Hello gentlemen (and the few ladies that lurk),
Following this thread (http://www.avforums.co.za/index.php/topic,23244.msg298539.html) about modifying the Parapix's bass boost gain from 12dB to 6dB at 33.5Hz, I'd like to share my plans with you.
First, let me state that the objective here is high quality bass from a compact enclosure for stereo-only use. The subwoofer (and it's brothers and sisters) won't be used for HT.
I'd like to use a Peerless SLS 10" woofer (http://www.madisoundspeakerstore.com/approx-10-woofers/peerless-sls-830668-10-woofer-coated-paper-cone/) in a heavily dampened, sealed 36L (a bit less with driver and bracing displacement) enclosure, powered by the Parapix subwoofer amplifier.
I've uploaded the WinISD project file and driver profile for anyone that wants to play with the model: http://files.etherdev.co.za/chris/Archive.zip
The modeled transfer function looks like this:
Full size: http://i.imgur.com/7AyaoKV.png
The blue line is the response without any EQ. The yellow line is with 6db gain at 33.5Hz - not sure what the slope is.
I don't imagine crossing much over 90Hz, so it makes sense to measure relative to 2dB (the response at 67Hz and 100Hz with a peak of 2.2dB) rather than 0dB.
Relative to 2dB, the F3 of the subwoofer without EQ is 54Hz. With EQ, that becomes 42Hz.
These figures are, relative to 0dB, 48Hz and 34Hz respectively.
The modeled cone excursion looks like this:
Full size: http://i.imgur.com/RwQKMsa.png
As you can see, it takes about 88 watts to drive the driver to rated Xmax (at 44Hz) without EQ. That's a fair amount of power.
Comparatively, it takes only 23 watts to driver the driver to rated Xmax (at 33Hz) with EQ as above. That's close on a quarter of the power.
The Parapix does about 120w into 8 ohms when bridged, so there should be enough headroom. Obviously there is some contingency with Xlim being slightly higher than Xmax.
Bass boost is controlled by a jumper the PCB, so I can mount a toggle switch in the enclosure to disable it at any time.
Perhaps the bass boost's center frequency and gain could be tweaked further to obtain a more linear transfer function.
Why Peerless, you ask? While a JBL (flame suit on) driver may model slightly better, it's likely that the Peerless driver will have lower distortion, better control and better transient response.
What is the consensus?
Don't even think about bass reflex :angrywife:
Cheers,
Chris
Following this thread (http://www.avforums.co.za/index.php/topic,23244.msg298539.html) about modifying the Parapix's bass boost gain from 12dB to 6dB at 33.5Hz, I'd like to share my plans with you.
First, let me state that the objective here is high quality bass from a compact enclosure for stereo-only use. The subwoofer (and it's brothers and sisters) won't be used for HT.
I'd like to use a Peerless SLS 10" woofer (http://www.madisoundspeakerstore.com/approx-10-woofers/peerless-sls-830668-10-woofer-coated-paper-cone/) in a heavily dampened, sealed 36L (a bit less with driver and bracing displacement) enclosure, powered by the Parapix subwoofer amplifier.
I've uploaded the WinISD project file and driver profile for anyone that wants to play with the model: http://files.etherdev.co.za/chris/Archive.zip
The modeled transfer function looks like this:
Full size: http://i.imgur.com/7AyaoKV.png
The blue line is the response without any EQ. The yellow line is with 6db gain at 33.5Hz - not sure what the slope is.
I don't imagine crossing much over 90Hz, so it makes sense to measure relative to 2dB (the response at 67Hz and 100Hz with a peak of 2.2dB) rather than 0dB.
Relative to 2dB, the F3 of the subwoofer without EQ is 54Hz. With EQ, that becomes 42Hz.
These figures are, relative to 0dB, 48Hz and 34Hz respectively.
The modeled cone excursion looks like this:
Full size: http://i.imgur.com/RwQKMsa.png
As you can see, it takes about 88 watts to drive the driver to rated Xmax (at 44Hz) without EQ. That's a fair amount of power.
Comparatively, it takes only 23 watts to driver the driver to rated Xmax (at 33Hz) with EQ as above. That's close on a quarter of the power.
The Parapix does about 120w into 8 ohms when bridged, so there should be enough headroom. Obviously there is some contingency with Xlim being slightly higher than Xmax.
Bass boost is controlled by a jumper the PCB, so I can mount a toggle switch in the enclosure to disable it at any time.
Perhaps the bass boost's center frequency and gain could be tweaked further to obtain a more linear transfer function.
Why Peerless, you ask? While a JBL (flame suit on) driver may model slightly better, it's likely that the Peerless driver will have lower distortion, better control and better transient response.
What is the consensus?
Don't even think about bass reflex :angrywife:
Cheers,
Chris
