tricking amp with speaker's impedance

Two questions, I saw it writen above that 3db isnt that much of a gain. I was under the impression that a 3db gain was received by the ear as twice as loud? Is this not true? Also i ran some high current amps back in the day that I needed to get the ohm load under 1ohm to get maximal power. The guy who sold me the amps said there was a device I could buy to accpomlish this (a device that would lower the ohms to give speakers more power) but it was somewhat pricey, does it exist? Are either of the two things Ive heard in the past true?

1) No, a 3db gain is not perceived by the ear as twice as loud. You'll see different textbooks say different things. 6-10db is 2x as loud. More textbooks I've seen list 10db as twice as loud. But even if you decide to say 6db is twice as loud, you'd say, "Well, 3db is 1/2 of 6db, so it must make the sound much louder." - Wrong again, most textbooks will also say that 3db is not much louder at all. Some even say the average ear is barely able to perceive this change. This all might sound rather inconsistent, but we perceive volume on a logarithmic scale, so it takes many times louder measured sound for us to perceive a significant volume change. i.e. at least a 4x increase in power to perceive a 2x difference (if you accept that 6db is perceived as 2x as loud). So, no - 3db is not twice as loud. If you're competing this is huge - because a machine does the measurement. If you're building a system for daily driving, it probably doesn't matter much. If you are already throwing a few hundred watts at a sub, increasing the power by less than double (i.e. stepping from a 300w amp to a 500w amp) won't really do much for you. On the other hand, if you want to make a huge difference in SPL, you really need to throw much more power at the subwoofer. i.e., jumping from 300w to 1200w would be twice as loud, assuming your subwoofer can handle it. But at this point you're beyond where you'd be for daily driving anyway. If you throw 1200w at a sub in a car, and actually listen at that level, you're in serious danger of damaging your hearing more every time you step into the car. 2) DYohn, I was also wondering about this question after reading this page re transformers: http://www.bcae1.com/trnimpmt.htm My guess is that it is nearly impossible to find the correctly sized transformer for this application, short of winding your own. - probably why you heard it was pricey. New Project: 2003 Pathfinder

re: the loudness discussion.  In general, an increase of 1db is by definition "noticable".  An increase of 10db is perceived as "twice as loud."  It often requires 10X the amplifier power to achieve this, or 3000 watts to sound twice as loud as 300 watts (assuming the same sound is being perceived from the same loudspeakers.)  Two sources producing equal loudness added together generate an average perceived increase of +3db.  Thus, two loudspeakers being supplied the same tone at the same relative power level will generate net SPL of approximately +3db greater than either one alone.Support the12volt.com

DYohn, excellent, thank you for clarifying both points. I continue to learn more from you and this board every week. kfrNew Project: 2003 Pathfinder

you will be getting at least 400 watts or so from the JL e1400D even at three ohms because it is pretty underrated.

DYohn answered this question I believe. Whether using a resistor or a transformer, it is not possible. New Project: 2003 Pathfinder

Thats what I thought, but I swear I rememer this shop owner telling me about a device he could order for me that would lower the OHM load of the amp. (Really dosent matter anymore since I dont run High current amps anymore) There was nothing better than pounding 3 10" DVC subs and being rated at 25wx2. :)