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Discussion Starter #1
Hello,
I have a 2xTempest (original) IB sub and recently swapped out some floorstanders (40hz -3dB) for NHT M5 monitors (75hz -3db). As I anticipated, resetting the crossover point has made the sub too localized and left a response valley in the 60-90hz range. I was wondering what opinions might be on what type of sub to go with for the 50-100hz fill I seek. I can do DIY, but I'm not sure about a driver that would be well-suited to this purpose (lighter, faster, higher FAR).

There is also the Hsu mid bass module, although WAF is a consideration and the Hsu stink in that department. Cambridge Soundworks (I know- typically lame:rolleyesno:) has their 6x6.5" sub on closeout for $450. It has a -3dB of 32hz or so and boxer layout reduces localization problems, and its slim, so I might be able to place it nearfield, a la Hsu, for big impact. Anyway, with the in-home trial, it might be worth a shot as long as I don't ask it to do anything below 50hz.

Opinions? Thanks,
JD
 

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Discussion Starter #3
Adding another sub would help. You don't need anything terribly big if you have solid output from the IB below 50hz. The best solution would be to relocate the IB, any chance of doing that?
It's not a freestanding manifold type. I don't really think that that would be the best solution. Even though the tempests are relatively light and compliant as IB drivers go, they still are not as "light on their former" as, say, an appropriate 8" driver. Ideally, I think a 2x8" sub with high SPL and modest extension would be the solution.
 

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Elite Shackster
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Those Tempests should be very linear to your crossover point. Just because they are not small and pliant doesn't mean they can't reproduce 50-100hz. Model up your subs in WinISD and see what ideal response looks like. Subwoofer response issues are almost always the result of room acoustics and subwoofer placement. But if it's nailed to a hole in the wall I understand not wanting to move it.

Adding a second lesser sub presents other issues to think about. It will get the same signal as your IB. An 8" sub trying to reproduce 20hz will result in distortion, something IB builders aim to minimize. When things get loud it won't be able to keep up with your IB as it runs into its limits on the low frequencies. The best way to implement this would be to do so with a high pass filter so it's limited to the bandwidth you need.

You'll also need to experiment with placement so that the two subs compliment each other and do not cause cancellations that could ruin frequency response.
 

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Discussion Starter #5
Those Tempests should be very linear to your crossover point. Just because they are not small and pliant doesn't mean they can't reproduce 50-100hz. Model up your subs in WinISD and see what ideal response looks like. Subwoofer response issues are almost always the result of room acoustics and subwoofer placement. But if it's nailed to a hole in the wall I understand not wanting to move it.

Adding a second lesser sub presents other issues to think about. It will get the same signal as your IB. An 8" sub trying to reproduce 20hz will result in distortion, something IB builders aim to minimize. When things get loud it won't be able to keep up with your IB as it runs into its limits on the low frequencies. The best way to implement this would be to do so with a high pass filter so it's limited to the bandwidth you need.

You'll also need to experiment with placement so that the two subs compliment each other and do not cause cancellations that could ruin frequency response.
I do quite a bit of measurement with my mics and RTA. True, measuring a frequency curve I'm sure it could extend well above 100 hz. Nevertheless, personally I have found that smaller, lighter drivers simply work better in the mid bass, regardless of what the RTA says. Might be just my imagination, but there are a lot of experts who agree with me, and most high-end speaker designs, even cost no object, in fact do not incorporate large drivers alone for the mid bass, if they include them at all.

Of course I would band limit the smaller sub and the whole point of my post is to attempt to identify a sub that would not be lesser for its intended purpose. Not all subs are designed for extreme extension, e.g. SVS cylinder. Too bad they are huge and ugly, IMHO. A tweeter and a sub both suck at each other's job. Right tool for right job.

Again, the IB sub can't move: Its in a crawl space under stairs to the right of the seats. There is no other location for one- all walls & floor & ceiling adjoin exterior (-4 degrees right now) or adjacent room. No closet.
 

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Elite Shackster
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Ya it was cooollllddd last night. -13 when I got up to start the truck. So are you wanting the DIY the midbass module as well? I see you were looking at the HSU for $450, is this your budget? The Shiva 12" in a sealed box with a plate amp might be a good solution for that budget. No problem keeping up with your IB above 50hz.

True, measuring a frequency curve I'm sure it could extend well above 100 hz. Nevertheless, personally I have found that smaller, lighter drivers simply work better in the mid bass, regardless of what the RTA says. Might be just my imagination, but there are a lot of experts who agree with me, and most high-end speaker designs, even cost no object, in fact do not incorporate large drivers alone for the mid bass, if they include them at all.
Not that I disagree with your experience that smaller drivers sound better or that drivers should be matched to their application, but I do want to clear up the notion that bigger drivers are less linear than smaller ones. This is not the case. Non linearities in woofer design come about as the driver reaches the limit of it's linear excursion, with power compression or as it reaches it's breakup modes. Larger drivers have lower breakup modes, but not near 100hz for a 15". Using the largest driver you can actually benefits low distortion as it'll have higher sensitivity and needs less excursion for a given power level. Less excursion, less power compression, higher linearity. This is a common misperception. There are several reasons a manufacturer could choose an 8" woofer over a 12" woofer for their speakers. It could be called upon to reproduce well above 100hz, it could be less expensive and they could be trying to keep the speaker from becoming extremely large. Distortion components from any driver will show up on your RTA as the fundamental + unwanted harmonic frequencies.
 

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Discussion Starter #7
Ah, yes. See you are CO. Maybe it'll kill a few beetles at least.

The first decision is whether to DIY or no. I'm pretty busy these days. I was hoping some other IB-heads had come across this problem of closing a response gap with localization issues, and see what they had done.

Quite frankly, there are so many tremendous values in the finished subs these days I'm not sure DIY would be cheaper, in parts cost alone. I don't have a fixed budget. But it needs to have good WAF and not too large. The old AV123 10" sealed would have been a good candidate, I think. Maybe two of them. If I can find the B5 NHT bases that matched the monitors that might be a good way to go, but long discontinued. They were 1x10", and a pretty good driver too. Passive, so I could rig up my own EQ & amp solution. But getting extra speaker wire to their locations (under L/R speakers) would be pretty tough. Likely end-up as a trip-wire.:yikes:

JD
 

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Elite Shackster
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You could use just about anything. I was going to recommend SVS, but even their cheapest subs are tuned to around 20hz, you'd just be wasting all of that. A basic sealed design would be your best bet as you can take advantage of the air spring at those frequencies for additional output and low distortion. Maybe a used Velodyne?
 
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