I am planning to build active subwoofer with 2 Westra SW300-2808 drivers in bassreflex box. I saw that many subwoofers that I can see in stores have drivers on bottom side of the box. What are the benefits of that kind of construction (except more SPL), and how can I calculate the right distance from the floor ? Does more distance means deeper bass because of more added mass of air in front of the speaker, or what ?
And one more thing. If bass is on the bottom side of the box, should the port also be on that side of box ?
Thank You in advance for any answer given.
And one more thing. If bass is on the bottom side of the box, should the port also be on that side of box ?
Thank You in advance for any answer given.
reply
I thought down firing subwoofers was a bad idea with weak motor systems/loose suspension such as rubber.Because the voice coil might shift,and suspension sag.
Not a problem with tight surrounds like cloth and paper and strong motor system though.
Am I right about loose rubber or foam suspensions sag if used in down firing subwoofers and the voice coil can shift???????
I thought down firing subwoofers was a bad idea with weak motor systems/loose suspension such as rubber.Because the voice coil might shift,and suspension sag.
Not a problem with tight surrounds like cloth and paper and strong motor system though.
Am I right about loose rubber or foam suspensions sag if used in down firing subwoofers and the voice coil can shift???????
re subs
I have 3 subs here at home.
All of them are used firing forward into the room.
I dont like subs firing into the floor due to absorption of the pressure wave and reflection of the pressure wave back in to the diaphragm.
So to keep it simple fire the drive unit into the room.
I looks less attractive than firing into the floor.
BUT IT IS A SUB NOT A COFFEE TABLE.
Also dont hide sub behind furniture etc just to keep er indoors happy.
regards David
I have 3 subs here at home.
All of them are used firing forward into the room.
I dont like subs firing into the floor due to absorption of the pressure wave and reflection of the pressure wave back in to the diaphragm.
So to keep it simple fire the drive unit into the room.
I looks less attractive than firing into the floor.
BUT IT IS A SUB NOT A COFFEE TABLE.
Also dont hide sub behind furniture etc just to keep er indoors happy.
regards David
Aaaaaah !
Now i don't know what to do.
Well, I guess I'll have to mount them in front of the cabinet.
If I mount them vertically, they will be dangerously too close to my TV, which will go crazy because of speaker's magnet. And I don't know where else to put my sub in the room.
Is there a way to magnetically shield my sub, so that it would not interfere with my TV ?
Now i don't know what to do.
Well, I guess I'll have to mount them in front of the cabinet.
If I mount them vertically, they will be dangerously too close to my TV, which will go crazy because of speaker's magnet. And I don't know where else to put my sub in the room.
Is there a way to magnetically shield my sub, so that it would not interfere with my TV ?
R U Opposed?
As a once-upon-a-time speaker designer, I'd agree that it makes sense to have the woofers opposed, to help cancel the forces that shake the cabinet. If possible, mount one facing out and one facing in, to "even out" suspension asymmetries.
I'd also agree that gravity makes everything sag over time. Just look at your coworkers
A tight suspension may take longer to sag, but those subs tend to have heavier moving mass also. Then again, reduced lifetime might be worth avoiding the "poke factor" of kids & pets. One interesting approach would be one on top and one on the bottom, then flip them periodically kinda like a mattress to reverse the gravitational sag.
I hazily recall that the air load from pointing down is not so big, unless you are really really close, in which case a port would not work well. Usually the down firing is a designers choice to avoid poking, have a better external appearance, and reduce distortion. That is, if the woofer is firing down, higher frequency distortion harmonics will be reduced at your ears compared to a forward firing woofer. (Side woofers can help a bit also).
If you want to "shield" the speakers magnetically, a sheet of metal inside the subwoofer cabinet (not right next to the magnet!) or TV cabinet should do it. Use steel or maybe even iron (not aluminum) and experiment. You don't have to line the entire inside most likely. There is no "magnetic insulator"; what you are doing is providing an easy path for the magnetic field lines to "flow" kinda like a short circuit, or the sport of curling.
As a once-upon-a-time speaker designer, I'd agree that it makes sense to have the woofers opposed, to help cancel the forces that shake the cabinet. If possible, mount one facing out and one facing in, to "even out" suspension asymmetries.
I'd also agree that gravity makes everything sag over time. Just look at your coworkers
A tight suspension may take longer to sag, but those subs tend to have heavier moving mass also. Then again, reduced lifetime might be worth avoiding the "poke factor" of kids & pets. One interesting approach would be one on top and one on the bottom, then flip them periodically kinda like a mattress to reverse the gravitational sag.
I hazily recall that the air load from pointing down is not so big, unless you are really really close, in which case a port would not work well. Usually the down firing is a designers choice to avoid poking, have a better external appearance, and reduce distortion. That is, if the woofer is firing down, higher frequency distortion harmonics will be reduced at your ears compared to a forward firing woofer. (Side woofers can help a bit also).
If you want to "shield" the speakers magnetically, a sheet of metal inside the subwoofer cabinet (not right next to the magnet!) or TV cabinet should do it. Use steel or maybe even iron (not aluminum) and experiment. You don't have to line the entire inside most likely. There is no "magnetic insulator"; what you are doing is providing an easy path for the magnetic field lines to "flow" kinda like a short circuit, or the sport of curling.
I tried making a downfiring sub once, and it sounded terrible. Partly this was because the floor had a basement underneath and wasn't made of solid concrete or similar. The sub excited all sorts of room-modes that I hadn't heard before and didn't sound natural. Even at low to moderate volumes there were unusual vibrations where at some frequencies the floor shook a lot but without much audible sound coming out.
Then, all I did was tilt the sub onto its side so its feet pointed into the air, and the improvement was uncanny.
If opposing woofers are not an option, how about using a very stiff box for the enclosure and suspending the whole thing by a pair of ropes like a miniature swing? That way if it's well balanced, vibrations need not be mechanically transmitted to the floor at all! 
CM
Then, all I did was tilt the sub onto its side so its feet pointed into the air, and the improvement was uncanny.
If opposing woofers are not an option, how about using a very stiff box for the enclosure and suspending the whole thing by a pair of ropes like a miniature swing? That way if it's well balanced, vibrations need not be mechanically transmitted to the floor at all!
CM
Nice one, but it wouldn't actually solve the problem. What you need is large quantities of liquid nitrogen, neodymium magnets, and super-conductive material so you can make a frictionless surface for your side-firing subwoofer to float around on.head_unit said:
...For downfiring subs you still need either a cancelling force or an anti-gravity device.CM
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.