I'm sorry about being slow in addressing this. However, the previous remarks have been very valid and accurate. I don't really see anything that I disagree with. There are certainly several areas of these topics that could be addressed, but I will address what appear to be the most prevalent queries regarding MY opinion and direction.
First, I fully agree with this comment regarding the SS8531:
These mid-woofers used in this configuration have excellent bass performance and smooth and detailed midrange.
This is very true, and has always been true regarding the Scanspeak 7" midwoofers. They are THE benchmark for bass performance among 7" drivers. In my few commercial auditions with the newer Scanspeak midwoofers, this continued to be true, but the midrange was slightly too mushy for me. It was very smooth, but lacked the detail and transparencey I seek. Nonetheless, the Scanspeaker midwoofers are very pleasing and the ACI Jaguar was a sublime implementation with the SS8545
. My very first DIY speaker was a Dennis Murphy crossover installed in one of Rick Craig's (Selah Audio) kits using the SS8545 and SEAS T25 tweeter. This speaker was called the STS. Here is a photo of this speaker from about 6 years ago:
Yes, it was very good. I built several pair of these speakers for local friends and lived with the STS for about 2 years. But the Scanspeak transparency remains lacking when compared to the SEAS W18. IMO, the only way to get the the SS midwoofer bass quality and the SEAS W18 midrange quality is via the Accuton C95. I now understand why folks pay a profound quantity of money for a 2-way Kharma speaker using the Accuton 95.
My only caveat that I should probably offer is that I haven't heard the SS8531 in a good 2-way DIY application. I have only auditioned this driver in a 2 commercial speakers. One was an MTM and the other was a 2-way. IMO, a good DIY implementation will most often sound superior to a good commercial implementation. I believe many average price commercial crossover designs are quite hasty in an effort to reduce R&D cost. Please for a moment imagine the cost of paying Dennis Murphy for 5,10, 50, or 100 hours of his time. Dennis has a PH.D. (very smart) and 30+ years of experience. I believe his "real" fees should be on par with Joe D'Appolito. I also believe part of this problem is quality control. Measuring a completed speaker is very important. My guess it that I make some sort of mistake in about 5-10% of speakers. A more significant factor are driver changes across production runs and rubbing voice coils (especially in tweeters). Most DIY folks spent significant time with their speakers in the design process and can isolate/eliminate the quality control problems.
Anyhoo, I am rambling. At the root of my response to the initial query regarding my desire for the the SS8531 is the sentiment... it's not going to happen. While it's a very good driver, I prefer more midrange clarity. And, candidly, following my few commercial auditions with the SS8531, I like the sound of the older SS8545 better.
Lin...yeah, I had read that. But I thought I read somewhere else that the 1801c would be offered in addition to the 1801b...can't find where..
Yes, I will continue to offer the 1801b with the SEAS W18 driver.
My initial adventure with the 1801 was rooted in my personal desire to have a speaker with better midrange and clarity than the STS. I built this speaker for ME. I will also build the 1801C for ME. In both cases, if other folks want to purchase the parts or a completed speaker I will be glad to share the experience.
I like the SS 18W-8531 paper cone speaker, in fact I am using 16 of them in my new Selah Audio line arrays
Wow, that's a wallop of a speaker and must be quite expensive! It should also be reasonably sensitive. Have you tried a low power SET?
Anybody who's biased against a Scan 8531 because of an impedance curve obviously spends their time pontificating instead of working to gain any relevant experience.
Yep, I generally agree.
I know some "purists" say that the 800hz impedance glitch means that the cone has some break-up at this point which means it isn't pistonic up to the point of xo, which is why some don't like it or choose others.
This is on the fringe of my knowledge, but I will offer another possibility. This is really only a guess with some foundation. At about 1000 hz there will be ripple when using a soft cone IF the surround is too forgiving/squishy. The hardness of rubber is often conveyed with a durometer measurement. Race car drivers will often use a durometer to test the hardness of their tires. It measures how soft/hard the rubber really is. Anyhoo, a soft cone on a loudspeaker must have a surround that sufficiently damps the edge cone resonance. If this doesn't happen, the edge of cone will eventually get "whiplash". The edge of the cone will move in the opposite direction of the center of the cone. The result is a pinch-point that significantly restricts cone movement. I have seen this in a few lesser drivers over the years. However, a very good implementation with a surround will nicely accommodate the cone edge resonance, but MAY (I really don't know) create a small impedance ripple because that cone edge control provides feedback to the motor when resisting the cone edge whiplash. Perhaps those little slits in the cone aren't really a "free-lunch", and necessitate further accommodation in the form of a stiffer surround. So, my guess is that this impedance peak is NOT due to a cone resonance, and MIGHT be due to an engineered necessity in the surround. In any event, this small impedance ripple isn't a valid reason to avoid the 8531. Regardles of the reason, the 8531 is a very good driver.
There appears to be a very small blip in these graphs too:
http://www.seas.no/Prestige%20Basser%20PDF/CA18RLY-H1217-08.pdf http://www.seas.no/Prestige%20Basser%20PDF/CD22RN4X-H1192-08.pdf http://www.seas.no/Prestige%20Basser%20PDF/CA26RE4X-H1316-08.pdf http://www.tymphany.com/datasheet/printview.php?id=126 The plot for the SS8531 doesn't really look like anything to be worried about.
http://www.tymphany.com/datasheet/printview.php?id=85 I will state for the record that stiff cones WILL have a cone resonance. All other cones flex. This is simply because the resonating energy inside the cone will either bounce ( stiff cone ) or be absorbed ( flexible cone ). This resonating energy will generally pile-up inside the cone when the 1/4 wavelength is short enough. A quick glance at the SEAS W18 and Accuton C95 graphs will convey this similarity.
W18 Waterfall via LspLab:
C95 from
www.soniccraft.com:
The older SS8545 did have a minor cone resonance at 2600hz and some other artifacts at higher hz according to Dennis Murphy.
And, for what it's worth, I prefer a the sound of a very well implemented paper cone driver over all the other flexible materials that appear more High-Tech. Paper cones can be very good and have very good resolution. It is completely unfair and unreasonable to group ALL paper cones into a "muddy sound" category" - especially when compared to their other flexible cone peers. I have been a long-time fan of the older Vifa M18 driver. This was a darn good paper cone driver IMO. Many folks called this driver the poor-man's SS8545 and I agree with this sentiment.
Whew, that became somewhat long. It's time for me to get some sleep.
I am going on vacation. My attendance to this topic will likely be very sparse until @ 15 August.
Dave
