The W15GTi subwoofer design thread

[DS-21]

Possibly out of grief from departing with the twin JBL 2235's used in the sweetest sounding subwoofer I've yet owned (http://www.audioheritage.org/vbulletin/showthread.php?t=7365). I recently bought a W15GTi off of eBay. Mk. I, because I prefer the dustcap. Assuming it gets to me in one piece, I'm going to use it as part of my home subwoofer system. I will build it into my TV stand, where it will supplement a corner-loaded pair of Peerless XLS12's (http://www.tymphany.com/papers/appxls12b.htm) in a PR alignment with the drivers push-pull on the front and back and the PR's opposing each other on either side. The XLS12's will each get their own NHT A1 monobloc, and I will likely order that Dayton 1000W/4ohm rackmount amp (http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=300-810&ctab=4#) currently on sale tomorrow to drive the W15GTi.

I know how some people (http://audioheritage.org/vbulletin/showpost.php?p=160727&postcount=11) are running them, but what about the rest of you who are using this woofer?

I was thinking of doing a simple sealed box (120L) with high Qtc (about 0.65) sealed box with the Dayton amp's parametric EQ to bring it up to the low end and better match the extension of the XLS12 sub. At rated Xmax, which according to recent testing is pretty highly overstated, it will reach 104.5dB at 20Hz, or about a dB less than the twin XLS12 sub. But then I started playing with different ported alignments. According to Unibox that same 120L but tuned to 20Hz will give a whopping 112dB at 20Hz, without reaching rated xmax when driven with 1000W, and with an overall FR curve similar enough to the XLS12 sub's that the main differences will come from the room rather than the native response. (Regardless of how I use the sub, I will EQ the whole bass subsystem with a Velodyne SMS-1, which will force me to employ the 17Hz high pass needed to protect the XLS12's globally, negating the VLF advantage of a sealed enclosure.) Obviously, a larger, lower-Q vented enclosure would be better still, but bigger isn't an option. The PR's would add cost, but I'd partially offset that by going with a cheaper amp such as the Buttkicker class D model.

So now that I've done my share of thinking out loud, what do you think?

[sourceoneaudio]

Here is my swing at the W15GTi MkII. Different high excursion PR companies posted in the thread also.


http://www.audioheritage.org/vbulletin/showthread.php?t=15201

Jeff
J/S-S1A :D

[toddalin]

The W15GTI woofer runs at 3 or 12 ohms. The selected amp is only rated down to 4 ohms. Assuming that you use the amp within its rated parameters, you would run the woofer at 12 ohms and the amp would only push about 384 watts into it. That results in a reduction of about 4 dB from your calcs.

These things like lots of power, but you should still be able to get plenty of volume. I run mine in my center channel, 3-chamber cabinet with an AlNiCo "2235" (reconed 2205) used for the center channel. I push the W15GTI with a Crown PSA-2XH run in bridged mono mode at 12 ohms. I have the ability to run both in parallel at about 5 ohms.

The 2235 produces more volume down to about 35 Hz where the W15GTI really takes over. If you search this forum, I did close mic testing on the speakers and ports that shows the differences with both speakers mounted in the same cabinet with the same porting.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/center-2235-w15gti.jpg

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Crown_Face.jpg

[DS-21]

The W15GTI woofer runs at 3 or 12 ohms. The selected amp is only rated down to 4 ohms. Assuming that you use the amp within its rated parameters, you would run the woofer at 12 ohms and the amp would only push about 384 watts into it. That results in a reduction of about 4 dB from your calcs.

I'm not too worried about the amp running at a nominal 3ohms. A friend of mine has run a sealed W15GTi at home using that Dayton amp to power it for several months now, and has not yet had any thermal issues. I know the coils are in parallel because I wired it up. Also, for a while I used an amp of very similar topology (NHT A1) that was likewise only rated to 4ohms on a JL Audio 15W6 (also dual six coils in parallel), including an outdoor party that had the sub going full-bore for the better part of six hours in 85deg weather, without incident.

However, if I find a more interesting amp deal I might jump on it.

[GordonW]

Jay,

If it were my project, THIS would be the passive radiator to end all passive radiators, for a W15. The 15" (or 18") TC Sounds passive radiators:

http://www.tcsounds.com/tcvmp.htm

1 5/8" excursion in each direction?! I'd say THAT should DO THE JOB!! Not cheap by any measure, but if you want the BEST for the job... this is it.

Another option, if you can get in contact with them (I've only gotten voice mail when I called them recently on the phone) would be the AE Speakers 15" passive. I've used those, and they were REALLY NICE. Much heavier and better built than either the Dayton or Adire passive radiators, and capable of significantly more excursion. Not quite what the TC Sounds monster will do, but good stuff... and if the pricing I got before still holds, a bit more economical than the TC Sounds units...

http://www.aespeakers.com/


Regards,
Gordon.

[sourceoneaudio]

Jay,

If it were my project, THIS would be the passive radiator to end all passive radiators, for a W15. The 15" (or 18") TC Sounds passive radiators:

http://www.tcsounds.com/tcvmp.htm

1 5/8" excursion in each direction?! I'd say THAT should DO THE JOB!! Not cheap by any measure, but if you want the BEST for the job... this is it.

Another option, if you can get in contact with them (I've only gotten voice mail when I called them recently on the phone) would be the AE Speakers 15" passive. I've used those, and they were REALLY NICE. Much heavier and better built than either the Dayton or Adire passive radiators, and capable of significantly more excursion. Not quite what the TC Sounds monster will do, but good stuff... and if the pricing I got before still holds, a bit more economical than the TC Sounds units...

http://www.aespeakers.com/


Regards,
Gordon.

I believe that AE Speakers bought or took over Stryke Audio which is one of the high excursion passives I was doing research on. The company TC Sounds looks to be the ultimate answer. I have been in communication with them and they are out of stock on all Passives at the moment. They are awaiting a new cone design. Expected delivery time is mid to late summer. :blink: Still awaiting an answer. I'm on list to contact when the passives become ava.

Jeff
J/S-S1A :D

[GordonW]

I think the back-order situation at TC Sounds is about to get better. I was able to get 10" passive radiators from them, last week. I'd assume the larger ones are probably on the way, AFAIK...

BTW: The 10" is the baddest mutha on the block, for its size. Kinda sinister looking, with that great big HUGE BOLT sticking out the back for the weight adjustment washers!!

Regards,
Gordon.


Regards,
Gordon.

[sourceoneaudio]

Yeah, you can add 2000 grams. They are the SHEEEEEEEET when it comes to a passive. Can you post a pic so I can see the new cone? Or did you get last years cone design?

Jeff
J/S-S1A :D

[DS-21]

I believe that AE Speakers bought or took over Stryke Audio which is one of the high excursion passives I was doing research on.

Same company, same person (John Janowitz). Had to change the name for legal reasons. They've been in a tenuous business position for years now.


The company TC Sounds looks to be the ultimate answer. I have been in communication with them and they are out of stock on all Passives at the moment. They are awaiting a new cone design. Expected delivery time is mid to late summer. :blink: Still awaiting an answer. I'm on list to contact when the passives become ava.Yeah, the TC ones do look great, though I hate logos on my gear. (The W15GTi will be cured of that problem when it finally arrives.) Not that they even have to because they're the only game in town right now for long-throw off-the-shelf PR's, given that Adire and AE have basically bowed out.

[toddalin]

Yeah, the TC ones do look great, though I hate logos on my gear. (The W15GTi will be cured of that problem when it finally arrives.)

On mine the logo/5,000 Watt sticker is a decal and a lacquer based paint will make it crinkle. :blink: (Been there done that..., don't go there. ;))

Find a water-based paint.

[DS-21]

Just a quick update. Since I started this threads my priorities changed a bit and I juggled things around. This driver is not in the main system. I decided to scrap my old home office sub and fold its Peerless XLS12 and XLS12-PR into the main system sub. So the main sub uses three of XLS12's with the matching PR, and the W15GTi went into the office. I built an ugly but decently-braced ~140L box for it - as a test, before I commission a box from someone who knows what she's doing - which with the T/S parameters of this specific driver (measured with FuzzMeasure Pro) comes out to a Qtc of about 0.612. A little on the high side for my taste in general, but the W15GTi's resistance to power compression makes its large signal performance barely different from its small signal performance. The extraordinarily low inductance of the W15GTi makes the sub a really good match with the mains in my office system (Tannoy CPA12 stage monitors with modified crossovers for L and R, Tannoy System 12 DMT II center) in terms of transient performance.

Modeled anechoic output is >100dB from 16Hz up and >104dB from 20Hz up, mechanically limited, which is plenty for my nearfieldish office setup. Ironically, my old office sub, the aforementioned Peerless XLS12 with a passive radiator in a ~40L enclosure, was capable of within 1dB of this sub's linear output from 16Hz up despite being a 12 with only 12.5mm of xmax. Goes to show what kind of in-passband gains can be had from well-designed ported/PR system compared to a sealed system; if I add PR's to this 140L sealed box, which is certainly an option, I expect >110dB mechanically-limited anechoic output from 16Hz up, or superior low-end performance to any commercial "hi-fi" subwoofer short of perhaps the Danley DTS-20, without the bandwidth restrictions of the Danley's bandpass/tapped horn design.

To power the new office sub, instead of the Dayton amp I ended up buying a Crown XTi2000 (keeping it in the Harman family, I guess), along with an ART Cleanbox to interface the pro amp with my receiver's RCA sub output. I love this amp. It sounds like, well, any competently-designed amp, which means it has no characteristic sound of its own whatsoever. The DSP front end is phenomenally easy to use; the hardest part is remembering to put my iMac or MacBook in cripple mode via Boot Camp so it can talk to the amp! It was more expensive than the Dayton amp, but with 5 completely adjustable bands of parametric EQ along with two available shelf filters and lowpass/highpass crossovers all in the digital domain it is much more flexible. Not to mention more powerful. I was considering buying a second Velodyne SMS-1 for the office system, but with this amp and my measurement rig (MacBook running FuzzMeasure/M-Audio Solo/Behringer ECM8000) there's no need for such a thing.