Mark_Seaton

UPDATE:  WW Speaker Cabinets has decided to re-focus on other areas of their business and keep the speaker cabinet sales to OEM rather than DIY sales.  After building up and testing a pair of X21's with the B&C 21DS115-4 driver for a customer I have decided to make a few refinements and offer this as a complete product for sale on our website.

This thread will be used for online questions, answers and general sharing with users.  As the cabinet designer I only provide direct feedback here on our forum for this product.  All sales will be handled directly through WW Speaker Cabinets on their website or by directly contacting them (admin@ww-pedestals.com).

WW Speaker Cabinets, a division of WW Displays, has been building all of Seaton Sound's enclosures for more than 8 years now.  They have long planned to expand to offering some useful enclosures for sale directly.  I am happy to announce that I have worked with WW Speaker Cabinets to insure their first subwoofer cabinet is acoustically worthy of their craftsmanship.  This first offering is the new X21 subwoofer cabinet.  

Do you have space and lust for a bigger and badder sub than you see in your price range?  Do you like the idea of selecting the woofer you like, having upgrade options, and the flexibility of using any amplification and DSP you like?  Are you handy enough to wire up and mount a massive 21" woofer?  Check out the new X21 subwoofer enclosure:

X21 Subwoofer Cabinet

[x21%20black%20d45]  [x21%20black%20grill%20black%2045] 

Details:

  • 21" ported subwoofer enclosure
  • Two Massive 6" Precision Port™ flared ports for quiet vent operation, low compression, and very high output
  • 310 Liter (~11 cu.ft.) net internal volume
  • 19Hz tuning frequency 
  • Intended useful range: 16-160Hz 
  • External dimensions of 32" tall, 24" wide, x 32" deep.
  • Precision lock-mitered, CNC construction for strength and clean corner joints
  • Carefully located, dadoed bracing
  • A selection of precision cut driver recess with physically verified bolt pattern for 6 different drivers with more to be added over time.
  • Driver mounting by screw-locked T-Nuts which have all been run through prior to shipment
  • Driver mounting screws included
  • Keyhole driver grab point at 6 o'clock position to enable positioning and later removal of the woofer if needed.
  • High strength neodymium magnets concealed in the face of the speaker.
  • Magnetically retained, fabric grill
  • Multiple veneer finishes and stain options
  • Bare MDF option for those looking to save or create their own custom finish. The lock mitered construction makes the finishing process dramatically easier when there is zero end grain to fill or attempt to conceal.  This is a BIG deal for those attempting gloss or smooth painted finishes.


While it's easy to sketch some dimensions of a large box and some ports, parts this large get tricky.  Ports behave longer than expected, tolerances become significant over long dimensions, and slight misalignment of holes become a pain with big, heavy woofers.  WW Speaker Cabinets has extensive experience constructing large items in their very large facility (see more).  The cabinet construction and finishing is typically the most difficult for Do It Yourselfers, and there is always a factor of reality vs computer simulations.  Here we can offer a very well engineered and constructed enclosure which has been tested to verify performance.  The price is not insignificant, but IMO there is significant value here.

There are now an assortment of high performance 21" subwoofers available on the market.  With a few filters most all are very useful and efficient in this low tuned cabinet.  Up to 1000W into the nominal driver load, even modest excursion drivers perform exceptionally well.  With higher performing drivers and their massive, 4.5" to 6" diameter voice coils, we can safely put 1600W to as much as 4000W to use with appropriate high pass filters (18-20Hz).

I will be adding some more detailed measurements, many of which are already linked on the X21 product pages for each driver family.  We will also be adding recommended filter settings to provide a smooth anechoic response to start from.

A few more pictures:

Bare MDF cabinet for you to finish as you like:

[x21%20unfinished%20front]    [x21%20unfinished%20d45] 

X21 subwoofer in white with magnetic, black fabric grill:
[x21%20white%2045d]  [x21%20white%2045d%20with%20grill] 

I know the huge 21" woofer is hard to grasp in scale, so here's a quick pic with a can of Coke.  No, that's not a 15" with some 4" ports.  [cool]
[X21vsCoke-quarter] 
[X21vsCoke-front] 

Here are few fun shots I took to put some scale to these massive woofers in the warehouse before testing with the 3 of the 4 drivers B&C was nice enough to get us for detailed measurement and testing:

[21vs8in-1]  [21vsbeer-3]
[21vsbeer-1] 

Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Mark_Seaton

While it was a bit cold outside for ideal measurements, we wanted to get a good idea of if the cabinet and drivers were behaving similar to what I expected from my models.  Correlation was in fact quite good with some estimations of real inductance and realities of the tuning and port end correction.  All drivers were measured with the same drive Voltage to show sensitivity, so the 8 Ohm drivers received less power, and 1 Ohm IPAL received more.  This is with no processing applied, where the recommended high pass filter will easily smooth the rising output below 20Hz.  A single wide PEQ at 100-120Hz or a shelf filter will easily set the desired shape for any rise in the upper octave.  Please note the subtle bumps around 35Hz and 55Hz are common to all measurements due to reflections from the hallway created by the 2 buildings along the parking lot.

[X21-setup1] 


First up, 4 B&C drivers.  From top to bottom at 20Hz: 21IPAL 1 Ohm, 21DS115 4 Ohm, 21SW152 4 Ohm, 21SW115 8 Ohm.  
[X21-BCcompare-1] 

Next up the PRV Audio 21SW4000-NDY-4 21" available from Parts Express:
[X21-PRV-LF1] 

and here we have the Beyma 21PW1400Fe 8 Ohm available through US Speaker:
[X21-Beyma-LF1] 

Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Mark_Seaton
Below are some recommended starting filter sets for the B&C drivers. These were intended for a rather flat outdoor response which will work well in larger rooms that such a large sub is likely to end up in.  For the enthusiasts choosing to unleash these in smaller spaces, you might want to taper down the 15-30Hz range more than in these graphs.  If someone is doing this please post here in the thread and I can offer suggestions.  I used a MiniDSP 2x4HD as an easy example, but I intentionally used filters available in more common DSP, including the Behringer DSP pro amps: 

For the B&C 21IPAL & 21DS115-4, we have the following filters used: 
1. L-R 2nd order high pass at 20Hz (2nd order Q=0.5 filter)
2. A 2nd order High Shelf at 100Hz cutting 14.5dB
3. A single parametric filter at 26Hz with a Q of 1.0 and +5dB of gain

This response is +/-3dB from 17-120Hz, and should be useful to 16Hz in-room:
Please note the 35Hz & 53Hz bumps are environmental and not characteristic of the sub or drivers.

Here is the B&C 21IPAL - 2 Ohm with the above filtering applied:
[21IPAL-Mini-Filters] 

Here we have the B&C 21DS115 - 4 Ohm with the above filtering applied:
[DS115-Mini-Filters] 

For the B&C 21SW152-4, we have similar filters used changing the parametric to +6dB at 25Hz and Q of 1.5: 
1. L-R 2nd order high pass at 20Hz (2nd order Q=0.5 filter)
2. A 2nd order High Shelf at 100Hz cutting 14.5dB
3. A single parametric filter at 25Hz with a Q of 1.5 and +6dB of gain

The B&C 21SW152 - 4 Ohm with the above filtering applied:
[SW152-Mini-Filters] 

For the B&C 21SW115-8, we have related but adjusted filters as listed below: 
1. Butterworth 2nd order high pass at 20Hz (2nd order Q=0.71 filter)
2. A 2nd order High Shelf at 65Hz cutting 10dB
3. A single parametric filter at 23Hz with a Q of 1.2 and +5dB of gain

The B&C 21SW115 - 8 Ohm with the above filtering applied:
[SW115-Mini-Filters] 

For the DSP's with filters you can set below 20Hz such as most of the MiniDSP products you could also experiment pushing the 2nd order high pass lower.  Here are each of the above drivers in the same respective order with the high pass lowered to 15Hz vs 20Hz above.  This does ask a little more from the driver and amp.  In the end the difference only moves the +/-3dB window about 0.5Hz lower and changes the shape of the curve in the 15-30Hz range.  In most home theater applications I recommend starting with the 20Hz setting above for a little better sound quality, attack and headroom.  Of course the beauty of a DIY product is you can experiment and choose which version you enjoy the most. [smile]

[21IPAL-Mini-Filters-15Hz] 
[DS115-Mini-Filters-15Hz] 
[SW152-Mini-Filters-15Hz] 
[SW115-Mini-Filters-15Hz] 

Here you can take a look at the raw vs filtered response.  Again, this was accomplished with a 2nd order high pass filter, a shelf filter, and one parametric boost.  When correcting the outdoor measured response a less is more approach usually makes for better results and less unexpected behavior.  In the same respective order you can see the with and without filtering overlaid:

[21IPAL-Mini-Filters-2] 
[DS115-Mini-Filters-2]  [SW152-Mini-Filters-2] 
[SW115-Mini-Filters-2] 
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Mark_Seaton
Reserved
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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DC3
Just saw these...I thought these were mainly pro audio and not for home theater.  It's interesting that these do not have the big surround like other drivers, but xmax at 22mm is the same as the UM-18 driver in the F18.  

Can ported work with sealed?  

Don
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Mark_Seaton

DC3 wrote:
Just saw these...I thought these were mainly pro audio and not for home theater.  It's interesting that these do not have the big surround like other drivers, but xmax at 22mm is the same as the UM-18 driver in the F18.  

Can ported work with sealed?  


Hi Don,

Any driver can be used for most any application.  It really just comes down to what is required to get maximum benefit from the driver in your application.  In simple terms, the 21" woofer has the surface area a smidge bigger than a pair of 15" woofers, or 50-55% more than an 18" woofer.  Most of the drivers are most useful to +/-14-20mm each way, where the suspension stiffens up.  One nice benefit of the pro heritage of these for DIYers is that it's exceptionally difficult to bottom these drivers out, even if you skip using the high pass I recommend.

Ultimately having ported and sealed subwoofers both covering the lowest frequencies is problematic unless you use additional filtering to cut the sealed subs at the low limit of the ported sub, and even then the capabilities will be quite different.  A sub like this should really be the primary bass maker, and if additional smaller subs are used, they should help with the upper octave of the sub range where position and modal issues are key.   In the range around the tuning frequency where the port has the most function, the output lags by ~180 deg.  This still produces lots of output because the driver is not moving much nor producing much output at this range.  As you move to lower frequencies both the port and driver start to move freely again and this is why you see the rapid cancellation well below the port tuning.  The port output works great on its own or with other subs having a similar port tuning frequency, but it will typically cancel with a sealed subwoofer or woofer tuned much lower.

I added a few more pictures to the end of the first post.  We really need a good shot with people in the picture for scale.  Here are two I had WW send me:
[X21vsCoke-quarter] [X21vsCoke-front] 
And here is some scale for those 21" woofers.  This is an 8" woofer next to the big 21IPAL from B&C:
[21vs8in-1] 

Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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DC3

Sam and I just finished Godzilla with the f2's and f18's slightly opened up....not sure how much more my ears and room can take.  Great products.  I like the looks of the X21...sure it is a stellar performer as well.  

Don
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Mark_Seaton
I just edited and added a series of graphs to post #3 above.  These graphs show what is possible with very simple filtering available in many DSP products such as the example MiniDSP 2x4HD as well as in most of the professional amplifiers models that have internal DSP which include examples like the budget friendly Behringer iNuke NU3000-DSP or the Crest Pro-Lite series with DSP among many others.

Here is one of the above examples showing the B&C 21DS115-4 Ohm with the following processing:
1. L-R 2nd order high pass at 20Hz (2nd order Q=0.5 filter)
2. A 2nd order High Shelf at 100Hz cutting 14.5dB
3. A single parametric filter at 26Hz with a Q of 1.0 and +5dB of gain

This response is +/-3dB from 17-120Hz, and should be useful to 16Hz in-room:
Please note the 35Hz & 53Hz bumps are environmental and not characteristic of the sub or drivers.
[DS115-Mini-Filters] 

Here you can see the raw and filtered response overlaid:
[DS115-Mini-Filters-2] 

And finally a look at what happens if you have a DSP that can push the high pass filter lower.  Similar could be accomplished a few ways with an additional filter in DSP that doesn't allow filtering below 20Hz, but this does ask a little more from the driver and amp.  In the end the difference only moves the +/-3dB window about 0.5Hz lower and changes the shape of the curve in the 15-30Hz range.  In most home theater applications I recommend starting with the 20Hz setting above for a little better sound quality, attack and headroom.  Of course the beauty of a DIY product is you can experiment and choose which version you enjoy the most. [smile]

[DS115-Mini-Filters-15Hz] 
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Stereodude
What a great idea Mark.  Now you just need a version with PRs instead of ports. [tongue]
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Mark_Seaton
I see now that I never updated this thread with a link to the massive amount of data Josh Ricci of Data-Bass collected on the X21 subwoofer.  He was already testing a B&C 21DS115 driver, so we got a box to him so he could test the driver and the X21 enclosures.  Not only did he measure the sub with the inexpensive Behringer iNuke 3000DSP I sent him, he also tested with his huge K20 amplifier.  Josh astutely asked early on what the tuning would be with one port plugged, which I confirmed was ~14.5Hz, so he managed to test that configuration as well with both amps making for 4 big sets of measurements.

Josh used the DSP parameters in post #3 for the 3000DSP (2 Vent) measurements where you can see the impressively flat response:
[Data-BassX21-3kDSP-2V]
Once Josh had measurements of the single port operation, I posted similar filters to get similarly flat response even while using common filters with a 20Hz minimum setting.  Here are the filter parameters and resulting response:

An iNuke DSP or similar can easily implement this.

For the 21DS115-4 as tested I have the following filters recommended:
1. BW 12 / 2nd order high pass at 20Hz (2nd order Q=0.7 filter)
2. A 2nd order Low Shelf at 20Hz boosting 6.0dB
3. A 2nd order High Shelf at 90Hz cutting 14.0dB

This gives a response that is +/-3dB from 14-200Hz, and should be useful to around 12Hz in-room.  Here is what I modeled up where this is just generic, so the exact shape may vary by a smidge:


 
[X21-1V-3filters] 
You can see the effective lowering of the tuning frequency in the comparative impedance response where the tuning frequency is ~ the minimum between the two lower peaks:

[WW%20Speakercabinets%20X-21%20B&C%2021DS115-4%20Impedance] 

Output at this low tuning was still quite impressive with the big flare on the single 6" diameter, straight port:

[X21-single-port%20CEA2011] 

Of course the numbers above 20Hz increase a bit with the 19Hz tuning and 2 large ports operating:
[X21-2port-CEA2011] 

Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Mark_Seaton
I should also add that WW-Speakercabinets sharpened the pencil a bit on the process and did lower prices some on all variations and finishes.  The black maple or black oak finishes with magnetic grill are now under $1k, and the lock-mitered MDF cabinet is just under $700.

I know guys are tired of seeing me standing next to subs for size, so we talked the director of marketing for WW to step in on this one. This definitely gives a better idea of scale. Sorry guys, she's married, and keep comments respectful, she's family at WW.
[X21-Andrea-400] 
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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theaterdesignco
Hello,

Great write up.  Did you ever try any of these 21's in a sealed enclosure? 

We have a customer who not only wants serious low end but the wow factor. 

We generally build these ourselves but I pointed him toward your F18 with 2nd and 3rd slave units.

Thank you,

Tyler
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