IB update
Sept 20, 2005 7:33:50 GMT -7
Post by cjpaul on Sept 20, 2005 7:33:50 GMT -7
Though I'm not thrilled that this is the way it worked out, I think I'd be remiss in not posting this. I have discovered that through the laws of acoustics that I generally understand but dont know the exact details of in this particular case, I've had to make a change to the way I'm using my IB.
What originally happened was that I set-up the dual baffle IB syestem and started to calibrate. I noticed a very severe drop in bass output vs. my previous single 15" sub setup in the corner. No matter I thought, I just goose the LFE output until it matched my main L/R again. Well, very soon after that, I discovered that the level of shaking in the room above my subs was WAY more than I ever expected. The drawers were rattling out of the end tables at loud volumes (i.e. demo volume, probably around refernce level which is more than my normal listening level). I also discovered that I had no headroom in my processor. Note, I had plenty of headroom with the subs, the drivers were still barely moving, but I had to crank my LFE trim ALL the way up to make the output match my mains.
At this point I decided that I needed more gain in the line-level output so I purchased a consumer to pro-gear line level matcher box. This thing worked but introduced an intollerable amount of noise into the signal. My subs are crossed over by the processor so any signal outside the processor is subject broadband noise. I was not only getting a nasty hum (that was not related to the cable line nor could be fixed by liftng the ground on any or all of my gear) but getting broadband pink noise from the subs as well. So that wasn't going to work either.
At this point I thought "what the hell" I mean, how was it possible to have better output and no level matching problems before. I set up the system to have one of the manifolds connected to the home theater only and the other connected to the stereo system only. BAM! I gain 15-20dB of output. I know this because where before I was at 0 (on a scale of -20 to 0) on the sub output and was a few dB lower than the mains, I am now at -15.5 and am actually a little bit hot on the HT side (i.e. a few dB higher than my mains). I know the first thought, and no, the subs are not electrically wired out of phase. Whatever issues is causing me to not be able to use them simultainiously is purely acoustic. I probably should have done a better job calculating where to put the subs, but to be honest, I put them wherever there was not "stuff" up in the ceiling (i.e. HVAC, gas lines, etc.).
The bright side to all of this is I still have PLENTY of output and get a bit more flexibility out of the sytem. For example, how I set it up, I use the corner loaded baffle for home theater and I use the other baffle which is more centered on the front wall for the stereo. So I have more output and headroom for home theater and excite fewer modes for stereo. I still need to run BOTH through the BFD, but I haven't had the time to do all the measurements.
Any way, I guess the bottom line is everything worked out, but the lesson is also, when people tell you to co-locate multiple subs, DO IT, especially if locating them involves cutting holes in your house.
What originally happened was that I set-up the dual baffle IB syestem and started to calibrate. I noticed a very severe drop in bass output vs. my previous single 15" sub setup in the corner. No matter I thought, I just goose the LFE output until it matched my main L/R again. Well, very soon after that, I discovered that the level of shaking in the room above my subs was WAY more than I ever expected. The drawers were rattling out of the end tables at loud volumes (i.e. demo volume, probably around refernce level which is more than my normal listening level). I also discovered that I had no headroom in my processor. Note, I had plenty of headroom with the subs, the drivers were still barely moving, but I had to crank my LFE trim ALL the way up to make the output match my mains.
At this point I decided that I needed more gain in the line-level output so I purchased a consumer to pro-gear line level matcher box. This thing worked but introduced an intollerable amount of noise into the signal. My subs are crossed over by the processor so any signal outside the processor is subject broadband noise. I was not only getting a nasty hum (that was not related to the cable line nor could be fixed by liftng the ground on any or all of my gear) but getting broadband pink noise from the subs as well. So that wasn't going to work either.
At this point I thought "what the hell" I mean, how was it possible to have better output and no level matching problems before. I set up the system to have one of the manifolds connected to the home theater only and the other connected to the stereo system only. BAM! I gain 15-20dB of output. I know this because where before I was at 0 (on a scale of -20 to 0) on the sub output and was a few dB lower than the mains, I am now at -15.5 and am actually a little bit hot on the HT side (i.e. a few dB higher than my mains). I know the first thought, and no, the subs are not electrically wired out of phase. Whatever issues is causing me to not be able to use them simultainiously is purely acoustic. I probably should have done a better job calculating where to put the subs, but to be honest, I put them wherever there was not "stuff" up in the ceiling (i.e. HVAC, gas lines, etc.).
The bright side to all of this is I still have PLENTY of output and get a bit more flexibility out of the sytem. For example, how I set it up, I use the corner loaded baffle for home theater and I use the other baffle which is more centered on the front wall for the stereo. So I have more output and headroom for home theater and excite fewer modes for stereo. I still need to run BOTH through the BFD, but I haven't had the time to do all the measurements.
Any way, I guess the bottom line is everything worked out, but the lesson is also, when people tell you to co-locate multiple subs, DO IT, especially if locating them involves cutting holes in your house.