Related web sites (external):
A Hsu Subwoofer with a RD75 Dipole System
(John Whittaker)

The placement of a subwoofer
(By Ingvar Öhman, translated by Per Arne Almeflo)

Optimum frequency response curves in the bass range
(By Ingvar Öhman, translated by Per Arne Almeflo)

Note: I don't necessarily agree with some of the methods detailed below, apart from my own! If you'd like to add your own experiences or methods to this page, please contact me via e-mail.

First, my own method:
Ideally, your main speakers should be capable of performing down to below 80 Hz, the point at which at which it's best to cross over to a single subwoofer, to avoid aberrations in the low bass response. The crossover ideally should be an active system, however you can rely on the natural rolloff of the main speakers if they are small. Normally, the best response is obtained when the subwoofer is located in or near a corner, typically one that is located to the rear of the listening position - experiment to find the best location for the subwoofer in your room, the one that gives the smoothest sounding response without boomy effects. Use a separate amplifier to drive the subwoofer, and adjust its volume level to the point where you just start to hear the effect of the subwoofer during normal music playback. If you follow these steps, you should end up with a system that has a smooth response way down into the low bass frequencies - if your subwoofer is up to the job!

John Whittaker (DIY Loudspeakers List)
John sent me a complete description of some tests he made with a Hsu subwoofer and his RD75 dipole speakers. Please see the following page for more details:

http://www.spiceisle.com/audiodiy/misc/hsu_rd75.htm

Conrad Drake (DIY Loudspeakers List)
"Well, IMHO, the "best" way is with a spl meter and a set up CD (such as the Chesky one). Alternately, guesstimate the roll-off point of the mains; play some full-blown piano; start with the sub turned right down & turn it up until you can _just_ start to here it. Then turn it back down a notch. I guess that's the two standard ways to get to first base with a basic system."

Jan Nielson (DIY Loudspeakers List)
"My experience with sub-woofer(s) can be expressed quite clearly: Use 2 not 1 Use the lowest possible XO - I would recommend 50-80 Hz. You must have some kind of continious variable phase correction to make the sub/sattelite systems work together through the XO-point."

John Janowitz (DIY Loudspeakers List)
"Well, using the parapix amp, you have some flexibility. It has the RCA inputs if you have that on your reciever, or it has the speaker level inputs, and the speaker level outputs too. I've put one into my main system, and one into a little bookshelf system. You should mention something about using a sub with the different types of inputs."

Richard Greene
My main audio system uses EPOS ES11 satellite speakers and two homemade seven cubic foot sealed box subs with one Audio Concepts DV12 12" bass driver in each. I recommend the current model Audio Control Richter Scale electronic crossover (24 dB per octave) / six band bass equalizer (list price is $350 - have not been able to find it discounted) for subwoofer integration.

I actually use an older model Richter Scale with an 18 dB/octave crossover fixed at 100 Hz. and five band (1/2 octave) bass equalizer for my subs. I use an AudioSource 10 band equalizer for my EPOS speakers to tame a midrange peak and cut the bass below 100 Hz. -- I don't use the Richter Scale output for them because one equalizer in the signal path is enough! I set both equalizers using pink noise and a sound analyzer.

I can't imagine integrating a sub and small satellite speakers like mine without the Richter Scale unless the sub crossover was below the useful frequency response of the satellite speakers -- perhaps a 50 Hz. 24 dB per octave crossover. Before buying my Richter Scale in the early 1980's, I had difficulty integrating subs and satellite speakers even with the use of a 10 band equalizer.

My only recommendation is to place more emphasis on locating subwoofers in room corners - most of the time other locations over-emphasize bass in the octave from 50 Hz to 100 Hz which is rarely needed. Corner placement provides more room gain below 50 Hz which usually is needed. Also, one sub playing mono provides smoother frequency response than two subs playing stereo. Somewhere between 75 Hz and 100 Hz bass becomes directional and mono is not better above 100 Hz, where I've found corner placement is not the best. I guess the answer is to use a 24 dB/oct crossover in the 50 Hz - 70 Hz region for the one sub placed in a corner and let the main speakers handle higher frequencies. I have heard subs placed right next to the listening position sound good too - they had crossovers at about 50 Hz.