IanW

The Fernie Room and the 4 Quad 57 Experiment

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For those that visited the Fernie room and didn't get what we were trying to do and anyone else who might be interested in what we were trying to do:

We were trying to reduce the 57 beaming and increase the stereo sweet spot. With the added benefit of the increased panel area from the 4 Quads to enable the electrostatics to be used in a large room.

PaulR's concept was to turn the speakers onto their side. This changes the treble panel from being horizontal (cause of treble beaming) to vertical (horizontal beaming). With 4 speakers in a line then there is a continuous treble beam across the room, thereby eliminating the vertical beaming (but likely to cause some comb filter effects). With the signal being processed by Foobar it was possible (Paul wrote a DSP plug in to do this) to output 4 signals, for the 4 speakers, each one having some left and some right signal. The extreme left speaker having mostly left, with the inner left speaker having more left then right. Vice versa for the right hand side. Thereby in theory increasing the size of the stereo window. We also had diffusers / absorbers behind each speaker to disperse / reduce the size of the audio signal that would be reflected around the room and potentially affect the sound adversely.

The painting stands from Screwfix plus some wooden planks got the 57s to an ideal height for the seats, so that the listener's ears would be well within the treble beam. With the distance to the speakers being enough that at the back you could stand and not hear any dullness as you were still well within the treble beam.

There were definitely good seats to sit in and the further back you went, the wider the stereo image became. So based on our listening and comments made it seems to have worked, but it isn't really going to be a practical solution for anyone!

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There were two main aspects to the signal processing, attenuation, mixing and delay d'oh.... There were three main aspects to the signal processing, attenuation, mixing and delay. And wishful thinking.

The 57 is a ridiculously capable device, apparently made from cheap ply and candles. It's very crudely constructed, except where it really matters. Awe inspiring engineering. Functionally about as good as it gets in every way, bar three, output level, bass extension, and directionality. And it's possible to live with all those in some environments. If I were single I'd be content with a pair.

Stacking pairs increases the output level to sufficient, gets you more bass, and improves vertical dispersion. Been there, done that, with 2x4 offcuts in a small hotel room. What would happen if you spread the individual speakers out horizontally? Loud and low as before. But now you sort of have a 4 or 5 meter wide tweeter, so the highs will be heard over a wider area. If you tip the speakers over, so that there are virtual rows of bass units, mid/tweeter and bass again, then the treble beams won't overlap and interfere. The added benefit is better vertical dispersion.

But what to drive the horizontal array with? The idealisation I used was to imagine two line sources somewhere behind the array, and then figure out what combination of the two would pass through each individual real speaker. In essence the further from the virtual source, the quieter and later. So I created a foobar2000 DSP component that implemented this, turning 2 channels into 4 by combining, attenuating and delaying. Using foobar meant that all the mechanics of handling inputs and outputs was handled. And it's free.

We had no idea whether this was going to work in practice, until a week ago in front of esteemed hifi guests in (the other) Paul's mostly refurbished back room, with no furnishings or carpets and sitting on a ladder running across chassis stands with offcuts of worktop it was tried for the first time. The results were plausible enough to justify giving it a go at the show. Where it worked much better than I was expecting. Really very pleased with how the system sounded. Mission accomplished, to do something novel, that worked in absolute hifi terms and using gear we had to hand.

Paul

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Very cool indeed! I would love to have heard it!

How did you wish our the appropriate delays and channel mixes? Science or suck it and see? What did you actually use?

As an aside I think that the DSP module that comes with J River would do this without you having to write your own plugin.

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Super Wammer

I couldn't get there this year and when I saw the photos my jaw dropped. Brilliant concept and sounds like it worked.

Have you further plans to develop it? Would love to hear them.

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Guest

I popped in early when you were still setting up and listened from one of the side seats on the front row, and I must admit it didn't really work for me. Popped back with Mrs. KW later on when things had calmed down a bit and sat in the centre seat on the front row. Wow!

There was certainly still a "sweet spot" on the front row of seats, where it sounded excellent, but I didn't try listening further back.

An excellent demo, though, and thanks for bringing it along. It's exciting to be at a time now, where DSP techniques are accessible enough that mad ideas like this can be tried out relatively easily. Both this setup and Ed9000's really demonstrate what can be achieved and they were both up there in the more memorable rooms at the show for me. :^

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Came for a quick listen and stayed for 35 minutes, any speakers that can get me listening to 4 Deep Purple tracks in a row must be very good and these were. Now how can I connect up my 988's and 989s.

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Very cool indeed! I would love to have heard it!

How did you wish our the appropriate delays and channel mixes? Science or suck it and see? What did you actually use?

It was all scientific, then suck it and see. I imagined virtual speakers behind the plane and organised delays and attenuation to align with where the virtual speakers were. It's configurable for width and depth from the imaginary speakers to the row of real ones. We only had four, but five or six would have been good.

As an aside I think that the DSP module that comes with J River would do this without you having to write your own plugin.

Possibly, but I wanted control... And we understood foobar. The whole setup was built from bits we had access to.

Paul

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Thanks Ian, it was the first time I have ever enjoyed Quads!

Cheers matey :P

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Cheers matey :P

Haha, well I must have listened to a dozen different pairs in all sorts different rooms so don't take it personally. I don't actually dislike them, they generally don't set my world alight is all.

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Given the constraints of the room-Height, lack of acoustic traps it sounded excellent. As many have advised a lot of the Scalford rooms can be very challenging. Sligolad used a pair of 63's I bought on Saturday. Virtually impossible to control the bass response. Really tight speakers back in my own home.

Fair play to the lads for a wonderful visual effort that also managed to sound really good.

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