Audioholics Reviews their first DIY Subwoofer, the CSS SDX12 Sealed Kit!

Matthew J Poes

Matthew J Poes

Senior Audioholic
Have you ever wondered how typical DIY subwoofers stack up against the commercial competition? With DIY subwoofers being one of the first DIY projects enthusiasts take on, and certainly one of the first speaker designs I took on, I was very curious how a DIY subwoofer would compare to a commercial offering in value and performance.

css.jpg


I finally got my opportunity when CSS loaned us a prebuilt sample of their SDX12 driver in a small sealed enclosure. This mighty driver is a very high excursion driver, likely with more linear excursion than most moderately priced commercial offerings. Further, it is optimized for a very small enclosure. In many ways, this DIY subwoofer matched the size and style of many sealed commercial subwoofers and I just happened to have this subwoofer at the same time as I had access to a handful of similar commercial offerings.

We at audioholics put this subwoofer through it's paces in exactly the same way we would have for any commercial subwoofer. This included full CEA-2010 testing. To see what we found, review my review in the link below and come back here to let us know what you think.

 
BoredSysAdmin

BoredSysAdmin

Audioholic Overlord
Finally DIY sub review on AH !!! Hurray and thank Matt!
 
ryanosaur

ryanosaur

Audioholic Ninja
Read it the other day when I saw it on the AH front page! Great write up Matthew. Thank you!!!
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Finally DIY sub review on AH !!! Hurray and thank Matt!
I hope to do more. I think that, for reviews, anything we review has to be a kit. I don't see us copying Data-Bass and reviewing drivers in generic boxes. It will need to be a kit from a company designed around a specific driver or set of drivers. Otherwise it puts too many variables into the mix.

I also don't see us necessarily testing any crazy over the top giant horn subwoofers. Now, watch, I'll probably eat those words, but for now at least, the problem is that getting such big subwoofers out into our field and providing them sufficient power is difficult. If I can use one of my 4000 watt RMS amps, we are ok. But a number of big subwoofers actually need 6000-10,000 watts and I just can't justify buying such amps for this. It also creates problems as I'm using a 20 amp circuit for all of this and a long power cord. Once we start approaching even 4000 watts, we run into power issues.

But...I do hope to keep reviewing more subs and speakers in the form of DIY kits and providing full and accurate measurements. I know that I've always wondered how these products compare and nobody ever does those comparisons.
 
lovinthehd

lovinthehd

Seriously, I have no life.
Nice, thanks for a new option for sub reviews! Would it be possible in the future to see analysis of the specific box design/size chosen in terms of modelling the driver parameters, especially interesting for those that might buy just a driver and build their own box.....I know that can get involved but might be also interesting to contrast the modelling vs the testing....
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Nice, thanks for a new option for sub reviews! Would it be possible in the future to see analysis of the specific box design/size chosen in terms of modelling the driver parameters, especially interesting for those that might buy just a driver and build their own box.....I know that can get involved but might be also interesting to contrast the modelling vs the testing....
I'll talk to Gene about how involved these DIY articles should get. I do think there is plenty of room for that here however. I'm no spring chicken when it comes to DIY.

The SDX12 was tested as a kit. After driver displacement and such, its about 1 cubic foot. It's a small box. However, if you model the box, you will see that larger boxes under-damp the response and with ported boxes will cause excess efficiency. It's both an amazing and amazingly challenging driver to DIY with. A ported box for example will end up being as much port as box. It's a very high excursion driver so it needs a large port area. Yet the box is small, an optimal ported box for 20hz tune would be 2 cubic feet. A port with a mouth that is 3x8", which is sufficient for this box, is 78" long. two 4" round ports would also work, thats 83" long. Where is that fitting in a 2 cubic foot box? Requires a lot of added external volume to provide sufficient space for the ports to wrap around.

That is why this driver works best with passive radiators for ported designs.

For sealed, it really works best in a 1-2 cubic foot box, with 1 providing optimal damping. 2 is under-damped but works fine too.

The driver performs well. It really likes/wants a lot of power. The driver can handle, on a dynamic basis, like 2000 watts or so. In testing, we didn't register high amounts of dynamic power, but under sustained SPL testing, we saw the amplifier drawing as much as 1700 watts. I don't think the system we used to measure wattage was totally accurate in that I don't think it was accurately measuring peak power. I don't think it can react fast enough. The numbers we were getting for burst tones was really low and didn't make a lot of sense. We don't normally measure so this was a bit of trial and error.

I personally think the midbass numbers are low and I also think that the sudden rise in 3rd harmonic implies the amp might have been clipping. I forgot to bring my laptop with the Behringer software to the field so when we tested, I wasn't able to monitor clipping in the software, only from the front display. I don't believe the sub would have reached 3dB or more higher, but I wouldn't be shocked if there was another dB or two in there above 50hz. Distortion levels were so high below 50hz that I feel confident those were excursion limits and that we did reach the limit of the driver below 50hz.

Here is a simulation comparison between the sealed and ported subs. This is being fed 2000 watts and the sealed sub has a bit of EQ in line with how I EQed it in use.
CSS SDX12 Model.png
To make those numbers better match what I measured, add 6-9dB to the measured numbers. The simulated numbers are crude straight calculations of watts in and sound out without any consideration of compression, so its more like peak. It's also assuming 1 meter. That should equate to 9dB but...I also don't know that you would see that fully realized in real life.

I do have access to a Lab Gruppen amp so I may borrow that for a test like this in the future. I have a few DIY subs kicking around I plan to test this coming summer. They probably won't be articles because they aren't kits. They are of my own mad design, but they should be interesting. Maybe a YT video and forum post.
 
Pogre

Pogre

Audioholic Warlord
Oh boy! I think it's cool you reviewed a diy option. I keep talking myself in and out of pursuing some diy myself.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Oh boy! I think it's cool you reviewed a diy option. I keep talking myself in and out of pursuing some diy myself.
do it!

what kind of DIY are you considering? Lots of good options. The main thing to keep in mind is that a)it’s not always the value it’s portrayed as, and b) not all designs are created equal.

with subs I sometimes see totally unrealistic claims made about DIY designs. If you post what you want to do we can probably give you various options. In time I hope to test more designs that interest people.

like with anything, there are trade offs defined by the laws of physics and costs of manufacturing. You can have high output, wide bandwidth, compact size, and a low price. But only three of those can be optimized in any one system.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
I'd love to see a review of one of the larger DIY options.
me too and it’s on the wish list. I’m hoping to be able to test these:

But we shall see. I have a baby on the way and won’t be able to spend my summer building subs and lugging then into a field. Testing big subs like this is hugely challenging. Because they are capable of so much output they increase the risk of creating noise problems. We get a permit to test and permission by the neighbors. We test in a field that puts us 250 ft (at a minimum) from any home. But increase output by 10-20 dB and it could be enough to become a nuisance. My permit basically says that if anyone complaints it’s no longer valid. It’s contingent on us not bothering anyone.

another challenge is that our mics are distortion limited to about 130-140dB max. I like to have a healthy margin between the distortion limit and actual measurements and we are often close to that already. We can move the mic back 6 feet but that increases noise and reduces the accuracy of the measurement potentially.

then we have power. We just don’t have enough. The amount of power needed to test these big subs is, as noted before, about 6000+ watts. Using smaller amps means that we might hit dynamic limits of the amp and sub together and the test wouldn’t be valid. You need a healthy margin. So if the sub can handle 2000 watts rms and 4000 peak (remember it’s a dynamic peak test) we need 2-3 dB or amp headroom, so 6000-8000 watts. We then run the risk of popping the breaker since that exceeds what the outlet can produce. Josh Ricci has higher power outlets at his disposal.

And then we have handling. James and I do this in our own. You all have seen the videos of us. We aren’t Gene, no big guns. 150lbs is close to our limit together for a sub. 200 is really pushing it into dangerous for us. Many of these crazy big DIY subs are in the 200+ lb range and without help can’t really manage it.

so if we can get access to some big diy designs, ensure we have sufficient power, and get some extra help in the field (and assuming I can take a day away from the new baby for this) we will measure some.
 
NINaudio

NINaudio

Audioholic General
me too and it’s on the wish list. I’m hoping to be able to test these:



And then we have handling. James and I do this in our own. You all have seen the videos of us. We aren’t Gene, no big guns. 150lbs is close to our limit together for a sub. 200 is really pushing it into dangerous for us. Many of these crazy big DIY subs are in the 200+ lb range and without help can’t really manage it.
I mainly meant larger driver sizes like 18's and 21's and not necessarily coffee table sized enclosures! I don't really see myself ever having one of those, so while it would be an interesting read, it wouldn't have much impact on what I might do later. I would love to see a test of the 21" flat packs, as that is probably about the largest I could see myself going outside of a dedicated theater room.
 
KEW

KEW

Audioholic Overlord
Thanks for a great review. I have often thought of DIY, but not yet! My problem is I'm not really sure that there are savings to be had (or that the savings are so small as not to be significant or be readily offset by factors such as warranty.
I had two items that compel me to post:
1) For "cons" for DIY, I would consider that major manufacturers of subs have tested and integrated the amp and driver at a level that would be hard to DIY! For example, Tom V. at PSA will say something like "Don't take it as a challenge, but these subs are pretty much bullet-proof" In other words as you push them to their limits, they will not blow the amp or driver. Most go one further by "refusing gracefully" if you push them to their limits. IOW, they will just limit the volume rather than have mechanical noise. As TLSGuy likes to say "sins of omission are better than sins of comission" and I would rather have a subwoofer that declines full dynamic reproduction rather than attempts and makes bad noises. It seems in your case that the driver you used could handle all of the power you had to give it based on the compression test. Is amp clipping not a concern at lower frequencies? In a way, it sounds like you managed to have a solution that protects you from bad sounds while also protects the components from failure? Was that dumb luck or is it a reasonable expectation?
In any case, I would appreciate your thoughts on this!
2) I really hate to be critical on this count, but I have always considered Martin Logan to be similar to Paradigm in that IME, they make pretty good products, but they are fairly expensive compared to what I would normally spend my money on or recommend to someone else as an "informed AH Dude". I don't see anyone here recommending M-L subs with any regularity (I do understand and appreciate that the M-L was similar in many of its characteristics).
If you put a DIY sub up against a value leader of the ID market, how would it fare? I would consider anything made by Hsu fare game on this count, but especially the HSU ULS-15 mk2 and the Outlaw X13 Ultra (which seems to go on sale for $1,000 or $1,100 on a regular basis)!. I am not sure a DIY sub can hang with either of these! I admire the guys who DIY their subs and see it as a good gateway project into speaker design, etc, However, I think comparison with recognized ID values makes for a good reality check on when it makes sense to DIY a subwoofer for most of us who would not buy a subwoofer from BestBuy (except, maybe a SVS)!

All of that said, my personal current champion for a DIY sub build would be TLSGuy's 10" transmission line subwoofer. My interest is based on the character of the TL bass from Dennis Murphy's Phil3 which I really like (maybe it is not TL, maybe it was just set up in the right room the right way, but I was impressed)! As a DIY project, the dimensions and weight of this probably increase the advantage of building it "on-site" instead of shipping it, and I do not know of a commercial transmission Line subwoofer being sold, period!
 
lovinthehd

lovinthehd

Seriously, I have no life.
I'll talk to Gene about how involved these DIY articles should get. I do think there is plenty of room for that here however. I'm no spring chicken when it comes to DIY.

The SDX12 was tested as a kit. After driver displacement and such, its about 1 cubic foot. It's a small box. However, if you model the box, you will see that larger boxes under-damp the response and with ported boxes will cause excess efficiency. It's both an amazing and amazingly challenging driver to DIY with. A ported box for example will end up being as much port as box. It's a very high excursion driver so it needs a large port area. Yet the box is small, an optimal ported box for 20hz tune would be 2 cubic feet. A port with a mouth that is 3x8", which is sufficient for this box, is 78" long. two 4" round ports would also work, thats 83" long. Where is that fitting in a 2 cubic foot box? Requires a lot of added external volume to provide sufficient space for the ports to wrap around.

That is why this driver works best with passive radiators for ported designs.

For sealed, it really works best in a 1-2 cubic foot box, with 1 providing optimal damping. 2 is under-damped but works fine too.

The driver performs well. It really likes/wants a lot of power. The driver can handle, on a dynamic basis, like 2000 watts or so. In testing, we didn't register high amounts of dynamic power, but under sustained SPL testing, we saw the amplifier drawing as much as 1700 watts. I don't think the system we used to measure wattage was totally accurate in that I don't think it was accurately measuring peak power. I don't think it can react fast enough. The numbers we were getting for burst tones was really low and didn't make a lot of sense. We don't normally measure so this was a bit of trial and error.

I personally think the midbass numbers are low and I also think that the sudden rise in 3rd harmonic implies the amp might have been clipping. I forgot to bring my laptop with the Behringer software to the field so when we tested, I wasn't able to monitor clipping in the software, only from the front display. I don't believe the sub would have reached 3dB or more higher, but I wouldn't be shocked if there was another dB or two in there above 50hz. Distortion levels were so high below 50hz that I feel confident those were excursion limits and that we did reach the limit of the driver below 50hz.

Here is a simulation comparison between the sealed and ported subs. This is being fed 2000 watts and the sealed sub has a bit of EQ in line with how I EQed it in use.
View attachment 34248
To make those numbers better match what I measured, add 6-9dB to the measured numbers. The simulated numbers are crude straight calculations of watts in and sound out without any consideration of compression, so its more like peak. It's also assuming 1 meter. That should equate to 9dB but...I also don't know that you would see that fully realized in real life.

I do have access to a Lab Gruppen amp so I may borrow that for a test like this in the future. I have a few DIY subs kicking around I plan to test this coming summer. They probably won't be articles because they aren't kits. They are of my own mad design, but they should be interesting. Maybe a YT video and forum post.
Cool, any expansion in that regard would be a plus I think. Kits are nice, but even some comments on how you could change design a bit with size or sealed vs ported for the particular driver, could be interesting.

Maybe you need some big amps like Josh uses....altho that Lab Gruppen might do it!
 
Verdinut

Verdinut

Audioholic Samurai
Thanks for a great review. I have often thought of DIY, but not yet! My problem is I'm not really sure that there are savings to be had (or that the savings are so small as not to be significant or be readily offset by factors such as warranty.
I had two items that compel me to post:
1) For "cons" for DIY, I would consider that major manufacturers of subs have tested and integrated the amp and driver at a level that would be hard to DIY! For example, Tom V. at PSA will say something like "Don't take it as a challenge, but these subs are pretty much bullet-proof" In other words as you push them to their limits, they will not blow the amp or driver. Most go one further by "refusing gracefully" if you push them to their limits. IOW, they will just limit the volume rather than have mechanical noise. As TLSGuy likes to say "sins of omission are better than sins of comission" and I would rather have a subwoofer that declines full dynamic reproduction rather than attempts and makes bad noises. It seems in your case that the driver you used could handle all of the power you had to give it based on the compression test. Is amp clipping not a concern at lower frequencies? In a way, it sounds like you managed to have a solution that protects you from bad sounds while also protects the components from failure? Was that dumb luck or is it a reasonable expectation?
In any case, I would appreciate your thoughts on this!
2) I really hate to be critical on this count, but I have always considered Martin Logan to be similar to Paradigm in that IME, they make pretty good products, but they are fairly expensive compared to what I would normally spend my money on or recommend to someone else as an "informed AH Dude". I don't see anyone here recommending M-L subs with any regularity (I do understand and appreciate that the M-L was similar in many of its characteristics).
If you put a DIY sub up against a value leader of the ID market, how would it fare? I would consider anything made by Hsu fare game on this count, but especially the HSU ULS-15 mk2 and the Outlaw X13 Ultra (which seems to go on sale for $1,000 or $1,100 on a regular basis)!. I am not sure a DIY sub can hang with either of these! I admire the guys who DIY their subs and see it as a good gateway project into speaker design, etc, However, I think comparison with recognized ID values makes for a good reality check on when it makes sense to DIY a subwoofer for most of us who would not buy a subwoofer from BestBuy (except, maybe a SVS)!

All of that said, my personal current champion for a DIY sub build would be TLSGuy's 10" transmission line subwoofer. My interest is based on the character of the TL bass from Dennis Murphy's Phil3 which I really like (maybe it is not TL, maybe it was just set up in the right room the right way, but I was impressed)! As a DIY project, the dimensions and weight of this probably increase the advantage of building it "on-site" instead of shipping it, and I do not know of a commercial transmission Line subwoofer being sold, period!
Kurt,

There will always be pros and cons about transmission line enclosures. But personally, I never have been that interested in building TL cabinets because of the inherent complexities in their implementation and construction.
But you can build excellent DIY ported subwoofer enclosures which can be comparable and perform better than many commercially sold ones and for a reduced financial outlay. In addition, as a speaker builder, you can enjoy a successful work and have the pleasure of showing to family and friends what you have achieved.

If you have the space, I strongly suggest that you build a ported box design using a good 15" subwoofer such as the Dayton RSS390HF-4 driver. This sub works pretty well in a 8 to 9 cf cabinet. Actually, I am using three of them in my HT system. You can get a response down to 20 Hz @ -3 dB. These subs are excellent for both music and movies, have a rather linear frequency response with low distortion. As those drivers have a power rating of 700 watts, you could easily drive two of them with either a very affordable Crown XLS 1502 or XLS 2002 or one of the QSC RMX or DCA power amps..
As for the material used for the enclosure, for a sub I would recommend 1 inch Baltic plywood as it resonates at frequencies higher than the ones generated by a sub. That is preferable to the MDF which is however the best product for a full range speaker building.
That's my 2 cents!

Should you need any additional info or hints for building one, I would be pleased to help.

Cheers,
 
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Verdinut

Verdinut

Audioholic Samurai
Using one of the 12 inch Dayton's RSS315HF sub, someone can build a very good ported enclosure with an internal net volume from 3¼ to 4 cf. Frequency response is rather smooth with an f3 at 25 Hz or so.
 
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Pogre

Pogre

Audioholic Warlord
do it!

what kind of DIY are you considering? Lots of good options. The main thing to keep in mind is that a)it’s not always the value it’s portrayed as, and b) not all designs are created equal.

with subs I sometimes see totally unrealistic claims made about DIY designs. If you post what you want to do we can probably give you various options. In time I hope to test more designs that interest people.

like with anything, there are trade offs defined by the laws of physics and costs of manufacturing. You can have high output, wide bandwidth, compact size, and a low price. But only three of those can be optimized in any one system.
I came close to building my own ported subs but after I priced it all out, as you point out, the savings were pretty small. Then when you factor in the work that goes into a nice finish... I called Dr Hsu, lol. Going with multiples and using the same amp will realize a little better value tho. For me the finishing work would be the most challenging part of the build.

And then there are transmission line speakers. I've seen a couple of flat packs that looked really nice. I know that's a pretty ambitious build for a newbie tho, but cutting my teeth on a kit or 2 I think would be invaluable experience. I dunno. Still think about it. If I could be confident in the finish I probably already would have. Subwoofers I think you can get away with a little more, but main speakers I'd definitely wanna get right.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
I think the main place where DIY subs can save money is with large ported designs and multiples.

a single 12” CSS sub kit has similar performance to a Monoprice sealed THX 12” sub. It’s a similar price too. But you could build two subs and use a single pro amp and now you are doing as well as a pair of the Monoprice subs but you are looking at about $400-$500 savings.

or like what I did for my main sub. I got a deal on an 18” driver that was discontinued and in this case an upgraded prototype version. I got a deal on a flat pack enclosure designed for something else. I built said enclosure and modified it to work with this driver. I spent about $350 on the driver and enclosure, had the glue and clamps, insulation, terminals, and amps.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Using one of the 12 inch Dayton's RSS315HF sub, someone can build a very good ported enclosure with an internal net volume from 3¼ to 4 cf. Frequency response is rather smooth with an f3 at 25 Hz or so.
I have that driver but in a sealed box. We could maybe play around with a ported version and do tests. It should have more midbass output than the CSS maybe, but doesn’t have anywhere near the excursion to compete down low. I’ve tested the sub before and bad issues with it but I think it was a noisy plate amp. It’s on my todo list to retest with an external amp.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Cool, any expansion in that regard would be a plus I think. Kits are nice, but even some comments on how you could change design a bit with size or sealed vs ported for the particular driver, could be interesting.

Maybe you need some big amps like Josh uses....altho that Lab Gruppen might do it!
well in this case the driver really likes a small box. The advantage is you get hiHF output density. The negative is it’s not very efficient and it’s hard to make a ported box for it. Not sure what else to say? Want me to post some alternative designs for it?

as for amps. I can’t go a lot bigger. Too much bigger will chance popping the breaker. We already use a 10 gauge 250’ cord. Imagine what an 8 gauge would cost.

I have two amps and each had a similar rating. About 1700-2000 watts into 4 ohms. The Crown can be bridged to produce ~4000 watts into 4 ohms. I used the Behringer because it’s more in line with how that driver and kit would be used. The crown makes me nervous. I don’t want to blow a manufactures driver, pop a breaker (it’s a huge pain to reset it), etc. it’s the one thing Josh does that I both admire and have little desire to replicate.
 

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