A Bit on the Slow Side

One of the enormous pleasures of being self-employed is the many exciting hours one spends doing paperwork related to taxes one must pay.

Fortunately, I am in a position to temper the extreme joy by having a beer (or two) at my left hand, and music emerging from my speakers. My computer speakers, actually, despite having a much better system in the same room. My desk isn’t ideally suited to them, geometry-wise. In any case, I find that I really must play music loud to have the desired effect, and since it is now quite late at night, having the full system going full bore would no doubt lead to a visit from my former police colleagues.

My computer speakers tend to be a little better than the average. For quite a while I was using a set of Bose Computer MusicMonitor speakers, which really are remarkably good for such tiny little things.

Note the proviso: ‘for such tiny little things’. In fact, sometimes I like to have a good blast of volume — say when I’m doing tax-related paperwork. And I pretty much always like to have well-extended bass.

So some months back I decided to put together a computer speaker system from some odds and sods I had laying around. For speakers I used the VAF Research DC-1 speakers which I purchased years ago as surround speakers. These still sound pretty decent, with good detail, but their very nature (bass driver is 100mm) limits what they can do at the bottom end.

Fortunately, back in the late 1990s I built myself a little subwoofer. A 203mm driver in a reasonably compact enclosure, made of 25mm MDF, bass reflex loaded. This was passive, but I had a little 50 watt subwoofer amp that I had also built. Using its crossover, though, left the main sound a little buzzy. So I tossed the little amplifier, and made use of my old home theatre receiver.

This is the Marantz SR-18 which had been my main receiver for many years, but its front end had been left behind by technology. It does Dolby Digital and DTS of course, but doesn’t support HDMI and only has 5.1 channels.

Oh, but what channels! It is rated at 140 watts from each of them, and this is actually an honest measurement (I checked myself). In two channel mode it runs at a clean 180 watts per channel.

Perhaps I should have sold it, but I couldn’t see ever getting more than a tiny amount, so it had been sitting aside in my office for a few years. As it happens, this was perfect for the job of driving my computer speakers because it has an old-fashioned way of connecting the pre and power parts of the unit: via the external world. It has six channel preamplifier outputs, and five channel power amplifier inputs, and jumpers to join five of the former with the five of the latter.

That meant that I could jump the subwoofer preamplifier output — which is normally fed to an active subwoofer — to one of the power amplifiers and use it to drive my own passive subwoofer.

I’ve generally been pleased with the sound. Far better than the Bose system, and with pretty decent bass (the system extends to just on 30 hertz — I designed the subwoofer for extension rather than volume, and it works well in this environment). The sound is ‘near field’ of course, which makes it pretty useful for a computer.

But I felt that the subwoofer was a little slow, lagging the stereo speakers.

As it happened, I was the slow thing in the system. Tonight I put on ‘The B-52s’ and the bass just sounded tired. Deep, yes, powerful enough, yes, but lagging. So I took a moment out (anything to avoid entering those receipts into the accounting software!) and fiddled with the ‘Speaker Distance’ menu in the receiver. The subwoofer is on the floor under my desk while the speakers are to the left and right of the monitor, about 850mm from my ears. The subwoofer is probably twice that range, or a little more. If it was a metre further, that would delay the sound by about 3 milliseconds, which I hadn’t bothered about.

But you can wind up the distance more than the physical measurement. If for reasons of phasing or whatever the subwoofer was significantly behind the main speakers, I could make some adjustment by increasing its distance in the setup menu of the receiver. That’s what I did. I wound it up to 1.8 metres further than the main speakers. That advances the signal to the subwoofer 6ms ahead of the signal to the main speakers, and — snap! — the bass was in glorious sync with the upper frequencies.

The B-52s, which are all about an extremely tight performance, had their bottom octaves matching the rest. I played Muse’s Showbiz end to end, and the kick drum was spot on, not to mention the deep synth bass. A good test CD for bass extension, and for even performance across the bottom three octaves, is Wendy Carlos’ Switched On Bach. The artificially generated bass isn’t subject to the vagaries of acoustic recording, so the Bach-written bass lines which dance up and down scales provide an excellent frequency balance test. As I write this, the ‘Prelude and Fugue #7 in E-Flat Major’ is just drawing to a close on the Prelude section with a wonderfully powerful and throbbing sustained E-Flat tone at 38.9 hertz. Thank goodness for subwoofers. There’s no way the Bose computer speakers could do this, nor even the VAF DC1 speakers alone.

Now my thrilling paperwork times so pass even more enjoyably.

Oh, if you’ve read this far (and even gone to the trouble of flipping the page!), one of you deserves a reward (you all do, but resources are limited). How about The Bourne Supremacy on Blu-ray, no label, no box, but a damned good movie and as far as your player is concerned, just like a bought one. Leave a remark in comments.

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