Testing 1, 2, 3, testing...

[David G]

I understand what you're saying about the cone modes/impedance glitch. I think where you and I differ is that I think if you can get the system final response flat and the cone modes don't impact the on and off axis FR too much, then the more advanced motor and better nonlinear distortion may be a better tradeoff. Especially in a two way, where a lot of excursion is demanded of the midwoofer.

I agree with you Mark. There's no right or wrong, we are all just choosing which problems/tradeoffs we're prepared to live with.

[David G]

Mark, I think you'll find the nonlinear LF distortion of the Revelators to be excellent. Very good motor design. But even the 7" has a big blip in the impedance curve at 800 Hz befor starting the usual ScanSpeak climb in the upper mids. The slitting may distribute the lower chaotic cone modes over a wider range (or the blip may be the suspension, as some speculate), but either way, there are problems.
Same with the 8" woofer, but in that case the dip in the FR due to the first flapper cone mode is quite visible in even the farfield response. (and $340?!?) It's really a fairly impessive woofer, with a nice trade-off of sensitivity and longish Xmax (9 mm) and impedance (8 ohms) (probably great for a ported three way), but it's not a midwoofer. It's just a baby versiopbn of the 26W/88161T, which has it's first major cone mode at 700 Hz. But has the same lovely motor.
~Jon

I've listened quite closely to my Scanspeaks (26W and 18W) at those frequencies where impedance blips occur, using tones etc, and haven't be able to discern any noticeable change in character. So, for myself at least, I feel satisfied that it isn't a major issue. Don't get me wrong though, I'd prefer those blips weren't there

[JonMarsh]

It appears that even the C79 has an impedance glitch at 800HZ. Perhaps those "ears" are the cause, even though they benefit the FR above 2K as opposed to the C89. Any speculation as to which of these 2 drivers will be the best performer as a mid in a 3-way? Jon you mentioned some possible combinations of RS225 C79, C13 or RS270, C89, C24. I think the highest the C89 should go is 2K based on the published distortion which is probably why you recommended the C24 as opposed to a C12 or C13? I'm about to spring for some accuton mids, already have the C44s but want something that is clean down to 250HZ or so. I guess I could save up for a C90 and retire from audio/be done with it. But man- $460 a pop!

Yeah, they are pricey- but they'd probably be the LAST midrange you'd ever buy--- or one would hope!

The C88 and C89 don't have the ears. I wasn't planning on using any of these much above 2 kHz, because of the CTC issue and achieving integration. With the C13 unmodified, it seems to me you must cross at 3-4 kHz. That's getting up there considering integration in the crossover region and polar lobing.

I intend to look at modifying the tweeters with additional diffraction control under the screen, and I'm looking at possible solutions for the grille resonance in the mids/midwoofer (I can't really call the C88 a midwoofer with just 3 mm of Xmax, but it's healthy for a midrange) It's a little bit of a PITA to consider modding or tweaking these drivers, but I think the core technology is so good it's worth some extra effort. Even so, it's debatable whether diffraction improvements would be audible, but I know you could get the on axis FR to look nicer (bragging rights).

Have you measured a blip in the impedance curve in the C79? The factory curves I've seen look pretty clean. I don't recall seeing any glitch in the measured data Marc sent for the C79 in that region unless it's a very low level (compared with say, RS225 glitch, SS midwoofer glitches, etc).
THAT I might be convinced was a suspension resonance. The other things I've measured clearly aren't, as nearfield shows big notches in FR.

~Jon

[TacoD]

I do not think the C90 is the perfect driver, so it will not be the last driver you'd ever buy . The factory curves of Thiel & Partner (aka Accuton) are not always that accurate, or atleast not for the older drivers.

[ThomasW]

Much was learned about the accuracy of the Accuton factory plots during the development of the M8a-MKII speaker project...

[Jed]

Have you measured a blip in the impedance curve in the C79? The factory curves I've seen look pretty clean.
~Jon

Jon,

I was referrring to Timmermann's measurements that are featured on the Accuton website.

[JonMarsh]

That IS a pretty small glitch; it's also rather narrow. I'm wondering what the source is; I don't see anything in the data files Marc sent.

[Jed]

That IS a pretty small glitch; it's also rather narrow. I'm wondering what the source is; I don't see anything in the data files Marc sent.

These measurements were taken by the head of Hobby HIFI magazine. If I can sell a few drivers I might pick up a pair of C90s- the specs are almost too good to be true. The most expensive driver I've ever purchased in the past was an Eton ER4, so the C90s are a bit of a leap- the price to pay for cutting edge technology! I'm picturing a Wilson Sophia/Watt-Puppy speaker with either RS28a or C12 + C90 and RS225s. RS270s would be nice for the added sensitivity but I've got the RS225s already. I must admit its funny thinking about combining a $460 midrange with $46-65 tweeters and woofers. 8)

[JonMarsh]

Yeah, but the midrange is where the biggest part of the music is, and where our ears are most sensitive to distortion.

And it's tough to find a similar midwoofer driver that beats the RS225 on the low end for 2-4x the money. You could get one of those super pricey SS 8's with the 9 mm Xmax for $300 or so... Tweeters? Well, you'd be pushing the C23-6 or C24-6 turf for better neutrality and distortion specs, though I do think they need to be modded slightly even then. (felt under the grille to kill some of the diffraction effects).

[Jed]

Jon,

I contacted madisound for availability of the accuton C90, and they said 2-3 months! However, they received a shipment yesterday and apparently they were shipped out the same day. I'm hoping they were referring to your order too.

Jed

[Jim Holtz]

Yeah, I agree on the cone mats...

I was just imagining entering a system with OW1's in a budget category...

C

Chris,

It just struck me that I mis spoke. :roll: What I meant was that the designs based on the M130 were always a favorite at the DIY events. It's a nice driver for $25. It doesn't even measure too bad based on Mark K's tests.

Jim

[JonMarsh]

Jon,

I contacted madisound for availability of the accuton C90, and they said 2-3 months! However, they received a shipment yesterday and apparently they were shipped out the same day. I'm hoping they were referring to your order too.

Jed

I belive they're a primary distributor (still) for Avalon, and the Isis is now in production and being advertised.

I did get notification from Adam today that "my" C90's were in and being shipped, so by Friday or Monday I should have them. :T

:dancenana: :dancenana: :dancenana: :dancenana: :dancenana: :dancenana: :dancenana: :dancenana: :dancenana: :dancenana:



~Jon

[ThomasW]

Is that the sound of someone's wallet draining..... :B

[cotdt]

hey Jed,
SEAS just came out with the NEW version of the Seas 5.5" Nextel mids:

http://seas.no/Product%20bilder/Art-pict.-M15CH002.opt..jpg

[JonMarsh]

Is that the sound of someone's wallet draining..... :B

Naw, you're confusing that with the big sucking sound coming out of my bank account.... sort of like the large floor standing Dirt Devil.

Fortunately I got a check for the seminar honorarium, and there should be something possible for my technical session presentation, though that will take time.

Got midranges?

Calculations show that even if I derate the cone excursion 50% the C88-6 on the planned baffle will have plenty of output from 250 Hz up for a 106-108 dB dipole (Arvo Part Grande).

I'll know for sure after I setup to do distortion measurements. Because of it's construction, it may require an aluminum baffle plate, like the little 5" Seas back in the 80's did.

[jdybnis]

I'll know for sure after I setup to do distortion measurements. Because of it's construction, it may require an aluminum baffle plate, like the little 5" Seas back in the 80's did.

Say more. What about a driver makes an aluminum baffle necessary?

[ThomasW]

There's not much open space on the back side of the basket. So an alu baffle insert allows the cone to breath better.

[Dennis H]

It might be a good candidate for rear mounting.

[JonMarsh]

That is another possibility, but then you'd kind of have a short "horn" in the front. Which would be better than masking the rear, due to a 1-1/4" baffle depth.

The issue is easier to explain with a picture than with words. Thomas I'm sure remembers the MMT that I build with this driver mounting concept (a 2-1/2 way).




I expect I will go with the aluminum plate concept, though. Give it some "breathing room".

[Dennis H]

You wouldn't need to have a horn in front if you bored the larger hole most of the way through the baffle kinda like the Phoenix. Leave enough wood for the screws if you don't want to magnet mount it and chamfer the backside if the baffle is really thick.

[JonMarsh]

The Phoenix baffle is only 1/3 the thickness of the Arvo Baffle. I don't like the large boards in the back of the Phoenix; in that regard I prefer the mounting method of the Orions. OTOH, the rear support to cut basket resonance (as is done for the W22 in the Orions) seems largely unnecessary to me for the C88-6. I'm more concerned with damping the grille response; have a few ideas to try out for that.


Of course, I may well use the aluminum baffle plate and rear mount the C88, which would be a bit cleaner overall in appearance and possibly front diffraction, too. Depends on how that might mate overall with the waveguide. Still thinking about that, and planning on building a milling fixture next weekend.

[Dennis H]

I'm not communicating very well today. Nothing new and the idea probably sucks anyway. I don't have a decent drawing program on this computer but this paint sketch will give you the idea. Screw it to the baffle from the back side. Should give plenty of breathing room without adapter plates (which have the potential to ring.)

[AJINFLA]

I'm sold on the de-coupled from baffle mid/midbass now, but I can see why gluing pucks on the back of $400+ drivers might sound rather unappealing 8O .
I really don't consider resale possibilities of drivers when I design, although I may have to as they continue to accumulate. Dennis' scalloped baffle should work real nice with aluminum.
Still not sold completely on the Accutons, but I'll reserve judgement till Jon tests them. I have some drivers in mind that I'd like to see them go up against, but I'm still waiting on that tax check. You know, the one thats in the mail :roll: .

cheers,

AJ

[JonMarsh]

I'm not communicating very well today. Nothing new and the idea probably sucks anyway. I don't have a decent drawing program on this computer but this paint sketch will give you the idea. Screw it to the baffle from the back side. Should give plenty of breathing room without adapter plates (which have the potential to ring.)

Thanks, Dennis- your intent is clearer.

My experience with 1/4" aluminum plate is that it's quite stiff and also not very reasonant; if I tapered the baffle down that thin, I still might want some reinforcement, such as with a metal plate. For example, imagine something like what you show, but with the plate in front, and the driver mounted to the rear of the plate, and the plate on the front panel, probably inset flush. I'd figured on tapering the baffle side wall anyway. If I have time after dinner I'll sketch out and post.

So AJ, what is your driver recommendation, other than the coax idea you're working on? Most of the Accuton's do have pretty linear motor assemblies, and the cone resonances are reasonably well damped- easier to work with than aluminum cone or magnesium cone drivers.

What I'm shooting for with the Arvo Grande and Arvo Venti are 250 Hz to 2 kHz midrange, and the tweeters and woofers above and below as required. I hope I'm going to actually get into the "waveguide" milling business this weekend, and get a little testing going there- including modding my Accuton tweeters. Even if I use them direct radiator, I want to clean up the area under the grill with a diffraction control. I'm going to keep one of each as a "control", and play with the other.

Wish me luck....

~Jon

[AJINFLA]

So AJ, what is your driver recommendation

I really can't give an absolute recommendation of a particular driver I am ever so keen on (yet) since its based a bit too much on conjecture than fact. Not good :naughty: .
Let me get my hands on one first (its a metal cone), do a little testing myself, gauge your interest on testing it or you actually test it, then I'll recommend it - if it doesn't completely suck .
Now would I be terribly upset if someone sprung for a JBL 218F to be tested (by you)? Heck no. That would be my top choice if I were forced at gunpoint to use a non metal/ceramic cone. The LSR6328P sounded pretty darn good to me (Yeah,yeah, I know its a box). And almost 16mm of xmax for a dipole bound driver? Yikes. Seems like it could be ideal (except that dang carbon fiber cone, oh yeah, and the 2ohms - for you passive guys ). But remember the reason why I wouldn't be sure I was hearing the Ayre you recommended, because I have difficulty isolating the sound of the amplifier itself from the upstream components, cables, speakers, etc, etc. interactions.
Well, same thing for the JBL. Unlike the folks who determine the "sound" of drivers by exchanging two in some box design of theirs, I can't isolate the sound of the 218F itself with the tweeter, box, crossover, amp, showroom, etc. intruding upon the evaluation. Sorry for my lead ears.

cheers,

AJ

[JonMarsh]

I really can't give an absolute recommendation of a particular driver I am ever so keen on (yet) since its based a bit too much on conjecture than fact. Not good :naughty: .
Let me get my hands on one first (its a metal cone), do a little testing myself, gauge your interest on testing it or you actually test it, then I'll recommend it - if it doesn't completely suck .
Now would I be terribly upset if someone sprung for a JBL 218F to be tested (by you)? Heck no. That would be my top choice if I were forced at gunpoint to use a non metal/ceramic cone. The LSR6328P sounded pretty darn good to me (Yeah,yeah, I know its a box). And almost 16mm of xmax for a dipole bound driver? Yikes. Seems like it could be ideal (except that dang carbon fiber cone, oh yeah, and the 2ohms - for you passive guys ). But remember the reason why I wouldn't be sure I was hearing the Ayre you recommended, because I have difficulty isolating the sound of the amplifier itself from the upstream components, cables, speakers, etc, etc. interactions.
Well, same thing for the JBL. Unlike the folks who determine the "sound" of drivers by exchanging two in some box design of theirs, I can't isolate the sound of the 218F itself with the tweeter, box, crossover, amp, showroom, etc. intruding upon the evaluation. Sorry for my lead ears.

cheers,

AJ

Looks pretty interesting. I believe those big JPL's Ayre was using used differential drive on the woofers, took, as well as a hellaciously laminated copper and steel pole piece setup.

Can you buy just that driver from JBL? How low does the tweeter go?

[jdybnis]

According to the JBL's price list for replacement parts that driver is $246

http://jblproservice.com/pdf/Transducer%20List/05%20Transducer%20List.pdf

[AJINFLA]

Hi Jon,

yes, the 218F is a DD unit with a 3rd "braking" coil added: (pg6) http://www.jblpro.com/pub/technote/J...-33%20rev3.pdf
The 6328P xo's the 218F @ 1.7k http://www.jblpro.com/LSR6300/PDF/JBL.LSR6328P.pdf
Now if they could just use that motor with a CMMD cone.. :W

cheers,

AJ

p.s. you might see why I want to use the 2268 as my (dipole) sub unit also

[cotdt]

no, a diamond cone

[JonMarsh]

Hi Jon,

yes, the 218F is a DD unit with a 3rd "braking" coil added: (pg6) http://www.jblpro.com/pub/technote/J...-33%20rev3.pdf
The 6328P xo's the 218F @ 1.7k http://www.jblpro.com/LSR6300/PDF/JBL.LSR6328P.pdf
Now if they could just use that motor with a CMMD cone.. :W

cheers,

AJ

p.s. you might see why I want to use the 2268 as my (dipole) sub unit also

Looks cool, when are you going to get some to test? A little pricey, but I'm hardly one to talk.

The NS12A-513 came in today- the cone is muy stiff, and the overall driver weight is rediculously low.... maybe a four 12 Arvo Venti is feasible after all?

[JonMarsh]

In other news of the strange...

FuzzMeasure

Image not available

Image not available

Image not available

This is version 1.3; version 2.0 coming soon.

Well, it's not Praxis, but it's a start.

[cjd]

And it's just measurement at this point, right?

C

[JonMarsh]

Right.... hey, us impoverished Mac users will take ANYTHING that looks like DIY speaker stuff.

Probably doesn't really do much more than Just MLS. For me, it's just a curiosity at this point, but what the heck... might play with the demo, if it's OK, at least it's an alternative possible to recommend. It looks pretty flexible about what kind of hardware it works with, but like any of the newer apps written with the Xcode tools, it's for late versions of OSX. It does export FRD files (don't think that TrueRTA will do that), supports mic cal files, does impedance measurements, T/S parameters, variable smoothing between 1/48th and 1/3 octave.

[Jim Holtz]

Peerless Nomex drivers?

I just noticed in Madisounds catalog that there is a standard Nomex series driver that doesn't have the ugly white frame. My opinion of course. :W Does anyone know how the Exclusive 830882 and standard 830873 compare performance wise? Not much difference in price and specs appear to be similar.

Thanks!

Jim

[JonMarsh]

Although Le is rated the same, inductance is higher with rising frequency in the 873- 2X higher. Not as much copper in the gap, I'd wager. If all other things in motor design and basket were equivalent, you'll probably still see more distortion in the midrange and above, and more higher order distortion, due to inductivity modulation. But, other thigns may not be equivalent.

It's like comparing the old 850467 against the 850439. The more "standard" driver is nominally flatter in frequency response and looks easier to work with. But the ultimate resolution and quality aren't as high.

That doesn't mean you can't make a very pleasant sounding system with it- could be the right choice in some circumstances. But for the money ($47), I'd question what the intended use was and look pretty closely at the alternatives.

Midrange driver? The 882 just isn't that much more expensive. If you're running up to 2500 Hz, I'll wager a nice dinner in the Bay area it will be cleaner in HD and IM. It could certainly be arguable whether you'll hear that in all cases, but my personal experience is that a system is the sum of a number of choices, and the devil is in the details. On a fairly high end system, in a good design, I think you will hear it, just as Jed is now finding that the paper cone Seas mid he was using isn't such a great match to the clarity of the Accuton tweeter. (but then the Nextel W15 has a lot of issues, especially for a Seas Excel driver- hard for me not to say, "What were they thinking?")

Midwoofer? I'd build a bigger cabinet and use an RS180. Or an 883. Neither of the smaller Peerless have enough Sd and Xmax to be taken seriously below 100 Hz.

BTW, the Peerless baskets are silver, not white. But if you don't like a light colored basket, well, you don't like it. There are many trade-offs and issues around speakers, and certainly esthetics are one.

[Jim Holtz]

Although Le is rated the same, inductance is higher with rising frequency in the 873- 2X higher. Not as much copper in the gap, I'd wager. If all other things in motor design and basket were equivalent, you'll probably still see more distortion in the midrange and above, and more higher order distortion, due to inductivity modulation. But, other thigns may not be equivalent.

It's like comparing the old 850467 against the 850439. The more "standard" driver is nominally flatter in frequency response and looks easier to work with. But the ultimate resolution and quality aren't as high.

That doesn't mean you can't make a very pleasant sounding system with it- could be the right choice in some circumstances. But for the money ($47), I'd question what the intended use was and look pretty closely at the alternatives.

Midrange driver? The 882 just isn't that much more expensive. If you're running up to 2500 Hz, I'll wager a nice dinner in the Bay area it will be cleaner in HD and IM. It could certainly be arguable whether you'll hear that in all cases, but my personal experience is that a system is the sum of a number of choices, and the devil is in the details. On a fairly high end system, in a good design, I think you will hear it, just as Jed is now finding that the paper cone Seas mid he was using isn't such a great match to the clarity of the Accuton tweeter. (but then the Nextel W15 has a lot of issues, especially for a Seas Excel driver- hard for me not to say, "What were they thinking?")

Midwoofer? I'd build a bigger cabinet and use an RS180. Or an 883. Neither of the smaller Peerless have enough Sd and Xmax to be taken seriously below 100 Hz.

BTW, the Peerless baskets are silver, not white. But if you don't like a light colored basket, well, you don't like it. There are many trade-offs and issues around speakers, and certainly esthetics are one.

Jon,

As usual, an excellent analysis of the drivers and exactly what I was looking for. I'm thinking in terms of a future project using one of the Nomex cone drivers as a mid with (2) RS225 woofers and a Fountek NeoCD3.0 ribbon. Just speculation at this point. I'm in the middle of building Dennis Murphy's RS 3-way with the H1212 and am struggling to get it done before Spring time hits and yard work/landscaping drags me outside. I love the open spaces and solitude our one acre lot in the country offers but it's a lot of work in the Spring. This *IS* my last year of landscaping. 8O I've had enough!

Thanks again Jon!

Best regards,

Jim

[cjd]

Jon: Probably doesn't help you any, but Speaker Workshop works quite well for modeling running on WINE under Linux. Not quite perfect, but very much usable. I have not tried using it for measurement in that environment, and I'm not sure it would happen.

C

[JonMarsh]

Jon: Probably doesn't help you any, but Speaker Workshop works quite well for modeling running on WINE under Linux. Not quite perfect, but very much usable. I have not tried using it for measurement in that environment, and I'm not sure it would happen.

C

Interesting, that doesn't surprise me. The simpler programs usually will, it's the ones where they're trying to stretch the boundaries of what is possible that often don't make it under emulation.

I've got a few things I'm going to try under VPC, like Edge and WINISD, and I may install Classic environment so I can try MacSpeakerEz. Of course, I do have my AMD Turion Laptop, it's just that sometimes I really like working only one system. I'm hankering for a PowerMac, and I figure one of those will do the VPC thing fairly adequately.

[JonMarsh]

TC2+ - some Basics

I wouldn't draw any big conclusions from this, but I've been doign a little more testing, similar in format to some woofer testing I did last year.



Nothing fancy, just some basics for first order comparisons for dipole use. First, a swept SPL plot. BTW, this was done in my preferred single 4 ohm VC mode- the DVC TC2+ measures flattest this way, though in a box where the power thermal power handling is needed, the conventional connection will be preferred.







Next, swept SPL plus HD2 and HD3 distortion at 2.83 VRMS drive. I'm interested in the basic linearity at moderate or modest SPLs. Sort of the inherent signature even if you're not pushing it hard. You might be surprised what I've seen with some woofers/sub drivers at this level in the past.


First, SPL and HD2



Then SPL and HD3.


Not bad at all, some rise in HD3 with increasing frequency, but still at pretty low levels.


Now, at ~100 dB.


2nd harmonic rises quite a bit compared with the lower level. Most people won't mind that; it will just make the bass sound "richer". But definition may suffer a little.

and HD3 at ~ 100 dB



I'd hoped to see a little lower HD in the upper bass/lower midrange, but this is pretty good compared to most of the competition.

[JonMarsh]

Aurasound NS12-513A

Something not so similar here. This is not really a sub driver, and the rear vent may prevent it from being a dipole woofer, as it's a little smaller than we normally like. I didn't hear anything untowards, but I need to do some higher level pure tone testing, probably. Still, this part has promise. Tinsel leads are woven into the spider, like the TC2+.

Oh, BTW, underhung neodymium motor, weighs about half of what a TC2+ or RS315HF does. Feels like less, though. Very stiff aluminum cone.







This is pretty amazing upper end performance for a 12" woofer, IMO.



Frequency response measured under the same conditions as above.



Not bad, huh? Flattest I've ever seen in a big woofer. Pretty slow rise in VC inductance.


More to come... need to eat dinner before uploading the rest.


OK, here's a teaser....




Dinner is done- time for 90 dB HD3




OK, this driver is only rated at a a little over 1/2 the Xmax of the TC2+, so we probably shouldn't expect too much at 100 dB, though with the somewhat limited range of the sweep (dipole main panel, remember), maybe things will look OK...






Note the declining distortion with increasing frequency- must be lots of copper in the gap, and of course, the amplitude of motion is declining.




Pretty respectable upper end distortion performance- will bear further investigation. Most 12's don't do well over 250 Hz. These might work well in the Arvo Grande or Arvo Venti (250-300 Hz crossover), and may even be a candidate to go all the way up to 500 Hz or so in the Saint-Saens. Depends on how low the 4th and 5th harmonic levels are. Will have to check.

[KJP]

No Dinner! More Measurments!!!!!

[Jed]

The driver I can't wait to see is the Accuton C90. If it as good as we all think it is, I've sold enough of my stockpile of "used" drivers that I can now afford them. The "old" C79 sure looks pretty nice in a more traditional 3-way with C12 and RS225 though. It will take some convincing that the C90 is $170 per driver better than the C79, if used as a midrange.

[AJINFLA]

I can't recall where I (think I) read it, but isn't this the first time Aura used shorting rings with their NRT motor? Seem to remember something like this.
I know its a curious question Jon, but how does the off-axis hold up? I absolutely hate when manufacturers don't show this on their FR plots. You've rekindled my interest in the NS10...

cheers,

AJ

[JonMarsh]

I was fairly interested in the original version of the NS10- white cone, different magnet basket, though the NRT motor in that case, too.

I will probably do some off axis stuff later, but for a driver that's this pistonic, (no notch mode before the upper breakup), off axis will be determined basically by radiating diameter. Should be pretty good up to 450-550. Let's see, I remember I was thinking a line source of 10's or 12's in combination with my RD50 for the Saint-Saens... this might just be the ticket. At least, it's something to check out further.

I hope to measure my C88's this weekend, too, and some other things, if time is available. Also want to get measurement data for the Modula MT/Elaine Marie Mk III with the Peerless 830883.

[capslock]

Jim, regarding Nomex vs. Exclusive, have a look at this: https://www.htguide.com/forum/showpo...&postcount=168

The regular Nomex have no copper, at all, just a 4 mm alu ring that sits below the pole plate and outside of the VC. The Exclusives add about 0.4 mm of copper cladding on the pole (to just below the pole plate) and a conductive alu phase plug.

The extra raggedness in the FR is in part due to the lower inductance (hence, an inductor in series will give in an FR more similar to the regular Nomex) and in part to the stiffer construction (extended former is attached to both cone and dustcap).