Hi everyone. I built my subwoofer following a design I found on the net - before I found this forum...
Anyhow, the sub uses a 12" Peerless XLS driver and 2x 12" Peerless passive radiators in a 50 litre box tuned to 20hz (I think).
However, I have two problems:
1. Having measured room FR with REW and an RS meter I have found the sub SLP drops dramatically around 24hz (not 20hz as expected)
2. I'm experiencing clipping even though I have the receiver sub volume set to -10db (the lowest is -12), and the other speakers around +1db to +3db, when I have the receiver master volume set to -8 (when playing WOTWs DVD). The sub 240 (8 ohm)/350(4 ohm) watt plate amp gain is set around 35-40%. I have checked the receiver output using the BFD input meter so as not to clip at the loudest passages (hence -10db setting). I have used no gain filters in the BFD.
My two main concerns are:
1. Have I tuned the passive radiators correctly? I have 335gms extra mass on each
PR giving a total of 760gms mass each (not sure how to interpret the recommended mass in WinISD)
2. Is my receiver or plate amp underpowered and therefore producing clipping? The main speakers seem fine at much louder volumes. WinISD seems to suggest I need 310 watts of power near 20hz - could that be why the sub amp is clipping?
Could someone take a look at the attached WinISD file for the sub and check it looks ok? I inserted a 6db boost at 35hz as per the sub amp specs - not sure if that is correct. The response magnitude thingy looks awful (all wobbly) doesn't it? Is amp power, driver and
PR cone excursion ok?
Blue's Peerless Sub.zip
For those who may have problems opening the file, the driver is already in WinISD as "Peerless XLS-12 308 SWR 51 147 NX..."
The Passive Radiator specs are as follows:
Vas: 169.60
Fs: 10.4
Xmax: 24
Qms: 15.2
Sd: 466
I'm thinking about rebuilding the sub - can anyone make any suggestions if that may significantly improve things (especially SLP/extension down at/to 20hz) - e.g. different tuning, bigger box, bigger amp, modifying the amp to get ride of the 35hz boost, etc.
My room is about 7 metres x 5 meters x 2.3 meters high. Sub is used for HT only.
Many thanks