A subwoofer journey...(CSS SDX12 + 3x APR12 Passive Radiators)

**technodanvan** · 27 April 2023, 11:35 Thursday

Thanks Jon, I'll have to keep that in mind for one of my future projects!

**technodanvan** · 09 May 2023, 20:03 Tuesday

It's getting quite cramped in here...

**theSven** · 10 May 2023, 09:24 Wednesday

Originally posted by technodanvan

It's getting quite cramped in here...

WOW!!! The paint job came out really good one these cabinets!!! When does assembly begin?

**technodanvan** · 10 May 2023, 12:44 Wednesday

I am very pleased with how they turned out, they are extremely smooth! I'm looking forward to setting them next to the Ardents to see how close they match - looks pretty good from a distance though! Assembly began last night. I'll completely finish one sub before working on the other due to space constraints. Steps are below:

1. Cut and install remaining foam inside the cabinet
2. Drill screw holes for amp installation, and (probably) widen existing screw holes for sub/PR installation by a hair. We'll just be using wood screws all around.
3. Make and install series wire on subwoofer.
4. Make and install binding posts and connection wire inside the subwoofer cabinet (and drill out these holes on subwoofer #2)
5. Lay down box, install subwoofer.
6. Stand cabinet up, lift onto mobile cart (cabinet will remain on rolling cart until such time baseplates are made, approximate weight once complete = 200 lbs).
7. Install remaining PRs
8. Connect to DATS to get an impedance reading - adjust PR weights as necessary to approach 20Hz tune
9. Install amplifier
10. Connect laptop to subwoofer, set up and upload initial DSP file
11. Connect to stereo
12. Set up subwoofer crossover on stereo
13. Hopefully make noise! (and adjust volume via DSP to get it 'close', then final adjustments on stereo.

For anyone wondering what a fair price is for covering a large box in epoxy, sanding, and painting with a satin finish - these were $900 apiece. I personally feel like that's a bargain as I hate painting but love the results. Total cost of this project for the pair approaches $5,000 but could be done much more affordably if you purchased a pro amp or Dayton plate amps for power and finished them yourself. The extreme construction probably isn't super necessary either, so you could probably save on materials.

I'm sure guys from AVSForum would say this is a silly project, a pro amp and a pair of 18"-24" subs from Harbottle or Stereo Integrity would smoke these for potentially less money. I guess my response would be super deep notes at super loud levels aren't really my goal here, musicality (and low distortion) is key, and these need to look good considering they won't be hidden (unlike a lot of subs used in serious home theaters on AVS).

Other folks may comment that for the price, a pair of (insert your favorite sub brand) 12"-15" subs probably would have been better value, plus they'd have a warranty. They might be right (I mean, I certainly have no experience with commercial subs either) but where's the fun in that?

I guess what I'm saying is, sometimes we do DIY because it's fun, unique, and fills specific goal, and not just because it can bring the best value.

**theSven** · 11 May 2023, 07:45 Thursday

Originally posted by technodanvan

I'm sure guys from AVSForum would say this is a silly project, a pro amp and a pair of 18"-24" subs from Harbottle or Stereo Integrity would smoke these for potentially less money. I guess my response would be super deep notes at super loud levels aren't really my goal here, musicality (and low distortion) is key, and these need to look good considering they won't be hidden (unlike a lot of subs used in serious home theaters on AVS).

Other folks may comment that for the price, a pair of (insert your favorite sub brand) 12"-15" subs probably would have been better value, plus they'd have a warranty. They might be right (I mean, I certainly have no experience with commercial subs either) but where's the fun in that?

I guess what I'm saying is, sometimes we do DIY because it's fun, unique, and fills specific goal, and not just because it can bring the best value.

You ended with the key point I would have brought up if you had not said it yourself! This is a custom build, DIY, and looks as good or better as a mass produced commercial option. I would have chosen the path you took any day over buying a commercial sub build. You designed and built something that matches your requirements instead of having to find an option that meets 90% of what you need and then change your setup around to work with it.

Looking forward to more photos as these cabinets get assembled!

**technodanvan** · 11 May 2023, 09:57 Thursday

I made some progress last night, got to Step 8 and stopped for the evening as I didn't have the manual for the Hypex amp handy. Tuning appears to be about right based on the impedance graph - I installed all but two disks in all PRs so Unibox appears pretty much dead on. I can always remove another disk if actual measurements dictate so. It also looks like this isn't really an 4 ohm part when with voice coils in series, it's closer to 5.5 - 6 in it's usable range. A few photos below.

Test fitting the amplifier.

Drilling out screw holes for the amplifier. As an aside, I really like the Big Gator Tools drill guides. Very handy when you want to be sure you are drilling straight (something I just cannot do by hand).

Series wire installed.

Sub and PRs installed. It looks bigger now. Definitely feels bigger too - hoisting this thing onto the cart with the sub installed was a literal pain. I need to get back to the gym!

Impedance.

**technodanvan** · 11 May 2023, 10:11 Thursday

I've also been thinking about how to safely move these things (and the Ardents...plus whatever else I make) when it comes time for a new home in the next few years. I'm kind of thinking about strapping them to quarter-sized pallets and using a mini pallet jack to get them around. Then use a truck with a lift gate. Any other bright ideas?

https://www.amazon.com/gp/product/B08FRM8S2M/ref=ox_sc_saved_title_1?smid=ATVPDKIKX0DER&psc=1

**Evil Twin** · 12 May 2023, 10:11 Friday

Originally posted by technodanvan

I am very pleased with how they turned out, they are extremely smooth! I'm looking forward to setting them next to the Ardents to see how close they match - looks pretty good from a distance though! Assembly began last night. I'll completely finish one sub before working on the other due to space constraints. Steps are below:

I guess what I'm saying is, sometimes we do DIY because it's fun, unique, and fills specific goal, and not just because it can bring the best value.[/SIZE][/FONT]

Sven commented on this, and OBVIOUSLY, I must concur with violent agreement, as a former Sith master of mine would say at times (sometimes even for things I proposed!)

That weight of loaded cabinets can become a serious issue without Yoda's force lift- it is one thing to do things on a screen, but moving them around one's HQ can be quite a different matter!

Ages ago I proposed a force cancelling subwoofer with dual Peerless STW-350F woofers, but just what one driver weighs is something to ponder. I have been thinking about doing that with my NIB Hypex DS 8.0- the actual measured impedance of the woofers is nearly double the spec sheet, and they're both identical. Also verified with LCR meter, besides the DATS tool. It should be feasible, though it would not reach the true potential of the drivers.

Even I am having trouble imagining moving it once built! It would likely be best to load the drivers in the room it will be used in.

**technodanvan** · 13 May 2023, 12:03 Saturday

Sub Number 2 is mostly assembled and an impedance sweep run. I almost didn't do it but figured I should check. Graph is almost identical to Sub Number 1, so I take that as a very good sign things are the way they're supposed to be.

As an aside, I've been playing music through subwoofer 1 pretty much every waking hour since I got it working. It's now placed in the corner I'm planning on using permanently. I haven't played any movies through it yet, but will do so once the second subwoofer is placed in the opposite corner. For music it sounds pretty good! I have the amplifier gain set to zero currently and it's pretty close by ear. Won't run any sweeps until the second subwoofer is placed, then I'll adjust accordingly via DSP on the Hypex amps.

**JonMarsh** · 13 May 2023, 12:20 Saturday

Trust, but verify EVERYTHING!

**technodanvan** · 13 May 2023, 19:37 Saturday

Exactly! Everything is set up now, just a quick upload to the amp and everything is running smoothly. Will play around with them for a week or two to let them break in a hair before measuring them and adjusting the DSP settings. Oddly enough, there is also an equalizer on the amps (in addition to the filter design) so I could opt to just use that as well.

As far as color matching goes, it's close enough that you probably wouldn't notice the difference if giving only a passing glance. The white on the subs is a bit 'cooler' (almost slightly gray?) than the warm tones on the Ardents. Unsure if a bamboo base will look weird with it now....that's a LOT of white to overcome, given their size.

**theSven** · 13 May 2023, 22:06 Saturday

Originally posted by technodanvan

Exactly! Everything is set up now, just a quick upload to the amp and everything is running smoothly. Will play around with them for a week or two to let them break in a hair before measuring them and adjusting the DSP settings. Oddly enough, there is also an equalizer on the amps (in addition to the filter design) so I could opt to just use that as well.

As far as color matching goes, it's close enough that you probably wouldn't notice the difference if giving only a passing glance. The white on the subs is a bit 'cooler' (almost slightly gray?) than the warm tones on the Ardents. Unsure if a bamboo base will look weird with it now....that's a LOT of white to overcome, given their size.

Splendid job on this build!!! I hope you get many good years of use out them too.

I had to post a photo of one of the FI subs. They are beastly looking things!!!! I think investing in a fork lift sounds reasonable to have a sub enclosure with a monster like that sub.

**technodanvan** · 14 May 2023, 15:18 Sunday

Yeah, and that's their neo version - I can only imagine the ferrite one. I may have to see how the Neo 18" 4.11 stacks up against others. It's about a grand though, so it'd need to be 2-3x better than a Dayton sub!

**technodanvan** · 18 May 2023, 17:49 Thursday

This weekend I'm hoping to dig out some microphones and measure the system, at least with Omnimic if nothing else. I'm unsure if I have the hardware to power my other microphone anymore. It sounds pretty darn good to my ear, but we all know how fallible that is. Everything is VERY clean though which I pointed out to my wife when I had music moderately loud - she noted it being loud, but I responded we were still able to hear each other at normal speaking voices.

Anyway, all I did was set up a low pass on each sub at 1,000Hz, then set my NAD M12 to have a 120Hz crossover on both the speakers and subs. I didn't trim anything, all individual volumes are at zero (including the plate amps). I would have thought I'd need to tweak it more by ear, but I have been very happy with the results thus far.

I have to say I'm slightly disappointed though, I have been unable to get my clothes to vibrate in my small room! I think the subwoofers can do it - it's like right on the verge I suspect - it's more that I'm afraid to push the Ardents any louder! That said, I have also not tried any movies yet, meaning I probably haven't reached into the 20Hz range yet. I will remedy that shortly...

**technodanvan** · 19 May 2023, 13:44 Friday

Making a gif is way harder than I thought it'd be. Any ideas what the file size limitations are theSven? Maybe 10MB?

I think the second to last bass hit is about 20Hz, with 30 fps it's not too clean. The last bass hit is around 10 Hz. This is the opening scene from Edge of Tomorrow, about 20-30 seconds into starting the movie. Has to be the DTS-HD track - they applied a high pass filter at 30Hz on the Dolby Atmos track accompanying the 4K version of the movie.

**technodanvan** · 11 August 2024, 12:09 Sunday

Now that it's been over a year since completing these, I have a couple additional thoughts.

1. CSS has debuted a new 10" subwoofer that, had it been available in 2022/2023 I think I might have gone for instead to reduce size a bit. Not that size is currently a huge problem for me, but it may have made more configurations possible if/when I move someday. Jon's mention of the CSS tweeter in another thread reminded me of this new 10...and the new waveguide tweeter. I need to make a purchase!

2. When I first had these set up and both working correctly I measured my system and found the bass about 4-5 db 'hot'. I dialed that back down a hair but do like a little extra 'oomph' so left it a bit hot. Quite some time later I noticed it not being so bassy at my listening position. Odd, but figured it was no big deal and still sounded rather great...until two days ago when I noticed that left sub simply wasn't playing. Or rather, it was, it was just an extremely low level. After diagnosing it over the weekend I am a bit embarrassed to conclude that has probably been this way since over a year ago. Let me explain. The Ncore amplifiers have an awful lot of settings on them, many by default and some of which would make sense if they were powering loudspeakers. By default, the amps are set to -40 dB to protect your drivers on first hookup. No big deal, I just set that to zero and we are good to go - at least when I first had them plugged in. Little did I know I forgot another setting on the left sub that I apparently got correct on the right. After a power cycle there is another setting that automatically resets the gain to -40dB. I think this feature is intended for loudspeakers since these can be used directly with a source and the volume turned up by remote control. Anyway, I unchecked that box, reset the gain to zero, and now I have a lot of extra bass I didn't have previously.

TL;DR: I've been happily running a single sub for a full year without realizing it.

**theSven** · 11 August 2024, 12:58 Sunday

Originally posted by technodanvan

Now that it's been over a year since completing these, I have a couple additional thoughts.

1. CSS has debuted a new 10" subwoofer that, had it been available in 2022/2023 I think I might have gone for instead to reduce size a bit. Not that size is currently a huge problem for me, but it may have made more configurations possible if/when I move someday. Jon's mention of the CSS tweeter in another thread reminded me of this new 10...and the new waveguide tweeter. I need to make a purchase!

2. When I first had these set up and both working correctly I measured my system and found the bass about 4-5 db 'hot'. I dialed that back down a hair but do like a little extra 'oomph' so left it a bit hot. Quite some time later I noticed it not being so bassy at my listening position. Odd, but figured it was no big deal and still sounded rather great...until two days ago when I noticed that left sub simply wasn't playing. Or rather, it was, it was just an extremely low level. After diagnosing it over the weekend I am a bit embarrassed to conclude that has probably been this way since over a year ago. Let me explain. The Ncore amplifiers have an awful lot of settings on them, many by default and some of which would make sense if they were powering loudspeakers. By default, the amps are set to -40 dB to protect your drivers on first hookup. No big deal, I just set that to zero and we are good to go - at least when I first had them plugged in. Little did I know I forgot another setting on the left sub that I apparently got correct on the right. After a power cycle there is another setting that automatically resets the gain to -40dB. I think this feature is intended for loudspeakers since these can be used directly with a source and the volume turned up by remote control. Anyway, I unchecked that box, reset the gain to zero, and now I have a lot of extra bass I didn't have previously.

TL;DR: I've been happily running a single sub for a full year without realizing it.

This story has a happy ending thankfully. I thought I was going to read and find that you blew the sub and had to get another one. Thankfully a tweak in the settings has the subs working as expected and the enjoyment continues.

I need to do a sub build next after I get the CC channel. I'm going to have to sell my sonotube now that it will no longer fit with the new CC and put a new setup there. I didn't know this hobby would be so addictive when I got into this. Always wanting to assemble or try something new 🤣.

**JonMarsh** · 01 September 2024, 13:06 Sunday

Originally posted by technodanvan

Thanks Jon! I think part of my problem was using the drill bit that came with the inserts (which seemed a little aggressive), and I should have had another step working up to that size.

A hint- for materials like BB ply, a good forstner bit may work better at getting the initial hole cleanly for the inserts. Takes longer, but works cleaner. I've got a big collection for specialized work.

**technodanvan** · 03 September 2024, 16:37 Tuesday

Originally posted by JonMarsh

A hint- for materials like BB ply, a good forstner bit may work better at getting the initial hole cleanly for the inserts. Takes longer, but works cleaner. I've got a big collection for specialized work.

This is a timely recommendation as I prepare to install some inserts for the PRs on the Crescendos. I haven't decided how I'll proceed on these as most attempts for inserts in the past have resulted in unsatisfactory happenings. A Forstner bit could be the path ahead, and I do have a Porter Cable set that hasn't seen much use on the small bits. Of course, then I'd need to hoist the panels onto the drill press and clamp them in place for each hole. Time consuming as you say, but the results may be worth it.

Now that I think about it, I really need to either make or purchase a larger table for the new press. I keep finagling random pieces of wood for that purpose, but for large panels like these it might not work well.

Anyway, I think I have both brass and stainless variants of EZ Lock inserts in my inventory, but I don't know their size or quantity. Need to check on that.

**JonMarsh** · 03 September 2024, 21:27 Tuesday

I've been a frequent EZ-Lok user- there's even some M3 EZ-Lok in the midrange panel mounts. But I'm in love with Rampa these days, as is Steve. Just installed some M4's in the base of the LF module of the Saint-Saens for locking down the LF crossover- have 1/4" thick nylon large diameter washers glue to the bottom side to act as spacers, and fender washers will go on top...

The Rampas install so cleanly with a mm Hex driver. I've become addicted to them... of course, they're hidden here!

**Scareurpasenger** · 04 September 2024, 21:03 Wednesday

My big gripe with the ezlock is they are a paint to drive in straight. I ended up making a threaded adapter to help with it and once I get a few threads in, I switch to the ezlock driver.

I have been eyeing the Rampa inserts but wondered if they were better in this regard.

**JonMarsh** · 04 September 2024, 21:23 Wednesday

Much, much better IMO. You've identified (correctly IMO) the biggest short comings with the EZ-Lok parts, getting them to thread straight and the driver tool they require. The Rampas work with mm sized hex wrenches, what ever you have on hand suited for the job. I have M4, M6, and M8 size parts.

Here's a sample pic...

**ergo** · 05 September 2024, 04:56 Thursday

Originally posted by technodanvan

[SIZE=14px][FONT=Arial].............and the belief they will only be getting more expensive down the line.]

That is very true - I have two Wavecor SW312WA05 subwoofer I bought back in 2020 and which are still sitting in box waiting for their time to be built into a music listening subs. I paid 574EUR for a pair and today a price of one is 511EUR in webshop in Netherlands 😮

Every now and then when I remember I have these waiting, I'm thinking of a way to go about building the woofers. This thread is very useful to widen and refresh the knowledge again. Back when i bought these I was pretty sure I'll just create a simple sealed enclosure, but some inside motivators wanted to put both in one box and try out force cancelling while the other inside forces were argumenting that two boxes are better to tackle room modes.

**JonMarsh** · 05 September 2024, 12:31 Thursday

Yeah, Ergo- slow work definitely takes time! Think about my Kurosawa project- all in a storage unit here with a lot of other things (fortunately much less expensive than CA), and the Accuton AS190 cell woofers I bought for a bit less than $500 each are now $1481 each here in the US from the Madisound distributor! Now, the hilarious thing is, I will probably change the midrange out to the Peerless FSL-0512, because it works so well, regardless of cost.

There's so many things for my retirement that purchasing them over the last 15 years has been a very valid investment in the future- in some cases, irreplaceable at anything remotely close to what I paid (like my 1996 Acura and the parts to convert it to a 2002 Type R JDM, or my Hammond B3 clone from an Italian company).

And I have an experiment ready to roll (further down the task cure) for revisiting my 90's slot loaded woofer designs (inspired by Janis subs), with some contemporary ultra low Qts Italian pro drivers (the ultra low Qts is a necessary parameter to achieve the right response plot in a small cabinet with only a small double slot interface on the front side). B&C 15SW115. Now, if you looked at the data sheet, you'd figure it for a typical high Fs high sensitivity pro woofer designed to play really loud... which it is. With a Qts of 0.24, and a nominal sensitivity of 96 dB. But, it also has an Xmax of about 14mm, and an absolutely brutal neodymium motor (hence the sensitivity and low Qts.

And depending on the "sealed" box size you are prepared to deal with, a - 3dB point of 25Hz and 150Hz are feasible, or if a bit more generous in box size, -3db at 18Hz and 160Hz. At least that's what VituixCAD tells me, and it seems to be using the same calculation methodology for this enclosure model as I was using back then, with Audax 15" pro drivers. It's just another experiment waiting in the wings, drivers boxed and eager to go when I have the time...

And it's not magic, the tradeoff is a substantial efficiency drop- Hoffman's Iron law still applies.

**Scareurpasenger** · 14 September 2024, 09:17 Saturday

Originally posted by JonMarsh

Much, much better IMO. You've identified (correctly IMO) the biggest short comings with the EZ-Lok parts, getting them to thread straight and the driver tool they require. The Rampas work with mm sized hex wrenches, what ever you have on hand suited for the job. I have M4, M6, and M8 size parts.

Here's a sample pic...

Well, I am sold! Tracking the different sizes down for a reasonable/best price lead me to the manufacturer. If you sign up for an account, you can get them at almost half compared to Amazon plus shipping. $30 for 100 and shipping is pretty static at $20 so it pays to order more than 100 at a time.

**JonMarsh** · 14 September 2024, 10:54 Saturday

Originally posted by technodanvan

Making a gif is way harder than I thought it'd be. Any ideas what the file size limitations are theSven? Maybe 10MB?

I think the second to last bass hit is about 20Hz, with 30 fps it's not too clean. The last bass hit is around 10 Hz. This is the opening scene from Edge of Tomorrow, about 20-30 seconds into starting the movie. Has to be the DTS-HD track - they applied a high pass filter at 30Hz on the Dolby Atmos track accompanying the 4K version of the movie.

What's the Fb of your finished system? Can you share an impedance plot? (they reveal a lot...)

**technodanvan** · 14 September 2024, 12:11 Saturday

I posted this one a while back, this was on first hookup so I imagine Fb has lowered a hair since then.

Sub 1:

Sub 2:

**JonMarsh** · 14 September 2024, 13:06 Saturday

My apologies for missing that- thanks for reposting. Looks like FB is at about 18 Hz, but judging from impedance curve, a pretty steep roll off to anti phase behavior at about 15 Hz.

**technodanvan** · 14 September 2024, 13:19 Saturday

I'm guessing that's why the PRs move a ton around Fb, but when that 10 Hz hit comes in they see very little movement?

**Evil Twin** · 14 September 2024, 13:51 Saturday

Originally posted by technodanvan

I posted this one a while back, this was on first hookup so I imagine Fb has lowered a hair since then.

Sub 1:

Sub 2:

Most interesting, though disturbing on some levels. I usually see a fairly strong agreement between Unibox impedance calculations and actual measurements, but in this case the level of the primary impedance peak and the anti phase impedance peak are quiet different from the calculations, and the transition to anti phase operation in the lower impedance peak is quite abrupt, suggesting a steep LF roll off, and an unusual Qms characteristic.

Now, when you describe your enclosure as being 70L, is that net, after allowing for the not insubstantial driver volume, or is that gross?

With 70L net, and 1100 g weight for each PR, Unibox calculates an Fb of 17Hz, and an F3 of 31 Hz, due to the roll off slope that results if tuning Fb below the driver resonance. The anti-phase impedance peak calculates at 12 Hz.

The upper impedance peak for both DATS and Unibox are at the same frequency (~32Hz) but at rather different levels.

It would be most interesting to use the method adopted by PuriFi to examine a ported system response, by using an extended LF cable microphone of small diameter barrel, and via a tubular hole that can be sealed afterwards, measure the internal sound pressure with a low level drive signal, 1W or less. This will by reciprocity give a good representation of the output of a vented or PR or sealed system, regardless of room placement. I believe I have convinced Jonmarsh to consider this evaluation for his Saint-Saens design, using a nominally expendable microphone with extended LF capabilities. As I understand it, though, he intends to employ this method with the single driver and single PR test cabinet, in case it seems further measurements are necessary to adjust system tuning.

Of course, as is well known, good intentions sometimes go before a fall... or fail.

**technodanvan** · 14 September 2024, 14:07 Saturday

Drill a hole in my beautiful sub(s)? I guess it could go through the bottom, but that would hurt my soul a bit to do that to such a nice paint job.

70L net sounds right, but it's been a while. I don't recall what I used for the volume of the sub assembly itself. I should get a mic back out and measure in-room system response again. I don't recall it being problematic at the listening position, but back further by my desk there is definitely a room mode.

A subwoofer journey...(CSS SDX12 + 3x APR12 Passive Radiators)

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