ZX Spectrum

ZX Spectrum

The Repository->DIY->ZX Spectrum

This design is available as a kit from Meniscus Audio, or the parts can be purchased separately.

This design was sort of a "bonus round" for me. I had the drivers on-hand (briefly), and was curious how well they'd work together. Yes, it was a decision based mostly on aesthetics; these are two very intriguing-looking drivers. But how would they sound? I put them in the Amiga/TRS-80 enclosure, measured, modeled, listened, and very quickly had something that sounded quite good--exceeding my expectations.

I won't go into much detail about cabinet construction, since it's all been covered in the Amiga and TRS-80 pages. The overall cabinet volume is 30 Liters and the vent is 2" in diameter, and 3.5" long. This tunes the box to 39 Hz, and provides an F3 of a very satisfying 34 Hz.

For a bookshelf design, you could build this into the Parts Express .75 cubic ft MTM enclosure. You will need a 2" diameter vent that is 3.5" long. This will get an F3 of 42 Hz. But fear not; these HiVi M6A have bass that kicks ass and takes names!

You really don't see any designs out there using the HiVi M6A. I'm not sure why. It's a nice-looking driver, and well-built to boot. It has about the same cone area as the Dayton RS180, and behaves somewhat similarly to it, with a few slight differences. The most noticeable difference is that the M6A provide a very solid low end, but the bass is still well-controlled, similar to--but not quite in the same league as--a Scan-Speak midwoofer. The midrange of the M-series drivers also has a subtle "warmth" that is very pleasing, and sometimes seems to be missing from other metal-cone drivers.

The BG Neo3 is pretty well-renowned for being a very good tweeter, and it is. You will never hear any sort of hiss or hash from them. In fact, its frequency response has a wide dip centered around 7000 Hz, which is where a lot of sibilance happens in recordings. As a result, the first few minutes you listen to this tweeter, it will sound a tad bit "dark" (Please don't say "veiled." I hate that word.). Human ears quickly adjust, however, and after a song or two the music will be quite clear. However, if you go listen to a normal dome tweeter after this (even one that measures ruler-flat like the XT25, the treble may seem somewhat accentuated because your ears will have to adjust again. This phenomenon is nothing to be alarmed about. The Neo3 is a very high-quality tweeter; it is extremely low-distortion, and fares quite well in the retail speaker market. The Neo3 rounds off this design nicely because it lends itself to long listening sessions without any fatigue. Additionally, this inherent sound works well with today's hyper-compressed music. This speaker gave a new lease on life to some recordings I had all but thrown out due to their smashed dynamic range.

Now for the crossover. I've never had this happen before (and I don't expect it will ever happen again), but I actually got this one right on the first try. Either that means I've been spending too much time looking at FR graphs or these are really good drivers--OK, maybe a bit of both. I've thrown all sorts of music at it and haven't found anything it doesn't like. I've listened for many hours non-stop and found these to be extremely musical, pleasing, yet still providing those fun details I'd never noticed in songs before.

A few small notes if you build the ZX Spectrum: don't forget to get the flush mount faceplate for the Neo3 PDR (They're sold in 2-packs. Don't buy two of them, or you'll end up with 4 faceplates like my dumb ass did). Also, note that the tweeter polarity is reversed.

All the parts can be purchased from Parts Express, however Madisound also carries the M6A, and Meniscus carries the Neo3 PDR. You might also find better deals on caps, coils, and resistors, if you shop around.

Completed Versions by other DIYers

This pair was built by [DoctorDyna]. He opted for a stand-mounted version, using the dimensions of the Parts Express .75 cu ft MTM enclosure. (8"W x 20"H x 13"D). I think the red color of the cabinet makes a nice contrast against the gold cone of the M6A.

by Paul Carmody | last updated Jan 1, 2012