ScanSpeak 6.5" Revelator vs. Illuminator Distortion Revisit - diyAudio
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Old 17th January 2016, 08:03 PM   #1
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Default ScanSpeak 6.5" Revelator vs. Illuminator Distortion Revisit

Hi Everyone,

When choosing between the 6.5" ScanSpeak Illuminator and Revelator I went with the Revelator in large part due to the comments Zaph made about the Revelator having lower distortion than the Illuminator.

Even though I wasn't really focused on measuring the Revelator, I did measure distortion recently, while doing more extensive measurements on a tweeter. One thing that came up was some distortion pops up in the upper end of the Revelators I wasn't expecting here, between 500Hz and 1kHz (ignore DB values!):

Click the image to open in full size.


The same distortion shows up without a crossover by the way. Since Zaph clearly has a lot more experience I was tempted to discount my measurements until I saw the same distortion pop up in another measurement set. Thanks to a review by SoundStage Network and the National Research Council of Canada's measurements of a Wilson Sophia which includes the same driver:

Click the image to open in full size.

Addmitedly, Zaph mentions not to use his measurements without duplicating his methods, but his old charts are perfectly flat distortion wise. I'm wondering if the Revelator has changed, or if Zaph's measurements somehow missed this, or if maybe he accidentally reversed the data for the Illuminator and Revelator?

Has anyone had a chance to measured the ScanSpeak 6.5 Illuminator and/or Revelators for distortion recently?


Best,


Erik
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Last edited by eriksquires; 17th January 2016 at 08:08 PM.
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Old 17th January 2016, 11:45 PM   #2
system7 is offline system7  United Kingdom
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I'm not sure where the problem is? That 500-1000Hz issue is doubtless the rubber surround edge reflection. Quite characteristic of ALL woofers. You can even see it in the impedance. Broadly speaking you can have foam surrounds, lossy rubber and corrugated paper all with different nodes and antinodes at the edge. The edge resonance is where the response usually bends and dips. Changing the surround material can alter the lossiness.

And then the 4-5kHz peak cone characteristic of all 6" drivers, being a half-wavelength thing, which shows in phase and Frequency Response.

http://www.scan-speak.dk/datasheet/pdf/18w-8531g00.pdf

Klippel publish some great datasheets. It's a complex business balancing all the damping, mass and rigidity trade-offs. Even weird stuff like rocking modes crop up.
https://www.klippel.de/know-how/literature/papers.html

Back in the day, we used to do something called white noise testing, which measured the broad spectrum noise produced by a narrow channel signal. A bit like crosstalk really. Audio engineers are ignorant of this technique, which IMO would show exactly why soft-domes are poor. They essentially have a poor signal to noise ratio.
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File Type: png Scanspeak 18W8531G00 Revelator.PNG (53.3 KB, 518 views)
File Type: jpg Scanspeak 18W 8531 G00 Waterfall.JPG (119.7 KB, 509 views)
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Last edited by system7; 17th January 2016 at 11:55 PM.
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Old 17th January 2016, 11:52 PM   #3
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Thanks Steve!!

The only problem is that it's not in Zaph's measurements, and I was hoping to get a better handle on the $100 more expensive ScanSpeak Illuminator 18WU/8741T-00 in terms of distortion or power output. I mean, the Dane's are not stupid, I can't believe it's $100 just for having a prettier motor structure.

I think part of what brought this up too was that RAAL was commenting on it appearing to be unusually high.

Maybe this is in fact exactly how a Revelator should look like, and the Illuminator is worse, I just cant' see it.

Best,


Erik
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Old 18th January 2016, 12:00 AM   #4
system7 is offline system7  United Kingdom
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Such different animals! Here's the pricier Illuminator.

http://www.scan-speak.dk/datasheet/pdf/18wu-8741t00.pdf

Don't fancy that one at all. Even if it's made of unobtanium.

My answer would be that sliced paper cones maybe have a downside. I wouldn't like you to come round and cut my cones with a stanley knife, then glue them back together! It's gotta be worse, hasn't it? Even if it produces some damping.
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Old 18th January 2016, 12:18 AM   #5
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Well, I tend to like multi-layer cones, such as the Focal W's or the Rohacell or carbon fiber composites I've listened to. The idea of two layers with different wave propagation characteristics being glued together to produce something that doesn't favor either's penchant for ringing makes sense to me, much like constrained-layer damping.

Plus, I really like my woofers. I give them new inductors often to show I care.

ERik
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Old 18th January 2016, 12:31 AM   #6
system7 is offline system7  United Kingdom
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The only problem with mixing materials while hoping for the BEST of both worlds is you might get the WORST of both worlds.

I believe Marilyn Monroe said to Albert Einstein that their children might be brainy AND goodlooking. Albert saw the other possibility...

TBH, I think these expensive low inductance speakers are very suited to wall mounting, because they filter easily and predictably with small bass coils.

That's how I'd use them. No bafflestep.
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Old 18th January 2016, 12:43 AM   #7
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Quote:
Originally Posted by system7 View Post
The only problem with mixing materials while hoping for the BEST of both worlds is you might get the WORST of both worlds.

I believe Marilyn Monroe said to Albert Einstein that their children might be brainy AND goodlooking. Albert saw the other possibility...

TBH, I think these expensive low inductance speakers are very suited to wall mounting, because they filter easily and predictably with small bass coils.

That's how I'd use them. No bafflestep.
Well, I did my baffle step with my low pass inductor, worked out pretty beautifully. Maybe that's why I don't get the fuss over BSC.

The one's I have sound great but largest "bookshelves" I've ever seen.

Best,


Erik
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Old 18th January 2016, 01:04 AM   #8
system7 is offline system7  United Kingdom
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Well, ERik, I enjoy talking to you.

The fact is, that when you place a speaker close to the wall, bafflestep becomes irrelevant. My latest fun LR2 speaker with the unavoidable power dip at crossover, which I am working on. Maybe a filler midrange driver at right angles to correct the power response... IDK...

Click the image to open in full size.

BTW, I'm not sure what's going in Joe Rasmussen's controversial thread at the moment, but the fun image I wanted to include to suggest that Quantum Mechanics is relevant is below. I love Physics Prof. Dick Feynman, inventor of QED. The best, most exact theory yet.
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Last edited by system7; 18th January 2016 at 01:08 AM.
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Old 18th January 2016, 08:04 AM   #9
BYRTT is offline BYRTT  Denmark
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Originally Posted by eriksquires View Post
...Plus, I really like my woofers. I give them new inductors often to show I care. .....
Like that one : )

Think have seen other good measured specs for that woofer over time online but can't remember where. Would it be too difficult next time you turn a bit on tone control and replace inductors than temporary place woofer on a bigger OB and measure it there, may tell if current enclosure is envolved.
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Old 18th January 2016, 08:41 PM   #10
wesayso is online now wesayso  Netherlands
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BYRTT, were you thinking about this site?
http://medleysmusings.com/ss18wu4741/
Klippel tests of the Scan Speak Illuminator 18WU 7".

A monster of a driver, a very good one I'd say.

BYRTT, there's some info on your Discovery series woofer there as well. I remembered these posts from my Car Audio days. Almost went with the Revelators, but price made me choose for something else, a couple of Herz ML1600's. Never regretted that decision but always wondered about that Revelator. But I'd have to say, that Illuminator looks real good in the test I linked.
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