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Discussion Starter · #1 ·
Hello. I own Infinity Kappa subwoofer with a switchable impedance 2ohm/4ohm. According to factory manual, T/S parameters change slightly when switching the impedance. Right now the subwoofer is running in 2ohm mode in a 1cu ft box (after driver displacement) with 1 pound of polyfill stuffed in it. Can I expect any improvement in SQ if I switch into 4ohm mode? I really don't want to try the actual switch right now because my amplifier is probably not strong enough to drive it with 4ohm load (only ~160watt RMS at 4ohm), but I could consider buying a new amplifier if any improvement in SQ can be expected, even though I enjoy its SQ as is already. The T/S specs are on the attached image.
 

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I believe there'll be barely an audible difference... at a higher impedance, the woofer probably has better control, as will the amp.

Try switching the impedance to 4 ohms on your current amp and see how that does compared to 2 ohms. With [email protected] from another amp, you can expect the sub to be 30% louder than with your current amp @ 4 ohms.
 

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Discussion Starter · #3 ·
Well, for what it's worth (some say, it's not worth much), I loaded both specs into WinISD alpha to see what it says. For perfect qtc of 0.707, in 4 ohm mode the recommended box is around 1.155 cubic ft. In 2ohm mode, the recommended box size is over 1.7cu ft. So based on this alone, I cat tell that right now, with 2ohm mode, my box is too small for perfect qtc, resulting currently in qtc of around 0.76. My understanding the lower qtc should result in better transient response and flatter frequency response, at least outside of car. I don't know if there is a big difference inside of car. I could certainly go for a bigger box, with either mode, up to 1.5 cu ft.

Next thing that catches my eye is that the BL, motor force factor, is different. It's much higher at 4ohms. Again, I have no idea what it means. I have googled for it, and the evidence is inconclusive. Some people say it means nothing. Nother say that BL^2/re is the real force factor that matters. Also, qms figures are different..

Finally, the sub will need a little more power to achieve the same SPL level in 4ohm mode. (something like 107watt vs 93watts for 103dB at 50Hz). So, if I drop into 4ohm mode, not only I lose half of wattage, I also lose some efficiency it seems, but I will try it some day (hate taking the sub out of the box only for an experiment.. specially with t-nuts guaranteed to start falling out of current positions..).


Mind you, with my current setup I can't tell any flaws in sound, but I am a relative noob and this is the best sub I have had so far. Anyways.. waiting for experts to comment.
 
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