"The Flatback Banned" OmniMet

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Cressy Snr
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#46 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Been auditioning them for the last hour and tweaking as I go. Ears in the first instance then checking with the spectrum analyser and pink noise for backup purposes.
Have got them singing now, with 3.3uF capacitor to the tweeter and a combination of tweaking the amount of stuffing in the end of the transmission line and gradually raising the height of the cabinet base above the floor by means of plywood blocks.
We're about two inches above the floor, with a small amount of damping in the narrow part of the line and they are really rather bloomin' good :lol: I'm well happy.

Getting those drivers right up to the wall has paid off handsomely in terms of soundstage size, depth and width. Stuff happening at the back of the studio or venue appears to be further back than the wall itself....crazy man.

Here's a pic taken earlier in the course of the auditioning process. As can be seen, the cab bases are quite close to the floor. They are higher now:
Image
Last edited by Cressy Snr on Sat May 20, 2017 4:31 pm, edited 3 times in total.
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#47 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Now I need to do the very fine adjustments to the cab heights, but we are just about right now.

There may be a case for making some short, 'fifties style tapered legs, a couple of inches long, to match whatever veneer they get, and give a nice retro look. These will raise the cab to the right height and look totally cool into the bargain.

So now I have two products that look the biz and sound the biz. I think within the obvious bass limits set by the Fs of this little driver, I have probably wrung as much out of a Faital 6PR110 as is possible at the bottom end, but it is the super mids this driver gives that is the defining characteristic of these two speakers. The rest is the icing on the cake.
It would seem that there is no end to my talents.

Just in case however, I'm working on my excuses for Owston. :lol:
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Dr Bunsen Honeydew
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#48 Re: "The Flatback Banned" OmniMet

Post by Dr Bunsen Honeydew »

I would try casters, good solid old fashioned metal ones. They couple very well I have found and will make hoovering life much easier for the missus, WAF factor :mrgreen: This guy does a wide variety http://www.ebay.co.uk/itm/Industrial-fu ... QGBGKwAW-w

You may get some resistance for selling as people don't understand coupling v uncoupling. The other thing I would do is increase weight and mass of the cabinet. As it is ply it wont need steel plate but a heavy lump at the bottom out of the way somewhere will surprise you what it will do for the bass.

You are now getting something I would be glad to put my name to, Can't wait to hear and for you to compare with 2's (BTW on their way to you Monday, PM me deliver address and phone number).
Cressy Snr
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#49 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Richard, you have a PM.

Thanks for that link...some great industrial looking castors there; just the thing for a hipster pad.
Last edited by Cressy Snr on Sat May 20, 2017 6:01 pm, edited 2 times in total.
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#50 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Frontal aspect, showing the very close proximity of the rear boundary to the main drivers. The left hand is not ideal but later this year, the staircase wall will be reinstated, so that particular problem will be removed.

Image

A bit of a dim pic as it is p*ssing down up here, but it shows very well the all-of-a-piece, purposeful "media centre" look these speakers give to the TV bench/screen setup. Once they are veneered in oak, they will match the TV bench very nicely.
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#51 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Oh the horror!
My speaker prototypes have castors! :shock:

Image

Nothing wrong with the sound either. :D

They are only cheap ones from B£Q at a couple of quid for four (reduced from £9) but yep they don't harm the sound at all....nice.
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pre65
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#52 Re: "The Flatback Banned" OmniMet

Post by pre65 »

Looking forward to hearing them at Owston.

I'm old enough to remember when castors on floor standing speakers was de rigueur. :lol:
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#53 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Aye, the hi-fi myths are dropping like nine pins (under certain circumstances) :wink:
My audio crediblity is now so far gone, there's no getting it back. :lol:
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#54 Re: "The Flatback Banned" OmniMet

Post by pre65 »

Cressy Snr wrote: Sun May 21, 2017 2:51 pm
My audio crediblity is now so far gone, there's no getting it back. :lol:
Like your (and my) taste in music ? :lol:
The only thing necessary for the triumph of evil is for good men to do nothing.

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#55 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Probably :mrgreen:

However, being serious for a moment, the forces being generated in my speaker are not like those generated in conventional ones, due to the up firing main driver. The reactions are mostly in the vertical plane ie directed at the floor and upwards away from the cabinet on alternate cycles, so there is no rocking motion being set up as there would be in a normal front-firing speaker.
The weight of the cabs is sufficient to fix things in space (would probably be even better with some weight in the base of the cab, as the Doc has commented on earlier) so there is little need for spikes as the things will couple through the castors perfectly well.
My mate and his missus were here last evening and they both commented. Though neither of them are hi-fi types, theynknow their music. "Lovely gentle musical sound" "no harsh notes" were a couple of observations they made. That was encouraging as that kind of thing is exactly what I'm aiming for.
I've longed for this kind of sound for all my 40 year period in hi-fi, and only recently have I come anywhere near to achieving it.
Whether the quality I've achieved is for everyone, is another matter entirely, but I believe wholeheartedly in this sound.
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#56 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Right,
Have a pair of the Doc's Cube 2s on loan at the moment and they are frankly superb sounding little buggers. I'll do a review on here and HFS, once I've listened a bit longer to them.
What they did though was to shine a spotlight on a certain lack of air and space coming from my own flatties in comparison.

I had said that the crossover cap would probably need attention on my own speakers due to the closer proximity of the main driver to the wall when compared to the pure OmniMets; well the Cube 2s certainly showed that the flatties indeed needed attention to the cap value.

So...I changed the cap value in the crossovers on the flatties from 3.3uF to 5.6uF easing the xover lower, and whaddya know the missing air and space came out. Images float free and height is much better. I think we are now about there with the flatties. Maybe they could stand another 1uF in parallel with the 5.6 to ease the xover freq that little bit lower, but this value is a definite improvement on the 3.3.

Here's the third octave spectrum analyer report showing the response of the flatties with the 5.6uF crossover cap.
Not bad at all between 50Hz and 20kHz.
Image
Last edited by Cressy Snr on Tue May 23, 2017 5:24 pm, edited 1 time in total.
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Dr Bunsen Honeydew
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#57 Re: "The Flatback Banned" OmniMet

Post by Dr Bunsen Honeydew »

Can you do a chart on the Cube 2 as they have never been measured, it may be interesting.

I use 3,3mfd, but different drivers different cap. I always call it the start point in Doc Mods.
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#58 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Yep, I'll do it later this evening.
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#59 Re: "The Flatback Banned" OmniMet

Post by Cressy Snr »

Ok Doc, here is the Cube chart:

Image

Remarkably similar to my flatties apart from the better bass extension.
It was difficult to match the levels with my own due to the differing efficiencies of the two systems.
I ended up with yours 2dB louder than mine on the pink noise test as I don't have a laboratory full of test gear, but I think the data, is sufficiently good to show the similarities and differences up nicely. The spike at 80Hz will be down to the box being a bit closer to the wall than ideal.

The really good bit from both charts is the flat midband to treble region, which shows in my case, the super complement between the Faital driver and the SB Acoustics ring tweeter, and in your case, the effectiveness of the doping strategy and the match to the tweeter with your drivers.

I think you have your vindication of the "speaker not fighting the room" aspect of your design right there in the chart.
It also shows how bloody good our ears are as speaker evaluation tools. :lol: :mrgreen:
Last edited by Cressy Snr on Tue May 23, 2017 7:13 pm, edited 1 time in total.
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#60 Re: "The Flatback Banned" OmniMet

Post by Dr Bunsen Honeydew »

Not bad voiced by ear 8) :P :wink:
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