I have a couple of orphan Utah woofers I'd like to build boxes for. I have used an online enclosure calculator, but when using the TS values I found online for these drivers, my results indicate I should build a 38 cubic foot vented box or a 19 cubic foot sealed box.
The original boxes they came from were vented and held two of these woofers. These enclosures aren't even 10 cu. ft.
I don't want to buy other woofers, I have these woofers and would like to employ them rather than putting them in the trash.
I do not need to get them to put out 20 Hz. I just want to mate them with a couple of Altec horns I have laying around. I would love to buy some Altec woofers but I cannot, nor do I want to buy Dayton woofers from Parts express. I want to build some reasonable cabinets that will get reasonable results out of these drivers.
I can build cabinets, but I need help designing them. Can anyone crunch some numbers for me?
The original boxes they came from were vented and held two of these woofers. These enclosures aren't even 10 cu. ft.
I don't want to buy other woofers, I have these woofers and would like to employ them rather than putting them in the trash.
I do not need to get them to put out 20 Hz. I just want to mate them with a couple of Altec horns I have laying around. I would love to buy some Altec woofers but I cannot, nor do I want to buy Dayton woofers from Parts express. I want to build some reasonable cabinets that will get reasonable results out of these drivers.
I can build cabinets, but I need help designing them. Can anyone crunch some numbers for me?
You require the T&S parameters of your speakers to be measured afresh,rather than relying on other data. However post what data you have so that the online calculator values can be checked.I usually find that they are compromised.
Probably what the OP is doing is calculating subwoofers volumes with bigger than needed net volume. You take advantage of high Q ripple when using it with passive crossovers.
Nothing wrong with the calculation of 38 cuft for a vented box.
If parameters are accurate, passive box would reach below 20 Hz.
Or a sealed box of 7 cuft for 40 Hz.
If parameters are accurate, passive box would reach below 20 Hz.
Or a sealed box of 7 cuft for 40 Hz.
You are correct. I assume these are proper numbers, the guy who published these numbers also published response and impedance curves.
Thanks.
Thanks, as a 7 ft box is a box I can live with, I may well just do that.
I assume a vented box would be more efficient/sensitive. If I would settle for 30 or 35 Hz could I then use a smaller box? The Altec horns I have are in the neighborhood of109db, I would of course add an load to the crossover, but I'd like to exploit the woofer's 94 db sensitivity as much as is practical.
Again, thanks.
The box calculator is likely giving you the numbers for an alignment that is "maximally flat". There is no reason at all why you must build your speaker that way. It's just one of an infinite number of possibilities, each with their own advantages and disadvantages.
If possible with your software, you might check out various scenarios by entering in the box volume that you WANT to use, and then calculating the low end frequency response that it would give (assuming TS parameters are accurate). Keep in mind that this is only useful below about 100-200Hz, and above that there will be many more deviations from the response due to other factors.
Even more illuminating is a program that can also calculate the impulse response, as this will clearly show when there is ringing or other issues. One such (free) program is Unibox, which you can find here:
software
It's towards the bottom of the page.
If possible with your software, you might check out various scenarios by entering in the box volume that you WANT to use, and then calculating the low end frequency response that it would give (assuming TS parameters are accurate). Keep in mind that this is only useful below about 100-200Hz, and above that there will be many more deviations from the response due to other factors.
Even more illuminating is a program that can also calculate the impulse response, as this will clearly show when there is ringing or other issues. One such (free) program is Unibox, which you can find here:
software
It's towards the bottom of the page.
Only in the low bass. If you can get 40 Hz sealed, the roll-off will likely work better with room-gain.
dave
Charlie is right about using a simulation software for checking
out reasonable options.
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