Running in

Astoundingly, the bass on my new speakers is opening up. The two 7" woofers don't have a great deal of linear excursion and I thought that this was limiting the low end (< 80Hz). However, today for some reason the base is as clear as a bell; perhaps a little too 'in your face'. What surprised me (but on reflection shouldn't have) is that with playing, the rubber suspension will soften a little and the impose slightly less damping. Perhaps running a 20Hz sine though them at fairly high power yesterday had something to do with it. It may not be an accurate sound, but as a bass player, hearing the bass lines so well defined is nice. 

So now I'll have to repeat all my measurements for the empirically-based crossovers (the ones I'm using at the moment were cobbled together from some components I bought based on the published performance of the drivers). The good news is that I didn't spend $80 mainly on coils I may not need. Coils are really pricey. I'm probably going to buy some enamel coated wire and wind my own.

Aja

This was one of the about three of four (audio) cassettes I took with me when I started working for IBM in 1983. I rented a room in Linstead Hall for about 6 weeks before the Hamlet Gardens house was up and running. I had two single-breasted pinstripe suits, one blue, one grey, a red tie, some M&S white shirts. Strange how vividly the music brings back some memories. The carpeting was a dark viridian; the room had a view over Princes Gardens. I remember getting up in the dark but I can't think why since I began work in late July. If have a feeling the room was #622, but that might have been my last year in college. The Linstead Hall I knew, built in 1968, is gone now, as is the house I grew up in. Such is life...

Phase IV (ants), Huey, Dewey and Louie.

In 1974, I went to see Phase IV. The B-feature at that showing, Silent Running, left a much more profound impression than the main feature. It has become something of a cult classic.

Phase IV complete

This post has nothing to do with ants. Twenty five years ago Graham kindly sold me at cost a pair of really nice bass drive units which I built into a pair of speakers. The only calculations I did were some fairly rough estimates of air volumes for the cabinets. I built a new design using the same drivers about 2 years later and the result was a slightly worse sounding speaker. I left them in my father's attic when I moved to France in 1990 and he, in turn, left them for the dustmen in one of his major clean-outs. So my 801 bass units are, regrettably, gone.

So when I set out to build another pair this August, I decided to use the cheapest drive units I could find. This time, however, I had some really remarkable design software thanks to Mark Zachmann, a computer, and some measuring equipment. The design was sketched in August I started cutting wood in September. The speaker (I decided to build only one prototype) saw its first activity this week.

Here it is next to one of the B&W DM6s I bought in 1979 and which has been my principle pair of speakers ever since. The crossover is sitting on the top of the DM6; I wanted to be able to adjust the component values without having to take the cabinet apart.  

I can't say for certain yet, since I'm listening to a B&W in one channel and my latest attempt on the other, but I think this time I've got something that sounds at least as good or even a tiny bit better than the B&Ws.

I've tried to do a farfield measurement and the only problem seems to be a bit (-15dB!) of a hole between 1-2k, but I'm not sure whether that's something to do with the room since the B&Ws exhibit a simialr problem when I measure their response. I've been listening to them almost continuously for three days and the sound is not in the least bit fatiguing, a good sign I think.  

So over the break I will be getting some more wood and building its companion. I know it's ugly, but I have yet to learn how to apply veneer. The drivers are Vifa D27TG45 (unfortunately no longer made but Scan-Speak makes some pretty similar ones), Scan-Speak Discovery 15M-4624G and a pair of Silver Flute W20RC38-08s. The Silver Flutes are made by a Chinese company, Vifa is a merger of a Chinese manufacturing firm and Danish designer.

I'm also thinking about building (Phase V) a two driver design using an Aurum Cantus  250F1 and an SB-Acoustics SB29RDC-C000-4 which I will probably cross over at about 700Hz.  Too much to do, too little time...

Over the weekend I wrote a program for 'tracing' loudspeaker driver frequency response. It's a copy of one that I found on the Frequency Response Date Consortium's website. It has a what I hope are some minor improvements over the original STL Tools written by Dave Scherf.

• Continuous tracing with the mouse button held down
• Status bar indicator of frequency and