posted
basically, I've recently found out why my brahma 15" box is louder at 38Hz (when tuned to 33Hz) then at 52Hz (when tuned to 48Hz)
evidently, I never checked the impendence of the box (I did, but winISD doesn't seem to be accurate with this) and basically, I'm wasting half my power at 52Hz. I think.
I need two things: how can i accurately get this data? and exactly what do I want for SPL? low impendence? that's what I think. And at 52Hz it was roughly 7ohms (series, not parellel, so.. 3ohms parellel?)
and that's a considerable waste of power.
lemme say my basic setup:
6.1 cu ft, 10x10x10.75 port, tuned to 48 or 50Hz (not sure on the truthful answer)
I need to find out what kinda box I need to get the most power out of it.
I'm loosing faith in winISD, but I'm looking more into lspCAD which seems better. but I do not have access to this program, nor have the money, could anyone help me with these numbers I need?
posted
Here's the easiest way to do it. Invite a bunch of buddies with DMM's to your house for a few brews. Then take one DMM, and place in series with the sub. Set this one to read current. Take a second DMM and place it in parallel with the sub. Set this one to read voltage. Now do a burp at very low levels, just enough so you can see the cone move about 1/8". Read voltage, read current. Divide voltage by current and hazzah. Do it at 38 Hz, swap boxes and do it again at 52 Hz.
BTW, a subwoofer cannot handle as much power when it is played near the box's tuning frequency. The reduced cone motion means reduced cooling. Impedance rises, effeciency also rises. There is nothing wrong here and nothing should need to be corrected.
Posts: 768 | From: Ottawa, On, Canada | Registered: May 2000
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posted
I did a lot like stated above. I made a cd that had 31tracks. Track 1 started at 20hz and each track after that went up by an increment of 1 cycle. I hooked up a dmm and a clamp on ampere meter to the speaker wire. I played through all the tracks at a reasonable level which I thought would create an accurate reading. Here are the results:
![[Smile]](smile.gif)
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