Final installment ...........
I am envisaging this as a DIY project. So far, it still involves wood-working skills. Imagine if you could buy the frame off the shelf at minimal cost. The other issue with this design is the cradle still transmits vibrations to the floor and up the poles to the PRV’s. Could I kill 2 birds with one stone?
In my head I had a design to use metal poles and scaffold fittings. Building scaffolding was too big and bulky, but what if they made something smaller?
A bit of googling and I found exactly what I wanted at
https://www.themetalstore.co.uk/products/mild-steel-suppliers-uk Not only that, they would deliver free & cut to size. I designed a metal cradle using 34mm tubes & fittings. Here was the result, £99 delivered!:
And fully assembled scaffold speaker:
The woofer assembly was now supported hammock style by a 2mm steel cable and is free to oscillate back and forth. I was concerned it might do this while listening to music, but it doesn’t. I tested with a frequency generator and oscillation does not occur until 5hz.
The effect of this is total isolation from the floor, in fact no vibes can be felt from the frame itself, nor in the poles supporting the PRV’s. This was the best sounding design bass with no reaction with the room or floor, and nothing to interfere with the PRV’s.
Cosmetically, of course, not to everyone's taste. They have an industrial look, but surprisingly my other half approves of the minimalist design. The eyes tend to be drawn to the woofers rather than the frame. Probably even less intrusive in black, but I love them as they are!
Another hifi buddy suggested a further modification to isolate the PRV’s by eliminating the cleats holding to the poles. After several protoypes, I worked out a method to hang the PRV’s using a cable similar to the woofers:
Eliminated one of the poles, joined the PRV’s together with a brass joining plate, and suspended by the top magnet on a cable. Very simple and this resulted in even better imaging and detail.
So I have been living with this system with over a year and got the itch again
I alway wondered what would happen with 4 x 18” woofers rather than 15”? TBH, the way I play the system the woofers are on their limit in my room when producing deep bass, being rated @ 500Watts. The 18’s would take 1000Watts and have similar efficiency. I recently bit the bullet and went for the Dayton UM18’s. They were not cheap at a EU rip-off price of 1500EU vs US price of $1000
A small frame adaptation allowed me to fit these:
Not sure exactly what I was expecting, but compared to the 15’s the system sounds like its been turbocharged. A huge increase in scale and dynamics with a doubling of everything! The bass can really be pushed now, but surprisingly, it stays in its place without overpowering the mid & highs. There is no muddying, just huge clean controlled bass that really slams with rock, but is also textured and detailed with jazz and acoustic music. I can achieve 110db concert levels that leave my ears ringing with no signs of strains or distortion in the system.
What have I learned on this journey?
• No baffle at all sounds best with fewer resonances and better imaging. Bass is not as extended, but this doesn’t matter for upper frequencies using a bass assisted system.
• You can get huge bass with no baffle, but you need heavy coned inefficent woofers with a large Xmax, low Fs and high wattage.
It took me 15 years to reach this point and I now feel I can relax and listen to a system that will deliver whatever I am in the mood to listen to. I think I now need to look elsewhere to direct my creativity.
BTW, if anyone is interested in any of the projects I made along the way, please contact me.............
