I've just acquired a Celestion CS 135 passive sub - it's awful. The sealed enclosure is 10l and the ported enclosure 12l. The main problem seems to be tuning frequency is too low and too narrow. Reducing the length of the by 50% brings some improvement.
Even if I knew the driver's TSP it would be irrelevant. It is likely 20 years old. The driver has the least physical resistance of any cone I've ever touched.
My fancy is to port the sealed enclosure to increase the response bandwidth.
All theories are welcome. The cabinet will likely be scrapped. It contains a working driver from a vintage product. Eventually, somebody, somewhere will buy the driver.
Even if I knew the driver's TSP it would be irrelevant. It is likely 20 years old. The driver has the least physical resistance of any cone I've ever touched.
My fancy is to port the sealed enclosure to increase the response bandwidth.
All theories are welcome. The cabinet will likely be scrapped. It contains a working driver from a vintage product. Eventually, somebody, somewhere will buy the driver.
I have no experience with this speaker, but I build a 6th order bandpass box. It has 20 Hz to 120 Hz bandwidth. I did not use a port but a passive radiator. It goes very deep, however there are problems with this construction:
- There is some spurious output above the higher cutoff frequency, which spoils the sound. Perhaps an active filter could help.
- The sound is annoying, probably due to the high group delay.
- Efficiency in the passband is very low.
I think a 6th order bandpass subwoofer is a bad idea. At least I was disappointed when I listened to it.
- There is some spurious output above the higher cutoff frequency, which spoils the sound. Perhaps an active filter could help.
- The sound is annoying, probably due to the high group delay.
- Efficiency in the passband is very low.
I think a 6th order bandpass subwoofer is a bad idea. At least I was disappointed when I listened to it.
I've worked with a few 6th order bandpass designs, and they can sound very very good. They need to be well-designed, though.
Can you measure the Thiele-Small parameters of the driver?
Chris
Can you measure the Thiele-Small parameters of the driver?
Chris
42 - 112 Hz seems all right to me. What frequency range do you need?
https://worldradiohistory.com/hd2/I...X/90s/Stereo-Review-1993-08-OCR-Page-0036.pdf
"A close-miked measurement of the subwoofer
response indicated maximum output
at 55 Hz, falling by 3 dB at 42 and 110
Hz and by 6 dB at 38 and 133 Hz."
https://worldradiohistory.com/hd2/I...X/90s/Stereo-Review-1993-08-OCR-Page-0037.pdf
Seems like a pretty decent design.
This quote (from page 36) might be misleading though - "The CS135 contains the crossover to the satellites, set at 112 Hz with a 12 -dB -per -octave low-pass section feeding bass to the subwoofer and 6 -dB -per -octave high-pass filters supplying middle and high frequencies to the satellites." Based on what I read about the same CS135 recently, that LP filter is actually the 4th order bandpass sub's acoustic filter - there's no electrical 12dB/oct LP filter in the crossover. This can be done fairly well if care is taken in the 4th order BP's design to minimize any out of band noise emerging from the vent.
response indicated maximum output
at 55 Hz, falling by 3 dB at 42 and 110
Hz and by 6 dB at 38 and 133 Hz."
https://worldradiohistory.com/hd2/I...X/90s/Stereo-Review-1993-08-OCR-Page-0037.pdf
Seems like a pretty decent design.
This quote (from page 36) might be misleading though - "The CS135 contains the crossover to the satellites, set at 112 Hz with a 12 -dB -per -octave low-pass section feeding bass to the subwoofer and 6 -dB -per -octave high-pass filters supplying middle and high frequencies to the satellites." Based on what I read about the same CS135 recently, that LP filter is actually the 4th order bandpass sub's acoustic filter - there's no electrical 12dB/oct LP filter in the crossover. This can be done fairly well if care is taken in the 4th order BP's design to minimize any out of band noise emerging from the vent.