subwoofer setup problem


I am trying to mate an ACI Titan II with my Thiel 22. The Thiels go down to 30 hz but the lowest crossover on the Titan is 35hz. Thus, there is an annoying overlap in frequency. I am considering several possible options and would appreciate some input. They are (1) get a REL sub whose lowest crossover point is 28 hz. (2) get an active crossover and cross my mains at a higher point. (3) use a passive 65hz filter between my preamp and amp that ACI has.
The passive filter is the cheapest route but will it do more harm (to the sound of my thiels) than good?

Thanks
Greg
kadlec
Sean, I agree, a sealed box of Q 0.5 is very hard to beat, but it's also extremely large if it's going to have good extension. It also has to be shaped and stuffed properly to absorb all the midbass and midrange output off the back of the cone, something that you get "for free" with a TL. Vented enclosures are just plain bad: poor damping and low output in the deep bass, and almost no absorptive material inside, which means the sound bounces around and comes back out through the cone and the port. All for a little extra efficiency? Yuck. I'm with you, for main speakers, give me a sealed box or a TL anyday. For subs, I'll make one exception: RELs with ARM loading, a "damped" form of reflex loading, where the frequency range is so low that it avoids these problems.
Karls, i think that most people don't realize that a vent is only "tuned" or "effective" at the one specific frequency that it is resonated at. As such, they are an absolute "mess" anywhere outside of that range and typically do WAY more harm than good.

Of course, i'm strictly talking about sound quality here as one can show tons of impressive arguments on paper. That is, if all you want is an increase in efficiency and bass extension. Yes, the vent does give you a greater quantity of bass, but it is done at the expense of quality. This can be seen with all of the ringing / poor transient response that takes place with a vented design Then again, i'm sure that i'm preaching to the choir on this one.

Hopefully, this will stir up a few others to check into what we are talking about and bring in some new converts to what is considered "old" technology. What is hard to believe though is that vented designs actually pre-date sealed designs. I guess that after listening to all of those early bass reflex models, they had to do SOMETHING to make it listenable. Hence the "breakthrough" technology of a sealed box.

Thank God for Edgar Vilchur and Henry Kloss !!! Sean
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Try the passive filters. I use them and find them very transparent. Not only that, they have improved the sound of every main speaker I've tried them with. Because they roll off at a gradual 6db octave rate, they make the transition smoother AND improve the dynamics of the mains. I'll be real surprised if you aren't able to get seamless with the Titan II, my Jaguars are strong to low 30s but with the 85Hz filters and my Titan IIs set around 50Hz it is superb. I was actually able to greatly reduce a major room peak for smoother, more extended bass than with the Jags alone.