lol neither do i.......but other 'experts' seem to think that using GR is 'basic' or something for beginners, and others use prime numbers or like you mentioned, fibonacci sequence. This is fine, but it can make these 'beginners' feel looked down upon by the doctors of maths that are here-although im sure in the most part this is NOT the intention.
Hi Mondogenerator, most certainly not the intention!
My maths (above about 6th grade level) sucks The primes seemed like a good idea at the time, but it depends on your measurement unit. I chose mm which is probably the worst because 1mm will make the difference between being prime or not, cm's might be better? Assuming you can get three (measurements) that meet your volume requirements. It would still be possible to build an inappropriate box (eg prone to pipe resonance) if the ratio is extreme in one dimension. I think from memory I started with one of the "accepted" ratios, and then found primes that were close to the various measurements that matched the ratio, so as not to cause potential problems... probably more a case of me being anal (or thinking I was clever) than any mathematical logic Tony.
Hi Mondogenerator, most certainly not the intention!
Tony.
Actually, units of measure are irrelevant- the important portion of the prime sequencing is the lack of base multiples- so there will be no overlap of frequencies reinforced. Ideally, these would be the lowest primes possible to maximize differential, so you should use the largest unit of measure you can to achieve the numerical distribution (without using 123). As long as the ratios are maintained, you're good.
This is really quite an interesting subject. I am building a self contained music system using a set of beovox 35 drivers and on the basis that I don't have access (yet) to a facility to test the Thiele-Small Parameters I thought whilst having some spare time I would knock up anow enclosure to see how the systems sounded. Having an interest in photography I arbitrarily chiselled a 4/3 dimension for the front (I had thought that just a front might help in testing free space parameters). At which point I thought why not expand on this approach and use phi to position the speakers. A bit of mumbo jumbo perhaps but interesting that by accident I have stumbled upon a possible means of speaker design. Thanks and would love to idea from anyone with suggestions or anyone device. This is a quite new but fascinating subject.
Thanks midrange, apologies for the ignorance but what is BSC? I have to admit that I have jumped in with both feet and have a huge amount to read up on. Is the discussion actually saying irrespective of the driver and it's TSP's you can generate an enclosure using ratios and arbitrarily chose depths. I have read somewhere waves lengths of certain frequencies are arbitrarily guide to the fundamental dimensions. But again, having skim read lots of threads and articles I can't remember if this relates to centre frequency of the response, a cross over frequency between each driver or the resonance ( I would expect B&OK to have kept this well out of the audio range.... but again I don't know a great deal at the moment
BSC is baffle step correction. It has to do with the way sound waves propagate, and how it affects the frequency response. Low frequencies will wrap around the speaker cabinet, and this can cause a 6dB loss. That is theoretical, and the response in a real room with limited space for sound waves to expand will be different. But a droop of several dB would be considered normal, and something that can be corrected with some response shaping in the crossover. The actual frequency where this occurs depends on the size of the cabinet or baffle the driver is mounted on. Wall mounting avoids this issue.
Ah, is this why a recessed speakers is important, to avoid any reflection and associated phase shift? Regarding frequency response I have two drivers, for which B&O have designed a cross over at 3khz. Do you, as I do, that this was done for cost saving and the inclusion of another driver to cover the mid range frequencies would be a better option to avoid a consistent response across the 2hz-20khz.
Another concern is that as frequencies increase there will be a 'roll off' of amplitude? Is this usually at the higher frequencies as they are absorbed more readily, assuming my cross overs and be designed to optimise the driver performance . Do I need to consider greater power at these amplitudes to keep a better audio quality.
Maybe if someone can provide a good design book to aid my understanding that would be great. I'm picking up bits from the Web but a go to guide would be great.
Cheers
Another concern is that as frequencies increase there will be a 'roll off' of amplitude? Is this usually at the higher frequencies as they are absorbed more readily, assuming my cross overs and be designed to optimise the driver performance . Do I need to consider greater power at these amplitudes to keep a better audio quality.
Maybe if someone can provide a good design book to aid my understanding that would be great. I'm picking up bits from the Web but a go to guide would be great.
Cheers
My take on the BBC thin wall design was that it was intended to allow low q resonance in the cabinet walls and to damp that well. They were looking for good intelligibility on voice and this contradicts your claim. Low Q is low amplitude and short duration.
Toole's take trumps your take....
https://books.google.com/books?id=t...nepage&q=toole resonance q audibility&f=false
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Not really. It depends how low the Q is and how much loss there is.
BBC-style thin-wall cabinets. Why so special? - Harbeth: made in the UK since 1977 - the world's most natural sounding loudspeakers
http://www.grahamaudio.co.uk/technology/cabinets/
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To be clear, this is a compensation. The 'lost' half of the power has been redirected. The correction applies to on axis pressure based on the assumption that the energy is lost. Is this what you meant to say?
This is about speaker cabinet resonances.
This is about room reflections.
Your comparing apples and oranges.
Both of cause are right, but speaker resonances is the topic here.
Toole's comments are still relevant and they are aimed at loudspeaker resonances if you read carefully.
This whole subject is complex and mostly driven by false assumptions etc. I have tried and tried to quantify loudspeaker cabinet resonances as a way to make judgments on cabinet construction, but I have never been able to find a clear example of a cabinet resonance in a far field measurement. I do make well damped cabinets and I believe that they make a small difference, but, after looking very carefully, I cannot substantiate this with actual data.
The best studies that I have seen, using FEA techniques, say that the cabinet radiation is usually very small unless one has a poorly designed cabinet. In this study the back panel, which was screwed on, was the only panel that radiated anything of significance. This makes perfect sense and suggests that the back panel should not be taken for granted. But all this detail on joint damping and thin walls, etc. appears to be without any supporting evidence.
This whole subject is complex and mostly driven by false assumptions etc. I have tried and tried to quantify loudspeaker cabinet resonances as a way to make judgments on cabinet construction, but I have never been able to find a clear example of a cabinet resonance in a far field measurement. I do make well damped cabinets and I believe that they make a small difference, but, after looking very carefully, I cannot substantiate this with actual data.
The best studies that I have seen, using FEA techniques, say that the cabinet radiation is usually very small unless one has a poorly designed cabinet. In this study the back panel, which was screwed on, was the only panel that radiated anything of significance. This makes perfect sense and suggests that the back panel should not be taken for granted. But all this detail on joint damping and thin walls, etc. appears to be without any supporting evidence.
There is a BBC published paper out there somewhere on the thin wall theory. The BBC still buy loudspeakers built to this principle from Harbeth for monitoring use.
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