Not another bleeding omni FFS!

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Cressy Snr
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#61 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Not disputing the tightness of IB bass Doc.
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#62 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

OK,
Here's the cross sectional drawing of the speaker:
Image
Not quite to scale, but it'll do for illustrative purposes.
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#63 Re: Not another bleeding omni FFS!

Post by steve s »

Dr Bunsen Honeydew wrote: Fri Aug 04, 2017 2:31 pm I find any line or port causes a phase (musical timing problem), so I wont use them, but I have an open mind, you might have solved that, you never know.

I am a sealed box man. Or just maybe with some persuasion an open baffle man, but not commercially.
Steve does tend to get a good balance at the bottom end, but i too dislike the ported sound effect, which it what it is

years ago I called it ducati bass.. And still stand by that !
Too slightly out of phase bangs make a boom.. But that boom sounds right to some
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#64 Re: Not another bleeding omni FFS!

Post by Nick »

I am intrigued, why Ducati? Is it because of the 90 degrees?
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#65 Re: Not another bleeding omni FFS!

Post by steve s »

Nick wrote: Wed Aug 09, 2017 1:29 pm I am intrigued, why Ducati? Is it because of the 90 degrees?
I knew you would bite on that one Nick
Yes the old 90s yam Trx had the same sound... with an exhaust on of course, the two bangs overlap to the ear... making a boom
Ported speakers have a very similar effect on the sound.. good ones may sound impressive but the bass is not what's on the recording . then room / amp / position soon muck things up...
Remember that afternoon at mine comparing ob bass to the Angel horns
All I could hear at first was the difference between those fostex 167 and the lowthers
Then after a painstaking time the penny dropped.. the bass was so much cleaner and real
I then realised over the next few years that a lot of people also don't hear what's there when it comes to hi fi...
It's all so easy to just listen to the good bits of any system... and have a mental block on what's not quite right.. i know that too well.

But you can't ram it down people throats when they don't hear it/ get it

I'm think Steve gets a good balance on his ported designs .. in the main down to Scott's design support on the mets which worked so well and gave Steve a good start
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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#66 Re: Not another bleeding omni FFS!

Post by Nick »

Yes the old 90s yam Trx had the same sound... with an exhaust on of course, the two bangs overlap to the ear... making a boom
I guessed that what you meant but the trx was a parallel twin, though I guess it depended on the way the cranks were offset.
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#67 Re: Not another bleeding omni FFS!

Post by pre65 »

Nick wrote: Wed Aug 09, 2017 4:56 pm
Yes the old 90s yam Trx had the same sound... with an exhaust on of course, the two bangs overlap to the ear... making a boom
I guessed that what you meant but the trx was a parallel twin, though I guess it depended on the way the cranks were offset.
270° parallel-twin engine.
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#68 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Well chaps.
Regarding the bass daboom-daboom Ducati sound. I have done a quick calculation of the cabinet volume and it falls on
Qtc = 0.85 for a sealed cab. Sooooo....

An educational bake-off can be carried out with transmission line versus acoustic suspension bass once the cabs have been fully built up. How's that for a bit of fortuosity? Of course I played for that (yeah right) :lol: :lol:

When the Doc got me to seal the port on the smaller model, the bass disappeared; mainly because the 6PR110 is simply not suited to sealed cab operation. The 10FE200 is a different animal. This could get very interesting.
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#69 Re: Not another bleeding omni FFS!

Post by steve s »

pre65 wrote: Wed Aug 09, 2017 5:00 pm
Nick wrote: Wed Aug 09, 2017 4:56 pm
Yes the old 90s yam Trx had the same sound... with an exhaust on of course, the two bangs overlap to the ear... making a boom
I guessed that what you meant but the trx was a parallel twin, though I guess it depended on the way the cranks were offset.
270° parallel-twin engine.
Thats right 90° between firing ..they made a lovely sound for a parallel twin, with the right exhaust of course .. but pinking in the cold and a crap gearbox
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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#70 Re: Not another bleeding omni FFS!

Post by steve s »

10" seems a big driver but it not really..
I have a pair of 10" wharfedales with big magnets ..supers I think.. in a 2 cub feet ported cabs they are a nice sound and do good bass..
I should get them out, along with the quad corner ribbons for a session once yours are done Steve
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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#71 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Sounds like a plan Steve.
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#72 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

After Neal's visit yesterday, I've decided I really MUST get on with these. I'll have to run the build in parallel with the SET; jumping between projects if I get bored with the other.
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#73 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Another redesign is currently underway. The basics, such as line length, expansion rate, mass loading port are all intact; it is the cabinet shape that is about to be changed to three sides straight, one side sloped and the cabs mirror imaged. The sloping top surface is to be ditched, so that the 10" driver fires straight upwards as it does in the smaller semi-omni.

Listening to the improvements to the sound of the smaller speakers currently doing service in the system, gained by the simple expedient of rotating the cab 90 degrees so that the slopes are mirrored to the outer edges of the cabinets, is an interesting experience. This has led to the conclusion, that for the chosen Allison/Dunn semi-omni arrangement to work at its optimum, the effectiveness of bass/mid driver to wall coupling is a major factor in the sound they make.

Because of the deliberate policy I adopted, of designing specifically for near wall placement to hold up the bottom end I can take absolute, maximum advantage of the close wall coupling of the up firing driver, and the problem of the slight midrange dip that bothers some people has been resolved to my satisfaction, and without having to mess with the crossovers in any way. I think the mid lift it is a combination of very hard wall coupling and the now assymmetric placement of the tweeter on an assymmetric front panel; either way it works beautifully.

So, the design of the larger speakers has been informed by the outcomes of the experiments with the smaller ones.
Drawings will follow soon.
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#74 Re: Not another bleeding omni FFS!

Post by ed »

steve s wrote: Wed Aug 09, 2017 3:02 pm

But you can't ram it down people throats when they don't hear it/ get it

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#75 Re: Not another bleeding omni FFS!

Post by Cressy Snr »

Cressy Snr wrote: Tue Sep 19, 2017 12:22 pm The sloping top surface is to be ditched.
No it isn't, I've decided to do a two way flooder for this one à la Mr Winlsow Burhoe of Direct Acoustics.com
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