[jgpmhl]

I have a question about subwoofers.  I have been experimenting with bipole and other speakers with smaller (mid)woofers.  As much as I like many aspects of the sound, I miss the bass.  Is it necessary to buy a 5.1/6.1/7.1 receiver/amplifier to make use of a sub, or is there a way to fit one to a "stereo"?

Jim

[warnerwh]

If your preamp has two sets of outputs you can just output to a sub that way. Or if you only have one set of outputs you can get an RCA splitter of use one of the adapters that makes your single set of outputs in to dual outputs. I use one of the latter and like it best. It's basically a solid piece machines with one set of male rca's on one end and two females on the other. Either way you're looking at under 10 dollars.

There's another way to hook up a sub too. You run your speaker wires from your amp to the plate amp of the sub. Then run wires from the plate amp to your main speakers. This way you use the crossover built into the sub. The amps on subs are designed for this.

I don't blame you for missing the bass. Without bass music isn't complete to me. I actually like an articulate and powerful bass which is on the strong side for some people.

So yes it's a piece of cake. Btw welcome to Audiocircle

[Rob Babcock]

Depends on the sub, too.  There's lots of ways to integrates subs into a system.  For starters, what gear are you using?  Any peices you don't want to replace no matter what?

[amplifierguru]

Hi Jim,

You could try active Bass extension. This is where a low boost filter is inserted in the signal path, usually between pre and power amplifiers and it is tuned to boost system response just where your speakers are starting to roll off. You can successfully achieve an extension to 0.6fo using this method. A speaker that's -3dB at 50Hz could be extended to 30Hz with 6dB more power in this narrow band.

A sub can be added to your stereo by using one that filters the lows out of the main L and R channels and usually sums it to the powered subwoofer.

Cheers,
Greg

[Bob Reynolds]

As Greg noted, you can add a bass management controller (crossover) between the preamp and amp.

Hsu Research: http://www.hsustore.com/high-pass.html or http://www.hsustore.com/highendcrossover.html

Paradigm: http://www.paradigm.com/Website/SiteParadigmProduct/ParadigmModels/HighPassSWControlUnits/controlunits.html

M&K: http://www.mksound.com/filters-bass_mgmt.php


Note that some subwoofers provide a high pass filter in the sub (Martin Logan for example), but that means you'll run long ICs from the preamp to the sub and then back to the amp. This increases the chances of the cabling picking up noise.

I use the M&K LFE-4. It's a multichannel device, but I use only left and right.

I think adding a subwoofer to your stereo system can be the best investment you can make. Using a bass management controller makes the integration fairly simple and increases the chances of a seamless match. Matching the sub level with that of the main speakers is usually a problem. Many people set it too high. You really should not be aware that a sub is in the system, i.e., the sub should not call attention to itself. You can download test tones for setting the level from M&K's pro site: http://www.mkprofessional.com/wav/index.htm

You might find this article of interest: http://www.mkprofessional.com/bass_mgmt.htm

-- Bob

[amplifierguru]

Hi Bob,

What I was trying to point out was that there is a simple solution that goes a long way to restoring bass energy for higher cutoff systems and that's to interpose some EQ. A simple way to do this and one which, in practice, works well is a Q=2 filter response -



This can be tuned manually to boost 6dB where the speaker has fallen in response by 6dB restoring the response to flat and then cutting input steeply below that, effectively cleaning up the sub-bass the speaker has no chance of reproducing. An extension to 0.6 of the std cutoff frequency is achievable, taking a 50Hz cutoff speaker to 30Hz! And at the same time reducing 'out of band' cone movement -



Sure it boosts amplifier power into the speaker but only over a very narrow range of frequencies.

Cheers,
Greg

[Bob Reynolds]

Hi Greg,

Thanks for the additional information/explanation. I was trying to add to the second paragraph of your original reply.

The technique you describe looks similar to what Merlin Music Systems does in their VSM speaker -- Bass Augmentation Module.

The question I posed to Bobby P. concerned the distortion produced by the woofer when this approach is applied. Have you traded quantity for quality?

Interesting stuff.

-- Bob

[Scotty]

Greg, is this bass boost approach below system resonance intended for vented alignment speakers or sealed box speakers? I am a little unclear on your intended application.
Scotty

[amplifierguru]

Yes Bob, it goes under the heading Bass Augmentation. Many compact subs have it built in - to exchange amplifier power for compactness.


Hi Scotty,

The method works well with both sealed and vented speakers. It's simple plug and play with sealed boxes, but to achieve a full 0.6fo extension in the vented box requires a retuning of the vent assistance which can generally be achieved by sleeving the vent by ~ 30%.

I have done this on vented enclosures I have designed, using a designed in 'oversize' vent diameter and a push in sleeve made from rubber thermal lagging tube of ~ 10mm wall thickness in the appropriate size for an interference fit.

It works very well giving cleaner, tighter and extended bass.

Cheers,
Greg

[Mike Dzurko]

Here's a good primer on subs:

http://www.audioc.com/library1/subprimer.htm

Even though I wrote it years ago, it covers many of the bases    Hope it helps!