Larger Semi-Omni Development

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Chunk McDaniel
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Re: Larger Semi-Omni Development

Unread post by Chunk McDaniel » Wed Aug 02, 2017 3:07 pm

Steve these look beautiful. Can't wait to see the finished speakers and read about how they sound. To me they look like a cross between artdeco and a huf haus design.

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SteveTheShadow
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Re: Larger Semi-Omni Development

Unread post by SteveTheShadow » Wed Aug 02, 2017 3:34 pm

:)

Tried the bare boxes on their backs with a couple of bath towels thrown inside each one and a 2nd order, low pass crossover at 200Hz.
The results were highly promising, both with music and the pink noise analysis. Not sorted by any means but as I said...promising.

Removing the bath towels from the cabs and playing music was highly entertaining. Haven't heard bass like that since my Dad's KB radiogram back in the 60s. And no that's not a compliment. :lol: :lol: :lol:

But..... the design once the cabs are properly braced and damped is definitely a goer, and that is the main thing at this stage of the proceedings.
BTE Designs modified Lenco L75 idler turntable, Rega R200 Tonearm, Goldring E3 MM cartridge, NVA Phono1 phono stage.
Mac-Mini music server with iTunes, AppleTV4 media streamer, Musical Fidelity M1 DAC,
NVA A20/P20, 25WPC stereo power amplifier/passive control unit,
own design, semi-omnidirectional, transmission line speakers- "The Flatback Banned".

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Dr Bunsen Honeydew
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Re: Larger Semi-Omni Development

Unread post by Dr Bunsen Honeydew » Wed Aug 02, 2017 4:12 pm

Get it right and you won't need any cabinet damping. You got away with just ply with the smaller driver, you may need to line those cabs to stop them sounding. Damping can never stop them sounding, it just acts as a filter, damping some, passing other, phase delay releasing other, very little is actually absorbed and turned to heat. The boom is yours learn to control it not try to kill it. The enclosure space is just another smaller room the music is playing in - think about it.

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SteveTheShadow
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Re: Larger Semi-Omni Development

Unread post by SteveTheShadow » Wed Aug 02, 2017 5:28 pm

Oh yes, the cabs will be lined.
I always tend to post step by step, good or bad to show people the processes I go through when designing, building and optimising a speaker. It's much better than throwing a load of graphs and figures around.
Sometimes my method of describing what is going on, can give the impression that I'm an absent minded prof type, bumbling about and getting lucky sometimes, but nothing could be further from the truth.
I used to always test that a sealed box worked properly with its associated driver by stuffing a couple of overcoats or wool blankets inside, then putting some mid bass heavy music through it. It gives a general idea of what is going on and whether you are on the right lines with the design. It doesn't account for cab vibration but it's very effective as a general assessment method.
As you say Doc, you can't just rely on killing the energy inside the box by stuffing the hell out of it because it won't work. All you end up doing is taking half the music away along with (you hope) the offending resonances.

The bottom end is a major factor in creating atmosphere and enabling a listener to feel the presence of an acoustic. Slug it with a ton of stuffing and you have just taken out most of the venue or studio location cues, dried out the presentation and made a flat earth monstrosity; disastrous on most music.
BTE Designs modified Lenco L75 idler turntable, Rega R200 Tonearm, Goldring E3 MM cartridge, NVA Phono1 phono stage.
Mac-Mini music server with iTunes, AppleTV4 media streamer, Musical Fidelity M1 DAC,
NVA A20/P20, 25WPC stereo power amplifier/passive control unit,
own design, semi-omnidirectional, transmission line speakers- "The Flatback Banned".

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Dr Bunsen Honeydew
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Re: Larger Semi-Omni Development

Unread post by Dr Bunsen Honeydew » Wed Aug 02, 2017 5:39 pm

"Slug it with a ton of stuffing and you have just taken out most of the venue or studio location cues, dried out the presentation and made a flat earth monstrosity; disastrous on most music." And that is what 90% of speaker manufacturers do and not just flat earth, ever looked inside what is purported to be a BBC design..

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SteveTheShadow
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Re: Larger Semi-Omni Development

Unread post by SteveTheShadow » Wed Aug 02, 2017 6:11 pm

Never looked inside a BBC speaker, but I've seen cross sectional drawings.
I had some KEF Celestes once and did open them up to see what was in them. They were filled to the gunwales with fibrous stuff but had no treatment applied to the cab walls. They were OK, but nothing special; dry sounding and no atmosphere. With a Linn K9 cart, on a Basik plus armed Axis mk 1 through a Naim Nait2 I had a forensic lab, not a music system.

I remember Jimmy Hughes writing about taking out the damping from speaker cabs and extolling the benefits, but he only had half the story as obviously you can't take out stuffing without treating the cabinet walls. I tried it and yes it was better in some respects but was coloured to hell in the upper bass and lower mids.

Somebody then discovered Deflex panels and we started to get somewhere, but still you had to do them yourself as the manufacturers never took to them, probably due to price point constraints. Being a Yorkshireman I wasn't paying over the odds for Deflex panels and used stick-on flashband from the builders' merchant to good effect instead. :lol:
BTE Designs modified Lenco L75 idler turntable, Rega R200 Tonearm, Goldring E3 MM cartridge, NVA Phono1 phono stage.
Mac-Mini music server with iTunes, AppleTV4 media streamer, Musical Fidelity M1 DAC,
NVA A20/P20, 25WPC stereo power amplifier/passive control unit,
own design, semi-omnidirectional, transmission line speakers- "The Flatback Banned".

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Dr Bunsen Honeydew
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Re: Larger Semi-Omni Development

Unread post by Dr Bunsen Honeydew » Wed Aug 02, 2017 6:19 pm

Don't damp the walls, stiffen them give them mass. That stuff still holds and releases.

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SteveTheShadow
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Re: Larger Semi-Omni Development

Unread post by SteveTheShadow » Thu Aug 03, 2017 11:58 am

Woke up this morning and a complete design rethink is in progress.
I'll be back in a few days, with something.
That's my process right out there. It's the way I work.
They're used to it on A-T so hang in there folks.
BTE Designs modified Lenco L75 idler turntable, Rega R200 Tonearm, Goldring E3 MM cartridge, NVA Phono1 phono stage.
Mac-Mini music server with iTunes, AppleTV4 media streamer, Musical Fidelity M1 DAC,
NVA A20/P20, 25WPC stereo power amplifier/passive control unit,
own design, semi-omnidirectional, transmission line speakers- "The Flatback Banned".

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Dr Bunsen Honeydew
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Re: Larger Semi-Omni Development

Unread post by Dr Bunsen Honeydew » Thu Aug 03, 2017 12:20 pm

:dance: Steve you are the most fun to follow speaker designer out there, and all for the right reasons.

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SteveTheShadow
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Re: Larger Semi-Omni Development

Unread post by SteveTheShadow » Thu Aug 03, 2017 3:08 pm

;)
Revision:
Image
BTE Designs modified Lenco L75 idler turntable, Rega R200 Tonearm, Goldring E3 MM cartridge, NVA Phono1 phono stage.
Mac-Mini music server with iTunes, AppleTV4 media streamer, Musical Fidelity M1 DAC,
NVA A20/P20, 25WPC stereo power amplifier/passive control unit,
own design, semi-omnidirectional, transmission line speakers- "The Flatback Banned".

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