I have recently stumbled onto this forum and quickly found that most of this stuff is way over my head, so maybe I need to start learning...
I've recently bought a pair of AN Super8's and am looking to start with building one of the boxes from the plans that come with them, primarily because they are nice and simple designs and that is probably as far as my woodworking skills stretch at this point in time. Depending on whether I go with the smaller or larger box, volumes are either approx. 25 or 43 litres.
I also recently downloaded WinISD and had a play with that. I plugged the T/S params for the ANS8's in there (Vented box, 1 speaker) and it comes up with a recommended box volume of 11 litres. This is obviously a lot less than either of the plans.
To check, I had a look at the plans for the BR box for the Fostex FE207E (http://www.madisound.com/pdf/fostexdrivers/FE207E.pdf) and their plans have a BR box volume of 35 litres. Again, I plugged the params in WinISD and it comes with a box volume of 13.2 litres.
Am I doing something wrong or is there another reason for the discrepancy in box recommended box sizes?
I've recently bought a pair of AN Super8's and am looking to start with building one of the boxes from the plans that come with them, primarily because they are nice and simple designs and that is probably as far as my woodworking skills stretch at this point in time. Depending on whether I go with the smaller or larger box, volumes are either approx. 25 or 43 litres.
I also recently downloaded WinISD and had a play with that. I plugged the T/S params for the ANS8's in there (Vented box, 1 speaker) and it comes up with a recommended box volume of 11 litres. This is obviously a lot less than either of the plans.
To check, I had a look at the plans for the BR box for the Fostex FE207E (http://www.madisound.com/pdf/fostexdrivers/FE207E.pdf) and their plans have a BR box volume of 35 litres. Again, I plugged the params in WinISD and it comes with a box volume of 13.2 litres.
Am I doing something wrong or is there another reason for the discrepancy in box recommended box sizes?
I've played with a few of the on-line box calculators as well as WinISD. They all agree on the enclosure volume for the same input variables.
In general, for the couple of drivers I've fiddled with, I've found that a sealed box volume comes in below the Vas of the driver whereas a ported box volume will be greater than Vas. I don't know if this extends to all drivers.
What drove Fostex to design their enclosure to be bigger than that suggested by WinISD is probably a question best answered by the applications engineers at Fostex... But what you could do is to enter the volume and port dimensions of Fostex' box into WinISD and see the resulting frequency response. I suspect they wanted a few dB of bass boost, hence, went with a bigger enclosure volume. That's my guess.
~Tom
In general, for the couple of drivers I've fiddled with, I've found that a sealed box volume comes in below the Vas of the driver whereas a ported box volume will be greater than Vas. I don't know if this extends to all drivers.
What drove Fostex to design their enclosure to be bigger than that suggested by WinISD is probably a question best answered by the applications engineers at Fostex... But what you could do is to enter the volume and port dimensions of Fostex' box into WinISD and see the resulting frequency response. I suspect they wanted a few dB of bass boost, hence, went with a bigger enclosure volume. That's my guess.
~Tom
Are you very familiar with the three variables that most affect the size of a bass reflex box, and what they mean? Or, for that matter, what's actually happening with a bass reflex box? By this I mean the effect of the output of the driver and the output of the port summing and producing the overall bass output of the speaker. Understanding that will give you an idea of why people might intentionally build a larger bass reflex box for a particular driver than the software's predicted ideal model.
At the risk of preaching to the choir, all I'll say is this: For low-Qts drivers such as the audio nirvana line, the predicted "max-flat" enclosure will be very small and produce very little, or no, deep bass. However if your goal is deeper bass output rather than max-flat (this is the tradeoff), you can make a larger cabinet with a lower tuning. Try putting these settings into WinISD and watch the change in bass output:
volume 20L, Fb 60hz
volume 30L, Fb 60hz
volume 30L, Fb 55hz
volume 40L, Fb 55hz
The bass output will have a gentle 3db downward trend, but the useful bass output has gone from ~90hz to ~55hz.
At the risk of preaching to the choir, all I'll say is this: For low-Qts drivers such as the audio nirvana line, the predicted "max-flat" enclosure will be very small and produce very little, or no, deep bass. However if your goal is deeper bass output rather than max-flat (this is the tradeoff), you can make a larger cabinet with a lower tuning. Try putting these settings into WinISD and watch the change in bass output:
volume 20L, Fb 60hz
volume 30L, Fb 60hz
volume 30L, Fb 55hz
volume 40L, Fb 55hz
The bass output will have a gentle 3db downward trend, but the useful bass output has gone from ~90hz to ~55hz.
I've been using winISD for years, it seems to default at a smooth roll off starting at 100hz but if you play with box size and port size you can get some really funky curves.
Bigger box almost always equals lower lows and don't let that smooth 100hz drop off curve fool you. I play my 5 string bass through every cabinet I build and they all handle the low B (28hz) just fine.
Bigger box almost always equals lower lows and don't let that smooth 100hz drop off curve fool you. I play my 5 string bass through every cabinet I build and they all handle the low B (28hz) just fine.
Hi,
Even if using the Nirvana? You are only guaranteed ~74 dB at 28 Hz at x-max.Max Passband at x-max is about 101.5 dB SPL for a flat tuned BR.
I found another picture in my folders showing similar design concept like in the previous posted picture:
b
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