PHT

Hi Scott: I know that you are busy until after July 8th. When you have a chance after that to measure the Le (or Lp and Ls) for both the Q15 and the Q18 drivers, I would greatly appreciate it! Thx, =>><<=robobob

Most likely. The question is: what is the Le or Lp and Ls parameters for the Q15 and Q18? Looking for a reasonably low inductance value for a good match to mid woofers. Thx

The web site FiCarAudio does not list Le (or alternatively Ls and Lp), the inductance parameters. Anyone know the values for the Q15 and the Q18? TIA =>><<=robobob

Thanks for the replies. "He is of the firm opinion that 15" and 18" subs cannot hit like 10" and 12" subs." Well, opinions are like arsehos.... Re transient response: I agree that in the sub operating range, voice coil inductance is usually less of a factor than the damping factor of the enclosure and the power of the magnet to stop the ringing after the note. I think his experience is with older technology subs where the larger diameter drivers with their greater mass and lower powered magnets (lower Bl) relative to the total mass would ring badly or keep on moving long enough past the signal to smear the quality. He mentioned having heard "open baffle" car subs and not likiing them. Is this just an install where the trunk or back of the cab is walled off with a baffle instead of building a box? If this is not sealed off well, that would explain why he thinks that the sound quality and clean hitting suffered. I am trying to clear up the confusion in his mind of open baffle and infinite baffle. They both have the word "baffle" in them, yeah they both must sound the same! In an I.B. installed properly in a house, there is little chance of the back wave leaking around the baffle and lowering the SPL and muddying up the quality. Anyone think that higher magnet strength (Bl) is a must for 15" and 18" subs to have clean transient response or to hit cleanly?

I am hoping that all of you with more experience in the car audio world can help me out. I am designing a home theater installation for a friend. My friend has never heard an I.B. (Infinite Baffle) sub but he plays guitar and has mucho experience with car subs. He is of the firm opinion that 15" and 18" subs cannot hit like 10" and 12" subs. I am recommending an I.B. sub installation, using 4 Q18's in 2 manifolds mounted in the attic, with each manifold having 2 drivers mounted on opposite sides but facing in the same direction and wired out of phase, for that extra 2nd harmonic cancellation. I had to sell my house (divorce) and am leasing now so I can't demo an I.B. sub for him. Sigh... He loves the sound of sealed subs over ported. I explain that an IB sub is just one biga$$ sealed sub but he goes back to his experience with open baffle subs in cars ??? and thinks lower sound quality and less hard hitting. I tried to explain the difference that small sealed boxes in small spaces like cars make to the transient response and that in an IB, with multiple drivers sharing the load, the lower excursion of each individual driver keeps them more linear, lowering distortion and improving transient response. It would really be great for his confidance in the I.B. route if I could get some expert opinions about the larger diameter drivers' performance in the car audio sub world. Then maybe I can get his mind around the IB concept. Is it a myth or true that the smaller diameter subs hit harder or have sharper transient response? Any help appreciated! =>><<=robobob