I thought I'd document this project here.
I've recently taken delivery of 2x Kartesian Acoustics Sub120 Ferrite drivers, 3x SB65 full-range units, and 2x SB Acoustics 5x8" passive radiators.
The Kartesian mini-subwoofers are newly-released (I got a pair from the first batch), and the specs are very impressive - check out the Klippel curves in the link above. These drivers should have very low distortion up until 11mm p/p travel, where the motor force starts to drop off.
They make it well into the kHz region before the response gets messy (with a peak around 7kHz), so there's plenty of overlap with...
The SB65 unit, which routinely receives high praise around here, so I've been wanting to try them out for a while.
There are a few different projects I can think of which would be interesting:
- First up, something like Xrk's Micro WAW, which is a nice little project. There are opportunities for first-order passive crossovers with excellent time-domain performance. The Kartesian LF driver should have a more extended LF response. Hornresp suggests extension down into the mid-30s should be possible, at useful SPLs.
- Next, a speaker inspired by Barleywater's omni+dipole=cardioid speaker, which resulted in excellent cardioid characteristics over a full decade (100Hz-1kHz). The smaller SB65 unit for the mid-high range would likely mean that cardioid range would move up by a couple of octaves, but some distortion testing (for the bottom of the cardioid bandwidth) will reveal how far they can be pushed.
In order to take the concept a step further, I'm planning on mounting the SB65 in a small U-frame enclosure with some acoustic stuffing & vents, with the hope of extending the cardioid bandwidth further into the kHz range with passive cancellation.
It would be nice if such a speaker could be made with passive crossovers, but for now I'll try with some DSP.
- A larger WAW with 2x woofers, mounted for force cancellation. That would allow more LF headroom, but I don't know how the drivers stack up in terms of output yet. If the Kartesian driver can out-run the SB65's >1kHz output, then I'll be looking for alternative wide-range units.
- Some kind of portable bluetooth speaker, if the rest aren't as good as I'd like them to be.
Each project would involve the 5x8" PRs to extend the LF response. This will allow me to change the LF tuning easily, avoid port chuffing, 1/4-wave resonances, etc.
The extra SB65 driver will be the subject of some experiments. Basket shaping? Cone damping? Phase plug? All of the above? Who knows.
A further option would be to double up the SB65 units for more output - might be particularly useful for the cardioid speaker.
At the moment, I have a couple of prototype boxes half-built, but have paused for now. I'll post some photos of the drivers and cabinets when I can.
Interesting stuff coming soon.
Seasons Greetings,
Chris
I've recently taken delivery of 2x Kartesian Acoustics Sub120 Ferrite drivers, 3x SB65 full-range units, and 2x SB Acoustics 5x8" passive radiators.
The Kartesian mini-subwoofers are newly-released (I got a pair from the first batch), and the specs are very impressive - check out the Klippel curves in the link above. These drivers should have very low distortion up until 11mm p/p travel, where the motor force starts to drop off.
They make it well into the kHz region before the response gets messy (with a peak around 7kHz), so there's plenty of overlap with...
The SB65 unit, which routinely receives high praise around here, so I've been wanting to try them out for a while.
There are a few different projects I can think of which would be interesting:
- First up, something like Xrk's Micro WAW, which is a nice little project. There are opportunities for first-order passive crossovers with excellent time-domain performance. The Kartesian LF driver should have a more extended LF response. Hornresp suggests extension down into the mid-30s should be possible, at useful SPLs.
- Next, a speaker inspired by Barleywater's omni+dipole=cardioid speaker, which resulted in excellent cardioid characteristics over a full decade (100Hz-1kHz). The smaller SB65 unit for the mid-high range would likely mean that cardioid range would move up by a couple of octaves, but some distortion testing (for the bottom of the cardioid bandwidth) will reveal how far they can be pushed.
In order to take the concept a step further, I'm planning on mounting the SB65 in a small U-frame enclosure with some acoustic stuffing & vents, with the hope of extending the cardioid bandwidth further into the kHz range with passive cancellation.
It would be nice if such a speaker could be made with passive crossovers, but for now I'll try with some DSP.
- A larger WAW with 2x woofers, mounted for force cancellation. That would allow more LF headroom, but I don't know how the drivers stack up in terms of output yet. If the Kartesian driver can out-run the SB65's >1kHz output, then I'll be looking for alternative wide-range units.
- Some kind of portable bluetooth speaker, if the rest aren't as good as I'd like them to be.
Each project would involve the 5x8" PRs to extend the LF response. This will allow me to change the LF tuning easily, avoid port chuffing, 1/4-wave resonances, etc.
The extra SB65 driver will be the subject of some experiments. Basket shaping? Cone damping? Phase plug? All of the above? Who knows.
A further option would be to double up the SB65 units for more output - might be particularly useful for the cardioid speaker.
At the moment, I have a couple of prototype boxes half-built, but have paused for now. I'll post some photos of the drivers and cabinets when I can.
Interesting stuff coming soon.
Seasons Greetings,
Chris
Last edited: