"The Flatback Banned" OmniMet

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Cressy Snr
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#1 "The Flatback Banned" OmniMet

Post by Cressy Snr »

Been out all day, but that patent from Roy Allison that the Doc pointed me to in the Omnimet thread, made intriguing reading. The man was clearly a genius, but as often happens with works of that stature, they don't quite make it for one reason or another. Pity he didn't do as well over here as he should have done.

Anyway, reading his bits about the distances to the boundaries, from the centres of the drivers being optimum when it was less than half of the narrowest dimension of the baffle it was fixed to, made me realise that the optimum on my design was not achievable because of the outward slope of the rear baffle.
I did a little experiment earlier this evening, which involved tilting the cabinets back so that the rear baffle became vertical, bringing the up-firing driver as close to the wall as I could get it. Not optimum of course because now the driver was angled backward at the wall. But doing that was enough to fill out the tone colours, solidify the stereo image, and give better depth perspectives; IOW a little more punch, voiced slightly differently for those who like a bit more welly.

In view of this, I've decided to add another OmniMet to the series. This one will have a flat back, so that the top driver can be positioned as close as possible to the rear wall. I'll get a prototype knocked up and see what gives.
I've called it "The Flatback Banned" in honour of one of my fave 70s funk groups, and to mark being banned indefinitely from hi-fi wigwam 'cos somebody found out I was a member of HFS. :lol: :lol: :lol:

Rough (and I mean rough) drawings below:
Image

So now we have three types: the straight Metronome, the OmniMet and the Flatback-Omni.
Let's see how this one pans out. I certainly seem to be on a creative roll at the 'mo. :)
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andrew Ivimey
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#2 Re: "The Flatback Banned" OmniMet

Post by andrew Ivimey »

Makes perfect sense to me...

Would actually pointing the driver at the wall (at what angle though) be a step too far?

What about upward pointing at say 45 degrees toward the corners as the two step (too far) version!?
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#3 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Hi Andrew,
The driver will just be pointing straight up rather than angled backwards at the wall.
Pointing upwards and sideways would make for an interesting and arty frontal aspect.
Might restrict where it could be placed, but it might be an interesting idea to store for future ref.
IIRC Shahinian do stuff like that and their speakers, though way beyond my means, seem to have an underground following.

Since building the Metronomes, then the OmniMets, my approach to speakers has changed completely. I've become a big fan of using the room to help the sound of your system rather than hinder it.
A nice, off the beaten track avenue to explore methinks. Omni sound for me seems to "just sound right"
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Ray P
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#4 Re: "The Flatback Banned" OmniMet

Post by Ray P »

Cressy Snr wrote: Sat Apr 22, 2017 11:02 pmSo now we have three types: the straight Metronome, the OmniMet and the Flatback-Omni.
Let's see how this one pans out. I certainly seem to be on a creative roll at the 'mo. :)
The flat-back should make the woodwork simpler too.

Ray
Sorry, I couldn't resist!
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#5 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Ray P wrote: Sun Apr 23, 2017 2:26 pm
Cressy Snr wrote: Sat Apr 22, 2017 11:02 pmSo now we have three types: the straight Metronome, the OmniMet and the Flatback-Omni.
Let's see how this one pans out. I certainly seem to be on a creative roll at the 'mo. :)
The flat-back should make the woodwork simpler too.

Ray
Too right it does.
The expansion horn type structure inside, is now simply two rectangles with simple bevels on the short edges, up against a vertical divider. No compound angles anywhere in the structure at all. :D
I now estimate cutting/assembly time at 2 days with veneering/ initial finish, one day plus final finishing in half a day.
That's 3 and one half days as opposed to a week.
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#6 Re: "The Flatback Banned" OmniMet

Post by Mike H »

andrew Ivimey wrote: Sun Apr 23, 2017 10:54 am Makes perfect sense to me...

Would actually pointing the driver at the wall (at what angle though) be a step too far?

What about upward pointing at say 45 degrees toward the corners as the two step (too far) version!?
I've seen this before, upwards, 90 degrees to wall, then you get a mirror image of the driver on the wall itself. Same as putting front driver speaker against a side wall.
 
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#7 Re: "The Flatback Banned" OmniMet

Post by Scottmoose »

Quite. A variation on the theme is how good nearfield arrays work, as Taylor & others demonstrated -it's just different boundary / boundaries in their case.
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Thermionic Idler
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#8 Re: "The Flatback Banned" OmniMet

Post by Thermionic Idler »

Wait... what? Since when was it okay to ban someone from a forum for being a member of another forum?? That's insane.

Loving the name Steve, and very interesting concept too. Looking forward to reading about these.
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#9 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

I had hardly visited the place in 18 months, and the reason given for my lifetime ban was a post I made 18 months ago in an argument with two forum "regulars" concerning the fact that CE and British Standards do not allow speaker drivers, stuffing or cabinet materials to be a source of ignition. It was like talking to a brick wall and I told them that.

I received a "you have been warned by Duvet" email 18 months after the fact, giving me 15 penalty points and a lifetime ban. Clearly they do not want my sort on their forum, which in itself I find quite funny. So referring to my speaker with that name just had to happen :lol: :lol:

It is clearly a "You're his friend so you can't be ours" situation, just like I have had to deal with from numerous bunches of 10 year old girls in every elementary school playground I've ever been on duty in. Similar in fact to a lot of the recent nonsense on here that arrives like clockwork, on cue, every time anything remotely controversial gets said.

Yes, the concept is interesting and as Scott and Mike have hinted at, bouncing the sound off a nearby room boundary is not a new idea. That Allison patent certainly increased my understanding of what is going on with my own speakers, and to an extent the Metronomes you have (with regards to the bass end).

Now I am rapidly becoming an evangelist for semi-omni operation. Shooting bass out of the bottom of a speaker cab to avoid setting the room going was my first attempt with the original Metronome. The method was copied from Castle's Harlech floorstanding speaker, which used a slot around the bottom of its cabinet to let the bass out, and of course the domestic home theatre sub market, that as a matter of course, tends fire it's bass drivers down at the floor.

For me as designer of the OmniMet, semi-omni operation is the final piece in the jigsaw that began with my first Mets and it was something I wasn't even intending to do. It hadn't even ocurred to me. Semi-omni, only came about because I was racking my brains, scribbling with a pencil and throwing screwed up sheets of paper about, trying to get a driver to sit half way along a folded, quarter-wave, quadratic expanding transmission line and still keep an elegant appearance to the outside of the truncated pyramid cabinet I was insisting on trying to use, in complete opposition to what anyone with any degree of common sense would have done.
Sitting the driver on the top of the cab, a la NVA Cube/ Allison 6, solved that particular problem, rather neatly, and the fact that as soon as I heard even the cardboard baffle, lash-ups sounding freaking awesome, made me realise I had got something rather special going on.

Combining down-firing, transmission line bass loading, with up and forward-firing semi-omni operation for the rest of the frequency range, just works beautifully well. OK the Doc is not entirely convinced by the bass loading I'm using, but as it is my design, I have to go with the loading that suits the driver I'm using.

I'm trying with this pair of semi-omni designs, fully tapered and flat backed, to marry three things together:

Musical communication
Audio cosmetics.
Visual cosmetics.
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Dr Bunsen Honeydew
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#10 Re: "The Flatback Banned" OmniMet

Post by Dr Bunsen Honeydew »

I will send you a pair of Cubes to try for comparison if you want. Though you will need stands for them, the advantage I see of your way is no stands.
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#11 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Dr Bunsen Honeydew wrote: Tue Apr 25, 2017 4:21 pm I will send you a pair of Cubes to try for comparison if you want. Though you will need stands for them...
That sounds like a plan to me Doc.
It would be interesting in lots of ways :)
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#12 Re: "The Flatback Banned" OmniMet

Post by Thermionic Idler »

Bloody hell, I've got a mind to see if I can get a room at next year's Scalford and exhibit the big Mets. "Oh yes, they do sound rather good don't they, these were designed and developed by a guy you BANNED for utterly spurious reasons, and I bought them to replace a pair of £6k commercial speakers that are quite well regarded in the industry".

How sad. Last year's Scalford was actually quite a good day out for us - highlights were some bloke announcing "welcome to the world of RRRRRRussian engineering", can't remember the name of the exhibitor but he was using a pair of Snell loudspeakers that looked remarkably similar to a model that Audio Note now sell - the Snell ones sounded a lot better (both were present). And of course I got to hear a Van Den Hul against lots of other manufacturer's offerings which helped me choose my next cartridge.

Just can't believe these guys would do anything so petty. Oh well, their loss.

I'd really like to hear these new creations when they're built. And "Flatback Banned" is genius! :lol:
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
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#13 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Cheers Dave, :wink:
I'm hoping to have both flat and tapered versions going at Owston in June, playing Herb Alpert, Matt Monro, Swing Out Sister, and Petula Clark.
Then they'll be "going" alright; straight out the window, along with my arse! :D :lol: :mrgreen:
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#14 Re: "The Flatback Banned" OmniMet

Post by Dave the bass »

"Herb Alpert, Matt Monro, Swing Out Sister, and Petula Clark"

:shock: Aaaaarrrhgghhhh!

I'm going to have to counteract that 'music' above with some extra-special specialist music I see ..... :)
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#15 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Yeterday, Apple Music slipped some terrifyingly specialist Mahavishnu Orchestra, and a bloody racket about summat to do with Willie Nelson by Miles Davis into a playlist whilst I was trying to read.
Bloody thing.
Have you hacked my account by any chance Dave? :D
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