about 8 years ago or so i built 4 sealed subs with 12" mivoc AW3000 drivers. i have been using them in my upstairs studio but quite quickly i came to the conclusion my studio monitors really didnt need any extra bass for production and little by little i stopped using them. so after several years with these subs built based on the versacube concept i have now decided to recycle the woofers into a home cinema subwoofer.
the home cinema room calls for a more compact solution, and also i felt like this time turning them into vented subs. after some research i found various plans of vented subs for this woofer, but none of them was to my liking.
so after putting in the driver data in Winisd and messing around with a few ideas i finally decided for an isobaric design. mainly since like this i can fit 4x12" in almost half the same space as the 4 single 12" subwoofers would have taken up.
the tricky part is i have a lot of cats and isobaric designs with the woofers cables etc visible would be too tempting for them
so i had to solve this issue in the design.
the solution i found was to use a setup fairly similar to a lot of PA subwoofers i have seen. the drivers are in the middle placed somewhat in a very open "V" shape and the vents fire on both sides of the drivers. the main issue i had during the design was the slotted vents. i had to finally opt for 2 vents to have as low airspeed as possible even during peaks. the first resonance of the vents is at 250Hz, far above the lowpass that will be at around 80Hz or slightly less. the whole idea with this sub is to add a lot of deep bass when needed.
volume of the box is 130 liters. (bracing has been taken into account) and the box is tuned to 27Hz. at max volume the airspeed in the vents is only 16m/s and the calculations say it will reach about 114dB down to 30hz and 109dB at 24Hz without any equalization. although at max volume the cone excursion looks like it will become an issue, so i might add a highpass into the signal chain to cut below 15-17Hz, in the simulation it shows it will take down the cone excursion enough.
the rings on the front-side where the woofers are going, are because i am going to mount the woofers from the front, using a MDF ring to separate the drivers. if i cant find good screws long enough for this i will look into some system like T nuts etc since i want to avoid making a maintenance opening for accessing the inside. but in case if i need to do it i have also prepared scetches for that
plots were made feeding the 4x AW3000 combo 600W.
at the moment i have planned the build using 30mm Mdf. this will be one heavy beast!
i hope to do this build at the same time as i build the Tarkus im planning.
the home cinema room calls for a more compact solution, and also i felt like this time turning them into vented subs. after some research i found various plans of vented subs for this woofer, but none of them was to my liking.
so after putting in the driver data in Winisd and messing around with a few ideas i finally decided for an isobaric design. mainly since like this i can fit 4x12" in almost half the same space as the 4 single 12" subwoofers would have taken up.
the tricky part is i have a lot of cats and isobaric designs with the woofers cables etc visible would be too tempting for them
so i had to solve this issue in the design. the solution i found was to use a setup fairly similar to a lot of PA subwoofers i have seen. the drivers are in the middle placed somewhat in a very open "V" shape and the vents fire on both sides of the drivers. the main issue i had during the design was the slotted vents. i had to finally opt for 2 vents to have as low airspeed as possible even during peaks. the first resonance of the vents is at 250Hz, far above the lowpass that will be at around 80Hz or slightly less. the whole idea with this sub is to add a lot of deep bass when needed.
volume of the box is 130 liters. (bracing has been taken into account) and the box is tuned to 27Hz. at max volume the airspeed in the vents is only 16m/s and the calculations say it will reach about 114dB down to 30hz and 109dB at 24Hz without any equalization. although at max volume the cone excursion looks like it will become an issue, so i might add a highpass into the signal chain to cut below 15-17Hz, in the simulation it shows it will take down the cone excursion enough.
the rings on the front-side where the woofers are going, are because i am going to mount the woofers from the front, using a MDF ring to separate the drivers. if i cant find good screws long enough for this i will look into some system like T nuts etc since i want to avoid making a maintenance opening for accessing the inside. but in case if i need to do it i have also prepared scetches for that
plots were made feeding the 4x AW3000 combo 600W.
at the moment i have planned the build using 30mm Mdf. this will be one heavy beast!
i hope to do this build at the same time as i build the Tarkus im planning.
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unfortunately these drivers are only recommended to use in bass-reflex systems tuned to 27-29hz.
also after plotting the sealed 35L boxes with same drivers (the setup i have and want to change) and comparing i see the isobaric design will have better bottom end.
sealed boxes in blue (no wonder i didnt like it too much - its just a big bump at 50-60hz
... ) the isobaric is in green. its up to 6db louder from 25 to 30hz. its a good start. i can always use my eq to add some more,
the closed boxes needed a lot of EQ to get low bass and needed to get low passed at around 60hz to sound good. also the sealed box suffered a lot from too high cone excursion long before rated power of the drivers.
s4m said:
thanks
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this guy (some german dude) has made a subwoofer with same driver, using only one driver in a bass-reflex in a 70 liter box.
hm.. strange music
https://www.playleets.com/watch/Ltd...ofer-ta-1050-mivoc-aw3000-cx2310-full-hd.html
hm.. strange music
https://www.playleets.com/watch/Ltd...ofer-ta-1050-mivoc-aw3000-cx2310-full-hd.html
yes i understood that i tried to get more spl at lower freqs, but it was no point.
the problem is when aiming for a tuning frequency much further down, this driver need a bigger enclosure to get better low extension, but a the same time the cone excursion increases so i can not go that way.
so i can only sacrifice spl at 30hz to get a little bit more low end.
maintaining same enclosure volume and only tuning down a bit more 25Hz) i get a flatter response.
so yes its possible, but it means some changes to the design. i will have a look at it though. i will need to make the vents longer, and add somehow more volume (the volume i loose with the longer vents...)
if i can figure out a way to pull it off without modifying the exterior design too much..... most likely adding a few cm in the back end might gain me the Liters i loose.
also one important aspect is i want to make sure i can cut the whole sub from one 2440x2050mm mdf board - because if it goes over that only the enclosure will cost over 100 euro
so its a juggling with measures and ideas... ill get back maybe with an other design.
i tried to get more spl at lower freqs, but it was no point.the problem is when aiming for a tuning frequency much further down, this driver need a bigger enclosure to get better low extension, but a the same time the cone excursion increases so i can not go that way.
so i can only sacrifice spl at 30hz to get a little bit more low end.
maintaining same enclosure volume and only tuning down a bit more 25Hz) i get a flatter response.
so yes its possible, but it means some changes to the design. i will have a look at it though. i will need to make the vents longer, and add somehow more volume (the volume i loose with the longer vents...)
if i can figure out a way to pull it off without modifying the exterior design too much..... most likely adding a few cm in the back end might gain me the Liters i loose.
also one important aspect is i want to make sure i can cut the whole sub from one 2440x2050mm mdf board - because if it goes over that only the enclosure will cost over 100 euro
so its a juggling with measures and ideas... ill get back maybe with an other design.
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thanks! i only been using sketchup since the beginning of january. but i used to do all my work sketches by hand before.. i work with wood. its so much more fun to do sketches in that program..about putting the sub on its side;
the problem is i need to have a piece of furniture on top of the sub with all the rack gear for the setup.
i did a new design already modifying the earlier one. i flipped the vents so they go now underneath. also i ended up adding a little bit of height to compensate for the loss of interior volume with the new vent placement.
the layout is a bit more complicated. im not sure if it even shows
vent opening inside are on the back wall, the vents go down and underneath, firing forwards.Attachments
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i have modified the sub sketch for building it with 25mm mdf, and now i have even more interior space.. the sub is now up at 149L.
i realized today i was doing the sim at less than the W rms the divers are rated at. since the amps can get to that and more, i need to change a few details to maintain the cone excursion below max..
mainly i need to change the tuning and vent size i think...
if i have the box tuned at 25 hz the cone excursion has a peak that goes over max at around 30hz and a peak above tuning point also above limit.
if i tune the box to 30hz the cone excursion peak above tuning point goes down to just below max, but the the cone excursion below tuning point goes up a lot.
if i reduce power input on the 25Hz design to get cone excursion below limit i loose too much SPL.
i really dont see any other way around this than tuning higher but at the same time i do not like the cone excursion below tuning point moving upwards - it would start clipping there at 26HZ
but anyhow - when i plot the original sealed enclosures of the drivers the cone excursion goes above limit already at 60Hz on nominal input... i never really noticed it though - i have them running at around 140W normally to leave head room for peaks, but i keep the peaks below clipping level - and i guess i never really noticed the distortion this far. not a good sign lol but i guess since this is subsonic its not easy to notice. (on a side note - bad design from the company i got the plans from )
either of the new designs will have more low bass at around 25hz to 30Hz than the original sealed boxes.
since im improving the subwoofers it seems not a good idea to admit the cone excursion to go over the limit, atleast not above tuning point.
well i guess i need to make a decision... either keep trying to get the cone excursion under control with the 25Hz tuning or simply go for the 30Hz tuning.
so i will need to modify the design again. if i tune to 30z i need to modify the port length, calculate new volume after moving the ports which in turn will affect the volume and port length..
the other option with 25Hz tuning - i really do not know any solution to the cone excursion problem.. besides playing at lower volumes but that in turn brings (obviously) down the SPL above tuning point, but this design even with lower input would have about 4db more at 20Hz
green=30Hz Red=25Hz
to me it looks like if i would choose the 25Hz tuning still...
i realized today i was doing the sim at less than the W rms the divers are rated at. since the amps can get to that and more, i need to change a few details to maintain the cone excursion below max..
mainly i need to change the tuning and vent size i think...
if i have the box tuned at 25 hz the cone excursion has a peak that goes over max at around 30hz and a peak above tuning point also above limit.
if i tune the box to 30hz the cone excursion peak above tuning point goes down to just below max, but the the cone excursion below tuning point goes up a lot.
if i reduce power input on the 25Hz design to get cone excursion below limit i loose too much SPL.
i really dont see any other way around this than tuning higher but at the same time i do not like the cone excursion below tuning point moving upwards - it would start clipping there at 26HZ
but anyhow - when i plot the original sealed enclosures of the drivers the cone excursion goes above limit already at 60Hz on nominal input... i never really noticed it though - i have them running at around 140W normally to leave head room for peaks, but i keep the peaks below clipping level - and i guess i never really noticed the distortion this far. not a good sign lol
but i guess since this is subsonic its not easy to notice. (on a side note - bad design from the company i got the plans from )either of the new designs will have more low bass at around 25hz to 30Hz than the original sealed boxes.
since im improving the subwoofers it seems not a good idea to admit the cone excursion to go over the limit, atleast not above tuning point.
well i guess i need to make a decision... either keep trying to get the cone excursion under control with the 25Hz tuning or simply go for the 30Hz tuning.
so i will need to modify the design again. if i tune to 30z i need to modify the port length, calculate new volume after moving the ports which in turn will affect the volume and port length..
the other option with 25Hz tuning - i really do not know any solution to the cone excursion problem.. besides playing at lower volumes but that in turn brings (obviously) down the SPL above tuning point, but this design even with lower input would have about 4db more at 20Hz
green=30Hz Red=25Hz
to me it looks like if i would choose the 25Hz tuning still...
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Going past Xmax by a mm or two is fine for typical drivers. Mark Audio drivers are an example of where this is not a case.
Note that if you're after more SPL, you'll gain a lot by going direct-radiating with all 4x 12" drivers.
High-power ported boxes need a high-pass (aka low-cut) filter to cut the infrasonic bass that will damage the driver.
Chris
Note that if you're after more SPL, you'll gain a lot by going direct-radiating with all 4x 12" drivers.
High-power ported boxes need a high-pass (aka low-cut) filter to cut the infrasonic bass that will damage the driver.
Chris
try a band pass design, they can be either designed for bandwidth or SPL gains. The great thing about BP boxes is they don't require a LPF with expensive Xover parts. nice feature for extra bass modules without plate amps. The bad thing is they need fairly accurate T/S parameters, IMO not possible with most lower cost drivers and their published data.
see the 2 BP in attached.
see the 2 BP in attached.
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BP boxes still require a low-pass filter. Simulate in Hornresp to see why
Chris
most sims don't take in accounts of high Le low pass effects of long excursion drivers. AFAIK Unibox is the only one.
I reckon it would be prudent to add a much smaller value in series anyway for large signal shifts. still waaay cheaper parts for LPF compared to a vented box.
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