Not another bleeding omni FFS!

Dedicated to those large boxes at one end of the room
simon
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#31 Re: Not another bleeding omni FFS!

Post by simon »

Good stuff, thanks all. So my thinking was a relatively small speaker for the lounge - OB midrange driver sat on top of an IB bass driver. With efficiency of 95+dB so I can use my low powered valve amps. Steve's design is 3 cu feet, which isn't as small as I like, but is around 96dB?

Whether matching an OB mid with an IB bass is a sane idea I'm not so sure - I've not seen too many about.
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#32 Re: Not another bleeding omni FFS!

Post by steve s »

simon wrote: Tue Jul 18, 2017 11:53 pm Good stuff, thanks all. So my thinking was a relatively small speaker for the lounge - OB midrange driver sat on top of an IB bass driver. With efficiency of 95+dB so I can use my low powered valve amps. Steve's design is 3 cu feet, which isn't as small as I like, but is around 96dB?

Whether matching an OB mid with an IB bass is a sane idea I'm not so sure - I've not seen too many about.
Ob mids is good, wharfedales top of the range in the 60's was type of box bass and ob mids

I've just taken apart some well made speakers from 1970. They where goodmans 15" in large boxes + wharfedale super 10 and super 5 in ob.. Great sounding combination, but too much in the crossover took the edge off the sound
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
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#33 Re: Not another bleeding omni FFS!

Post by IslandPink »

simon wrote: Tue Jul 18, 2017 11:53 pm Good stuff, thanks all. So my thinking was a relatively small speaker for the lounge - OB midrange driver sat on top of an IB bass driver. With efficiency of 95+dB so I can use my low powered valve amps. Steve's design is 3 cu feet, which isn't as small as I like, but is around 96dB?

Whether matching an OB mid with an IB bass is a sane idea I'm not so sure - I've not seen too many about.
Dear Mr. Ron Hopeful -
How about <90dB/w ? :D ( for a smaller box )
First things first - I think OB mids and IB bass is a good option, one I have toyed with on paper and could still try at some stage.

If you want a smaller box, you have to accept less efficiency - it's a rule ( and must come down to some laws of physics I'm sure ) . The SB one I mentioned needs at least 150L , and is around 90dB/w for a 'textbook' Qtc of 0.7 . If you go down to small boxes like RD's then you're looking at 85dB/w tops.
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#34 Re: Not another bleeding omni FFS!

Post by simon »

I know I know, I want the moon on a stick. (And if I can't have it I'm going to sulk and stamp my feet :-)) Your SB example was illuminating for me, thanks.

I'd better shut up now and let Steve have his thread back. It's been very useful, and it'll be interesting to see how you develop it.

(Further thoughts on Steve's 15" Celestions required...)
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#35 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Right, the ply has been obtained, so I'll get going on the cutting list for the bass boxes tomorrow.
These will be the first part of the project and will be optimised properly before the midrange and treble box is built.

Adequate bracing is the hook on which will hang the success or failure of these bass cabinets.
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#36 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Bass boxes under construction:
Image

Image

Front panel is inset by half an inch.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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#37 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

One pair of roughed up bass boxes:
Image
Bracing etc will be installed later this week.

Very retro :wink:
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#38 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Been researching 1960s and '70s radiogram images this afternoon, and the speaker grille variations from this era are fascinating in either their beauty or their sheer hideousness.

For the bass boxes, I'm going for a two part front panel trim; the upper half being plum coloured rexine in the grand Dansette tradition, whilst the lower grille covering the bass driver is a cream coloured basketweave, behind 2" spaced, half inch dark hardwood square section, polished vertical slats. Veneer will be blonde wood.

I'm going all out for the early 1960s look for these speakers, because the wider than deep profile is never going to compete with the tall, slim, line arrays normally found in today's hi-fi rooms. These will be the polar opposite of everything that common sense says the modern listener wants.

Forensic dissection of the music is out, hyper detailed sterility is out, pinpoint imaging is out, hi-fi is right out.
Warmth is in, room filling widescreen presentation is in, fun is in, music is in. Hi-fi can go stick itself where the sun don't shine. I no longer care about hi-fi. I'm building for me and if others like what they hear, that's great; if they don't then whatever. I am building what I believe in, I'm not about to be second guessing all the time, playing non stop fecking catch up.

Have cut the depth down to 11.5 inches which has pushed the internal volume of the bass box down to 2.3 cu ft, pushing the bare box qtc to 0.95, however the stuffing, if done properly, should pull the volume seen by the driver back up a bit.

Fitting the back on with duck tape, laying the box on its back, shoving a BAF filled cushion inside and dropping the driver in, it passes my cone tap test beautifully, giving just a dull thud, with no echo and that without any bracing or lining, so things look good for the bass boxes.
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#39 Re: Not another bleeding omni FFS!

Post by steve s »

Forensic dissection of the music is out, hyper detailed sterility is out, pinpoint imaging is out, hi-fi is right out.
Warmth is in, room filling widescreen presentation is in, fun is in, music is in. Hi-fi can go stick itself where the sun don't shine. I no longer care about hi-fi. I'm building for me and if others like what they hear, that's great; if they don't then whatever. I am building what I believe in, I'm not about to be second guessing all the time, playing non stop fecking catch up.
Good for you Steve... can't wait to hear and see them.
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
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#40 Re: Not another bleeding omni FFS!

Post by steve s »

simon wrote: Wed Jul 19, 2017 1:07 pm I know I know, I want the moon on a stick. (And if I can't have it I'm going to sulk and stamp my feet :-)) Your SB example was illuminating for me, thanks.

I'd better shut up now and let Steve have his thread back. It's been very useful, and it'll be interesting to see how you develop it.

(Further thoughts on Steve's 15" Celestions required...)
Just re read this Simon.. If it was about the speakers I had just taken apart, they where a pair of Goodman 81's.
they have nice light paper cone, big powerfull magnet and are 25 watt rms, in my view perfect ? My view is they beat any of the tannoys...
They are my second pair and I have an idea to implement them all in an unusual way
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
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#41 Re: Not another bleeding omni FFS!

Post by simon »

Thanks Steve, I meant I needed to think more, but I'll always listen to good advice :-).

I have some slightly damaged Goodmans 401s and a pair of 51s put away for a rainy day. I've never found any T/S parameters for them though so I'd be in the realm of experimentation with them, and I don't have the experience for that yet. Can't help thinking they should make nice bass helpers in a box though?
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#42 Re: Not another bleeding omni FFS!

Post by Thermionic Idler »

Cressy Snr wrote: Sun Jul 30, 2017 10:56 pm Been researching 1960s and '70s radiogram images this afternoon
Who hasn't spent a happy Sunday afternoon doing exactly that. i know I have. Quite frequently.

These are going to look great, I just know it. Looking forward to hearing them.
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#43 Re: Not another bleeding omni FFS!

Post by chris661 »

Simon, let me know if you'd like the drivers measuring - T/S takes a few minutes. Frequency response plots take a while longer.

Chris
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#44 Re: Not another bleeding omni FFS!

Post by simon »

Cool, thanks Chris! Next time I'm up in the loft I'll look them out. I'm almost sure I know where they are :-).
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#45 Re: Not another bleeding omni FFS!

Post by IslandPink »

Next to the Fostex 208 cabinets ?
"Once you find out ... the Circumstances ; then you can go out"
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