Most of the "performance gains" (reduced distortion) are only seen if the drivers are mounted face to face or magnet to magnet.
The same can be obtained with both woofers driving the room by facing one woofer cone out and the other magnet out.
Should I embark on this ambitious project based on KEF drivers?
- Thread starter kingscoins83
- Start date
Most of the "performance gains" (reduced distortion) are only seen if the drivers are mounted face to face or magnet to magnet.
The same can be obtained with both woofers driving the room by facing one woofer cone out and the other magnet out.
The problem with your original plan is that each B139 has the cone area of about a 10" woofer.
Passive radiators "take the load" off of the main drivers and should have more volume
displacement (VD) than the main driver. If you have two 10" drivers as main woofers
then, as a rule of thumb, you should have two 12" passive radiators.
I'd put the B139s toward the bottom of the cabinet and a port vent toward the top to
make it more like a ML TL, you don't need as long of a port to tune low that way. Use
a 3" port, 4" is better if you can tune it low enough, and tune to the mid 20's.
Those B139s are 8 ohms so you'll want to wire them in parallel for a 4 ohm load - hope
that you have a high current amp capable of driving 4 ohms.
I doubt that the B200s would work as lower bass drivers due to inadequate voltage
sensitivity as compared to the pair of B139s at 4 ohms.
Is the plan for passive or active crossovers?
Passive radiators "take the load" off of the main drivers and should have more volume
displacement (VD) than the main driver. If you have two 10" drivers as main woofers
then, as a rule of thumb, you should have two 12" passive radiators.
I'd put the B139s toward the bottom of the cabinet and a port vent toward the top to
make it more like a ML TL, you don't need as long of a port to tune low that way. Use
a 3" port, 4" is better if you can tune it low enough, and tune to the mid 20's.
Those B139s are 8 ohms so you'll want to wire them in parallel for a 4 ohm load - hope
that you have a high current amp capable of driving 4 ohms.
I doubt that the B200s would work as lower bass drivers due to inadequate voltage
sensitivity as compared to the pair of B139s at 4 ohms.
Is the plan for passive or active crossovers?
Last edited:
Here are the B139 SP1044 specs:
http://img.usaudiomart.com/uploads/large/601531-kef_b139_sp1044_matched_pair_bass_driver.gif
Fs = 22.8 Hz
Vas = 99 l
Qts = .37
A pair of these in 100 l tuned to 23 Hz would be very close to a B6 alignment that would
be down 9 dB at 23 Hz without a 2nd order boost filter or -3dB with the matching filter.
The Qts is slightly low, but the woofer inductor DC resistance will raise the effective Qts
for close to a perfect fit.
There are many ways to jam this into a better alignment.
You could drop the box volume to about 70 l, and raise the tuning to 28 Hz and probably
not need a boost filter. If you want the most powerful deep bass stick with a bigger box.
Even tuned to 28 Hz they will have very impressive bass.
Plug them into a simulator for more detail.
http://img.usaudiomart.com/uploads/large/601531-kef_b139_sp1044_matched_pair_bass_driver.gif
Fs = 22.8 Hz
Vas = 99 l
Qts = .37
A pair of these in 100 l tuned to 23 Hz would be very close to a B6 alignment that would
be down 9 dB at 23 Hz without a 2nd order boost filter or -3dB with the matching filter.
The Qts is slightly low, but the woofer inductor DC resistance will raise the effective Qts
for close to a perfect fit.
There are many ways to jam this into a better alignment.
You could drop the box volume to about 70 l, and raise the tuning to 28 Hz and probably
not need a boost filter. If you want the most powerful deep bass stick with a bigger box.
Even tuned to 28 Hz they will have very impressive bass.
Plug them into a simulator for more detail.
sqlsavior
Lunatic Member
Rather than building a pair of four-way speakers, I would build two three-way pairs with the drivers you have.
I would use an 18 dB/octave Butterworth high pass on the tweeters, and probably 6 dB/octave low pass filters on the mid-ranges and woofers. Whether or not to add a 6 dB/octave high-pass on the midranges as well would depend on experimental results.
Pair A would use T-27, B-110, B-139
Pair B would use T-27, B-140, B-139 + passive radiators.
I would consider splitting pair B into two cabinets/side, a two-way, and a bass box. Pair A would use a sealed alignment.
This way, you not only make use of all your drivers, you also avoid a fair amount of complexity in the crossovers, which should be easier to design, and sound better as well.
I would use an 18 dB/octave Butterworth high pass on the tweeters, and probably 6 dB/octave low pass filters on the mid-ranges and woofers. Whether or not to add a 6 dB/octave high-pass on the midranges as well would depend on experimental results.
Pair A would use T-27, B-110, B-139
Pair B would use T-27, B-140, B-139 + passive radiators.
I would consider splitting pair B into two cabinets/side, a two-way, and a bass box. Pair A would use a sealed alignment.
This way, you not only make use of all your drivers, you also avoid a fair amount of complexity in the crossovers, which should be easier to design, and sound better as well.
kingscoins83
Member
Thank you all for your replies and I apologize for the slow answer rate. I thought it would be less complicated, but as it is always when you want to do something wright, it takes time and a lot of money. Unfortunately I have neither for the moment, so I guess I will put an end to this project and let others that are more passionate to make use of the drivers.