Klippel stuff: More Kef, Pioneer in-wall drivers, PHD mid, Aura NS6, SB, and Scan

[erinh]

In the past couple months I've managed to run quite a bit of drivers through the paces. You may have already seen this posted but I thought it might be cool to throw them all in to one post and give my thoughts on the results for a change. Trying to switch it up...


Odd-ball, not commercially available as individual, but cool-to-see drivers:

• Kef LS50 drive unit.
  This comes out of Kef's Flagship $1500 LS50 bookshelf monitors. I don't have a way to flush mount these... well, okay, I DO, but I didn't have the time so the HF content is going to be messed up a bit. I know this because I later flushed these in and had much smoother response on the top end. I need to update the site with this... huh... ANYWAY (SQUIRREL!)...
  
  If you look at the Q100 and R500 drive units I've tested, what you'd see is a combination in looks. And that's essentially what you get in performance. The ribbed cone of the R-series improves the breakup from the Q100 model and the z-flex suspension from the Q-series increases linear throw. It's essentially a best of both worlds driver. Given its purpose in the bookshelf, it makes sense that it's intended to cover a broader range. Though, the R-series concentric is still the better mid-range performer as its surround is much more shallow than the Z-flex based woofers so there's a smoother transition in to the HF range. In addition, the R-series has a lower inductance steady-state value and a lower overall inductance range through excursion. Back to the surround, though, the R-series has a sloppier suspension; but it should be High Passed above the point where this matters anyway based on it's use in the Kef towers where it's crossed around 300-500hz in various models. The LS50 & Q-series have a more symmetric suspension curve which leads to lowered 2nd order distortion near Fs, and both have more linear excursion than the R-series (Q100 @ 1.9mm, LS50 @ 2.9mm, R-series @ 1.5mm).
  
  Application matters. And Kef has implemented each driver nominally, IMO.
  
  
  
• Pioneer S-IW691 in-wall 5.25" concentric and 6.5" woofer.
  Jay (yep, he's still alive) sent me these about a year ago and I finally tested them for him. We were both underwhelmed with the results in regards to the woofer. The linear excursion is very low at 1.7mm one-way. I think we both expected at least a little bit more out of it. The suspension offset of about 2.0mm could be centered up to gain another 1.0mm in linear throw. That would help it at least some. There was considerable mechannical noise from the woofer during testing as well.
  
  Overall, though, the FR of the woofer, mid, and tweeterr is smooth (as with the kef, I didn't flush mount this which affects the HF response smoothness on-axis). The HD sweep shows low distortion on the tweeter but higher distortion (about 2%) through the nominal passband of the mid. By nominal passband, I mean 200hz-3khz. Below 200hz you can really see the suspension lighting up the 2nd order distortion pushing it above 10% THD at 100hz. I'd guess, though, the mid is crossed high... maybe even as high as the 500hz region, given the 6.5" woofer is so close and can cross higher without running in to lobing issues. The woofer has about 1% THD above 100hz and reaches 3% THD at about 80hz. At 50hz, you're at 10% THD which correlates with the Klippel's 1.7mm linear throw. Of course, these are all without a filter; once you add a filter things change. Especially for suspension-based distortion parameters.
  
  Assuming proper crossover for the 3-way as a system, I'd expect great FR but the speaker really needs to be paid attention to at loud volumes if you don't use a >80hz HPF with a steep filter.

8" Mid/Woofers:
I bought a few different 8" woofers to test out because I am building a set of towers for my house and was considering going with a dual 8" configuration. So, I ordered up some more budget minded ones, along with the Scan 8" Rev. Here they are:

• SB Acoustics SB23NACS45-8 8″ Woofer
• Scanspeak 22W/8534G00 Discovery 8″ Woofer
• ScanSpeak Revelator 22W/8857T-00 8″ Woofer, Aluminum Cone

Overall takeaway...
The one with the most throw is the Scan rev. Shouldn't really be a surprise. The Discovery and the SB, IMO, are more suited for a mid/woofer type setup where the Scan is more suited for woofer duty. There's not a whole lot of value in the Scan Rev, but it does perform very well in regards to pure linear throw. That said, for my application, it was going to be used. More on this below. The suspension is funky; not sure how much of this is surround based but given what I heard/saw during testing, I'm assuming it's predominantly spider. One of you guys with more insight in to this can probably tell me better. I have my thoughts but don't want to get in to it ATM.

In terms of throw, both the SB & Scan Disco weren't what I was hoping for. The scan was about 1.5mm off linear xmax spec; the SB was about 2mm off. Splitting hairs, maybe, but still... They both use shorting rings and their inductance over current and throw is really low. I didn't measure FR for any of the 8's, simply because I didn't feel the need. I do trust the mfg specs enough in this regard that I didn't see the overwhelming need to do that myself. In addition, I personally just didn't have the time and since I'm not going to use them above 500hz or so, where they're still omni, the breakup concern wasn't immediate. Based on the mfg FR in combination with my measured high-ish sensitivity, and apparent use of inductance control, I will re-iterate, I think the SB & Discovery 8" drivers are really good options for someone with a horn setup or low-crossed tweeter. IOW, good options for 2-way systems. They both have good sensitivity (for standard sensitivity drivers), 8" cone area, and decent linear excursion relative to Fs, that crossing high-ish maybe above 80hz and below 1khz would satisfy most anyone's need for clean output.

I also didn't run HD sweeps for any of these drivers. Again, this is really based on my needs and time constraints. I stand by my recommendations, still.

All said and done, I wound up ordering a set of 10" Revelators for my application. I trust they'll have the 9mm linear throw, as the 8" did which provides me plenty of clean output. Where I'm going to cross works well with where lobing becomes an issue, baffle step and floor bounce occur. And it gets me the surface area I want at nearly half the price of what I was going to spend.



Others:

• PHD FB 4.1
  I was given the PHD below last May by a PHD rep and asked to run it through the Klippel and post the results. He was as curious as I was. Since they're gaining ground here in the US, I figure it was a good driver to test. Overall, I wasn't impressed. It's not terrible, but it's just not really what I expected and TBH, it does some things in the FR which I haven't seen before (not in a good way) in an area I wouldn't expect. Then again, THIS particular driver is not overly priced like some of the 'flavor of the month' brands. I think retail for a pair is in the $150 ballpark. (don't hold me to that).
  
  The sensitivity is a touch low at about 86.9dB; about 1dB less sensitive than some of the more popular drivers lately. Fs @ 113hz is a bit higher than I'd expect for a 4" driver. Linear throw is limited by Bl at 1.4mm. Okay inductance, with about 0.15mH swing peaking at ~0.35 and going down to ~0.25mH. FR shows about a 4dB bump right around 1.6khz that is obseved in every axis. Not sure if this is surround related; my gut says it is when I see the same bump show up in the HD results. Given people will most likely try to use this from 300hz and above, I'd have to say be cautious. At 300hz the THD is 3%. Above 500hz to about 3khz, THD is about 2%. So, I'd pay attention to your HPF location and slope in regards to audible distortion. After the small bump in FR at 1.6khz, there's a wide dip that extends to about to about 5khz, with the bottom being only -5dB @ ~3khz from the main response line. This is the area that concerns me the most just because it's jumping around (up at 1.6khz, down at 3khz, up at 5khz) and this is going to make it tougher to work with in regards to mating a tweeter. There's just not much linearity in the response curve itself in a critical area that we are sensitive to. As with anything I say about a speaker being potentially problematic, YMMV.
  
  
• Aura Sound NS6-255-8A
  At my GTG last November, a fellow (think his name is Carlton) handed me a box full of these to play with. I gave them to someone else at the meet, and only kept one to test. In hindsight, I should have tested (2) just for consistency sake, but I didn't. For the $20 or whatever price is used to be*, they're pretty good performers. Pretty much in line with what you'd expect based on others' feedback (Ahem... Chad). Good motor and suspension symmetry. A coil-out offset in regards to the motor, but not enough to really matter (as was the case with the SB above). High inductance even with the shorting ring, though, ranging from ~0.60 to 0.30 for a delta of 0.30 at rest to the extremes. Quite good FR with usability at least to 3khz. Good distortion results down to 200hz, mainly caused by 3rd order, where 2nd order takes over below 200hz. Total usable range, IMHO, with my levels of listening and music type would be 100-2.5khz with at least 2nd order on bottom and top. YMMV.
  
  *Note: I've seen these drivers priced as high as $100 on eBay lately.

and some random pictures just because I like 'em...

[BigAl205]

Those KEF driver just look awesome.