Subjective
In our subwoofer test car, the KFC-W2503’s response seemed relatively flat with perhaps a touch of emphasis in the 40 to 80 Hz region. As long as power levels remain at the saner end of the spectrum, this woofer sounds really good. However, as drive level increases, things seem to get a bit softer. The effect is most noticeable with highly dynamic program material. Things like big orchestral hits and large bass drums lose impact when compared to our reference woofer. On material with a very limited dynamic range (i.e., boom, pop, rap), the overall system balance seems to get progressively thinner as the volume is increased past a certain point. Jumping from a comfortable listening level to the grin-inducing neighbor-irritating range leaves you reaching for the subwoofer level control to even out the bottom end.

Now, don’t go reading that last paragraph and start thinking that this woofer is a lemon — it’s as far from that as possible. As Richard pointed out in a recent column, there are three major points to consider in terms of woofer performance: sound quality, sensitivity, and maximum SPL. At best, you can have any two, but not all three. It’s also possible to have only one of the three or even none — that would be the lemon. In actual use, as long as you have the one aspect that’s important to you, the other two can either be remedied or ignored. In car audio, sensitivity is nearly irrelevant — power is cheap. That leaves SQ and SPL. The question to ask yourself is “Do I intend to listen to music or burp test tones?” If 99 percent of the people buying woofers answered honestly, then they would be shopping for woofers that sound good. If the good sounding woofer isn’t loud enough, then use more than one of them.

The KFC-W2503 seems to fit that description pretty well and it doesn’t look like a wallet buster. It does have its limits, but the woofer is quite graceful once the limits are reached or even exceeded. Don’t get the idea that it’s indestructible, but I’ll be the first to admit to driving the devil out of this thing and I never heard a snap crackle or pop. I didn’t notice the 130-watt “RMS” power rating until well after our objective tests. This thing survived a sine wave sweep in excess of twice its power rating without ill effect — there’s definitely something to say about that.

Objective
Impedance measurements for this system show a maximum of 43 ohms at 60 Hz and a minimum of 3.7 ohms at 20 Hz. Average impedance measured 8 ohms. Out-of-car measurements show a slight rise in response below 100 Hz, followed by a 12 dB-per-octave roll-off below system resonance. In-car measurements show an overall response that fits within a window of about 5 dB and a 1-watt sensitivity that averages 93.8 dB between 10 Hz and 50 Hz. The system exhibited about 3 dB of power compression on the 100-watt in-car sweep and a maximum of about 6 dB at 300 watts. Maximum SPL at 300 watts measured 119 dB at 58 Hz.