I have one. I have had it since it was released way back in 1996. Yes it is an old piece of technology. But is much better than almost all of the new stuff.
The Four.1 will put out 13.5V max (which can actually be achieved if you have a proper electrical system setup in your car).
It will put out a min of 11.5 volts with a crappy electrical system.
Install it and turn down the gains on all of your other stereo components (amps/crossovers/signal processors/etc.) and be prepared for a very, very noticable increase in volume and sound quality.
Definately a must for car audio.
The great thing about it is it's simplicity.
While a fancy digital EQ with is graphics and preset levels looks great, it is no where near as effective.
Almost all (there are a few expensive exceptions) digital EQ's work on a fix band design; so when you increase the level of 3kHz by 3dB, that is all that is adjusted.
Whereas the Four.1 works on a bell curve design; when you increase 3Khz by 3db you increase 2.7kHz by 2.5dB, you increase 2.5kHz by 2dB, you increase 2.2kHz by 1.5dB, etc.
This allows for better tuning of a system.
Also, digital EQ's increase signal levels in steps, 1dB, 3dB, etc.
Whereas the Four.1 (since it is analog) allows for much motre precise tuning, 1.1dB,1.2dB,1.200001bB,etc.
And as everyone should know, analog will always reproduce music better than digital, why, because music IS an analog signal.
