Hi DIY'ers,
A couple of years ago, I pulled an old speaker enclosure (21" tall, 12" wide, 10" depth) out of a dumpster and sanded it down to make a woofer + passive radiator enclosure. Not knowing much about proper design techniques for woofer enclosures, I just made two cutouts in the front face and installed one of these:
Dayton Audio SD215-88 8" Shielded DVC Subwoofer 295-480
and then I installed a similar-sized passive radiator (with no additional weights) above that. After that, I veneered it and stained it and it looks like a really great cabinet. Again, I had good woodworking skills, but had no idea about adding weights to radiators, sizing enclosures, etc.
As expected, though, the cabinet is having some issues in the sound quality department (excessive ringing, isn't quite as punchy as I'd like). Obviously, this is because the enclosure is twice the size of the "ideal" size for a sealed enclosure. I don't really have the motivation to cut a new box to spec if there is any possibility of making some changes to the current box I have. Is this possible? I've heard there are some things one can do with polyfill or internal baffles, but I don't have the experience to know if this is true, or how much to use. Am I going to have to suck it up and make a new enclosure?
Thanks!
-Stephen
A couple of years ago, I pulled an old speaker enclosure (21" tall, 12" wide, 10" depth) out of a dumpster and sanded it down to make a woofer + passive radiator enclosure. Not knowing much about proper design techniques for woofer enclosures, I just made two cutouts in the front face and installed one of these:
Dayton Audio SD215-88 8" Shielded DVC Subwoofer 295-480
and then I installed a similar-sized passive radiator (with no additional weights) above that. After that, I veneered it and stained it and it looks like a really great cabinet. Again, I had good woodworking skills, but had no idea about adding weights to radiators, sizing enclosures, etc.
As expected, though, the cabinet is having some issues in the sound quality department (excessive ringing, isn't quite as punchy as I'd like). Obviously, this is because the enclosure is twice the size of the "ideal" size for a sealed enclosure. I don't really have the motivation to cut a new box to spec if there is any possibility of making some changes to the current box I have. Is this possible? I've heard there are some things one can do with polyfill or internal baffles, but I don't have the experience to know if this is true, or how much to use. Am I going to have to suck it up and make a new enclosure?
Thanks!
-Stephen
You can add things like wood pieces to the inside of the cabinet to use up some of the excess volume. Polyfil will actually make the woofer think the cabinet is slightly larger if you stuff it.
If you are using a passive radiator, then you need to apply the rules for that kind of loading, which are like ported (vented) rules, not 'sealed' rules...
As I understand passive radiators, you just have to design a ported cabinet, then tune the passive radiator to resonate the box as if it were the port.
If you need to reduce volume, rigid styrofoam insulation should be sufficiently stiff, doesn't weigh much, and can probably be picked up for free at construction sites or recycling yards.
If you need to reduce volume, rigid styrofoam insulation should be sufficiently stiff, doesn't weigh much, and can probably be picked up for free at construction sites or recycling yards.
If you want to try different volumes, put tins of food or bottles of water (all full) inside to take up the proposed volume and see if you like it. When you are happy with the sound, calulate the volume of everything you have added and figure out how to remove it from the cabinet.
You could add triangular fillets in the corners which also might help with internal reflections. Another favourite is to add different sized blocks of wood with the ends chamfered to the back panel to make the reflections from the back of the speaker cone more diffused (like the inside of an anechoic chamber).
HTH,
Brian
You could add triangular fillets in the corners which also might help with internal reflections. Another favourite is to add different sized blocks of wood with the ends chamfered to the back panel to make the reflections from the back of the speaker cone more diffused (like the inside of an anechoic chamber).
HTH,
Brian
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