are subwoofers anti-audiophile?

Grannyrig, No sub has a brick wall filter causing it stop producing sound at an end point like 40hz. I don't know your sub well but it likely either has a 12 or 24db/octave filter. The cutoff frequency is usually - 3db. Add to this ALL sytems have driver/ room interactions which (particularly below 250 hz) can be the MAIN determinant of the sound. Subs can bring this out in spades if not set up properly. Even with a 12db/octave filter I can't imagine a 40hz cutoff frequency affecting the " midrange" (250hz) at which point it would be >30db down UNLESS : 1)The volume on the sub was too high 2) There are serious room interaction problems (most likely) or 3)there is a problem with the sub. If you have measured the frequency as flat ( + /- 3db or so) from 25hz and up then my only answer would be 3) above. If it is not then it is 1) or 2) imho. Phase, relative driver distances , quarter wavelength cancellations all can affect sound. Integration can be very frustrating and it will likely not be perfect but it is almost always worth it with dynamic (box) speakers. - Jim

The physics favor separate bass enclosures.

The best locations for higher frequencies (as close as possible to the listener to maintain a higher ratio of direct sound to the reflections without being too close for the drivers to integrate correctly) aren't the best locations for bass (where you get minimal interaction with room modes and are close to boundaries so that you aren't getting nulls where the bass driver is odd multiples of 1/4 wave length from the boundary).

More bass sources also produce more uniform bass response, especially over multiple seats. Floyd Toole does a great job summarizing this in _Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms_. Earl Geddes and Duke LeJeune of Audio Kinesis sell commercial systems that work that way.

Due to cosine alpha polar response (-3dB @ 45 degrees, -6dB at 60, -12dB at 75, and theoretically no output 90 degrees off axis although a -20dB null may be more typical in practice) dipole bass doesn't couple to a room's height modes, has weaker coupling to the width modes depending on toe-in, and some effects on length effects due to the rear wave being 180 degrees out of phase with the front where a conventional speaker's bass response has essentially the same amplitude and phase at all angles. Unfortunately, this comes at the expense of dumping a lot of displacement into the acoustic short circuit - a 14" deep speaker takes 2X the displacement of a monopole to produce the same SPL at 80Hz, 4X at 40Hz, and 8X at 20Hz. That big stack of drivers gets expensive, and the alternative of doubling enclosure size instead isn't practical.

Subwoofer problems come entirely from the implementation.

Achieving a correct acoustic cross-over is often an issue.

Amplitude changes imply phase changes, including those coming from the mechanical high-pass at the bottom end of a driver's output and the analog filters in cross-overs.

The net result is that when you mix an arbitrary sub-woofer, main-speakers, and cross-over frequency the combination does not sum flat.

Siegfried Linkwitz has a nice on-line example:
http://www.linkwitzlab.com/frontiers_5.htm#T

Until recently (DSP manipulation of phase and amplitude has gone mainstream with Audyssey) most consumer gear has not included the tools necessary to address that, and this is still lacking in the minimalist gear sold to the audiophile market.

THX works around the problem in the home theater environment by specifying electrical and acoustical filter functions that sum correctly - 4th order Linkwitz Riley low-pass on the sub-woofer, 2nd order electrical and acoustic high-pass functions for main speakers.

REL works around it by providing an adjustable low-pass that can be adjusted to mate well to the speaker's mechanical high-pass function, although this does not relieve the speakers (especially 2-way ported designs) of low-frequency content that can cause distortion problems.

Some sub-woofers have problems.

Non-flat tunings are often used giving them a one-note character.

High distortion, port noises, and shallow slopes can lead to sub-woofer localization.

Many sub-woofers aren't good matches for smaller rooms.

Pressure sources have increased output as frequencies drop bellow the room's fundamental resonance (the speed of sound which is 1130 feet/second or 330 meters/second for the metric crowd divided by twice the room's longest dimension; 57Hz for a small 10' long room, 28Hz for a 20' room); with an infinitely rigid room producing 12dB/octave. The excess low-bass from a sub which is flat below the room's fundamental resonance can make a system sound slow. This could be fixed by a sub-woofer with a higher mechanical high-pass frequency (which wouldn't sell well, because consumers buy based on frequency extension) or an electronic filter.

Some placements are problematic.

Bass source and lister locations determine what room modes will affect you. Big room modes (you can have over 10dB, or 10X the acoustic power) at the wrong frequency (I've found the 70Hz height mode to be especially noticeable) can produce a one-note sound.

Parametric equalization can fix it for one location, but audiophiles often aren't into that sort of thing.

Most people over use their subwoofers. Used properly- a high quality subwoofer will help 90% of the speakers out there. As a rule I say cross over between 60-80 and turn the volume down a bit and enjoy

Aldavis,

Thanks for the input. The volume setting on the sub is 2 out of ten in a room 24X18. (Very low)

I have bass traps and other room tuning devices properly set up. I have run various room set-up CD's from the likes of RIVES etc. I really do think it was set up pretty close to perfectly.

The sub seems to have a great reputation by owners and the industry.

I simply found it did "mess with" both mids and highs in my home. A good audio friend also went through the same situation and turned off the sub for better sound. I heard his sytem with and without the sub and agreed with him.

Proper set up and room interaction etc... all serve up a very tricky situation , at best, with a sub.

All I know is when I played the sub all by itself I was amazed how how little it was actually doing. One would think a sub set-up to be so tame could never negatively impact mids, imaging, highs etc.. However,it did.

I bought a Martin Logan Dynamo subwoofer (sealed design) recently because I thought that it would be a very musical sub. I did my best to integrate it with my speakers (Quad 12L2). I spent a lot of time on that until I thought I had it set up just right. Then I decided to try it with the subwoofer off...it was much better! The Quads put out lots of bass for their size and a little bit of corner reinforcement and it just sounds a lot more integrated than I could ever manage to get when using a sub. So I am totally off of subwoofers now.

With all that said, I was a little limited in where I could place the sub. Perhaps there is a way it could have sounded better. But I don't believe you can improve the integration of bass, midrange, and treble by adding another speaker to the mix. It only introduces new variables and new issues to deal with. In all liklihood it will sound worse, if you are lucky and/or know what you are doing it may sound just as good with a bit more added low end.

I will be moving to a bookshelf speaker with a 7 or 8 inch driver in the near future, to get something with the integration I am looking for and a bit more bass weight and sense of scale.