They're Here!

[JonMarsh]

Well, not HERE, but here.







:B :B :B :B :B :B :B :B :B :B :B :B :B :B :B :B :B :B :B

:T :T :T :T :T :T :T :T :T :T :T :T :T :T :T :T :T :T

[Bent]

Specs say 1600 Hz and up - how low will you push them before they turn inside out?

Ben.

[cjd]

Gah!

I

Don't

Need

This

Right

Now.



Must Resist.

Must




Resist


...

[JonMarsh]

He he, I'd say it depends on how you cross them... I woudn't do a 2nd or third order below 1600, but we have our ways....

Chris, you want them.... you know you want them...

[Evil Twin]

Chris.... feel the power.... feel the power of the dark side...


Come over, Chris... you can sense through the force what these would do for your next system... your path is inevitable... there's no point in resisting...

Join us, Chris!

[cjd]

dude, I got "Dark Side" M&M's the other day. :P Is that close enough?

Really, I'm not sure they're in the budget right now - my wife has two classes this sememster and her work pay-back is only going to cover ~$400 of the $5000 until Jan 4th of next year (meaning, we get it all back eventually but just not yet).

*sigh*

I'll have to see. At which point I'm sure they'll be all gone.

C

[Evil Twin]

That's a lot of educational expense to float; I understand and agree it's a good investment...

I doubt they'll be disappearing for very long- I think Darren must realize there's some pent up demand. I had to resist going nuts myself.... but I'm not a monk, so a few are on the way.. :B

[Captain Cojo]

I couldnt resist...7 coming my way... :T 8O 8O :T

[Brian Bunge]

And dealer price pushes cost to below $40!!!! I'll still probably have to wait a few weeks to buy a couple.

[awm]

Drop-in for XT-25?

Hi, Jon -- I was wondering if this could be used a a virtual drop-in replacement for the xt-25 in the M8a?

Thanks,
Andy

[JonMarsh]

I need to check the impedance curve on the production parts... with the proto I have, that is the case. MarkK is talking about collecting a few of the early parts from 1st purchasers and doing some tests (checking Fs, alignment, and correlating LF distortion).

The biggest change that might occur is tweaking the tweeter zobel, if the Fs is different on the production parts. The driver panel size is compatible with the XT25 and SS9800, but if you cut the magnet hole a little undersized or tight, you might have to open it up a bit.

~Jon

[JoshK]

just went to PE's site this morning (also went yesterday) and noticed they were in, was going to post but it looks like you guys are more privvy that I.

[Kramer]

Im able to hold off. I see most of these initial projects as RS180-based.

Not that there is anything wrong with the RS180, but I want to do a high-end project next (like something with Jon's favorite Peerless HDS - that he always links to :wink: ).

[Andrew Pratt]

So would this be a significant upgrade from the XT25? Also better/equal/worse then the 27TDFC?

[Evil Twin]

Lower distortion, especially high order harmonics, than the 27TDFC. Unlike the 27TDFC, impedance and size is compatible, should drop in.

[Andrew Pratt]

You are evil

[Kramer]

What about that big drop-off beyond 10K?
The 9950 seem to hold the line better (even off axis).

[JonMarsh]

It does have a dip between 13K and 20K, whose size is dependent on the diffusor configuration, as the proposed modifications by DLR shows. This is basically due to the dome remaining pistonic- there's a path delay between the center and edges- I've seen this with other hard dome tweeters, if you remove some of the lenses or diffusors they come with, but then they seem to always sound better without them, to my ears.

OTOH, it has lower harmonic distortion than the 9950, especially the higher order harmonics. You pays your money, you takes your chances... or rather, your preferences. I like clean reonance free metal domes, (like the sound character of the SS98000), and this one is very similar, only better- cleaner and louder.

Just my 0.02.

~Jon

[vinceb]

(going to just jump in with a post here, I wondered where everyone went when the home theater forum diy board died, guess I found it...)

Evil, sir, would you allow your kindly alter ego to consider a design with the extremis? Maybe a MT or even a MMT? I've been on the brink of ordering some of the Adire kits to go with my lonely extremis (6 of them for matching surround setup) but this is very intriguing idea. After the thread with the MMT I got thinking MMT for LR and MT for center and surround, but then I thought maybe MMT across the front and MT for surround, then I got thinking MMT.....

I was kind of thinking MMT in the front now and convert to MMT in back later. I guess it partly depends on how evil the crossovers are Thank you for your consideration of this matter, and please don't do that evil collar-choke dark side force thing on me :E

[capslock]

Well, I guess those RS180/TDFC projects could also stand an adaptation to RS28. The TDC would also be a good choice, even in comparison to the RS28. Ths TDFC is nice, but I think I prefer the TDC (just deferroed one of my TDFC which makes it a TDC)....

[Jam_Master_J]

This is perfect timing. Now I can really start getting parts together for M8 MTMs. I finish my last exam on Friday and start my full time job on Monday so I'll have the cash to make this happen. Thanks for the update Jon.

-JMJ

[cjd]

capslock: What do you find the difference to be without the ferro? You have me curious since I quite like the TDFC as-is but have been vaguely curious about the TDC.

In other news, I do know I'll be adapting my MTM to the RS28A (it'll also debut with a lower than current crossover point, hopefully improving CC performance significantly).

C

[dawaro]

Actually in an e-mail from Jon last week he mentioned that he had finished a preliminary design for a MTM with the RS28 and the Extremis so you may not have to wait long.

[JonMarsh]

At this rate I'm going to have to run a seperate version of my Franklin PlanPlus software just to track all the variants to post on these different projects! Sheeeshhh!

Vince,

Grahams MT project has most of the initial crossover work done by yours truly- the overall design is a collaboration with contruction and feedback by Graham. As noted by David, I do have an MTM/MMT version worked out, which I'll post shortly- using- ta da- the RS28a. So take that, Dan Wiggins.

David, I've been getting home late and won't catch up with emails at home till the weekend- you'll hear from me soon.

As posted on the Modula MTM sticky thread, there will be an alternative tweeter crossover posted shortly, derived from having done a version of the Arvo with the RS28a (which really took little more than changing the zobels compared with the SS9800, and not by much.)

Gawd, I can't believe how far I've fallen, turning into a schill for Dan and Darren. NOW who's fallen to the Dark side? :E :rant:

And I thought I was going to pawn THAT off on Evil Twin- instead, he's doing the fun projects, like the Saen-Saints. Where's the fairness in that?


I think I need to go home and lift a brewski- preferrably something German...

:beer:

And if that doesn't get the job done, I'll get out one of those Tequila's Hank recommended and put on Avril Lavigne REAL LOUD! :banghead:

arty:


~Jon

[Evil Twin]

You are evil

You don't know the half of it... you probably think Anakin Skywalker had a mispent youth, I can tell you stories of the dark side...

six foot monolithic towers housing only a single 10" woofer, driven by the energy output of a complete turbolaser battery generator (aka Phase Linear 700), rattling windows and shelves with Saint-Saens symphonies...

careening through the streets and mountain paths on a land speeder at speeds which would cause even the hair of a grown wookie to turn gray and fall out... (no wonder ThomasW looks like he does these days

dual 12" subwoofer cabinets so stiff they ring like a bell when suspended by a string before veneering...

faceted speaker cabinets that make Avalon tower speakers look like mini-monitors...

[jdybnis]

faceted speaker cabinets that make Avalon tower speakers look like mini-monitors...

:lol: That one's my favorite. I'm visualizing something that sits on Easter Island and gets offered a lot of goat's blood (or whatever the hip sacrificial offering is these days). The thought is truly frightening. :lol:

[vinceb]

Started adding up the components for the crossovers. Hmmm. Could I drop these into the kit 61 design without changing the crossovers? I want good sound in a small cab that plays very loud when needed without stress. I can always upgrade the crossovers later. There looks to be about a 2db difference, with the RS28A around 90db efficient, so I guess a resistor is in order there to tweak it, but other than that what do you think? I don't know enough to be able to determine whether the crossover is addressing the Usher's bump around 1400hz - wait, scratch that, the usher in the kit 61 is the shielded version which doesn't have that bump. The impedance looks the same in the crossover region, is that enough of a match?

Thanks for your thoughts,
Vince

[cjd]

Well - it looks like I"m going to have to pick some of these up. I get different results using Jeff B's crossover program than Speaker Workshop gives. And I'm not entirely sure which to believe. I suspect Jeff B's is accurate but I can't figure out why SW is NOT correct.

Mostly, SW says it's about 3dB lower output on the RS150's only (the tweeter it models almost exactly the same). I'm entirely confused. They do not predict the same response on the RS150's though, at all. Probably because Jeff B's doesn't quite do elliptics right (actually, some testing proves it so.)

Of course, aside from the addition of a resistor on the tweeter, it's two other components that change. Or something. Maybe.

C

[dawaro]

Hey no problem Jon, I figured you had been pretty busy. I must warn you though, I think I have finally figured out how to do the elliptic's in LspCAD 5.25. I have a couple of different designs I have a million questions on.

[JonMarsh]

Started adding up the components for the crossovers. Hmmm. Could I drop these into the kit 61 design without changing the crossovers? I want good sound in a small cab that plays very loud when needed without stress. I can always upgrade the crossovers later. There looks to be about a 2db difference, with the RS28A around 90db efficient, so I guess a resistor is in order there to tweak it, but other than that what do you think? I don't know enough to be able to determine whether the crossover is addressing the Usher's bump around 1400hz - wait, scratch that, the usher in the kit 61 is the shielded version which doesn't have that bump. The impedance looks the same in the crossover region, is that enough of a match?

Thanks for your thoughts,
Vince

The sensitivity of the Extremis 6 is a lot lower than the published spec- it's not surprising given the long Xmax and T/S parameters. I'm not really familiar with the Kit 61- the initial design I started with for an MT was a version in a 0.75 cu. foot enclosure (Parts Express), but when Graham and I were analyzing the performance using Unibox, it seemed only sensible to try for a more extended alignment using a larger enclosure, which is how the one he took to the Toronto DIY meet came about. (use the forum search tool to find all the discussion about the Extremis).

As far as the crossover optimization, we wanted to avoid some areas where the Extremis cone is starting to exhibit stored energy, so I used the same kind of steep slope topology as for metal cone drivers like the RS180, with modification to the baffle step compensation due to the slight downslope in the response which the Extremis has. This also helps the off axis power response, becaue if you do as Dan as suggested in some forums, and run it up to 3 kHz, you have something of a mismatch between the dispersion of the midwoofer (beamy) and the dispersion of the tweeter. I strive to keep the 30 degree and 45 degree off axis repsonse as flat and smooth as possible through the crossover region; that's one reason these systems sound pretty good, and surprisingly similar, is that I'm really controllling the voicing of the system, instead of letting the drivers do it.

The price to that, of course, is component cost. But we're talking about a $99 midwoofer- this crossover was originally developed for a $50 HiVi 8" woofer midwoofer, and did a very nice job optimizing it's behavior, too. It's a corollary of Hoffmans Iron law that to get an Extremis to respond with close to the same efficiency and just as deep in the bass, takes about the same size enclosure as a larger driver, like a good 8" unit. The Extremis will go lower in a smaller enclosure, but that's partly because with it's T/S parameters, true midband sensitivity is on the order of 83-84 dB tops, not 86 or 87 dB.

~Jon

[JonMarsh]

What about that big drop-off beyond 10K?
The 9950 seem to hold the line better (even off axis).

One other tidbit to put up- really, the RS28a holds up very well off axis, as DLR's measurements show- it rivals or exceeds most 1" dome tweeters in that regard, and has a very smooth drop off, doesn't seem to develop strange strange dips and glitches. The 15 degree off axis response is excellent- even compared with 1" drivers- and this defines much of the sound, as there's a lot greater power response contribution from this portion of the tweeter's repsonse than the on axis. This is why I do a lot of my develepment stuff 15 degrees off axis, then just go back and check on axis.





I have suspicions that it's behaving a bit more pistonically than some of the soft dome tweeters- and this can only help.

~Jon

[Jonasz]

Looking at the parameters of the SS9800 it has a Xmax of 0.1mm wich is pretty bad in my book. The RS28 is supposed to be a 9800 on steroids if I'm not wrong , does it have a greater Xmax? I just received my RS 10" today and looking at the build quality I will for sure buy more RS-series drivers starting with the tweeters. :P

Jonas

[JonMarsh]

Yeah, a SS9800 on SERIOUS steroids is how I'd describe the RS28A- they hand in with the Milleinum pretty well at low frequencies and very high drive levels (but so does the 27TDFC!) but the high order harmonics are quite a bit lower for the RS28A...




Dayton RS28a Prototype distortion, tone cluster centered at 1 kHz, Millennium Excel is red, RS280A is black. If you reverse them, the red disappears, essentially.

One man's "air" may be another man's distortion.

Courtesy of MarkK

~Jon

[Jam_Master_J]

That off-axis performance seems promising. This will be great for my set of MTMs I'm building since most of my listening is outside of the sweet spot.

[JonMarsh]

Today, they actually ARE here!

Like I've been hearing a few places, the diffuser on the inside of the grille is a skosh off center. NBD, as I was planning on taking them off, anyway. PE and Usher have done a real nice job with these; I hope I'll find a little time to play with them this wekend, at least run some curves, but I've got a honey do list from work for this weekend already that just won't quit... :roll:

[Jonasz]

So, now I guess several of you boys (and girls?) have had your RS28's for some time. Do they live up to the expectations? Are they SS9800- and Milenniumkillers or are they "just" very good tweeters for the dollar?

Jonas

[TacoD]

I do not think it is a Seas Millenium killer, it uses a different type of cone, so those are not 1:1 comparable imho.

[JonMarsh]

Man, this is so painful, work has been so busy I've had essentially zip to zero time for speakers the last several weeks (aka "April"). May doesn't look to be much better, weekends have just amounted to telecommuting/working from home, and getting ready for travel during week.

Today is Dallas, tonight I fly to Chicago. Mineapolis after that.

I haven't had a chance to listen to my production parts yet. The proto sounded great in the single Arvo, even without a fully optimized crossover (ie., crossover as done for SS98000)

~Jon

[DIY_newbie]

Man, this is so painful, work has been so busy I've had essentially zip to zero time for speakers the last several weeks (aka "April"). May doesn't look to be much better, weekends have just amounted to telecommuting/working from home, and getting ready for travel during week.

Today is Dallas, tonight I fly to Chicago. Mineapolis after that.

I haven't had a chance to listen to my production parts yet. The proto sounded great in the single Arvo, even without a fully optimized crossover (ie., crossover as done for SS98000)

~Jon

Jon,

Where abouts in Dallas? I live in Dallas and work at Texas Instruments..

--Chris

[cuda65]

Hey Jon:

I will wave to you as I drive by O'Hare later tonight. Hope you get the chance to work on your speakers again soon.

[JonMarsh]

I hope so, too!

In Minneapolis today, (Thursday), have a Technical seminar to give for our local customers sponsored through distribution (NOT on speakers, I'm afraid ), then some specific customer meetings on critical topics in the afternoon. Have to report back to Europe when I get home late tonight so we can pull the trigger on a new product project with the correct data. THEN I'll get to go to bed... sometime in the wee hours...

~Jon

[Jonasz]

I have now actually ordered a pair. They will hopefully be used in a dipole MTM with Seas W22 and dual XLS12.

[JonMarsh]

Should be sweet in that application- I'm chomping at the bit to get a few more designs done with these, but work has been crazy of late, plus have some other things going on (getting a new NEC CRT projector from a guy in San Diego- will pick up in a week or so, when I can get time)