coral 4A-70 project - sound absorbing stuff
hi,
regards allproof product line and its application to my experiment...
can get samples of the various materials and had thought selective application of 'quietwave ... flexible visco-elastic, constrained layer, self damping' rubber and chalk sheet to inside of panels if they seemed too lively; and take a few sharp tools to an 'acoustic pyramid' tile - maybe a few peaks at the ' u-bend ' and a flat slice on the surface behind the driver and maybe applied near the mouth ....
also, for space below the driver, have been offered surplus 'green' polyester wall insulation material and, as this is sheep country, shouldn't be to hard to find long hair wool as an alternative (not keen on handling fibreglass, haven't enjoyed previous encounters)
suggestions welcome,
thanks,
adam
hi,
regards allproof product line and its application to my experiment...
can get samples of the various materials and had thought selective application of 'quietwave ... flexible visco-elastic, constrained layer, self damping' rubber and chalk sheet to inside of panels if they seemed too lively; and take a few sharp tools to an 'acoustic pyramid' tile - maybe a few peaks at the ' u-bend ' and a flat slice on the surface behind the driver and maybe applied near the mouth ....
also, for space below the driver, have been offered surplus 'green' polyester wall insulation material and, as this is sheep country, shouldn't be to hard to find long hair wool as an alternative (not keen on handling fibreglass, haven't enjoyed previous encounters)
suggestions welcome,
thanks,
adam
Hello Guys,
Please excuse me but I need some opinions. I built my BIB using Fostex 168EZ sigma drivers and while the highs and mids are excellent, the bass is anemic. I followed the chart religiously when building the cabs. I tried the stuffing suggestion in Jeff's website but still the bass is not to my liking.
I'm suspecting that the loss of bass is due to my oval secondary baffle (from 1 1/2 inch sugar maple) on top of the front plywood piece where I mount my driver is adding too much space between the driver and the slant hence the no loading.
I'm tempted to connect the lower half of my Linkwitz Orions to fill out the bass. Thanks. Godspeed.
Please excuse me but I need some opinions. I built my BIB using Fostex 168EZ sigma drivers and while the highs and mids are excellent, the bass is anemic. I followed the chart religiously when building the cabs. I tried the stuffing suggestion in Jeff's website but still the bass is not to my liking.
I'm suspecting that the loss of bass is due to my oval secondary baffle (from 1 1/2 inch sugar maple) on top of the front plywood piece where I mount my driver is adding too much space between the driver and the slant hence the no loading.
I'm tempted to connect the lower half of my Linkwitz Orions to fill out the bass. Thanks. Godspeed.
Another cause of low performance in the bass is sometimes leaks in the seal between the driver and the enclosure. In your case, having a secondary baffle there are double opportunity for leaks.
I made the walls of the driver hole tight by applying pva to them. Before that they leaked through the ldf/hdf combination I used. The bad side of scrap material
I also used the seal tape that came in the box of the drivers (mine are FE166E so not much different from yours) and they have adequate bass when driven from a flea power amp and plenty of it when driven witha a 15+15W amp.
My ceilings are 8' high.
I made the walls of the driver hole tight by applying pva to them. Before that they leaked through the ldf/hdf combination I used. The bad side of scrap material
I also used the seal tape that came in the box of the drivers (mine are FE166E so not much different from yours) and they have adequate bass when driven from a flea power amp and plenty of it when driven witha a 15+15W amp.
My ceilings are 8' high.
Thanks for replying guys. I have to measure the distance from the mouth to my ceiling when I get home tonight. My secondary baffles were sealed with silicone and the drivers were mounted with weather strip gasket between the flange and the maple suprabaffle. There might be leaking because one side panel for each cabinet were not permanently glued yet for I'm experimenting on the stuffing.
Out of phase? Oh My, maybe, let me check that too. I remember that the speaker terminal with the red marking is the positive side for the drivers but let me re-check. Thanks a lot guys and Godspeed.
Out of phase? Oh My, maybe, let me check that too. I remember that the speaker terminal with the red marking is the positive side for the drivers but let me re-check. Thanks a lot guys and Godspeed.
Doc Jr 8156 said:
Phase check is done with a couple wires and an AA battery. The Positive end of the battery to the positive (red) terminal and Negative end to the negative. You'll hear a noise which is suddenly loud. Watch the cone for movement outward rather than inward. If not so, the reverse is actually the positive.
My ceilings are 8ft high. I checked the polarity and they are fine. I also checked if there is some leaking between the supra baffles and the cabinet and resealed the speakers again. Are BIB's meant to be placed in corners? The bass improved as I moved them hear the front wall of my listening room. Thanks a lot. Godspeed.
Re: coral 4A-70 project - sound absorbing stuff
Greets!
IME with LF pipe horns, i.e. I never considered building one for a > ~500 Hz XO, so no BIBs per se, acoustic or even R-19 'unfaced' fiberglass insulation (or its 'itchless' variant, R-25 Miraflex) was by far the best choice of those available (AFAIK) to me, but unfortunately Miraflex has apparently been taken off the market. A pity and significant loss to the DIY community IMO. Glad I have several leftover bags.
Browsing Owens-Corning's 'Down Under' products shows their 1" duct insulation, so a good choice for the bottom and the side walls around the driver with 'unfaced' wadded up in its peak as required. Note that this is where damping is maximum over the widest BW, so getting it right at this point before any other is applied is key to best performance with the least amount.
By all means though, if you have the time/patience to do a lot of testing, there may be some gems in their offerings that I missed in a quick site scan. The main thing is that it must be absolutely air-tight to get meaningful/repeatable results.
GM
arustyrednail said:
Greets!
IME with LF pipe horns, i.e. I never considered building one for a > ~500 Hz XO, so no BIBs per se, acoustic or even R-19 'unfaced' fiberglass insulation (or its 'itchless' variant, R-25 Miraflex) was by far the best choice of those available (AFAIK) to me, but unfortunately Miraflex has apparently been taken off the market.
A pity and significant loss to the DIY community IMO. Glad I have several leftover bags. Browsing Owens-Corning's 'Down Under' products shows their 1" duct insulation, so a good choice for the bottom and the side walls around the driver with 'unfaced' wadded up in its peak as required. Note that this is where damping is maximum over the widest BW, so getting it right at this point before any other is applied is key to best performance with the least amount.
By all means though, if you have the time/patience to do a lot of testing, there may be some gems in their offerings that I missed in a quick site scan. The main thing is that it must be absolutely air-tight to get meaningful/repeatable results.
GM
Doc Jr 8156 said:
Greets!
Unless a half WL pipe horn is acoustically too small (which won't happen using the SS if the driver's T/S specs aren't too far off), there's typically too much gain if the driver has a fairly flat on-axis response, so that it need not be in a corner in these cases. Drivers with a 'fast' rising response on axis such as the 168 has requires either corner loading or some BSC and/or a combination of the two.
WRT the rear of the driver firing into a 'tunnel', this acts as a low pass filter same as any vented alignment, so it won't reduce bass output per se, only some portion of its BW higher up, though this 'hole' in the response can make it sound weak, especially with a strongly rising response driver. Still, we want the driver to be able to 'breathe', so doing some form of baffle chamfering to create at least a 90 deg included angle expansion behind the driver is desirable.
GM
Scottmoose said:Pity about the Miraflex.
Don't know, I didn't actually see any docs on the subject, just old marketing announcements and an O-C search yielded nothing ~relevant other than suggesting duct board insulation. Maybe it's made from the same material technology, which makes sense since the air we breathe flows over/through it. Guess I'll have to query the local O-C distributor.
BTW, haven't forgotten about you, just haven't done any PMs lately.
GM
