Let me start by apologizing about beating this dead horse of a topic. I have two 15's that are from an old car stereo system I had and I want to build a bass cab out of them. They are in a box already. These are their specs: Size: 15" Magnet: 100 oz Power handling: 600 watts RMS/800 peak #v.coils/Impedance: dual 4 ohm v.c. Freq. Resp.: 18-2500Hz Efficiency: 87dB (1W @ 1M) Fs/Hz: 25 Re: 6.8 Qts: 0.58 Vas/liter/ft3: 145.9/5.15 Xmax: 13.7 Depth: 7-1/8" I have and ampeg svt6pro for my amp with these specs: RMS Power Output (8 Ohms): 750-Watts RMS Power Output (4 Ohms): 1100-Watts Preamp: Tubes (2 x 12AX7) Driver Tubes: 2 x 12AU7, 2 x 12AX7 Power Amp: Solid State Tone Controls: Bass and Treble Mid Tone Control: 4-Band Semi-Parametric Ultra Low/High Boosts: Yes Balanced Line Out: Yes, Pre/Post with Level and Ground Lift Effects Loop: Yes Preamp Out/Power Amp In: Yes Dimensions (W x H x D inches): 19 x 3.5 x 15 Weight: 41 Pounds From what I have gathered from all the research I have done is that this is a hard task. I think it will work if I get some speakers for mids and highs and use a crossover of some sort to separate out the different frequencies for the different speakers. Any suggestions/concerns/advice is greatly appreciated.