ChrisA
Second Unit
- Joined
- Nov 25, 1999
- Messages
- 478
I have been creating a cost no object/no restraints subwoofer that is superior to the Krell MRS and Wilson XS... It is what the Wilson XS should have been.
First and foremost, I would like to wholeheartedly thank Deon Bearden and Greg Monfort for their continual advice and support during their busy schedules. Deon spent July through September putting up with my endless questions and phone calls. Deon and Greg taught me an incredible amount and I very much appreciate it. If it wasn't for the both of them, I would not have been able to gone this far. Between their tutoring and lots of reading, the Black Hole subwoofer was born...
The $18,500+ Wilson XS subwoofer still uses the original first generation aura 1808 driver). Later, Seismic came out with an improved cone, the epoxy cone, called the 8196E. Just recently, they came out with the most advaced driver yet, the 8196HK..honeycomb kevlar with a new Butyl surround
The Black Hole Subwoofer uses the new HK driver. The Seismic 8196 HK driver is an amazing driver... 4 inch underhung design with radially arrayed neodymium magnets.
The Seismic 8196 HK driver (Honeycomb Kevlar) uses (2) cones, with the layer of honeycomb Kevlar in between. So although it appears the same.. the stiffness and the mass has greatly increased... The Fs is appreciably lower... Barry, Owner of Seismic Systems sent me parameters with an Fs around 15 Hz. Either way, it is a significant improvement in the driver, and will yield a flatter response curve (The Wilson XS still uses the paper cone, not even the Epoxy cone... The Wilson XS is also very underported).
The BLACK HOLE Sub (Single unit)
External Dimensions: 45" H x 28" W x 43.75" D
(Front baffle is 2.5" thick)
* 1.25 inch thick A/A Marine grade plywood throughout
* 2.5 inch baffle, double layer
* All 1.25 inch marine ply shelf bracing with horizontal
and vertical shelf bracing interlocking with 'I-beam' support of intersecting vertical and horizontal shelf braces.
* 9.75 inch internal diameter tube port made from 3/8 inch thick fiberboard, 10.5 inch outer diameter from www.cubiconcorp.com
* 0701 WBT binding posts!
* All cuts were precision, done with best cabinet
shop and expert millwork in Philadelphia.
* Weight, approximately 400 lbs. Will have final
result next month.
All commercial subs use extensive analog boosting and EQ extensively, while the BLACK HOLE design requires no equalization whatsoever do to the nature of this particular sub and its EBS alignment. (Albiet, the room can always use adjustment, hence the Meridian Room correction
) Sealed subwoofers have increasing amounts of distortion as frequency decreases due to larger excursions... The excursion actually decreases, as most of you know, in a ported design a fair bit above and below the tuning frequency... The tuning frequncy in my design, the BLACK HOLE Sub is around 13-14 Hz. So while sealed subs are straining, the BLACK HOLE is at its BEST! I still have to do special electrical measurment to determine the final tuning frequency when all is said and done.
As someone once told me, "The subs that sound the best are those that can accurately reproduce the most bandwith!" (Assuming competent design of course). That is the KEY phrase. At level matched volume levels, the Black Hole sub will sound superior to other subwoofers. This is NOT about quantity, This is about Quality, and QUANTITY OF QUALITY. It is about reproducing the most bandwith into the deepest octaves, in the most linear fashion possible.
One of the best things about the BLACK HOLE is the low power requirements, you dont need gobs of power to get tremendous bass, this keeps voice coils cool and keeps the Qts of the driver operating at normal (cool) values with nominal voice coil resistance). When drivers heat up lots of bad things happen, including unwanted changes in the way they behave. I'll find the article that describes just how superior the Seismic 8196 driver is... It is almost unbelieveable.. Even at full rated power, this driver displays only 1-2% power compression, unparalleled power Conversion, 1100watts continuous 5000watts peak. This sub driver is designed for moderate to large enclosures.
I am very happy with the design and all out approach. I would like to build and sell more of these subs when I am done making them, however, they would be very expensive... aproximately $8,000.00 per subwoofer, $16,000.00 for a pair ala Wilson XS style, Either laminated together or sepaerate for more portability. In other words, I will build more for someone who has the money, desire, to own such an incredible subwoofer... I'm keeping these 4 for sure, using two stacked wilson XS style in the two from corners....
but I figure, why should I be the only one?
They outperform any commercial subwoofer, including the Wilson XS and Krell MRS, so I will sell them.
Again, I'd be happy to laminate two of these together and then laminate a surface on them to make this into a two driver subwoofer, to make a Wilson XS killer. Although the appeal is that this design uses a better driver, better materials, and a better ported design overall... so why even laminate two of them together when the can be stacked and more portable (rhetorical)...
I have a *max* port velocity of 15 M/s, full excursion... Wilson's is considerably higher, I estimate 25 M/s port velocity...
Commercial subwoofers put massive constraints on size due to shipping costs and limited market for large subwoofers. Every commercial sub manufacturer cuts corners in that regard, even Krell MRS and the 'huge' Wilson XS.
Admittedly, the Black Hole sub is significantly larger than the Wilson XS, but it is VERY reasonable when you can stack two BLACK HOLE subs (7.5 feet tall). The advantage to keeping them separate is not only portability, it is serior in terms of reducing standing waves... Wilson's 7 foot tall cbinet is entirely open internally. Why not divide a Wilson XS in half and elarging the port size, use more rigid materials for cabinet, a better crosbracing scheme, a better driver, etc... If you don't want the portability of separate enclosures and want maximum cabinet coupling, I will gladly laminate the Two Black Hole subs together to make a Wilson XS style sub... which is what I designed them for originally. By the way, the Wilson XS sub uses 1 inch MDF... Marine grade plywood has alomst 3 times the modulus of elasticity than even the best medite MDF...
BTW, The drivers used in the Krell MRS are decent, but nothing special IMO. They aren't even the top 15 inch driver from TC sounds...
> They use the Standard TC 15. 2.3" long
> coil, .5" gap height. 1.5" suround.
> Double stack 7.5" magnets. BL^2/Re of ~~ > 150.
The big point here is RIGIDITY, not DAMPING per see. There is a big difference between building a subwoofer and building a full range design which must cover the entire spectrum...
Subwoofers are easy to build once you know the basics...
Rigidity is the key to subwoofer enclosures, you cannot 'damp' the speaker sufficiently unless you build the subwwofer into the side of a mountain (slight exageration, but true). Therefore, you must shift the resonance of the box as high as possible above the operating bandwidth of the subwoofer. The material with the highest Modulus of elasticity is the most rigid and will 'move the least' and resonate only at higher frequencies...
Marine Ply and Baltic Birch are equally strong and offer a MOE of around 1,800,000 psi... that is approximately 3 times more rigid than even the best medite MDF. The reason commercial manufactures take short cuts here is because it is very hard to finish Plywood. I am making another laminate
on top of the plywood, proably 1/8" mdf with Black oak, or fiberglass coating then finished in flat black... I do not want piano black... the black hole sub must not only be magnificent in every aspect, it must absorb all light!
Dedicated subwoofers are least critical in shape of the box, especially if their operating range is going to be 0-80 Hz or less... The wavelenghts are so large that standing waves inside the box are not critical... true that you DO have to consider harmonics in BOTH direction... but only in a full range speaker is this more critical because bas drivers are crossed over much higher. Ideally, a SPHERE is the best shape, but if you keep the sub crossed at 60 Hz fourth order or thereabouts, you don't run into real life
standing wave problems. Now if I were doing a FULL RANGE SPEAKER, I would very much be tempted to put the bass driver in a spherical enclosure BECAUSE Bass drivers in 3 way speakers tend to get crossed over around 400 Hz, or thereabouts... The key is to separate what is best for a dedicated subwoofer and what is best for a bass driver in a full range design. In a full range design, it is oten best to actually use plywood or baltic birch internally, laminated to a second piece of MDF externally... this will give damping and rigidity. FOR DEDICATED SUBWOOFERS, RIGIDITY IS THE KEY. It is superior to use (2) layers of Baltic Birch or Marine Plywood, instead of a combo (MDF/Ply). I located hard to find A/A marine grade plywood 1.25 inches thick! Very hard to find... This is the best case scenerio. I also created the shelf braces (best possible scenerio) out of the 1.25 inch thick Marine Ply... Marine ply also has the advantage of being waterproof, and will last 'forever' at the very least it will resist humidity.....
Here are some pictures taken over the last few weeks ... I'll keep updating.
I started the construction process by laminating two layers of 1.25 inch thick marine grade plywood together for the baffle construction. A complete 'sheet' of Tightbond was applied between layers and approximately 600 pounds of force was created by stacking multiple layers of plywood (not shown) on top of the two layers.
Here are some of the tools, including (2) of the Large Bessey wood clamps...
http://users.erols.com/healthnutt/Getting%20Ready.jpg
Here is a picture of the (4) Seismic 8196 HK drivers with the new butyl surround. You cannot see much of the surround because I left the protective shipping layer on the outer rim. http://users.erols.com/healthnutt/Dr...%20baffles.jpg
Here are the ports from www.cubiconcorp.com done to my specification: The inside needs to be finished nicely, with a piano black finish. These are the raw ports. 3/8 thick fiberboard!
http://users.erols.com/healthnutt/ThePorts.jpg
Here are the sides of these 1.25 inch thick Marine grade plywood:
http://users.erols.com/healthnutt/Plywood-side.jpg
Here the 2 sheets are being held together and aligned. I then piloted with countersink, from the inside face of the baffle.... This was clamping just to align and drill pilot holes. Clamping for gluing was described above.
http://users.erols.com/healthnutt/Clampfordrilling.jpg
My place is a Black Hole Sub Factory now: http://users.erols.com/healthnutt/subfactory.jpg
I like to use a lot of glue, then simply wipe it up, especially as you clamp and screw... These Square drive screws are really top-notch..
I love these 2.5 inch baffles, at 100 lbs., I think they define rigidity.
http://users.erols.com/healthnutt/seriousbaffle.jpg
A nice day today.. I used a drill guide to get the driver holes on the baffle perfect, McFeeley's Large T-Nuts are great, and really worked for me.
http://users.erols.com/healthnutt/driverandbaffle2.jpg http://users.erols.com/healthnutt/Driverinbaffle.jpg http://users.erols.com/healthnutt/Dr...hindbaffle.jpg
The new Rotary (random Orbit) was 100% what I needed.
Further, the Porter cable profile sander is VERY NICE! http://users.erols.com/healthnutt/subbaccessories2.jpg
The WBT Binding posts and Kimber wire for internal wiring: http://users.erols.com/healthnutt/subaccessories.jpg
Here I am ready to put the baffle on... a little glue
anyone? http://users.erols.com/healthnutt/GLUE.jpg
The ports fit 100% snuggly and will be glued into their support structure, which is also a part of the vetical crossbrace (all bracing is shelf bracing AND interlocking (the best). That Millwork really did an incredible job with the precision cutting schedule I gave them.I had last week off and worked constantly. Everything went extremely well, although I have some serious wrist, hand, and finger pain. I went through 20 tubes of silicon (5 per sub), endless tightbond (25'ish containers), etc... After all 4 were siliconed, a day later they were fiberglassed according to spec...
http://users.erols.com/healthnutt/Ti...0nsulation.jpg
The Port tubes were then glued into place. 2 part epoxy was used for gluing the port tube internally. The port actually is placed through the 2.5 inch thick front baffle.
http://users.erols.com/healthnutt/Re...r%20Panel..jpg
I took no more pictures were taken because I was too messy to even grab the camera. Autobody filler was used to seal all screw holes. This is recomended over wood filler by cabinet shops. "Bondo" is actually 2 part epoxy and is stronger, binds better and does not shrink. Only a 50-75 of a carton of 1500 screws remained, so there were a lot of countersinking holes to fill.
I then used the random orbit sander to smooth out the surface to be prepared for lamination of a Wilson Art Solid Black laminate. I chose the matte, texturized finish. Although the high gloss, smooth finish would have provided a piano black finish, I felt it was better to make the black Hole sub non reflecting, as I like total darkness in my A/V room.
I was entertaining slate, mrble, granite, Black Corian, etc.. but that was to expensive for my budget. Certainly anything can be used, inculding exotic woods...
The inside of the rear panel was painted flat black-- since the port tube has a 9.75 inch internal diameter, you would be able to see to the back panel. When you look inside the flat black port tube, you see NOTHING! The port disappears. I can't wait to see them once they have been laminated.
All I can tell you is that these cabinets are knuckle busters, perhaps even tank busters. The crossbracing scheme is very satisfying and provides incredible rigidity--I would not change a thing. This cabinet is totally optimized for this design.
The 4 black Hole subs are now at the cabinet shop as of yesterday--they are going to be finished within the next two weeks.
When I get them back, the next step will be to put some insulation on the rear wall, as well as mount the binding posts to the rear wall. The WBT 0701 binding posts, with the extension kit (shown in previous pictures) can go through 1.5 inch thick material with no countersinking. Then finally, I will mount the HK driver with appropriate gaskets... I'll take some more pictures when they come back from the cabinet shop.
First and foremost, I would like to wholeheartedly thank Deon Bearden and Greg Monfort for their continual advice and support during their busy schedules. Deon spent July through September putting up with my endless questions and phone calls. Deon and Greg taught me an incredible amount and I very much appreciate it. If it wasn't for the both of them, I would not have been able to gone this far. Between their tutoring and lots of reading, the Black Hole subwoofer was born...
The $18,500+ Wilson XS subwoofer still uses the original first generation aura 1808 driver). Later, Seismic came out with an improved cone, the epoxy cone, called the 8196E. Just recently, they came out with the most advaced driver yet, the 8196HK..honeycomb kevlar with a new Butyl surround
The Black Hole Subwoofer uses the new HK driver. The Seismic 8196 HK driver is an amazing driver... 4 inch underhung design with radially arrayed neodymium magnets.
The Seismic 8196 HK driver (Honeycomb Kevlar) uses (2) cones, with the layer of honeycomb Kevlar in between. So although it appears the same.. the stiffness and the mass has greatly increased... The Fs is appreciably lower... Barry, Owner of Seismic Systems sent me parameters with an Fs around 15 Hz. Either way, it is a significant improvement in the driver, and will yield a flatter response curve (The Wilson XS still uses the paper cone, not even the Epoxy cone... The Wilson XS is also very underported).
The BLACK HOLE Sub (Single unit)
External Dimensions: 45" H x 28" W x 43.75" D
(Front baffle is 2.5" thick)
* 1.25 inch thick A/A Marine grade plywood throughout
* 2.5 inch baffle, double layer
* All 1.25 inch marine ply shelf bracing with horizontal
and vertical shelf bracing interlocking with 'I-beam' support of intersecting vertical and horizontal shelf braces.
* 9.75 inch internal diameter tube port made from 3/8 inch thick fiberboard, 10.5 inch outer diameter from www.cubiconcorp.com
* 0701 WBT binding posts!
* All cuts were precision, done with best cabinet
shop and expert millwork in Philadelphia.
* Weight, approximately 400 lbs. Will have final
result next month.
All commercial subs use extensive analog boosting and EQ extensively, while the BLACK HOLE design requires no equalization whatsoever do to the nature of this particular sub and its EBS alignment. (Albiet, the room can always use adjustment, hence the Meridian Room correction
) Sealed subwoofers have increasing amounts of distortion as frequency decreases due to larger excursions... The excursion actually decreases, as most of you know, in a ported design a fair bit above and below the tuning frequency... The tuning frequncy in my design, the BLACK HOLE Sub is around 13-14 Hz. So while sealed subs are straining, the BLACK HOLE is at its BEST! I still have to do special electrical measurment to determine the final tuning frequency when all is said and done. As someone once told me, "The subs that sound the best are those that can accurately reproduce the most bandwith!" (Assuming competent design of course). That is the KEY phrase. At level matched volume levels, the Black Hole sub will sound superior to other subwoofers. This is NOT about quantity, This is about Quality, and QUANTITY OF QUALITY. It is about reproducing the most bandwith into the deepest octaves, in the most linear fashion possible.
One of the best things about the BLACK HOLE is the low power requirements, you dont need gobs of power to get tremendous bass, this keeps voice coils cool and keeps the Qts of the driver operating at normal (cool) values with nominal voice coil resistance). When drivers heat up lots of bad things happen, including unwanted changes in the way they behave. I'll find the article that describes just how superior the Seismic 8196 driver is... It is almost unbelieveable.. Even at full rated power, this driver displays only 1-2% power compression, unparalleled power Conversion, 1100watts continuous 5000watts peak. This sub driver is designed for moderate to large enclosures.
I am very happy with the design and all out approach. I would like to build and sell more of these subs when I am done making them, however, they would be very expensive... aproximately $8,000.00 per subwoofer, $16,000.00 for a pair ala Wilson XS style, Either laminated together or sepaerate for more portability. In other words, I will build more for someone who has the money, desire, to own such an incredible subwoofer... I'm keeping these 4 for sure, using two stacked wilson XS style in the two from corners....
but I figure, why should I be the only one?
They outperform any commercial subwoofer, including the Wilson XS and Krell MRS, so I will sell them.
Again, I'd be happy to laminate two of these together and then laminate a surface on them to make this into a two driver subwoofer, to make a Wilson XS killer. Although the appeal is that this design uses a better driver, better materials, and a better ported design overall... so why even laminate two of them together when the can be stacked and more portable (rhetorical)...
I have a *max* port velocity of 15 M/s, full excursion... Wilson's is considerably higher, I estimate 25 M/s port velocity...
Commercial subwoofers put massive constraints on size due to shipping costs and limited market for large subwoofers. Every commercial sub manufacturer cuts corners in that regard, even Krell MRS and the 'huge' Wilson XS.
Admittedly, the Black Hole sub is significantly larger than the Wilson XS, but it is VERY reasonable when you can stack two BLACK HOLE subs (7.5 feet tall). The advantage to keeping them separate is not only portability, it is serior in terms of reducing standing waves... Wilson's 7 foot tall cbinet is entirely open internally. Why not divide a Wilson XS in half and elarging the port size, use more rigid materials for cabinet, a better crosbracing scheme, a better driver, etc... If you don't want the portability of separate enclosures and want maximum cabinet coupling, I will gladly laminate the Two Black Hole subs together to make a Wilson XS style sub... which is what I designed them for originally. By the way, the Wilson XS sub uses 1 inch MDF... Marine grade plywood has alomst 3 times the modulus of elasticity than even the best medite MDF...
BTW, The drivers used in the Krell MRS are decent, but nothing special IMO. They aren't even the top 15 inch driver from TC sounds...
> They use the Standard TC 15. 2.3" long
> coil, .5" gap height. 1.5" suround.
> Double stack 7.5" magnets. BL^2/Re of ~~ > 150.
The big point here is RIGIDITY, not DAMPING per see. There is a big difference between building a subwoofer and building a full range design which must cover the entire spectrum...
Subwoofers are easy to build once you know the basics...
Rigidity is the key to subwoofer enclosures, you cannot 'damp' the speaker sufficiently unless you build the subwwofer into the side of a mountain (slight exageration, but true). Therefore, you must shift the resonance of the box as high as possible above the operating bandwidth of the subwoofer. The material with the highest Modulus of elasticity is the most rigid and will 'move the least' and resonate only at higher frequencies...
Marine Ply and Baltic Birch are equally strong and offer a MOE of around 1,800,000 psi... that is approximately 3 times more rigid than even the best medite MDF. The reason commercial manufactures take short cuts here is because it is very hard to finish Plywood. I am making another laminate
on top of the plywood, proably 1/8" mdf with Black oak, or fiberglass coating then finished in flat black... I do not want piano black... the black hole sub must not only be magnificent in every aspect, it must absorb all light!
Dedicated subwoofers are least critical in shape of the box, especially if their operating range is going to be 0-80 Hz or less... The wavelenghts are so large that standing waves inside the box are not critical... true that you DO have to consider harmonics in BOTH direction... but only in a full range speaker is this more critical because bas drivers are crossed over much higher. Ideally, a SPHERE is the best shape, but if you keep the sub crossed at 60 Hz fourth order or thereabouts, you don't run into real life
standing wave problems. Now if I were doing a FULL RANGE SPEAKER, I would very much be tempted to put the bass driver in a spherical enclosure BECAUSE Bass drivers in 3 way speakers tend to get crossed over around 400 Hz, or thereabouts... The key is to separate what is best for a dedicated subwoofer and what is best for a bass driver in a full range design. In a full range design, it is oten best to actually use plywood or baltic birch internally, laminated to a second piece of MDF externally... this will give damping and rigidity. FOR DEDICATED SUBWOOFERS, RIGIDITY IS THE KEY. It is superior to use (2) layers of Baltic Birch or Marine Plywood, instead of a combo (MDF/Ply). I located hard to find A/A marine grade plywood 1.25 inches thick! Very hard to find... This is the best case scenerio. I also created the shelf braces (best possible scenerio) out of the 1.25 inch thick Marine Ply... Marine ply also has the advantage of being waterproof, and will last 'forever' at the very least it will resist humidity.....
Here are some pictures taken over the last few weeks ... I'll keep updating.
I started the construction process by laminating two layers of 1.25 inch thick marine grade plywood together for the baffle construction. A complete 'sheet' of Tightbond was applied between layers and approximately 600 pounds of force was created by stacking multiple layers of plywood (not shown) on top of the two layers.
Here are some of the tools, including (2) of the Large Bessey wood clamps...
http://users.erols.com/healthnutt/Getting%20Ready.jpg
Here is a picture of the (4) Seismic 8196 HK drivers with the new butyl surround. You cannot see much of the surround because I left the protective shipping layer on the outer rim. http://users.erols.com/healthnutt/Dr...%20baffles.jpg
Here are the ports from www.cubiconcorp.com done to my specification: The inside needs to be finished nicely, with a piano black finish. These are the raw ports. 3/8 thick fiberboard!
http://users.erols.com/healthnutt/ThePorts.jpg
Here are the sides of these 1.25 inch thick Marine grade plywood:
http://users.erols.com/healthnutt/Plywood-side.jpg
Here the 2 sheets are being held together and aligned. I then piloted with countersink, from the inside face of the baffle.... This was clamping just to align and drill pilot holes. Clamping for gluing was described above.
http://users.erols.com/healthnutt/Clampfordrilling.jpg
My place is a Black Hole Sub Factory now: http://users.erols.com/healthnutt/subfactory.jpg
I like to use a lot of glue, then simply wipe it up, especially as you clamp and screw... These Square drive screws are really top-notch..
I love these 2.5 inch baffles, at 100 lbs., I think they define rigidity.
http://users.erols.com/healthnutt/seriousbaffle.jpg
A nice day today.. I used a drill guide to get the driver holes on the baffle perfect, McFeeley's Large T-Nuts are great, and really worked for me.
http://users.erols.com/healthnutt/driverandbaffle2.jpg http://users.erols.com/healthnutt/Driverinbaffle.jpg http://users.erols.com/healthnutt/Dr...hindbaffle.jpg
The new Rotary (random Orbit) was 100% what I needed.
Further, the Porter cable profile sander is VERY NICE! http://users.erols.com/healthnutt/subbaccessories2.jpg
The WBT Binding posts and Kimber wire for internal wiring: http://users.erols.com/healthnutt/subaccessories.jpg
Here I am ready to put the baffle on... a little glue
anyone? http://users.erols.com/healthnutt/GLUE.jpg
The ports fit 100% snuggly and will be glued into their support structure, which is also a part of the vetical crossbrace (all bracing is shelf bracing AND interlocking (the best). That Millwork really did an incredible job with the precision cutting schedule I gave them.I had last week off and worked constantly. Everything went extremely well, although I have some serious wrist, hand, and finger pain. I went through 20 tubes of silicon (5 per sub), endless tightbond (25'ish containers), etc... After all 4 were siliconed, a day later they were fiberglassed according to spec...
http://users.erols.com/healthnutt/Ti...0nsulation.jpg
The Port tubes were then glued into place. 2 part epoxy was used for gluing the port tube internally. The port actually is placed through the 2.5 inch thick front baffle.
http://users.erols.com/healthnutt/Re...r%20Panel..jpg
I took no more pictures were taken because I was too messy to even grab the camera. Autobody filler was used to seal all screw holes. This is recomended over wood filler by cabinet shops. "Bondo" is actually 2 part epoxy and is stronger, binds better and does not shrink. Only a 50-75 of a carton of 1500 screws remained, so there were a lot of countersinking holes to fill.
I then used the random orbit sander to smooth out the surface to be prepared for lamination of a Wilson Art Solid Black laminate. I chose the matte, texturized finish. Although the high gloss, smooth finish would have provided a piano black finish, I felt it was better to make the black Hole sub non reflecting, as I like total darkness in my A/V room.
I was entertaining slate, mrble, granite, Black Corian, etc.. but that was to expensive for my budget. Certainly anything can be used, inculding exotic woods...
The inside of the rear panel was painted flat black-- since the port tube has a 9.75 inch internal diameter, you would be able to see to the back panel. When you look inside the flat black port tube, you see NOTHING! The port disappears. I can't wait to see them once they have been laminated.
All I can tell you is that these cabinets are knuckle busters, perhaps even tank busters. The crossbracing scheme is very satisfying and provides incredible rigidity--I would not change a thing. This cabinet is totally optimized for this design.
The 4 black Hole subs are now at the cabinet shop as of yesterday--they are going to be finished within the next two weeks.
When I get them back, the next step will be to put some insulation on the rear wall, as well as mount the binding posts to the rear wall. The WBT 0701 binding posts, with the extension kit (shown in previous pictures) can go through 1.5 inch thick material with no countersinking. Then finally, I will mount the HK driver with appropriate gaskets... I'll take some more pictures when they come back from the cabinet shop.
