Thursday, February 10, 2011

Strategies, large and small

To move forward in the audio hobby, you should have a strategy.  There are many possibilities nowadays. Unfortunately, it looks like a lot of the current audiophile products are of the "fake snake oil" variety, they don't actually work, but people feel they work because they believe in them.  The tendency toward superstition in humans is very well known...

My strategy is largely to avoid things that look or smell like "fake snake oil", or at least not to get overly obsessive about them.  Sure, I may try a tweak here or there, something that makes sense to me like power conditioning or replacing electrolytic capacitors with polyethylene film capacitors.  (I am well aware that power conditioners are quite controversial, and in fact I do not plug my power amplifier into mine, only signal processing equipment.)

Instead, my strategy is to focus on the well known, things that unquestionably make a difference, no question about audibility, but which is better?  There are vast opportunities of this nature in audio, and I would like to bring more into thinking about audio reproduction like I do.  I can see that I am not alone, however, lots of board now (such as DIYAudio) are filled with audiophiles having a more objective orientation.  That does not mean I treasure flat frequency response above all else (see my last post).  But at least I want to have some understanding of the colorations I employ to make the audio magic work.

It is clear to me that a very important part of this is getting the bass right.  Mind you, I don't believe it's entirely clear what exactly "right" is, and it may vary from one person to the next.   It is clear to most people who have investigated this that the best sounding frequency response in a room is not flat.  Rooms themselves have low frequency resonances and gain, and within that context if you hear "flat" reproduction it really falls flat.

So this is a subjective art, basically fiddling with the bass until you get it to sound right on most recordings.  Now there are many approaches to that.  Some people go through many different speaker systems, and/or try many different speaker and listening positions with those speakers.  Others stick with favored speaker and try room acoustical treatments or DSP.  Still others fiddle with magic points and tourmaline crystals.

I actually have been through many speaker systems in the past, and I think that is one of the best things to do, but it is not my current approach because I already have very good speakers.  Currently I am mainly trying to get the bass right by adjusting the speaker positions, delays, crossover, and digital signal processing.  It is clear now I may also benefit from some room acoustic treatments to fix room boom not at the listening position.  It's clear that neither DSP doesn't offer a complete solution to getting the best bass response.

So now I am getting down to the layer of strategies where I am now.  Since January, I've been working with a new crossover design that keeps the subwoofer below major resonances around 100 Hz, and the panels above those resonances.  This works very well, though seems a bit lightweight in the midbass (yes, it seems light around 100Hz even though it measures basically flat).

Now there are several other possible crossover strategies.  One is to do a more honest ("real") crossover, with subwoofer lowpass and midrange highpass both set at the same frequency, say, 100Hz.  That will likely produce lots of "boom" around 100Hz which is currently being suppressed.  It wouldn't be a nice way to use the system without further changes.  Those additional changes could be either done manually, by setting a parametric EQ depression around 100Hz to cancel the boom, or by running Tact do do a Room Correction, or both individually or simultaneously.  But those approaches may work out better than trying to cover up the resonances by underlapping the crossover.

Another obvious strategy is to run the Acoustat full range without sub.  Well not if you like head banging bass as I sometimes do.

Another strategy is to run the Acoustats full range with subwoofer merely serving in augmentation mode.

Similar to that would be to crossover the Acoustats as low as possible, such as 40 Hz.  I tried that before, didn't like some of the panel resonances I heard running that way, but those may be the very resonances I fixed with notch filters this week.

Yet another is to run the sub as high as possible (it's supposed to have flat clean dynamic response to 250Hz) and cross the Acoustats at that point.  That would keep as much bass out of the Acoustats as possible, and give the Tact as much freedom as possible to correct the frequency response (which will definitely be needing lots of correction in the midbass when powered by dynamic ported woofer).

I think for now I'm going to stick with the crossover-around-100Hz strategy, and work it up to get better midbass, or attempt to get some satisfaction with the "real crossover plus EQ" approach.

1 comment:

  1. Dear Charles,

    I definitely agree that underlapping crossover frequencies isn't the way to go because of the phase interference it causes. But I feel that good subwoofer that directly connected to an amplifier has a high enough damping factor to maintain good control of the subwoofer eliminates for the most part the need for room treatments because except for sustained bass notes such as organ pedal note doesn't give the bass enough time to excite nasty room resonances.

    By the way do you really mean "false snake oil" because that would mean it was the real thing and not "snake oil" at all?

    Best regards,