After some delays I have decided to post information about my latest speaker build in progress. My hope is that others can learn from my process, making speaker building seem more approachable, and that I can learn from the knowledge of the ASR userbase.
This project started with the impulse buy of four Rival carbon pulp woofers.
https://rhythmaudiodesign.com/collections/rival-acoustics/products/r176-p-08-carbon-pulp
I bought them because I was told they are as good as Wavecor/Revelator woofers. I think I paid $50 apiece, rather than the 150-200 for woofers of similar quality. So, the question is what to do with them?
A 17cm woofer is getting to be a bit big to integrate with a direct radiating tweeter in my opinion. Everyone does it, but polar responses are not going to look great unless the woofer has great HF extension (not the case here - typical paper cone breakup), your tweeter is a beast (beastly tweeters are common nowadays) and you use a second order crossover. For this approach to work, ideally the tweeter's acoustic center would be located over the woofer's, necessitating a sloped or stepped baffle.
A more elegant solution is the use of a waveguide loaded tweeter, but how to approach this?
- Off the shelf waveguide tweeters (Wavecor 30mm, Seas DXT, Morel?) don't have particularly large waveguides, although they are better than nothing
- There is a SEOS waveguide for dome tweeters, but the tweeter it was designed for is NLA
- Visaton makes a waveguide/dome combo, but it is hard to get in the USA and the tweeter itself didn't seem that great
In the end I decided to use the Visaton waveguide (148R) and adapt it to a series of tweeters to see what the performance looked like. I 3D printed adapters with the thickness of the existing faceplate, enabling a very seamless transition from the dome to the waveguide opening:
I tested 3 tweeters - the Dayton RST28f, the SB acoustics SB26STAC and at SEAS 27mm unit. Of the three, the Dayton had the smoothest response and the best high frequency extension. As a bonus, the RST28f is an extremely robust tweeter with a low resonance, allowing a low crossover point even without a waveguide.
Cabinets
For me, the hardest part of a DIY build is making the cabinets; I like woodworking but I don't have a great space for it now. As a result I enlisted https://www.speakerhardware.com/ to build some cabinets to my specifications.
I provided a sketchup model and a detailed drawing of the front and back panels, and for a reasonable price I was provided with two nice cabinets made from baltic birch plywood. Dimensions are 8x11x16", and the cabinet is tuned to around 43hz. Maximum power/xmax limited SPL is 105db/1m,
The cabinet is designed to be DIY friendly - the rear panel can be completely removed to make crossover changes easily. It is attached to cleats which are lined with thin neoprene for an airtight seal, probably not essential for a ported cabinet.
The cabinet is lined with mass loaded butyl rubber:
https://www.amazon.com/gp/product/B01KZ5X7KO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I've never used this but it certainly makes the cabinet 'seem' better; it doesn't ring at all and it's quite a bit heavier.
After that, I used a combination of 2" open cell foam and 1" cotton acoustic dampening to line the cabinet.
I'll put some pictures of the cabinet up later, but basically it looks like a typical european DIY speaker - think Troels Gravesen's designs.
Cost:
People often ask if DIY is worth it - I can't answer that question for you, but I can provide some idea of cost. For me, this speaker's cost breakdown looks like this:
Rival Woofers - $120 (big discount)
Tweeters - $60 (on sale)
Waveguides - $26
3D printed adapters - $40
Cabinets - $160
Hardware, speaker lining and stuff - $70
So, total outlay at this point is under 500 dollars. The crossovers will probably require another $60, just as a rough estimate (I expect crossover design to be simple.) Will this equal the performance of an 700 dollar speaker? I think so... but mostly it's just fun to make your own speakers, and it's great to be able to tweak the tonal balance to your room.
Design Tools:
- ARTA measurement software for distortion measurement and polar measurements
- Vituixcad for 3d visualization and crossover design
- Calibrated Dayton EMM microphone
- Behringer audio interface
It is probably possible to design a speaker using a USB mic but I'd advise against it. A usb mic provides no way of measuring the delay between the outgoing measurement stimulus and the measured signal coming back from the speaker. This makes it very cumbersome to extract the time-of-flight of the sound coming from the speaker - you don't know if the signal you have is delayed due to the physical position of the drivers tested, or because of some kind of latency in the capture process. ARTA allows you to 'loop back' the outgoing signal into one of your mic inputs, which provides higher accuracy. This makes crossover design much more accurate.
Hopefully measurements of the drivers in the completed cabinets soon.
This project started with the impulse buy of four Rival carbon pulp woofers.
https://rhythmaudiodesign.com/collections/rival-acoustics/products/r176-p-08-carbon-pulp
I bought them because I was told they are as good as Wavecor/Revelator woofers. I think I paid $50 apiece, rather than the 150-200 for woofers of similar quality. So, the question is what to do with them?
A 17cm woofer is getting to be a bit big to integrate with a direct radiating tweeter in my opinion. Everyone does it, but polar responses are not going to look great unless the woofer has great HF extension (not the case here - typical paper cone breakup), your tweeter is a beast (beastly tweeters are common nowadays) and you use a second order crossover. For this approach to work, ideally the tweeter's acoustic center would be located over the woofer's, necessitating a sloped or stepped baffle.
A more elegant solution is the use of a waveguide loaded tweeter, but how to approach this?
- Off the shelf waveguide tweeters (Wavecor 30mm, Seas DXT, Morel?) don't have particularly large waveguides, although they are better than nothing
- There is a SEOS waveguide for dome tweeters, but the tweeter it was designed for is NLA
- Visaton makes a waveguide/dome combo, but it is hard to get in the USA and the tweeter itself didn't seem that great
In the end I decided to use the Visaton waveguide (148R) and adapt it to a series of tweeters to see what the performance looked like. I 3D printed adapters with the thickness of the existing faceplate, enabling a very seamless transition from the dome to the waveguide opening:
I tested 3 tweeters - the Dayton RST28f, the SB acoustics SB26STAC and at SEAS 27mm unit. Of the three, the Dayton had the smoothest response and the best high frequency extension. As a bonus, the RST28f is an extremely robust tweeter with a low resonance, allowing a low crossover point even without a waveguide.
Cabinets
For me, the hardest part of a DIY build is making the cabinets; I like woodworking but I don't have a great space for it now. As a result I enlisted https://www.speakerhardware.com/ to build some cabinets to my specifications.
I provided a sketchup model and a detailed drawing of the front and back panels, and for a reasonable price I was provided with two nice cabinets made from baltic birch plywood. Dimensions are 8x11x16", and the cabinet is tuned to around 43hz. Maximum power/xmax limited SPL is 105db/1m,
The cabinet is designed to be DIY friendly - the rear panel can be completely removed to make crossover changes easily. It is attached to cleats which are lined with thin neoprene for an airtight seal, probably not essential for a ported cabinet.
The cabinet is lined with mass loaded butyl rubber:
https://www.amazon.com/gp/product/B01KZ5X7KO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I've never used this but it certainly makes the cabinet 'seem' better; it doesn't ring at all and it's quite a bit heavier.
After that, I used a combination of 2" open cell foam and 1" cotton acoustic dampening to line the cabinet.
I'll put some pictures of the cabinet up later, but basically it looks like a typical european DIY speaker - think Troels Gravesen's designs.
Cost:
People often ask if DIY is worth it - I can't answer that question for you, but I can provide some idea of cost. For me, this speaker's cost breakdown looks like this:
Rival Woofers - $120 (big discount)
Tweeters - $60 (on sale)
Waveguides - $26
3D printed adapters - $40
Cabinets - $160
Hardware, speaker lining and stuff - $70
So, total outlay at this point is under 500 dollars. The crossovers will probably require another $60, just as a rough estimate (I expect crossover design to be simple.) Will this equal the performance of an 700 dollar speaker? I think so... but mostly it's just fun to make your own speakers, and it's great to be able to tweak the tonal balance to your room.
Design Tools:
- ARTA measurement software for distortion measurement and polar measurements
- Vituixcad for 3d visualization and crossover design
- Calibrated Dayton EMM microphone
- Behringer audio interface
It is probably possible to design a speaker using a USB mic but I'd advise against it. A usb mic provides no way of measuring the delay between the outgoing measurement stimulus and the measured signal coming back from the speaker. This makes it very cumbersome to extract the time-of-flight of the sound coming from the speaker - you don't know if the signal you have is delayed due to the physical position of the drivers tested, or because of some kind of latency in the capture process. ARTA allows you to 'loop back' the outgoing signal into one of your mic inputs, which provides higher accuracy. This makes crossover design much more accurate.
Hopefully measurements of the drivers in the completed cabinets soon.