I love 70’s HiFi speakers. Particularly the ones with the removable from panel and white cone speakers. I wanted a pair of small to medium ones for my desk, but those on ebay where either for pickup only from a far city, expensive or in poor condition. In particular the foam speaker surrounds and chipboard boxes often have not aged well.
late last year I gave up and started thinking about a set I made in the early 90’s. I had used crossovers and speakers I had from the early 80’s and some leftover veneered MDF. The boxes size was based on the size of the leftover timber I had. The woofers were low quality and the crossovers were worse, but I was quite pleased with the cabinets.
Woofers
I looked and found the speakers and crossovers listed in a 1984 Dick Smith catalogue. The speakers were advertised as “200mm Air Suspension with Aluminium Voice Coil.” Dual voice cone and dual 4 and 8 ohms, for bookshelf systems or PA.
I’m not convinced that a do everything speaker does it all well, but it is what I had and as a friend doesn’t like people saying, it is what it is. In 1984 they were $24.95 each. I think I paid half of that when they were on special. While one of mine had a dual cone, the other had lost the small secondary cone in the middle. I like to have the speakers exposed and this wasn’t a good look.
A more sensible person may have purchased replacement speaker cone caps, or replaced the speakers but I had an idea or more accurately a bodge that I wanted to try out. I wanted to make my own from garbage and risk shorting them out if it went badly wrong. I had been looking at the bottom of aluminium drink cans and thinking they looked good enough to use in a project. So I grabbed a few cans. Pear cider was chosen as it was hopped to lead to a more refreshingly crisp sound 🙂
I tried a few ways or removing the bottom from the cans. The fastest, although maybe the most dangerous was to hold the can gently against a disk sander. It quickly ground through the lip at the bottom and the bottom fell in.
I did a few and left one as it was and painted the other two; one white and one black. The silver looked ok but didn’t really match the speakers. The white just made the white of the speakers look more yellowed than they already were. Matt black was the winner.
The cap was going to sit across the wires going to the voice coil. I didn’t really want to short out the speaker and even though they had a protective coating over them I did take care to ensure the metal cap had not sharp bits and was not in contact with the wires. I know there is a special type of glue for speakers but I didn’t have any so went with Selleys Shoe repair glue. This seemed the most appropriate of what I had. speakers are like shoes in that they move and flex a lot 🙂 I did have speaker glue once and it seemed similar.
Crossovers
Onto the crossovers. The original ones were also listed in the same Dick Smith catalogue for $8.95 each. “The special inductor/capacitor circuit ensures good crossovover characteristics“. A bold claim given what I found when I opened one up.
Inside is just a capacitor for the tweeter and inductor for the woofer. Just a very basic crossover with a 6dB/octive slope. Most of the little I know about crossovers comes from an Electronics Today International project article from June 1975 for building a pair of two way speakers, the ETI400. I dreamed of these speakers and ended up building them around 1981, although to be honest I deviated quite a bit from the design. This is where the woofers and crossovers that I had in the new boxes came from. The ETI400 speakers used Phillips drivers and I could not get those and would not have been able to afford them anyway. It also had a crossover that needed to be home made. It had 3 capacitors, 2 inductors and 3 resistors, to both give it a 12dB/octive slope and dampen the more efficient tweeter.
Originally, I used the Disk Smith crossovers but eventually replaced them with the ones from the article. The article states, “The cross-over network described in this article must be used exactly as specified if the intended performance is to be obtained. A simpler version of the network – or a simple series capacitor – is not ‘almost as good’“. I can confirm that, it was like light and day. Those original speaker EIT400 boxes now live in the shed and are connected to an old Yamaha amplifier with disintegrating chipboard case and mismatched knobs. They are used regularly and still sound good.
I decided to replace these old ones in the boxes I’m now updating as I already knew the ones I had didn’t sound good with my speakers. Rather than building crossovers I decided to buy a set. A browse of ebay showed that crossovers are still more expensive than you may first think for something that is often just 2 coils and 2 capacitors. I decided to go with these 2Pcs 400W Speaker Frequency Divider 2 Way 2 Unit Hi-Fi Soundshelf Crossover L5O2. I believe these have a 12dB/octive slope and have a crossover Frequency of 3200Hz
Terminals
I had used a basic pair of push type speaker terminals. These are ok and you don’t really see them anyway. The downside is they can be fiddly to get the wires in when they are in a tight spot and it surprising how many times I seem to need to do that.
I found the ones below on Amazon Kalevel 2pcs Speaker Box Terminal Cup Square with 2 Pair Banana Plugs Screw Type Binding Post Subwoofer Box Terminal Cup 3.2in Banana Plugs 4mm for 2-Way DIY Home Car Stereo with Screws. They are not super high quality but are reasonable quality, and these are not high end speakers. The price was good, it came with binding posts and only required a round hole to be cut for fitting.
End result
It was very satisfying updating something I already had. I’m very happy with the look. My desk now feels a bit more enjoyable to work at. The sound has definitely improved, but I think that is entirely due to replacing the crossovers. I’ve been able to improve something that I already had and not bring more stuff into the house.
They sound good when watching YouTube videos and I use them all the time when I’m in Zoom and Teams meetings. I would only describe them as average for music. Far better than most desktop speakers, but not like high quality HiFi speakers. Those woofers are just not great and the tweeter may be more efficient than the woofer and so is a bit louder. While the crossover is better it is just a generic one and not designed for the speakers I am using.
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