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Post by MartinT on Mar 24, 2015 14:06:53 GMT
The problem with steel plates in anything other than a simple box is that you'd never match the shape with the cabinet walls.
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Post by ChrisB on Mar 24, 2015 14:10:59 GMT
I think it's accepted that complete coverage is unlikely to be possible Martin - especially if you're going in through the bass driver hole! Adding mass is the goal. It would be easier with some of the BBC type designs where the entire back comes off. I added 12mm of steel to my SD OBSs - albeit to the underside - years and years ago and it was one of the best value modifications I ever made to my gear.
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Post by danielquinn on Mar 24, 2015 14:13:27 GMT
steel doesnt have a fixed resonant frequency, it will depend on its properties. 5mm glued to wood will resonate at a frequency well outside the audio spectrum .
magico are of course making an enviable reputation for metal bodied speakers . But at a price .
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Post by Deleted on Mar 24, 2015 14:43:43 GMT
Unfortunately no. The resonant frequency depends on Square Root (stiffness/mass). That is not too surprising - if something is stiffer with the same mass, the resonant frequency goes up. And if its mass goes down (and the stiffness stays the same) the resonant frequency goes up.
That actually is why honeycomb structures are used in many applications (space vehicles, high end audio etc) - very low mass, and very high stiffness. So the resonant frequency wins out and goes up.
Unfortunately adding steel plates to wood increases the stiffness and also the mass - so the resonant frequency will remain much the same.
The effect of adding steel plates is likely to improve sound quality through two mechanisms:
(i) Even though the resonant frequency will be by and large unchanged, the amplitude by which the panel deflects under the acoustic pressure changes in the box will be lower. So the panel vibration will go down - you could verify that by buying a stethoscope from eBay and doing a subjective before and after.
(ii) Depending on the adhesive used to bond the steel to the wood, you might get a constrained layer damping effect. If the adhesive is flexible (silicone bath sealant etc), then although the resonant frequency will be about the same (by the above argument) the Q will be much reduced, so it will have a smaller impact on the sound.
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Post by MartinT on Mar 24, 2015 14:51:52 GMT
magico are of course making an enviable reputation for metal bodied speakers . But at a price . I have liked one Magico demo very much but on another occasion didn't think much of their dry sound. I think I prefer Wilson overall, at a similar price, who also put a great deal of their resources into dead cabinets.
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Post by MartinT on Mar 24, 2015 14:54:04 GMT
My speakers are 130kg each with 30kg of lead shot in the base compartment making 160kg total each.
Do you think I need more mass?
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Post by pre65 on Mar 24, 2015 14:58:34 GMT
Unfortunately no. The resonant frequency depends on Square Root (stiffness/mass). That is not too surprising - if something is stiffer with the same mass, the resonant frequency goes up. And if its mass goes down (and the stiffness stays the same) the resonant frequency goes up. That actually is why honeycomb structures are used in many applications (space vehicles, high end audio etc) - very low mass, and very high stiffness. So the resonant frequency wins out and goes up. Unfortunately adding steel plates to wood increases the stiffness and also the mass - so the resonant frequency will remain much the same. The effect of adding steel plates is likely to improve sound quality through two mechanisms: (i) Even though the resonant frequency will be by and large unchanged, the amplitude by which the panel deflects under the acoustic pressure changes in the box will be lower. So the panel vibration will go down - you could verify that by buying a stethoscope from eBay and doing a subjective before and after. (ii) Depending on the adhesive used to bond the steel to the wood, you might get a constrained layer damping effect. If the adhesive is flexible (silicone bath sealant etc), then although the resonant frequency will be about the same (by the above argument) the Q will be much reduced, so it will have a smaller impact on the sound. Thanks Craig, I see you had a spell at one of the major UK speaker manufacturers.
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Post by danielquinn on Mar 24, 2015 15:01:38 GMT
If the resonant frequency is "a natural frequency of vibration determined by the physical parameters of the vibrating object."
I fail to see how it can remain the same if steel is added ?
I agree that the metal lining will make the cabinet less active shall we say .
constrained layer damping sounds like another form of attenuation similar to wadding
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Post by jandl100 on Mar 24, 2015 15:13:36 GMT
The problem with doing adhoc mods to a well thought out design is that you could be jeopardising overall performance in a random manner - most folk simply don't have the tools to see what would happen if you mod the cabinet, for example.
You might like the result, which is fair enough - but it may not be more accurate.
Ya ain't getting your hands on my MBLs !!
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Post by pre65 on Mar 24, 2015 15:15:10 GMT
If the resonant frequency is "a natural frequency of vibration determined by the physical parameters of the vibrating object." I fail to see how it can remain the same if steel is added ? I agree that the metal lining will make the cabinet less active shall we say . constrained layer damping sounds like another form of attenuation similar to wadding Constrained layer damping is one reason why Baltic birch plywood is good for speaker cabinets and slate is good for turntable plinths.
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Post by danielquinn on Mar 24, 2015 15:16:56 GMT
What makes you think it is well thought out design most designs except for the very very expensive are built with compromises and I bet dealer speakers actually have less than 10% of the purchase price on materials . Thus a 10k speaker probably as less than £1000 in parts .
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Post by danielquinn on Mar 24, 2015 15:17:51 GMT
If the resonant frequency is "a natural frequency of vibration determined by the physical parameters of the vibrating object." I fail to see how it can remain the same if steel is added ? I agree that the metal lining will make the cabinet less active shall we say . constrained layer damping sounds like another form of attenuation similar to wadding Constrained layer damping is one reason why Baltic birch plywood is good for speaker cabinets and slate is good for turntable plinths. Says who and for what reason ?
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Post by pre65 on Mar 24, 2015 15:29:35 GMT
Constrained layer damping is one reason why Baltic birch plywood is good for speaker cabinets and slate is good for turntable plinths. Says who and for what reason ? You are more likely to take it in if you do some research on the subject.
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Post by John on Mar 24, 2015 15:36:27 GMT
With regards to mass I think it will depend on the design of the speakers so I can see being important for boxed speakers whilst with OBs not as critical. Good isolation from the baffle is important with OB and the size can be quite critical depending on the drivers used I am totally comfortable with some speakers sounding better with insulation and some without.
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Post by danielquinn on Mar 24, 2015 15:39:02 GMT
If you make a point on a forum and you are expecting people to take it seriously it is for you to elucidate your point or dont expect people to take it seriously .
i have read a lot of bollocks about CLD , it just seems to be a fancy name for a filter or attenuation .
hifi is awash with bastardised science propping up cod explanations .
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Post by John on Mar 24, 2015 15:42:35 GMT
Guys this was supposed to be a friendly thread. Lets get back on track around speaker Myths
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Post by John on Mar 24, 2015 15:45:21 GMT
I really do not want to start moderating but will if this continues
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Post by danielquinn on Mar 24, 2015 15:46:06 GMT
Ta, I do , but if i did not comment, your comment would stand in isolation and as TONYC as pointed out that would simply not do for DQ the moral crusader for truth in hifi ps - calm down john
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Post by Deleted on Mar 24, 2015 15:55:14 GMT
What makes you think it is well thought out design most designs except for the very very expensive are built with compromises and I bet dealer speakers actually have less than 10% of the purchase price on materials . Thus a 10k speaker probably as less than £1000 in parts . The pricing of speakers is an interesting topic. Each part of the chain from manufacturer to customer adds 50% or more to the price. Lets say you have a raw material cost of £1000 and 50 hours of build time and finishing in a high end loudspeaker - so a total of around £2500 prime cost once packing materials are taken into account. You sell those to an importer for £2500 + 50% = £3750. That means that the manufacturer has a gross margin of £1250 to the manufacturer. The importer sells them to the dealer for £3750 + 50% = £5600. And the dealer sells them for £5600 x 1.5 = £8400. Now do the sums. How many are you going to build of these £10k loudspeakers? Market in the UK, 1 pair per month say - big competition and vanishingly small market. Global market (problematic in its own way) say ten times that, 10 pairs per month, 120 pairs per annum. That gives the manufacturer a gross margin of £150,000 per annum, or £100k after tax. From that the manufacturer has to fund development of new products, and service any loans they have taken out to finance the business. And it is those hard facts behind the "10% of the purchase price on materials . Thus a 10k speaker probably as less than £1000 in parts" which explains why so many loudspeaker companies end up defunct. Even big ones are often saved from financial disaster by being bought by the Chinese and Koreans. Not just speaker companies - audio electronics companies too - lots and lots end up going into receivership.
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Post by pre65 on Mar 24, 2015 15:55:52 GMT
hifi is awash with bastardised science propping up cod explanations . Sorry Daniel, but that sounds a bit fishy.
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