the woofer now.

But core saturation only really occurs at the signal peaks (unless its REALLY saturated).  That means at those moments all kinds of hash can get through to the woofer.  Some of that hash would be high frequencies from the amplifier (that should have been blocked by the inductor) and some would be from the inductor itself.  You see, when an inductor (or transformer) saturates, it generates all kinds of harmonic distortion.

Then we have even more uglies to add to the mix.  The back emf of the distortion products generated by the saturated inductor are "reflected" back to the amplifier.  If the amp uses negative feedback, it will try to correct for this.  Some of the distortion it will get rid of, some it won't and because of any phase errors in the feedback loop, the amp will generate distortion products of its own and send them right back down to the speaker.  Such a back emf would be quite complex - both from a frequency and dynamic standpoint -  and well outside what the amplifier would "expect" to see.  We sure can't blame it if it can't handle the whole mess.

And guess who's sitting there while all of this is going on?  Your beloved little tweeter - that's who.  Then of course, since many of these distortion products will lie in the tweeter's operating band, the High Pass circuit will more than oblige and drive them right down that poor little tweeter's throat.  Now you can hear them in all their glory.  What these nasty things will do to soundstage, imaging, detail, resolution - you name it...is anybody's guess.  One thing for certain though, you can bet it ain't good.

So...what does it sound like.  Well, I took the long way to get there but I'd say... a BIG, WET, FART!

Karsten has posted more above on the subjective effects, so I'll leave it at that.  With regards to:

One strange thing, which I can't explain (maybe Bob can) is that the upgrade also has a substantial impact even at relatively low listening levels.

Karsten is partially correct in his assessment that there's still pretty big transients coming through, even at low volumes.  Above and beyond that I would suspect that the old inductor's core had a poor hysteresis response.  That would manifest at any level, regardless of amplitude.  Cheap steel sounds bad at any volume.

Dissertation complete.  I'll go quietly now.

-Bob

[JoshK]

Excellent explaination of hysterisis Bob!   

[Aether Audio]

Thanks Josh!

[JoshK]

I learned something. 

[mixsit]

Question re; the up grade.. Is there any custom tuning of the crossovers to the individual speaker sets? How would that work?
Wayne

[Russell Dawkins]

I wonder whether this was what I was hearing when I reported hearing strain setting in starting at 85 dB (at 2m) with my Timepiece 2.1s and Nuforce ref 9SEs.

http://www.audiocircle.com/index.php?topic=33093.20

At the time it didn't make sense - it sounded like I was starting to run out of steam at what should have been 1 watt output from an amp supposedly capable of 150 WRMS into 8 ohms, but if my personal thinking on this is right - that transients on uncompressed acoustic recordings actually peak, if only very briefly, at around 20 dB above average (and indicated) levels - then there would have been very brief 100W peaks trying to get through and perhaps triggering the saturation distortion Bob describes.

Karsten - thanks for this! Could you describe the distortion from inductor saturation as a "strained" sound?

[BrunoB]

I have been using a Mundorf zero ohm coil (ZOC) in my series crossover for several years. Unfortunately, I haven't made a A-B comparison with a ferrite coil - I just wanted the lowest series resistance. The ZOC are huge compared  to the equivalent Erse coil.

Here is the link to the ZOC:
http://www.mundorf.com/english/bauteile/spulen/null-ohm.htm#

The German magazine hobby-hifi (DIY speaker building) often uses Mundorf parts for their high end XO. They compared a ZOC to a smaller ferrite coil and measured substantial distorsions with the small ferrite and none with the ZOC, under the same conditions. Unfortunately, the paper did not provide details.

Bruno

[Karsten]

Russell,

I guess you could describe as sort of a "strained" sound. Another thing I noticed, is that this inductor acted sort of "current limiting" maybe because of the poor hysteresis response. At some point I experimented with EQ in the low end, but it was like the speaker did not really respond to this.

On top of this, the new crossover design Bob made, really makes the speaker a much easier load. This means that your NuForce amps will have a lot easier work to do and better reserves to drive the speakers. After the Continuums were upgraded, the NuForce Ref 9 did a really good job on those, actually the first two customers who heard this bought a set of Ref 9SE.

Karsten

PS I'll be gone until Wednesday, so I will probably not be able to reply to eventual questions until then.

[Aether Audio]

Wayne,

The new topology is more stable and seldom requires much, if any tweaking.  For an upgrade we'll need the tweeter assembly along with the crossover sent back so we can modify both.  There's a circuit on the tweeter assembly that gets completely removed so there's a little work involved.  Besides, I'm anal about frequency response linearity so it gives me the chance to check/tweak everything if need be. 

They're all my children and I try to keep my kids disciplined.  They've been behaving rather poorly lately so I need to straighten their asses out.  I can't blame them much though as it's my fault.  Neglectful parenting leads to less than optimal behavior. 


Russell,

Yeah, my Ref 9s never really had the "ummpf" the TPs needed.  They worked pretty good on the 2 woofer models but that's because the amps put out almost double the juice into 4-Ohms.  Just guessing, but I don't think the inductor issue is as pronounced on the TPs because its value is twice that of the 4-Ohm designs.  That being the case, its core is twice the size and less likely to saturate.

On the other hand, the low level improvements that Karsten has noticed tells me that core is made of crap steel.  That being the case, it will have too much hysteresis (core memory) and will add distortion at any volume level.  If it were me, I'd want to get the damned things out of there and be done with it.

As a little adjunct to the hysteresis issue, I'd like to add that ANY hysteresis is a bad thing.  Air (as in air-core coils) exhibits zero hysteresis and has infinite permeability.  That means an air-core coil will never saturate at any level and has no memory.  The saturation issue is actually easier to deal with than hysteresis though.  Just use a bigger core and it's less likely to ever occur.

Everyone,

Hysteresis on the other hand, is a lot harder to deal with.  What you want to use is a material that has the lowest possible tendency to ever be made into a permanent magnet.  The engineering term used to describe the material's ability to keep its magnetic domains aligned in one direction or "retained" is call "Retentivity."  High retentivity = high hysteresis and is exactly what you want to use in making a permanent magnet.  It's the last thing you want to use in an audio coil though.  The silicon atoms alloyed in silicon-steel tend to isolate one iron atom from the next in the crystalline lattice, keeping their tendency for their latent ferro-magnetic properties (mutual alignment) from manifesting.

Some companies use ferrite cores, but I don't like them.  Ferrite is nothing more than iron oxide sintered with silica and the goal is to achieve the same effect.  It's greatest advantage is that it goes into saturation "softly" as compared to silicon-steel which saturates abruptly.  Sort of like a SS amp compared to a tube amp when they go into clipping.  In ferrites, the silica acts like a distributed air-gap throughout the core. 

The reason I mention it is that in silicon-steel EI cores, an air-gap between the center leg of the "E" section, where it would contact the "I," often will have engineered in an intentional gap.  The gap then prevents the two segments from actually touching one another physically.  If adjusted accurately, the gap will cause the inductor to go into saturation softly, just like in a ferrite.  That's what the Mundorf "Zero-Ohms Inductor" uses.

The benefit is that now this inductor will have all the benefits if silicon-steel with the added benefit of soft-saturation like the ferrite - without its major drawback.  What's that?  Although ferrites saturate softly, it comes at the price of greater over-all hysteresis.  Ferrite's major advantage is in high frequency switching power supplies.  The hysteresis in that case can actually be a good thing as it tends to slow down the dI/dT (rate of current change vs. rate of time change) of the driving circuit.  That lowers in-rush current into the transformer and reduces the chance that the driving transistors will latch "on" and blow themselves up.  There's no advantage in any of this for audio applications, so that's why I don't like ferrites.

Just ask me, I'll tell you all about it.

-Bob

[Aether Audio]

Friends,

Just to beat a dead horse a little more, I thought I'd pass along some more info for the truly obsessed.

Here's a good link on the issues regarding "Wound Components" (i.e., coils & transformers):

http://www.ee.surrey.ac.uk/Workshop/advice/coils/power_loss.html

Then specifically, here's a sub-article from that page on hysteresis:

http://www.ee.surrey.ac.uk/Workshop/advice/coils/power_loss.html#hyst

Those of you that are strictly music lovers should probably skip this.  For my fellow twisted brothers...

Have fun!
-Bob