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AHA! - ScanSpeak mid-woofs do measure better!
AHA! - ScanSpeak mid-woofs do measure better!
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Old 12th April 2018, 09:54 PM   #1
eriksquires is offline eriksquires  United States
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Default AHA! - ScanSpeak mid-woofs do measure better!

Hi Everyone,

Not to beat a dead horse, but I feel vindicated enough to run through the mall in flip flops and swim trunks yelling "You reek a lot!"

In previous discussions, the arguments were made that the ScanSpeak Revelator 18W series mid-woofers had particularly bad ringing. My comments, made like the genteel bohemian that I am, were that the 18W/4531 I used simply did not measure nearly as bad as the ScanSpeak spec sheets, and I wondered at the time if the drivers had not gone through some improvement.

Well, here we go, my buddy Troels independently validated my observations:

He posts the original ScanSpeak image:

Click the image to open in full size.

As well as his own measurements which are much closer to what I measured, and published:

Click the image to open in full size.

So, for whatever reason, when it comes to these series of driver, ScanSpeak's measurements are not up to date. These are much better measuring and sounding drivers than the spec would lead you to believe.
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Old 26th May 2018, 03:36 PM   #2
eriksquires is offline eriksquires  United States
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Update: The discrepancy which Troels mentions above is exactly what I see, but for a different driver. I was talking about the 18W/4531, while Troels experimented with the 18WU/8741/T00. However, his observations and conclusions are exactly the same as mine:

Quote:
And I was really surprised to find the ScanSpeak 18WU performing exceptionally well compared to the infinite baffle response found at ScanSpeak's data sheet:
Even the difference in measurement from published to in cabinet are practically the same.

Troels attributes the difference to infinite vs. actual baffles, but at the top of the mid-woofer's range, that doesn't make much sense to me. I want to think this is more of an engineering change that was not documented. Let me go look at Zaphs data in a bit.
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Last edited by eriksquires; 26th May 2018 at 03:42 PM.
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Old 26th May 2018, 03:54 PM   #3
eriksquires is offline eriksquires  United States
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Should have done this before, but here is a comparison of the 18W/8531 from the spec sheet:

AHA! - ScanSpeak mid-woofs do measure better!-18w-8531g-curve-jpg

From Zaph's comparison page:

AHA! - ScanSpeak mid-woofs do measure better!-18w8531g-fr-gif

And not exactly the same driver, but my own measurements with the 4531 (4 Ohm) variant:

AHA! - ScanSpeak mid-woofs do measure better!-myown-jpg

Notice that my chart uses a fine-scale, and that there is a little hump, but it's nowhere near the magnitude of the hump in the spec, and it's certainly not a shelf.

You can see in the yellow line the final slope after 2nd order filtering applied. There is a notch filter and Zobel but they don't contribute to this discussion. They just flatten the slope. You may review the full crossover design in the attachments on this thread:

SNR-1 : Mundorf / Scanspeak 2 Way

Based on this review, I remain commited to my original thesis: The 18W/x531 mid-woofers are very good sounding and very easy to integrate with a tweeter in a two-way system.

Best,


E
Attached Images
File Type: jpg 18w-8531g-curve.jpg (120.9 KB, 499 views)
File Type: gif 18W8531G-FR.gif (11.9 KB, 487 views)
File Type: jpg MyOwn.jpg (110.5 KB, 491 views)
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Last edited by eriksquires; 26th May 2018 at 04:01 PM.
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Old 26th May 2018, 04:06 PM   #4
Juhazi is offline Juhazi  Finland
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Erik, what are your baffle dimensions? Datasheet measurements are usually in IEC (wide) baffle. Modern decorative narrow baffles give +2 or even 3dB step typically between 600-1200Hz.
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Old 26th May 2018, 04:30 PM   #5
eriksquires is offline eriksquires  United States
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Juhazi:

10.5" x 18"

Best,

E
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Old 26th May 2018, 06:28 PM   #6
Juhazi is offline Juhazi  Finland
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Yepyep,
The wise designer knows the typical implementation of the driver (s)he is designing! So (s)he implements the baffle diffractions in the response.
Attached Images
File Type: jpg 18W in baffle.jpg (255.9 KB, 120 views)
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Old 26th May 2018, 06:46 PM   #7
eriksquires is offline eriksquires  United States
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Juhazi,

Yes indeed. Edge is still my favorite.

The point I was trying to make though was that if you look at the raw spec sheets, these drivers look completely unmanageable, but the reality is they are much better.

Best,

E
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Old 26th May 2018, 07:47 PM   #8
ScottG is offline ScottG  United States
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Quote:
Originally Posted by eriksquires View Post
So, for whatever reason, when it comes to these series of driver, ScanSpeak's measurements are not up to date. These are much better measuring and sounding drivers than the spec would lead you to believe.
-as noted by Troels: it's the interaction with the baffle.

I've heard these woofers in a few designs (all 2-ways) and didn't particularly like them anywhere except around 90-400 hz. Fairly clean and "punchy" in this region (despite not being very efficient) with a bass reflex design and an amplifier with enough current. Depth above average in this region, though not great. (..the "Illumintors" are slightly less "clear" but have more depth and better imaging in the same bandwidth.)

I'm really not sure why people would pay that much for this particular midbass (..with a design that has the potential to de-laminate).
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Old 26th May 2018, 07:52 PM   #9
eriksquires is offline eriksquires  United States
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Quote:
Originally Posted by ScottG View Post
-as noted by Troels: it's the interaction with the baffle.
Which is clear from the quote from him in my second post, above. To refresh, Troels said this:

Quote:
And I was really surprised to find the ScanSpeak 18WU performing exceptionally well compared to the infinite baffle response found at ScanSpeak's data sheet:
It is also clear, from the phrase I quoted directly, that he's very surprised at how big a difference there is overall. So am I.

Quote:
Originally Posted by ScottG View Post
I've heard these woofers in a few designs (all 2-ways) and didn't particularly like them anywhere except around 90-400 hz. Fairly clean and "punchy" in this region (despite not being very efficient) with a bass reflex design and an amplifier with enough current. Depth above average in this region, though not great. (..the "Illumintors" are slightly less "clear" but have more depth and better imaging in the same bandwidth.)

I'm really not sure why people would pay that much for this particular midbass (..with a design that has the potential to de-laminate).
We'll absolutely have to disagree. I have never ever heard a mid-bass I liked more.

Best,


Erik
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Last edited by eriksquires; 26th May 2018 at 08:12 PM.
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Old 26th May 2018, 08:13 PM   #10
ScottG is offline ScottG  United States
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Quote:
Originally Posted by eriksquires View Post



We'll absolutely have to disagree. I have never ever heard a mid-bass I liked more.

Best,


Erik

..it depends on what you are "looking"/listening for, and in what design.

I'd go for a 5 1/4" SB15MFC30-8 at about 1/4 of the price in a heart-beat (vs. the Scan), even with the loss in lower freq. extension. Provided it's loaded properly, it's substantially better above 100 hz, particularly as it transitions to any typical tweeter (for multiple reasons).

IF you can design around the limitations of tweeter integration with a 10" - then the Discover 10" 26W/4534G is quite a bit better (with everything assuming proper loading) and can also provide lower freq. extension.
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Last edited by ScottG; 26th May 2018 at 08:17 PM.
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