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|21st September 2016, 12:02 AM||#1|
Join Date: Apr 2015
Location: Bristol, UK
Peavey PV118 - "PRO 18 WOOFER" - Lets see what they can do!!
So I've been donated ,very kindly, these very very cheap subwoofers that are incredibly noisy above 120Hz, even with a steep low pass at 80 Hz, and have a very small dynamic range by reaching a non-linear response early on due to their tiny xmax.
Here's a link to them,
The only way I can get them to sound okay is by making them stand, facing the corner and chucking a load of pillows in front of them to absorb the higher mode harmonics and port noise.
They're currently mounted in a 260 ltr reflex cab with a single triangular port measuring 12.5 x 12.5 cm and 15mm deep, therefore a port area of 78 cm3.
The T/S Parameters of the drivers are;
Re - 6.3 ohms
Sd - 1260 cm3
BL - 25.10
Fo - 28.8 Hz
Vas - 365.1 lts
Cms - 117.9 uM/N
Mms - 239.01
Qms - 9.29
Qes - 0.391
Qts - 0.375
Xmax - 3.5mm
Le - 1.96
Power AES - 200 Watts
Power Program - 400 watts
Lets see what we can do to get the most out of these drivers!!
The priorities of this build are the following;
- Extend maximum output
- Reproduce From 40Hz up to 140 ish
- Preferably less than 400 Lts
- Preferably an acoustic bandpass to reduce harmonic distortion outside of operating frequency.
- It would be nice to be able to have dynamic range above 60Hz for transient kick drums, but bellow 60Hz I'm not so bothered. For example, if its reaching Xmax at 40Hz with a consistent low synth tone and only using 20 watts but has the availability to utilise the extra thermal capacity of the coil by applying a transient "kick drum" without reaching xmax above 60Hz. I hope that makes sense.
I'll publish my findings
Cheers all, you're the best
|21st September 2016, 01:08 AM||#2|
Join Date: Nov 2007
Probably the best thing you could do is to keep the boxes and replace the drivers with something like the B&C 18TBX100, which provides 9mm of Xmax and should be able to get considerably louder in those boxes without sounding distorted.
As for those drivers, a 4th order BP alignment would push the resonance frequency up for the same passband as a vented alignment, which may be a good thing according to the needs you've specified. Just don't expect perfect bandpass behavior.
|22nd September 2016, 05:54 PM||#3|
Join Date: Feb 2006
Port is wrong. You make a perfect tuning with a 260L@30Hz or 255L@32Hz. Use x2 ports 11.8 diam & 14 length or in the former a double port (x2 - 25 cm apart) 11.8 cm/17 cm. Get a good clean 100 watt amp for this BR. Port area/surface between 200/300 cm2. Another thing in case of using one port make it 19cm diam and 22 cm length for the 32 Hz tuning.
Uriah Heep - Return To Fantasy 1975
Last edited by Inductor; 22nd September 2016 at 06:01 PM.
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