If your main is quick, and you can stretch your budget 2-3 hundred dollars, you'd be well advised to go with a (used) ML Depth.
You didn't mention your room size, but you should only need one, and placed right between your mains. I think the "Balanced Force" driver placement is the best sub design innovation in years.
I use a pair of Depths to great success. I am considering upgrading to two Descents. the ML subs are hard to beat for the money. the Depth is by far the biggest bang for the buck in the line. They are small and produce lotsa bass in small to medium size rooms.
Another issue to consider besides the sub itself is how do you plan on connecting the sub into your system. Simply connecting a sub (no matter whose it is) in parallel with your main speakers doesn't always work well. I'm disappointed that ML doesn't provide an outboard active xover for integrating their subs.
Unless you want to consider M&K, I would visit with Mike at ACI. He's a good guy.
The ML subs do have an onboard crossover. THere are quite a few lowpass settings, two highpass settings, a number of phase adjustments, and a 25hz level control.
Bob, the ML Depth does indeed provide (line level, not speaker cable) high-pass outputs, if so desired. At 40Hz, 70Hz, and "none". The "none" position is to daisy-chain another Depth onto the first. Then you use the high-pass outs on the last sub to go to your main amp.
My experience has been that I get best performance when I allow the main speakers, whatever they are, to run full range, and then bring in the sub just the slightest amount necessary, so that it's only noticed if it's suddenly turned off.
Naturally , phase, cut-off freq., and x-over slope must be properly adjusted to match the mains as well as the room.
The Depth also provides a second set of line level ins and outs to be driven by the LFE (low frequency effects) ouputs of a (separate) 5.1 processor. These inputs are signal sensing and mute the "regular" 2-channel inputs when you are playing surround material through a processor.
Nsgarch, I'm familiar with the ML Depth. The line level connections are "single-ended" which makes running long lines over to the sub less than optimal. If you were going to use the builtin low pass filter, you've doubled the cost of the cabling plus the exposure to noise. It's just a poor design decision on their part. ML is not alone in this design.
I agree that when a sub is properly setup it should not make its presence known. It's also possible that having multiple sources of bass in a room (running left & right full range) can yield good results if you're lucky. For the rest of us, following M&K's suggestions probably makes sense.http://www.mkprofessional.com/bass_mgmt.htm
Bob, (you mean the built in high pass filter, don't you?) Anyway I run a 24' pair of SE Straightwire Maestros to my Depth, and it's as quiet as a chair. The Descent has XLRs, as I'm sure you know. I just happen to like the speed of the Depth.
From the Depth to my main power amp is only a meter, so that piece of IC wouldn't cost much more, if I wanted to do it that way, which I don't -- I have another 24' pair of Purist XLRs going to the main amp, since I run the CLSs full range anyway.
I thought Ken Kreisels article was interesting, especially the part about one sub for all bass being preferable in a control room environment. BTW, that nifty "MK" logo? Designed for them by yours truly about forty years ago!
Nsgarch, yes, high-pass filter - sorry about that.
I have a lot of respect for ML as an engineering company. It just seems to me that having an outboard xover (and balanced inputs) would be preferable for many situations.
Over the last year or so, I've become a big fan of M&K gear and the company. Re: the M&K logo... Well that's cool. They (and you, as well) have been at it for quite a long time.
ACI makes extremely good subs. My ACI Titan meshed very well for music listening using my Taylo Reference Monitors when they were used as my mains. It has a lot of flexability and the ACI driver is quite good.
I confess I also am a fan of the ML subs too... I like both.
I am still researching my options and really appreciate all the help regarding the choices for my situation. I really don't know what would be the best way of connecting the sub as the last time I owned a sub I was using a big home theater receiver as my pre/pro. I am currently using the new Superphon Revelation III preamp which I love. It does have two sets of main outputs (rca). I hope to make a decision soon.
There's only two ways of connecting the sub relative to the main speakers: series and parallel. I'm a fan of the series approach where the main speakers are high-passed and the bass comes from a single source in the room, the sub. The series approach allows for biamping with the subwoofer's amplifier. Others have found the parallel approach to work, as well. Though I think it has less technical merit.
You can read the M&K comments on bass management at the link I posted above.
Can any of you with direct experience with the Martin Logan high pass filter on the Depth or Grotto comment on the quality of that filter. Will it degrade the sound any?