Does the world need another 6+1 design? Not in the least. But I need one. Three, in fact. These will be the center channel and surrounds for the next iteration of my home theater. I've designed and built a two-way a bit over two years ago that were then gifted. They featured the ZA14 and the SB29RDNC. Getting back to today, Brandon's/Augerpro's work on waveguides has just about perfected a waveguide for the SB26ADC/CDC tweeter. Combine one of those gems with the SB17NBAC, and you have ... the Bromo? That won't do. Besides, the Bromo doesn't have the time offset built into the cabinet.
(Hey, Bear. Um... Are you now talking about the SBA-61 from Troels Gravesen?)
Shut up, disembodied voice. I started this thread with the acknowledgment that the world doesn't need another one of these things. And yes, I'm aware that other people have also mentioned similar pairings with one Brandon's waveguides (including the developer himself). So... I'm not breaking any new ground here. In fact, I'm trying to pave over a cowpath that was turned into a multi-lane superhighway a long time ago. But since I apparently like to make mistakes in full view of the public, here we go.
What's my hook here? Cutting boards. These are being made out of bamboo cutting boards. I will now pause to accept all of your apologies for not understanding the awesomeness of my creativity.
(An overpriced IKEA hack, Bear? That is pretty weak.)
Well, fine. Let's get to it anyway.
Project name: Dvärgmusik (bad Swedish translation for Dwarf Music)
Since everything in my household that gets named has a name related to Tolkien, these are going to be the Thorin II-ways. You didn't think that the humor got any better, did you? I'm not going with the Bromo's because I really don't like the white anodizing for the CAC series. Since SBA could just as easily create a darker gray than the NBAC and still use the CAC anodizing process, I just don't dig the aesthetic. I'm not going with the Troels design because a) I'm really just not a fan of the stepped baffles that have become his signature design element, and b) Jantzen only accepts credit cards with some European security protocol that isn't supported by any of my cards. Also, I don't wire anybody money. The dwarf theme was chosen because these are about as short and small as I can reasonably make them given the driver compliment and design goals.
Since my Helios speakers are up and running, I can spend some time on these. Also, I'm overdue for getting to play with actual crossover design, so let's get to it.
What are the key design parameters?
Target completion: 2Q21 (just as exact as a died-in-the-wool product manager would do it, but without any pesky customers for the sales team to deal with)
Drivers and Noteworthy Parts:
Since I do expect to cheat off of the Smart Kid's test paper, at least a bit, I know that I'm probably aiming at about a 2kHz Fc. The Bromo does what all factory two-way designs seem to do, in that it has an Fc at 3kHz. The Purifi model design also has a 3 kHz crossover point. This is also what people used to do with the SEAS Excel line. Since the only real flaw in the SB26 design is that the sensitivity is on the low-end for a full-sized tweeter, the waveguide will help with this.
Waveguide Benefits:
One important note: the dimensions, above, work for 19mm/0.748" bamboo lumber. The cutting boards I used were consistently about 16.3mm according to my digital calipers. That would cause a reduction of about 0.25" in each dimension.
(Hey, Bear. Um... Are you now talking about the SBA-61 from Troels Gravesen?)
Shut up, disembodied voice. I started this thread with the acknowledgment that the world doesn't need another one of these things. And yes, I'm aware that other people have also mentioned similar pairings with one Brandon's waveguides (including the developer himself). So... I'm not breaking any new ground here. In fact, I'm trying to pave over a cowpath that was turned into a multi-lane superhighway a long time ago. But since I apparently like to make mistakes in full view of the public, here we go.
What's my hook here? Cutting boards. These are being made out of bamboo cutting boards. I will now pause to accept all of your apologies for not understanding the awesomeness of my creativity.
(An overpriced IKEA hack, Bear? That is pretty weak.)
Well, fine. Let's get to it anyway.
Project name: Dvärgmusik (bad Swedish translation for Dwarf Music)
Since everything in my household that gets named has a name related to Tolkien, these are going to be the Thorin II-ways. You didn't think that the humor got any better, did you? I'm not going with the Bromo's because I really don't like the white anodizing for the CAC series. Since SBA could just as easily create a darker gray than the NBAC and still use the CAC anodizing process, I just don't dig the aesthetic. I'm not going with the Troels design because a) I'm really just not a fan of the stepped baffles that have become his signature design element, and b) Jantzen only accepts credit cards with some European security protocol that isn't supported by any of my cards. Also, I don't wire anybody money. The dwarf theme was chosen because these are about as short and small as I can reasonably make them given the driver compliment and design goals.
Since my Helios speakers are up and running, I can spend some time on these. Also, I'm overdue for getting to play with actual crossover design, so let's get to it.
What are the key design parameters?
- 105dB at 1m (+20dB of headroom from a 75dB baseline 3m from the source)
- Low distortion
- Only needs ~100 watts of power to reach full SPL
- Specifically designed to cross to a subwoofer (80 Hz for 100W, or around 100Hz for 200W)
- Clean midrange and good phase transition through the crossover region
- Keep impedance as close to 4ohms or above as much as possible
- Eliminating the need for bass allows a much smaller sealed cabinet, even for a driver designed for vented applications
Target completion: 2Q21 (just as exact as a died-in-the-wool product manager would do it, but without any pesky customers for the sales team to deal with)
Drivers and Noteworthy Parts:
- SB17NBAC-4
- SB26ADC
- 5" SB26 waveguide, version J (no phase shield, 0.75" depth)
- External crossovers connected via 4-pole SpeakOn connectors
- 0.5 pounds of stuffing
- Sealed enclosure (note the lack of low-end bass)
- 7 Aptitlig 11x17 cutting boards per cabinet (19mm bamboo is also used)
- Dimensions: 9" wide x 13.5" high x 9" deep; ~10L gross, 9L net
Since I do expect to cheat off of the Smart Kid's test paper, at least a bit, I know that I'm probably aiming at about a 2kHz Fc. The Bromo does what all factory two-way designs seem to do, in that it has an Fc at 3kHz. The Purifi model design also has a 3 kHz crossover point. This is also what people used to do with the SEAS Excel line. Since the only real flaw in the SB26 design is that the sensitivity is on the low-end for a full-sized tweeter, the waveguide will help with this.
Waveguide Benefits:
- Improved sensitivity at the bottom of the tweeter's operating range
- The above allows for higher sensitivity and/or a lower crossover point
- Improved directivity matching to a woofer (TANSTAAFL; that increased sensitivity comes from the energy that is not being radiated outwards)
- Better Z-axis/Time alignment with a woofer (I'm expecting the SB17 to be around 18mm behind the baffle at 2kHz)
- Reduced crossover complexity/cost for the tweeter, though I'm not holding out for a "one cap to rule them all" HP filter.
One important note: the dimensions, above, work for 19mm/0.748" bamboo lumber. The cutting boards I used were consistently about 16.3mm according to my digital calipers. That would cause a reduction of about 0.25" in each dimension.
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