# My experience with the CSS SDX7



## Neil (Dec 9, 2005)

I have received a number of pm's and emails from friends and strangers alike asking to hear more about the CSS SDX7 after I wrote about them on AudioJunkies.com. Just to give you a little background, Bob from CSS sent these to me with a pair of Extremis' in the hopes that I would be able to supply some measurements for both the SDX7 and Extremis. Unfortunately, I ran out of time and haven't captured any FR, THD, IMD, etc. But what follows is my opinion based on a few excerpts from earlier posts I made.

Almost forgot...you can get the SDX7 from www.creativesound.ca for $100. I imagine they'll be available from Kyle at acoustic-visions.com in the near future as well, but I believe he's still out of town at the moment.

Pictures and full thread.



> The first thing you'll notice is that though they are similar in approach (and motor topology; they both use XBL^2), they are very different. They feature very different motors, for starts. The Extremis' motor is considerably larger and utilizes a pole vent, while the SDX7 uses 8 1/8" circular vents into the gap itself.
> 
> They both feature cast aluminum baskets that appear to be from the same parts vendor. However, they are very different in terms of their design. The Extremis has very little venting except for four evenly spaced and narrow windows just above where the frame mounts to the top plate. The SDX7, on the other hand, has a very open frame with significant venting below the spider. As far as mounting is concerned, the SDX7 has six mounting points, whereas the Extremis has 4. The mounting flanges are roughly the same.
> 
> ...





> Alright, so testing fell through due to time constraints, but I figured I should post my thoughts on the SDX7 directly compared to the Extremis.
> 
> First, I thought the Extremis set a pretty good standard for bass output from a 7" driver. The SDX7 meets and exceeds that standard. Not only is it capable of more output and a little more low frequency extension, it is also MUCH more detailed. It is significantly cleaner than the Extremis through a good chunk of it's bandwidth. Noise (both aerodynamic and assembly related) on the Extremis is quite high, whereas the SDX7 is very quiet.
> 
> ...


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## durwood (Mar 7, 2007)

Thanks for the review! Would love to see some kipple tests for these, but either way thanks for your comments. Hadn't seen these until now.

EDIt: WOW 11.1mm of XMAX?


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## Neil (Dec 9, 2005)

durwood said:


> Thanks for the review! Would love to see some kipple tests for these, but either way thanks for your comments. Hadn't seen these until now.


I can tell you that where the Extremis Xmag figures were overstated (actually closer to 9-10mm than the 13mm they quoted), the SDX7 is pretty much spot on the 11mm quote. And yes, verified Klippel results hosted for the public eye would be nice...it's a shame they are now going to be extremely few and far between.


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## mvw2 (Oct 2, 2005)

So...I should sell my Extremis woofers... 

Good to see some comments on this woofer. I've seen it up on CSS for a while now. It's good to see it has a little more detail as this is one thing the Extremis does lack (only slightly).

Have you ever listened to the AA Poly mids before? These used a phase plug, smaller motor, etc. and did offer quite a bit different sound than the Extremis, punchier/tighter yet not as monstrous midbass(more constrained/controlled), more open and extended midrange. The AA Poly actually reminded me a lot of the Seas Excels I had, a very similar feel/presence but a bit dirtier/rougher around the edges.


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## npdang (Jul 29, 2005)

Yugh.. why a linear roll?


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## Neil (Dec 9, 2005)

npdang said:


> Yugh.. why a linear roll?


Yes, that was one thing that really surprised me. For a driver that is focused on quality and uses a number of high quality parts, it lacks the progressive roll spider that (in my opinion) should be automatic on a long throw 6.5"/7" driver. I need to edit that into my original comments.


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## Neil (Dec 9, 2005)

mvw2 said:


> So...I should sell my Extremis woofers...
> 
> Good to see some comments on this woofer. I've seen it up on CSS for a while now. It's good to see it has a little more detail as this is one thing the Extremis does lack (only slightly).
> 
> Have you ever listened to the AA Poly mids before? These used a phase plug, smaller motor, etc. and did offer quite a bit different sound than the Extremis, punchier/tighter yet not as monstrous midbass(more constrained/controlled), more open and extended midrange. The AA Poly actually reminded me a lot of the Seas Excels I had, a very similar feel/presence but a bit dirtier/rougher around the edges.


Yes, I have heard the Poly's...I actually blew a pair getting a bit wild in the house and have been meaning to replace them at some point.

The SDX7 is better than the Poly for midbass and lowbass, in my opinion. I would say the SDX7 is perhaps the best 7" driver I have heard for that purpose. But I think the Poly is easier used in a 2 way....no notch filter really necessary, no low xover point if wanting to avoid breakup, and no dip in the 800 Hz region. However, from about 500-600 Hz down, the SDX7 is a lot better, both in terms of impact and detail.

Just my opinion on it.


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## durwood (Mar 7, 2007)

npdang said:


> Yugh.. why a linear roll?


So one would expect non-linear excursion distortion then?


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## mvw2 (Oct 2, 2005)

Did you feel the Polys felt a bit constrained in the lower frequencies, not as loose? It offered good punch because of it, but it felt choked depth wise. It's a similar experience with the Excel woofers with their high loss surround.

I don't mean to pry more, but could you give a sort of an overview comparison between the SDX7, Extremis, and AA Poly in a broader sense?:blush:


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## Abmolech (Nov 2, 2006)

> So one would expect non-linear excursion distortion then?


It could expect you to use a non linear compliance device.
IE an enclosure...


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## Neil (Dec 9, 2005)

durwood said:


> So one would expect non-linear excursion distortion then?


Potentially, yes. That is one aspect of non-linear distortion. A lot more considerations there, for sure.



mvw2 said:


> Did you feel the Polys felt a bit constrained in the lower frequencies, not as loose? It offered good punch because of it, but it felt choked depth wise. It's a similar experience with the Excel woofers with their high loss surround.
> 
> I don't mean to pry more, but could you give a sort of an overview comparison between the SDX7, Extremis, and AA Poly in a broader sense?:blush:


I would call the Poly a sort of middle ground driver. It is very tough to compare multiple drivers against each other, but I'll try.

The Extremis is an OK driver, but it thrives off of huge output at low frequencies...I really don't find it very articulate and would describe the top end as very hazy and at times very boring. It is very well suited in something like the old Exodus Audio 641 kits, but I personally do not find it very musical.

The Poly is more usable than the Extremis. It doesn't have the same type of impact on the bottom end (you described as constrained...that's pretty close) but it is a lot better over a wide bandwidth than the Extremis....a more open sound that lends itself to a bit more extended top end. It doesn't have the same output or detail as the SDX7 on the bottom end, but the total package makes it perhaps a bit more suitable for 2 ways with small format tweeters.

The SDX7 is capable of more output at low frequencies and can articulate better than both the Extremis and the Poly. There isn't the slightly hazy sound that both the Extremis and the Poly have but depending on the singer and instrumentation, the SDX7 could come across as both shouty and subdued...direct result from break-up (second harmonic for G5-C6) and the dip Bob says is at 800 hz (around G5 for many sopranos). Both of these can be controlled with the EQ, though, while I don't believe the Poly or the Extremis can get back much detail.

I look at this from an application standpoint...in a 2 way with a small format tweeter, I think I would probably go with the Poly for it's wider usable bandwidth. In a 2 way with a large format tweeter, I would consider it a bit closer race between all three. And in a 3 way (basically anything below 500-600 Hz), the SDX7 is the clear winner.

Hope that gave you some insight. I think you really need to hear these drivers for yourself.


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## mvw2 (Oct 2, 2005)

If it was $100 for a pair I would. I just don't dislike my Extremis woofers enough to develop a need to plop down $200 for a pair of drivers that do slightly better. Then there's the Peerless SLS woofer(both 7" and 8") and the XLS 8", heck even Dayton's 8" Reference sub. When I'm discussing midbass only, other options start to open up. I just haven't had the need to step to something other than the Extremis woofers yet. As well, I am a slight fan of a smoother, fuller bass presence, so the Extremis does fit my tastes pretty well. I wouldn't mind a slightly less I guess I could call muddy bottom end, but I could probably cross 10Hz higher and not have it.

The SDX7 is a neat driver for anyone looking. I'm just not looking yet.


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## dogstar (Jan 31, 2007)

Thanks for the review and opinions.

I saw these things, and while the are incredibly sexy, I need something that will play nicely with a small format tweet... 

Guess I'd have to constrain these to the house if I do pull the trigger on them.... what a shame


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## mvw2 (Oct 2, 2005)

Well, depending on the tweeter and a little EQing, you might not have to.

So...who's giving npdang the first one?


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## Neil (Dec 9, 2005)

mvw2 said:


> Well, depending on the tweeter and a little EQing, you might not have to.
> 
> So...who's giving npdang the first one?


He almost got the pair I had, but time was short and I sent them back to Bob at CSS. I intend to get another 4 in the near future that I hope to take measurements of. No Klippel, though, but I don't know of anyone that will be able to provide Klippel results in public anymore.


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## demon2091tb (May 30, 2005)

mvw2 said:


> So...I should sell my Extremis woofers...


  

Are they really supposed to have better cleaner output from 300hz on down, if so i may look into them....


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## Luke352 (Jul 24, 2006)

I'm also interested in there output below say 400hz, I was pretty set on getting some Seas L18's but these have me interested aswell, have you used the Seas drivers before if so how would would you compare the two for midbass output 63hz through to 150hz roughly.


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## durwood (Mar 7, 2007)

Punk0Rama said:


> He almost got the pair I had, but time was short and I sent them back to Bob at CSS. I intend to get another 4 in the near future that I hope to take measurements of. No Klippel, though, but I don't know of anyone that will be able to provide Klippel results in public anymore.


So does that mean werewolf actually took his ball and went home? That's a damn shame.


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## newtitan (Mar 7, 2005)

Punk0Rama said:


> No Klippel, though, but I don't know of anyone that will be able to provide Klippel results in public anymore.


 
wait a second so that means no more DIYMA klippel results? what in the heeezy?


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## OgreDave (Jul 13, 2005)

Unless someone wants to buy one


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## sd97cl (May 29, 2007)

Luke352 said:


> I'm also interested in there output below say 400hz, I was pretty set on getting some Seas L18's but these have me interested aswell, have you used the Seas drivers before if so how would would you compare the two for midbass output 63hz through to 150hz roughly.



I was wondering the same.


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## Neil (Dec 9, 2005)

I have only used so many drivers, guys. 

I haven't used L18's...I have used other Seas drivers before, though. And I personally believe the SDX7 is the best 7" midbass driver I have heard (at the very least, 300-400 Hz down and pretty close to the best even up to 500-600 Hz)...it's up top where it isn't perfect but very usable.

For those who have posted that own the Extremis...the SDX7 really is an improvement in virtually every aspect.


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## dogstar (Jan 31, 2007)

Do you think a Seas Neo tweet would pair with these drivers?

If not, do you have any suggestions that would work as far as compact tweeters?

I'm active on a H701, so I have a fair bit of tuning potential, and lots of time to fiddle with it.


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## Lumadar (Sep 28, 2007)

DevilDriver said:


> The SDX7 is better than the Poly for midbass and lowbass, in my opinion. I would say the SDX7 is perhaps the best 7" driver I have heard for that purpose. But I think the Poly is easier used in a 2 way....no notch filter really necessary, no low xover point if wanting to avoid breakup, and no dip in the 800 Hz region. However, from about 500-600 Hz down, the SDX7 is a lot better, both in terms of impact and detail.
> 
> Just my opinion on it.


So would you suggest the SDx7 for someone like myself with an H701 at their disposal looking to do an active 2-way system? Or is there a better driver in the $200 and below market (pair) ?


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## Soundsaround (Apr 22, 2006)

I'm very tempted to give these a try.
Is there any improvement over the Extremis in terms of sensitivity? It doesn't really look like it on paper.
I have [email protected] going to my B&Cs rated at 91.5db 1w/1m sensitivity and I have to assume that my overall output is going to plummet with these.


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## Neil (Dec 9, 2005)

Lumadar said:


> So would you suggest the SDx7 for someone like myself with an H701 at their disposal looking to do an active 2-way system? Or is there a better driver in the $200 and below market (pair) ?


You are probably the best candidate for these drivers in a 2 way. Is there a better driver? For a 2 way, there are definitely some others that are easier to integrate with improved upper midrange performance. The SDX7 becomes a better and better 7" driver (when compared against others) the lower in frequency you go. 



Soundsaround said:


> I'm very tempted to give these a try.
> Is there any improvement over the Extremis in terms of sensitivity? It doesn't really look like it on paper.
> I have [email protected] going to my B&Cs rated at 91.5db 1w/1m sensitivity and I have to assume that my overall output is going to plummet with these.


At mid to upper frequencies, there isn't much of an improvement over the Extremis. At low frequencies, where sensitivity matters much less, I would pick the SDX7 over the Extremis. 150W @ 8 ohms is more than enough for either driver, though.


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