I picked up a pair of these drivers for cheap and have decided to build a cabinet for them.
Link to the manufacturer's page: FaitalPRO | LF Loudspeakers | 18XL1800
Aims:
- Go at least as loud as four of my 15" subs
- Get nice and low - 30Hz would be nice
- Easy enough to move by myself
- Take everything a bridged Powersoft T602 will throw at it
After some playing with Hornresp, I settled on a boring ported box. 250L chamber volume, port of 1000cm^2 area and 80cm long.
That just about matches 4x 15"s (the 15"s put out a couple more dB at 100Hz, but I'm crossing over there anyway), while getting 10Hz lower. Today's super-woofers are impressive.
Now, the cabinet tuning comes out around 30Hz, which means there's a lot of excursion around 40Hz - 27mm peak (Xmax=20mm) if the T602 puts a full-power sine tone there.
So, I tested a driver in free-air conditions with one channel of the amplifier. Cone excursion got to in excess of 50mm p/p with a lot of wind noise, but there wasn't much sign of the driver "locking up" at that sort of cone travel. I actually ended up clipping the amplifier trying to make the driver struggle.
Probably fine, then. Under normal use there would be a few different frequencies happening at once, so I don't think it'll be a huge problem.
The port velocity gets to around 32m/s with a 3rd order 27Hz highpass filter in place. That's a little on the high side for linear operation, but it's another compromise - a bigger port would mean a bigger cabinet, and it's already around 1/4 of the total cabinet volume.
Driven to the ragged edge, this subwoofer will probably start showing compression in the 30-40Hz range, but there's still a lot of output potential there.
See attachments for a couple of drawings of what I've got so far. I don't think there's anything special happening with this design, but I have tried to avoid any bracing inside the port, in order to keep air flow as smooth as possible. The brace against the back panel is a compromise - I didn't want to leave a panel that large free to resonate.
I'm planning on a tip-and-roll setup for moving this around - the form factor should make life nice and easy.
The wood supplier has a 2-3 week wait at the moment, and I'm planning on placing the order some time next week. Stay tuned.
Chris
Link to the manufacturer's page: FaitalPRO | LF Loudspeakers | 18XL1800
Aims:
- Go at least as loud as four of my 15" subs
- Get nice and low - 30Hz would be nice
- Easy enough to move by myself
- Take everything a bridged Powersoft T602 will throw at it
After some playing with Hornresp, I settled on a boring ported box. 250L chamber volume, port of 1000cm^2 area and 80cm long.
That just about matches 4x 15"s (the 15"s put out a couple more dB at 100Hz, but I'm crossing over there anyway), while getting 10Hz lower. Today's super-woofers are impressive.
Now, the cabinet tuning comes out around 30Hz, which means there's a lot of excursion around 40Hz - 27mm peak (Xmax=20mm) if the T602 puts a full-power sine tone there.
So, I tested a driver in free-air conditions with one channel of the amplifier. Cone excursion got to in excess of 50mm p/p with a lot of wind noise, but there wasn't much sign of the driver "locking up" at that sort of cone travel. I actually ended up clipping the amplifier trying to make the driver struggle.
Probably fine, then. Under normal use there would be a few different frequencies happening at once, so I don't think it'll be a huge problem.
The port velocity gets to around 32m/s with a 3rd order 27Hz highpass filter in place. That's a little on the high side for linear operation, but it's another compromise - a bigger port would mean a bigger cabinet, and it's already around 1/4 of the total cabinet volume.
Driven to the ragged edge, this subwoofer will probably start showing compression in the 30-40Hz range, but there's still a lot of output potential there.
See attachments for a couple of drawings of what I've got so far. I don't think there's anything special happening with this design, but I have tried to avoid any bracing inside the port, in order to keep air flow as smooth as possible. The brace against the back panel is a compromise - I didn't want to leave a panel that large free to resonate.
I'm planning on a tip-and-roll setup for moving this around - the form factor should make life nice and easy.
The wood supplier has a 2-3 week wait at the moment, and I'm planning on placing the order some time next week. Stay tuned.
Chris
Attachments
Hi Chris there is some discussion on port velocity here:Ricci's CKRAM Subwoofer and Files - Bass Projects - Data-Bass Forums
The conclusion been that although you get compression with 35m/s there isn't much that can be done about it with high excursion drivers. The other concern with long ports is that as you make them longer you push a cancellation notch down into the passband. The driver cover idea in the linked thread also gives a few dB more efficiency in the upper bass (and gets rid of large expensive, rattling grills).
The conclusion been that although you get compression with 35m/s there isn't much that can be done about it with high excursion drivers. The other concern with long ports is that as you make them longer you push a cancellation notch down into the passband. The driver cover idea in the linked thread also gives a few dB more efficiency in the upper bass (and gets rid of large expensive, rattling grills).
Thanks for the link - interesting reading.
The circular covers look interesting. I ran a rough sim and found it resulted in a wide bump around 200Hz, but wide enough to add a couple of dB of boost around 100Hz.
... Plus, it's a nice way of re-using baffle cutouts.
Some investigation to be done there - thanks for the lead!
Chris
The circular covers look interesting. I ran a rough sim and found it resulted in a wide bump around 200Hz, but wide enough to add a couple of dB of boost around 100Hz.
... Plus, it's a nice way of re-using baffle cutouts.
Some investigation to be done there - thanks for the lead!
Chris
Chris,
Impressive driver specs!
I wouldn't worry about 32m/s port velocity- at that output level the drivers can use some air cooling ;^).
Your cabinet looks to be about the same volume as my Keystone design, curious as to how one of those drivers in a TH would compare to the pair in the BR.
Although the Keystone opening makes the response a bit different than Hornresp predictions, the inputs below would give a reasonably close approximation for comparison.
Art
Attachments
Hi Art,
I did try a few THs and unfortunately these drivers don't quite have the BL for it - 25.4 for the Faital, where the B&C 18SW115 comes in at 30.3.
I suppose the compromise in trying to get so much Xmax is that the magnetic field is stretched a little thinner.
The Keystone results vary according to which Hornresp inputs I use: one gives a 33Hz tuning frequency and a large bump in output around 40Hz, while the other is tuned in the high-30s, with a smaller bump around 45Hz and a steep rolloff below that.
Both models keep up with the 2x18" ported box over a narrow frequency range, and lose out elsewhere. A pair of THs beat the 2x18" over the range (though it's within a dB around 60Hz), but with a lumpier response, less HF bandwidth, more boxes and more wood.
I like output density as a feature of my designs, so while the comparison with the THs is interesting, I'd like to stick with ported boxes for the dB/cu.ft.
Chris
I did try a few THs and unfortunately these drivers don't quite have the BL for it - 25.4 for the Faital, where the B&C 18SW115 comes in at 30.3.
I suppose the compromise in trying to get so much Xmax is that the magnetic field is stretched a little thinner.
The Keystone results vary according to which Hornresp inputs I use: one gives a 33Hz tuning frequency and a large bump in output around 40Hz, while the other is tuned in the high-30s, with a smaller bump around 45Hz and a steep rolloff below that.
Both models keep up with the 2x18" ported box over a narrow frequency range, and lose out elsewhere. A pair of THs beat the 2x18" over the range (though it's within a dB around 60Hz), but with a lumpier response, less HF bandwidth, more boxes and more wood.
I like output density as a feature of my designs, so while the comparison with the THs is interesting, I'd like to stick with ported boxes for the dB/cu.ft.
Chris
Looks awesome, good luck with it.
One thing maybe worth considering - if you can tolerate a bigger box at all, try assigning that extra volume to Vb - that will then result in a shorter vent length for any given tuning & port area, so for example a 50l increase in Vb might only result in a 30-odd l increase in total box size. You might even manage a larger vent area if you do that.
Cheers,
David.
Yeah, a little more volume and a little less port does get a smidge more output, although we're looking at less than a dB difference. Adding 100L gets me another 2dB below 40Hz, with slightly more excursion used. The extra output would be nice, but that's a serious increase in size.
At the moment, the panels fit beautifully on a pair of 4x8' sheets, with over 91% of the material utilised (and that's without considering the small braces).
External dimensions are:
124cm tall, 75cm deep, 54cm wide, plus or minus a few mm.
Weight will come in around 80-90kg, which isn't too bad. I won't be able to dead-lift it, but I've spent time with similar cabinets and found them fine to get on/off a wheel board etc.
Chris
At the moment, the panels fit beautifully on a pair of 4x8' sheets, with over 91% of the material utilised (and that's without considering the small braces).
External dimensions are:
124cm tall, 75cm deep, 54cm wide, plus or minus a few mm.
Weight will come in around 80-90kg, which isn't too bad. I won't be able to dead-lift it, but I've spent time with similar cabinets and found them fine to get on/off a wheel board etc.
Chris
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.