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- Aug 28, 2008
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After having grown tired of my dual 15" JBL build which i documented here almost two years ago i decided on a new build
To be honest JimGore's IB thread got me motivated to start up a new project.
Goals of the project were as follows
1. More compact enclosure, preferrably sealed
2. Would be used for 60% movies and 40% music
3. Decent low end extension.......obviously
4. A spare Cerwin Vega driver i had lying around had to be used
5. Had to be finished off in a high gloss piano black finish to blend in with the aesthestics of the rest of the system
Finding drivers in SA suitable for home theater application proved once again to be rather difficult.......or let me rather rephrase, impossible!
Thank goodness the T/S of the Cerwin Wega VMAX 15" sub showed that it would in fact be very useful for a home build sub.
These specs are as follows:
Fs 23.4 Hz
Qts 0.56
Qms 4.2
Qes 0.63
Vas 2.9 ft3 / 82.32 liters
Xmax 17 mm ;D
Revc 3.3 ohms/coil
After some modeling using WinISD it was decided that a 120litre box with total internal volume of 100litres would be built. I wanted a perfectly square box as this IMHO looks best
Builders Warehouse had a special going on 16mm Supawood @R399 for a 1,8m x 2,8m sheet! Bargain so i had them cut the wood for me too as i brought along a cut sheet.
This is where the problems started. Some cuts were out by 2-5mm. Had i known this while i was there i most surely would have had them cut me a new sheet
During the course of the week i found a device i have been searching for high and low. A gentleman advertised a Behringer Feedback Destroyer on gumtree which i quickly snapped up. Now just to source an spl meter, if anyone knows where i could purchase a Radio Shack please let me know.
The sub will be powered with a Samson SX1800. The CV will therefore be getting 1800w rms @2ohm once eq'ing has been done and SS filters are in place. More than enough power
Here are some charts comparing the CV in a ported 200litre enclosure (orange) and a 100litre sealed (yellow) with linkwitz transformer which will be mimiced by the BFD
According to JG i would need an amp with enough power to do this and a driver with enough excursion. Neither would be an issue
Both boxes with 200w power. Overexcursion
But.......the Feedback Destroyer will be used to to create a filter with a steep dropoff at 20Hz and below
Thus giving a -3db of 21Hz which i have been told is pretty decent
Note that it was simulated with 200w of power. I currently have the sub connected at 8ohms which is roughly 300w rms. After the necessary SS filters are in place i will try it out at 2ohms with 1800w and see how the sub takes it
To be honest JimGore's IB thread got me motivated to start up a new project.
Goals of the project were as follows
1. More compact enclosure, preferrably sealed
2. Would be used for 60% movies and 40% music
3. Decent low end extension.......obviously
4. A spare Cerwin Vega driver i had lying around had to be used
5. Had to be finished off in a high gloss piano black finish to blend in with the aesthestics of the rest of the system
Finding drivers in SA suitable for home theater application proved once again to be rather difficult.......or let me rather rephrase, impossible!
Thank goodness the T/S of the Cerwin Wega VMAX 15" sub showed that it would in fact be very useful for a home build sub.
These specs are as follows:
Fs 23.4 Hz
Qts 0.56
Qms 4.2
Qes 0.63
Vas 2.9 ft3 / 82.32 liters
Xmax 17 mm ;D
Revc 3.3 ohms/coil
After some modeling using WinISD it was decided that a 120litre box with total internal volume of 100litres would be built. I wanted a perfectly square box as this IMHO looks best
Builders Warehouse had a special going on 16mm Supawood @R399 for a 1,8m x 2,8m sheet! Bargain so i had them cut the wood for me too as i brought along a cut sheet.
This is where the problems started. Some cuts were out by 2-5mm. Had i known this while i was there i most surely would have had them cut me a new sheet
During the course of the week i found a device i have been searching for high and low. A gentleman advertised a Behringer Feedback Destroyer on gumtree which i quickly snapped up. Now just to source an spl meter, if anyone knows where i could purchase a Radio Shack please let me know.
The sub will be powered with a Samson SX1800. The CV will therefore be getting 1800w rms @2ohm once eq'ing has been done and SS filters are in place. More than enough power
Here are some charts comparing the CV in a ported 200litre enclosure (orange) and a 100litre sealed (yellow) with linkwitz transformer which will be mimiced by the BFD
According to JG i would need an amp with enough power to do this and a driver with enough excursion. Neither would be an issue
Both boxes with 200w power. Overexcursion
But.......the Feedback Destroyer will be used to to create a filter with a steep dropoff at 20Hz and below
Thus giving a -3db of 21Hz which i have been told is pretty decent
Note that it was simulated with 200w of power. I currently have the sub connected at 8ohms which is roughly 300w rms. After the necessary SS filters are in place i will try it out at 2ohms with 1800w and see how the sub takes it
