Response to Q's regarding some recent designs (Accuton C90)

[Jed]

I decided to just start a new thread discussing some questions that came up regarding the use of this driver in a project.
2009 Version:
C173 T6 90

Jed,

What SPL is that? 85db? It looks VERY good though.

I'm listening to this driver in a 3way with the Illuminator tweeter and Scan Speak 26W. Quite simply this mid is the most transparent mid I've ever heard......

Well I guess at the price you should get something for the money!

Here's the Illuminator Air Circ tweeter distortion at around 85-90db:


Here's the Scan Speak 26W 8 ohm:

This is on par with the best I've ever seen. Also the Frequency response was very flat. Sorry no picture of that right now.

By the way; yes the test was around 85-90db in this box:

Jed,

How would you compare the 26W to other drivers you have used for midbass and bass purposed?

It has a very linear FR and VERY low harmonic distortion profile. Plenty of Xmax to boot. There's not much better out there than the 26W. By the way this is the aluminum cone version. The paper cone version looks interesting as well, but the FR doesn't look as nice as the 26W from the graphs I've seen. Might have to test that out for myself sometime.

Hi Jed,

Whew! You are definitely in the high end with that combo. I've not heard that particular Accuton driver but totally agree with your comments on the ones I've heard. They simply have a see through quality I've not heard from other drivers.

That said, I about had a heart attack when I saw the price! Unbelievable! How come no love for the C82 or whatever it's called now? It's still extremely spendy by my standards at $275 but it's less than 1/2 the price of this driver.

BTW, I really like your new Lineup Maxx MKII design. The 22TAF-G is a favorite of mine and I'm still in love with the W4-1337. I'm a big Seas fan too. :T Anyway, a very very nice selection of drivers, IMHO.

Jim

Thanks for the props Jim! Are you going to Dayton this year? Maybe if time permits I can bring the new Lineup Maxx L16mk2

As for the C82, if they use the same motor as the used in the past I doubt it comes remotely close to the C90's performance. Want to send a pair for me to test?

Jed, I do not understand the combo of Scanspeak tweeter with the Thiel&Partner mid. I would rather see an metal cone tweeter. Also with these kind of drivers I expect a cabinet which has bigger round overs, you do not want to introduce edge distortions of the cabinet.

I think JonM best answered this in his response below. Also note that even though the cone materials are not the same, the sonic signature is close because of each driver's low harmonic distortion profile and linear response. I do not detect timbre mismatching, which I deduce is because of those qualities. Also, I doubt the Accuton tweeters can hit the transfer functions I used for this speaker without audible distortion.

As for the roundover, I ended up using a 28mm chamfer which works well to minimize diffraction.

Why not higher sensitivity drivers to match the mid? Or multiple bass drivers are least. Last time I reviewed all of the Scan Speak 8" drivers, they were all very low Qt and all very inefficient.

Out of respect to Evil Twin, back on topic, and I look forward to seeing your survey of bass drivers.

It's the 26W woofer, so not much different than other 10" drivers with low distortion. It will work well in a 60L box tuned below FS. The bass is lean and tight. It is fast and without a hint of boominess. Just clean sound. If the track is bass heavy, so will the sound get portrayed through this speaker. One of the trade-offs was getting the deepest bass response (selected the 10" for that reason), and it had to fit in a reasonable sized box. Dual 8" drivers would work well, but the impedance would likely be lower with the parallel connections and would be limited to a higher F3. This speaker will hit the high 20s in room.

[JonMarsh]

Sounds like a good plan, Jed- I suspect there are many people curious about your experience using the "big Accuton".

OTOH, I think it's a bit funny when people think that hard cone mids must be accompanied by hard cone tweeters- what I suspect you're really looking for in this case is drivers with high dynamic performance and resolution, and both the C173N-T6-90 and the D3004/66000 fit that bill to a "T".

Let's face it, if you're talking about a hard cone unit or soft cone unit and you think it must be matched with another of similar construction, at that point you need a reality check because it indicates that their performance OR the implementation in a typical design is flawed.

The last design I did and posted on the forum, the NeoD CC uses an "unholy" combination of plastic cone woofer, metal dome midrange, and soft dome tweeter- but used together in their optimum ranges, I believe. That's probably why ThomasW felt they were my most neutral sounding design to date, as you tended to not hear the speaker or it's signature, just the music.

The nice thing about the "good" stuff, like the D26CN55, for example, is that it's just amazingly neutral and get's out of the way of the music. Used properly, it sounds very similar to another old favorite of mine, the Scanspeak D2904/98000. The point with either of those is that properly used, they don't contribute much of their own signature.

Some components can achieve that only with some substantial effort, and perhaps choosing the frequency range judiciously. In the end, that's the job of the designer.

[Paul Ebert]

So, Jed, I think it's time to plan the CNYDIY event we've discussed so you can show off this design.

[Face]

I want to use that mid with a SS D2904/7100 for my next project.

[Jed]

So, Jed, I think it's time to plan the CNYDIY event we've discussed so you can show off this design.

Given my schedule right now it might be difficult to help organize anything but I might be able to make it out to Dayton again. Not sure what I'd bring but it would likely be the Lineup Maxx L16s or the quad woofer version I've been dreaming of for some time now. Let's face it, not many people have room for wide speakers.

This design might end up in some DIY gatherings. Likely Iowa, because that's where they will reside in the end.

I want to use that mid with a SS D2904/7100 for my next project.

Should be a great combo!

The nice thing about the "good" stuff, like the D26CN55, for example, is that it's just amazingly neutral and get's out of the way of the music. Used properly, it sounds very similar to another old favorite of mine, the Scanspeak D2904/98000. The point with either of those is that properly used, they don't contribute much of their own signature.
.

I couldn't agree more and this is my finding as well. Your philosophies serve us well, Jon.

[Hdale85]

It gets hard to compete at events with things like these as they go into the Ultimate class and some people just have lots more money then others I imagine They do look very nice and interesting though and I wish I could hear them!

[brucemck2]

Jed, other than cost, would there be any advantage to mating the T6-90 with one of the new Raal ribbons rather than the dome?

[Jed]

Jed, other than cost, would there be any advantage to mating the T6-90 with one of the new Raal ribbons rather than the dome?

The RAALs that I heard were very very good. Unfortunately the OEM RAAL is not allowed in kits, which is where this one will be offered. The other disadvantage of most ribbons is that shallower slopes put more stress on them, so it puts some limitations on the allowable target transfer functions.

[Jed]

It gets hard to compete at events with things like these !

These won't be competing in any events. Well, where DIY is concerned.

Also if you want to hear them make a trip to Rochester this weekend!

[Bear]

Jed, other than cost, would there be any advantage to mating the T6-90 with one of the new Raal ribbons rather than the dome?

In the price range of the 140D's, the Focal TBe tweeters might be an interesting experiment, as well.

[Hdale85]

Hah be pretty hard for me to make a trip anywhere at this point Busy busy...

[brucemck2]

Jed, approximately how low and how high can you cross the T6-90 and still have it's outstanding sonics?

Since I listen to a lot of small group or solo vocals, I've always like the idea of having most of the vocal range covered by a single driver ... if I could get 80hz or 100hz up to 1500hz or maybe even 2000hz that'd really nail the bulk of the range.

[JonMarsh]

I'm not Jed, so perhaps I shouldn't intrude- I'd remind you though, that the nominal crossover point will depend a lot on the kind of target function you choose; the wider the driver overlap (lower order), then the more restricted the bandpass range.

Considering the driver performance, and limited Xmax,




This is measured with a nominal baffle width of 9", at 0 degrees, 15 degrees, 30 degrees, and 45 degrees.

A working range of 250 to perhaps as high as 2500 Hz might be reasonable; presuming you want consistent off axis performance. Let's remember that the much smaller C79 is usually crossed at about 3500 Hz max. A lot comes down to what sort of tweeter you match to it, and how steep a slope you think it needs, and whether you want to control the group delay of the overall system response. A target transfer function I'm looking at for this driver in a three way system would have a nominal 2 kHz upper crossover point, and a lower point at -6 dB of about 350 Hz, perhaps a little lower. Perhaps not.

I'm curious what Jed chose in his speaker pictured in this thread. :W

[Jed]

I'm curious what Jed chose in his speaker pictured in this thread. :W

About 360hz and 2.2k.

[Jed]

Jed, approximately how low and how high can you cross the T6-90 and still have it's outstanding sonics?

Depends a bit on what you're matching up with it. On the low end I don't think I'd take it much lower than 250hz. Drivers have a certain slope that they like given their outputs and a entire slew of other variables. Lately I've been going more for elegant simplicity, so while I could try a lower crossover point, the 26W is excellent up to 800hz or so. Therefore, the need to cross low is not necessary in that circumstance.

The top end is not really limited by it's harmonic distortion profile (at least in this 2009 sample), in fact you could take it up higher than I did, but the tradeoff is the off axis response/power response of a larger diameter mid is not up to par with mid domes/cones of a smaller diameter (see Jon's plots for reference). Crossing higher is better reserved for smaller diameter mids which can better match the dispersion and power response characteristics given the pistonic nature of most tweeters used in their best suited passbands. Note: small mids have their limitations as well.

[Rick Craig]

Nicel design! At one point I was told they had discontinued that mid and the "96" was the replacement. I did a high sensitivity design with a ATC 15", Raven ribbon, and the 96. It certainly was one of the best sounding mids that I've ever used.

[Jed]

Nicel design!

Thanks...

Accuton drivers are difficult to get in general. Once they go out of stock at madisound it takes months to get a new batch in.

[JonMarsh]

Thanks...

Accuton drivers are difficult to get in general. Once they go out of stock at madisound it takes months to get a new batch in.

Isn't that the truth- I waited for my C90-T5s about 5 months in 2006.

[Jed]

Note the C44 and C79 are out of stock right now. Let's see how long it takes for Accuton to send a new shipment.

[JonMarsh]

Sometimes you have to work with one of the other vendors- just got a pair of C79 this week from Soniccraft. Drivers that are popular in commercial speakers are hard to source now- Accuton is barely keeping up with OEM demand- DIY doesn't mean squat to them.

[Jed]

Well look at that. C44 and C79 back in stock! Maybe Accuton heard our cries? :-)

[Evil Twin]

I sense a sigh of relief within the Force....

[TacoD]

Well look at that. C44 and C79 back in stock! Maybe Accuton heard our cries? :-)

Thiel & Partner (aka Accuton in the USA), is also difficult to get in Europe.


BTW, in my experience hard dome tweeters have a tat more resolution compared to their soft dome counterparts. As the Acccuton is very revealing and in my book the Scanspeak domes are not the last word in resolution I would pick something different. I do not want to suggest it is a bad sounding system/ combination .

[xyrium]

Holy rehash batman...

Guys,

Sorry to revitalize such an old thread, but I was wondering; the C173 T/S parameters seem to lend themselves towards a nice sealed two way design. Would you be in agreement, or are the xmax capabilities of this driver precluding it from such duty?

By going with V. Dickason's notes on sealed woofer choice in LDC7, fs/Qes produces a really nice figure for EBP of 49.

Edit: To clarify, I'm speaking of the C173-6-92.

-Paul

[JonMarsh]

The "C173" designator encompasses a wide range of drivers with the same basic basket size, but substantial differences in motor design and cone configuration. The C173N-6-90 is a dedicated midrange, as I think you're familiar with, Paul.

I'm sort of speculating here, but I believe the 92 is discontinued as of now, other than stocks on hand- it's not on Accuton's web site. I expect it's replaced by one of the other higher Qts C173 models with better damping of the upper cone resonance. But who knows? The parameters of this driver can be suited to a sealed box, or a ported with the right size; the Xmax limitation is unfortunate, and I suspect the motor isn't any better than the 94 or 95 as regards midrange distortion, being the same basic design.

The 95 and 95E (with damping inserts) variants have Qts in a range reasonable for ported enclosures, but don't have the extended top end of the -90, and appear to have higher midrange distortion due to resonance amplification of their cone resonance showing up in the 500 Hz to 1500 Hz area - or something is! By Accuton's plots- haven't measured that model myself. This driver doesn't use the underhung neodymium motor of the 90.

The -94 has a very low resonance, but the Qts is still rather low, 0.19, and the midrange not that clear...

The -96E is the new bass-midrange that's a bit "mis-billed" - being cited at 94 dB sensitivity, yet the LF sensitivity in the 100-200 Hz area is apparently only 88 dB, like the other midrange/bass units, but I'm betting with rather low Le resulting in the rising frequency response hitting 94-95 dB in the 1-2 kHz area. The published distortion looks solid on this one, it also appears to use the underhung motor like the -90; the 95 and 94 variants don't. I suspect they have a bit of copper in the gap of that motor, and I suspect it's expensive as heck, as the drivers using it are. The 96 is basically a similar driver without the damping inserts.

I personally suspect that the 96E is similar to what Kharma uses in the Mini Exquisite; duals, 2.5 way, and ported, with a custom Accuton diamond tweeter.

If you want the pellucid midrange described of the original C173N-T6-90, you're probably going to have to use one of the underhung motor models- the motor is definitely a part of what delivers the goods.

[xyrium]

Ahh, thanks Jon. I'm trying to find a woofer to do a sealed monitor design with. I had it down to

Morel CAW938
SEAS Prestige CA22RNX
SEAS Prestige L22RNX/P

I think I like the fact that most of these roll off around 3k, so I'm thinking even a 2nd order filter would be fine. Either way, once I get closer to a price target (that Accuton was way at the top of the budget anyway) I'll start a post seeking some opinions.

Thanks again!
Paul

[Jed]

The C173 92 is back in stock at madisound now.