Unconventional speaker designs

My favourite design of B & O speaker. Incidentally you can get aftermarket replacement wooden frets for the 8000 and 6000 models to update then visually to the current B & O style. As with all of these designs, being active helps overcome limitations imposed their slender aesthetics and probably works well (with the correct connectors) with many of the pre-amp DACs/Streamers on the market today.

Not as ‘unconventional’, outlandish or as pricey as many in this thread but I’ve owned a few speaker pairs that may qualify.

My Celestion AVF302s - effectively a sealed box two-way mounted on a very fancy glass stand. Visually unobtrusive and sounded ok but with very limited bass output. I owned them for many years.

The Piega T60 Micro AMTs. Full aluminium construction (very rigid from thin walls, increasing internal volume for size). AMT tweeter and a relatively large number of small woofers. Certainly not ‘another wooden box’. Going further up the Piega range one moves through ribbon tweeters to coaxial midrange/treble and the Master Line Series incorporates open-baffle for the midrange/treble in a line array.


With the grilles on.

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Finally, my own four piece, four-way open baffle design.
Evolved over a year, it is semi-active and incorporates:

  1. Any stereo amplifier (with a stereo pre-out) powering the 8 inch SB acoustics full range drivers and Audison Prima rear firing ambient tweeters. I’ve used the adjustable passive crossovers that came with the tweeters but the FR drivers have no filtering - a direct link with the amplifier to eliminate phase issues and crossover loss. About 90 dB efficient.

  1. 2 x 8 inch SB Acoustics bass drivers per main baffle wired to 4 ohms. These are active and run from approximately 190hz and down. About 93db efficient in 4 ohms.

  2. 2 x 15 inch SB Audience Bianco OB woofers in seperate bass modules that run from 90hz and down. They can operate much higher but I prefer the twin 8s higher up. They are 98db efficient.

Both 2 and 3 are run actively from a Genesis Four Channel car amplifier, the Biancos in bridged mono mode (circa 300 WPC into 4 ohms). I can adjust crossover filtering and amp gain to suit driver type and room placement. Pictured here with its power supply.

The whole system fills our 5m x 3.5 metre sun/cinema room with ease. The sound is very spacious and, not surprisingly, free of boxiness.

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That must need a huge amount of bass boost to overcome the degree of cancellation due to the minimal baffle on the bass unit.

There’s a bit more baffle wrapped around the sides, and isn’t the roll off rather gentle for a dipole? They’re also a fair way from the rear wall.

Here’s more details from AlexP too

It’s a really interesting approach, I’d love to hear the setup!

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IIRC roll-off is 6dB/octave below the frequency where the baffle width is 1/4 wavelength. Looking at your pics the baffle width including wrap-around is less than 1/4 of the ~12ft wavelength of 90Hz, so the baffles serves no function other than as supporting frame, and output will be 6 dB down at 45Hz and 12dB down at 22.5Hz, assuming the driver has linear response down to that. So for linear output with that speaker @AlexP would need 6dB per octave boost, with 6dB more amp output (4x the power) at 45 Hz, and 12 dB (8x the amp power) if he/she wants undiminished at 22.5Hz

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Also known as a football!:smile::smile::smile:

It appears the 20 hexagonal faces contain drivers, so what about the 12 pentagons? And did they experiment with other solids eg a regular dodecahedron?

Sorry, it,s my inner mathematician coming out.

Roger

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Don’t have a single idea PM.

Why? It’s something I don’t really understand, aren’t you relying on room reflections (which will differ per room) and adding phase issues? There’s probably something I’m missing.

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We are away at the moment but from memory, the in-room response is pretty flat down to circa 40 hz then it does roll off from there. Perhaps the room helps? Interestingly using the same Bianco 15, both Joseph Crowe and Javad Shadzi reported strong output down to 40hz and then roll off - same as my experience.

As for bass boost, the driver is very efficient and the amplifier is actually running on a lower gain setting. I’m very sensitive to what I deem excessive bass - I prefer leaner/dry bass response, which is what I get from this system. The Arcam amplifier I use does have bass controls (in the digital domain) which are in 1db increments at 40hz - I preferred the sound flat.

It’s a more common in speakers than one might think: Beonickie seems particularly keen and his designs seem to receive universal acclaim.

It’s actually quite simple - I felt the FR drivers lacked top-end sparkle so I researched tweeters/super tweeters. A very interesting GR Research video on phase issues and forward firing super tweeters made me wonder about the best way to trial/integrate tweeters.

For a variety of reasons I went for the Audisons. When they arrived I tried them forward firing - it worked but I found the effect a bit too hot in the treble. I angled them rearwards and the problem was solved. The result was good treble extension and greater sound stage depth. They are affixed to the top of the baffle with ‘black-tac’ so I can adjust them through a full 360 degrees if I wish. I can also unplug them should I want to, but I have not once felt the need.

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My understanding is that a natural sounding in-room response is actually slightly sloping across the spectrum from mid bass upwards, by something like 2dB per octave.

As for preference, of course everyone’s taste is different, and it seems that bass shyness is not uncommon, however in my case I don’t like bass diminished, and when music goes low I want to feel it properly. If forced to choose between exagerated or diminished bass I’d choose exagerated, though it needs to be well controlled with due tautness, and not mask the rest of the music.

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Before installing the tweeters there was a definite roll off in the higher octaves - now the response is much flatter higher up. My hearing does trail off at 16khz anyway.

Ref bass output, the in-room sweet spot happens to be at the listening position (our sofa) - move forward a metre and the bass response does become weaker. My understanding is that dipole bass can have this characteristic - it interacts with the room in a different way from ported or sealed enclosures. I would describe this system as having a textured and punchy bass response - individual notes can be heard very clearly - its less of a ‘rumble’ or ‘fat’ bass set-up.

The other ‘main system’ employs four active 10inch sealed subwoofers. Personally I prefer more drivers running well within excursion rather than a smaller number ‘maxed out’. For me the beauty of active control of bass response is the ability to tune it to ear/room.

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That is how bass should be (I’ve only ever heard rumble when I had an idler wheel turntable, or in movie soundtracks!

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RAID, Redundant Array of Inexpensive Drivers. :wink:

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Is this not just a model of a 1960s telephone atop a kitchen bin?

More a disaster

I heard these sometime ago, the scene was impressive and really 3D, but their specific voice was rather sharp and brilliant…

As bad as pre merger Focals?

Not as bad as late 90s JMLab (Focal), and the 3D soundstage was a true plus…