Here are the homebuilt speakers that reside in my man cave.
When a friend of mine purchased of a pair of 12” high compliance woofers my journey toward the construction of these speakers actually began. I was amazed by the bass produced by these newer style woofers, but my speaker building career had started before that.
I was used to the old style paper coned woofers, those with a very stiff suspension. My original home built speakers used a Marsland 8” woofer with a whizzer cone. It had a 40 oz ceramic magnet and 40 -14,000Hz frequency response. They came from Gladstone Electronics in Toronto. Mounted in a bass reflex cabinet, the design of which was published in an electronics magazine (I forget which one) but the issue was from 1964. Those speakers sounded fantastic to me at the time. My father had the lumber yard cut the plywood to the sizes shown in the article, I just had to put it together almost like a kit!
Next reasoning that bigger was better I purchased similar type speakers but 12” they had a front plate holding two 4” paper coned tweeters, made by Radio Speakers of Canada, also from Gladstone. As I recall they were also recommended to be used in a bass reflex cabinet. The actual construction details were sparser but they recommended a box shape in accordance with the “Golden Rectangle”. I built a couple of slightly different designed boxes they sounded good but didn’t really blow me away. I remember adding a dome tweeter to the cabinet coupled through a 2 μFD capacitor and noticing the much improved high end. The paper coned tweeters attached to the woofers were not very good.
Back to the high compliance woofers, I had decided that I wanted to build a three way speaker system; the new woofers were good for bass but not very good for mid frequencies. With information from speaker building books and my own intuition, I came up with a cabinet design that was wide enough to accommodate the woofer but not much more. To get the cabinet volume up I made it deeper. At that time I was noticing that narrower speakers seemed to sound better than wider ones, better dispersion I guess. I no longer followed the speaker builder books recommendation of dimensions in the shape of the golden rectangle. Intuitively just by looking at it in the catalogue, I thought that the Philips domed midrange would be ideal for reproducing the midrange, and I was right. I ended up building four speakers using the unbranded woofer, Philips midrange (or squawker) and Peerless domed tweeter, as well as an unbranded three way crossover, most components came from Addison Electronics in Montreal. Latter on I decided to add a passive radiator to the design. I cut the opening in the bottom (floor) of the cabinet and mounted the passive radiator there. I then added Shepherd Casters to the bottom of the speaker to raise it off the floor. The bass response was amazing, hardly accurate but a perfect complement for the mainly rock music that I was listening to at the time. I covered the speakers with cork wall tiles and ordered custom made foam grills for them as well. Those speakers served well for several years, but then I got the speaker building bug again.
When I started reading about the benefits of bi-amplification. It made perfect sense to me. If you look at a typical audio music waveform on an oscilloscope screen you will notice high frequencies riding on top of the bass waveform but at a much lower level than the bass. If the level is raised to the point of clipping much of that higher frequency waveform gets chopped off, that process causes even more high frequency energy but its all distortion. Clipping sounds terrible on any system, it’s funny how some people don’t think that music isn't loud unless it is clipping! In a bi-amped system even If the bass was to clip much of the distortion products will fall outside the frequency range of the speaker and thus not be as audibled. With the bass removed from a signal the remainder can easily be driven to very high levels without any distortion due to clipping.
For awhile I was toying with the idea of using oak whisky barrels as cabinets for my woofers. That would have made a separate enclosure for the mid/high frequencies necessary. I had been reading about the benefits of running multiple drivers in a speaker system. The main one being lower distortion, each speaker has to move a shorter distance for the same sound output level. I decided I wanted to use four midrange and four tweeters per speaker, that way they could be connected in series parallel to keep the impedance at eight ohms. All drivers and the crossover network were Philips branded. I chose the new fabric domed Philips midrange (the old ones had paper cones), and similar matching tweeters. I then started to experiment. First I tried mounting the speakers in a cubed shaped enclosure; I was hoping that the wide dispersion of the drivers would be enough to create an omnidirectional speaker. The results were terrible; the speakers beamed in four directions and were almost silent off axis. Next I tried a cabinet design roughly in the shape of a Bose 901 speaker. Three mid/tweeter combination were mounted on the front the last one on the back. I hung the speaker from the floor joists in the basement, below it sat a woofer in a separate cabinet. Well the disjointed sound of that experiment showed me that the woofer needs to be very close to the other drivers or it just doesn’t sound right at all.
I had decided that I wanted to use two 12” woofers for the bass. My speaker book from Philips showed recommended enclosure volumes for their various woofers, but nothing about running two woofers in one enclosure. So again by intuition I assumed it should be about twice the volume as for a single speaker. I constructed another cabinet to hold the two woofers, and mounted two squawkers and two tweeters above them; it would have been approximately twice as high as my other set of speakers. The other two squawkers and tweeters were mounted on top of the enclosure. I wasn’t an attempting to create a direct/reflecting type speaker (In fact I had started reading negative reviews of that approach causing a blurring of the stereo image). I just did it as a way to ensure that when you got up and walked around the room you could still hear each speaker directly and also to mount them all on the front panel would have necessitated a monstrous sized enclosure. It worked out as intended. In fact they sound so good that they have remained my main speakers for forty plus years!
I used pre finished shelving to cover the speaker sides and back and ordered custom made foam grills for the front and top. Shepherd Casters were again added to the bottom of the speakers to allow easy movement and positioning of the speakers.
Later on I added a couple of toggle switches to the bottom of the speakers, one to connect the woofers in series (16 ohm) or parallel (4 ohm). Another switch was added to connect the speakers for normal (non bi-amped) operation. In the (normal) position only one woofer is driven (to keep 8 ohm impedance) via the 3-way crossover. The second woofer then acts like a passive radiator. In the Bi-amped position the woofers are connected separately bypassing the crossover. Some crossover components are also bypassed so that the midrange does not receive double crossover filtering during bi-amp operation.