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Offline Simon Briggs  
#21 Posted : 29 December 2008 16:43:02(UTC)
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Some good ideas floating around here, sealed bass will be used but a Nola style mid using a light sensitive 170mm cone Hmm....
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#22 Posted : 29 December 2008 17:34:07(UTC)
zonepress

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There is also the neat-looking concept of cardioid bass:
http://www.aes.org/e-lib/browse.cfm?elib=12663
http://www.wvier.de/text...cial%20of%20Coupling.pdf
which is not quite new:
http://www.lansingherita...ro-systems/814/page1.jpg
but (unless one can engineer a semi-enclosure with a lossy back, like Altec or Geithain) it involves a dipole and a monopole, i.e. at least three LF drivers per channel: a tall order.
The good thing about the latter is that one may infinitely vary its radiation pattern from monopole to cardioid to dipole and back very easily, e.g. use one stereo amp per channel, drive the dipole with one channel and the monopole with the other, and then play with the balance control.
BigGrin

Edited by user 29 December 2008 17:38:42(UTC)  | Reason: Not specified

Sumer is icumen in!
Offline dcathro  
#23 Posted : 29 December 2008 21:12:22(UTC)
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Keith wrote:
Because they use such relatively cheap drivers?


The accuton drivers used in Avalon speakers are certainly not cheap!
Keith  
#24 Posted : 29 December 2008 21:39:49(UTC)
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Compared to good compression drivers they are.
Offline dcathro  
#25 Posted : 29 December 2008 21:56:00(UTC)
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Keith wrote:
Compared to good compression drivers they are.


Not an area I have played with. Can you give some examples and figures?
Offline Simon Briggs  
#26 Posted : 29 December 2008 22:26:45(UTC)
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At the moment I have decided for design number two to look at the sealed box option, I will have a play with a few basic drivers over the next few days and come back with my thoughts. I will still consider units in the 220-300mm bracket.

DM
Offline Henry Cleo  
#27 Posted : 30 December 2008 00:26:14(UTC)
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What about the Jordan JX92S?

Over on the DIy audio boards, veteran designer Ted Jordan's JX92S has a keen following. It's a versatile 4 inch "full range" driver which can sound amazingly clear and fast, and can produce ridiculous bass for its size when in the right enclosure. I use a pair in transmission line cabinets and there is plenty of bass. It is also used in a number of commercial designs.
There are 3 problems:
They're aluminium and can get peaky at around 16K - but there are various recipes for calming the peaks. Then you have a single driver which can cover from below 50Hz to 20kHz
They're expensive - but many of the designs don't have any crossovers.
They're 5 Ohms - but someone has designed a Zobel
Personally - I love them, and I know a guy who sold his electrostatics when he heard them.
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#28 Posted : 30 December 2008 00:38:31(UTC)
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Henry Cleo wrote:
can produce ridiculous bass for its size when in the right enclosure
I'm afraid this is fake bass. It reminds me of this trick we did as kids: prop our handeld transistor radios on teacups to fill out the sound. Just making various air cavities resonate so that they can make an impression. Bass means lots of real air moving in a real fashion, there is no way around this.
Sumer is icumen in!
Offline Henry Cleo  
#29 Posted : 30 December 2008 07:54:40(UTC)
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zonepress wrote:
Henry Cleo wrote:
can produce ridiculous bass for its size when in the right enclosure
I'm afraid this is fake bass. It reminds me of this trick we did as kids: prop our handeld transistor radios on teacups to fill out the sound. Just making various air cavities resonate so that they can make an impression. Bass means lots of real air moving in a real fashion, there is no way around this.


You’re right – it is “fake bass”, but isn’t all hifi sound “fake”? It is after all just an attempted reproduction of an event or performance that often never took place in the form in which it is presented. Many performances are assembled from different takes or tracks laid down at different times and assembled into the illusion of a single seamless event by editing and then enhanced by mixing and processing We know we are not at a real event listening to real musicians performing in real time, but we become complicit in the illusion through what Aristotle called the “suspension of disbelief”. We enjoy the self-deception of the pretence but we know it isn’t real.

Within the limitations of its size, the JX92S can do a wonderful job of creating the illusion of bass notes. Perhaps I should have said “ridiculously deceptive amounts of illusory bass for a speaker of its size”.

By the way I use them with a subwoofer and am looking at design using them as the mid in an open baffle with an 18 inch woofer.
Offline Cemil  
#30 Posted : 30 December 2008 10:36:43(UTC)
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Keith wrote:
Because they use such relatively cheap drivers?


I think Magicos use expensive drivers (mind you only 2 of them in the Mini 2) and very expensive crossover parts. Still, most of the considerable money goes into the superb box. Wilson uses cheaper (but more) drivers for an equivalent priced model AFAIK, but are equally obsessed with the box. Avalon's drivers aren't cheap either ..

I specially referred to Magico Mini as it is basically a mini-monitor (gone extreme, for sure), and a striking example of what can be achieved when the cabinet is done right.
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#31 Posted : 30 December 2008 13:19:35(UTC)
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The indefatigable Zaph has posted some Le(X) measurements on drivers he has tested:
http://www.zaphaudio.com/Le(x)
The vagaries of voice coil inductance variation depending on displacement are many. As far as I know, such specs are not widely available. I suspect that this is partly due to the fact that it might reveal substandard quality on behalf of driver manufacturers. There are only two ways to eliminate this source of nonlinearity: one is to make a voice coil much, much shorter than the magnetic gap, so that the coil always moves within a uniform magnetic field while constrained by its mechanics. The other way is to make the coil much, much longer than the gap, in which case the total flux remains unchanged, albeit a certain number of coil turns always remain "unused" as far as force generation is concerned. The former way is expensive, because it calls for a very large magnet. The latter is cheap. I guess most manufacturers go for the middle way, which is probably the worst because it makes force generation vary with displacement, and therefore not proportional to current alone as it should be. As far as I know, there is no way for DIYers to obtain these parameters other that measuring them for themselves, or hiring the services of consultancy firms like Klippel. There is magazine called "Voice Coil" that may be doing such tests, but it is strictly a trade publication, so I cannot know for sure. Darkmatter, is this a parameter you have looked into in your past designs?

Edited by user 30 December 2008 13:22:31(UTC)  | Reason: Not specified

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Offline Simon Briggs  
#32 Posted : 30 December 2008 13:23:46(UTC)
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Yes and one I reckon is all to often ignored by manufacturers. It needs to be considered when you are equalising a system and it's crossover among other things.
Thanks for the V/C link, pitty it is only available state side as far as I know.

DM

Edited by user 30 December 2008 13:26:07(UTC)  | Reason: Not specified

User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#33 Posted : 30 December 2008 13:26:55(UTC)
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Neat! It is my impression that very few manufacturers do things the hard way and shoulder the expense of using strictly underhung, linear motors in their designs. I've been told that ATC is one of them, I wonder who else is.
Sumer is icumen in!
Offline Simon Briggs  
#34 Posted : 30 December 2008 13:30:35(UTC)
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I will reopen the book on this one so to speak, and do some more research.

DM
Offline Togil  
#35 Posted : 30 December 2008 13:40:46(UTC)
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Cemil wrote:
Keith wrote:
Because they use such relatively cheap drivers?


I think Magicos use expensive drivers (mind you only 2 of them in the Mini 2) and very expensive crossover parts. Still, most of the considerable money goes into the superb box. Wilson uses cheaper (but more) drivers for an equivalent priced model AFAIK, but are equally obsessed with the box. Avalon's drivers aren't cheap either ..

I specially referred to Magico Mini as it is basically a mini-monitor (gone extreme, for sure), and a striking example of what can be achieved when the cabinet is done right.


The recent article by Jonathan Valin comparing his Magico Minis with Quad ESLs is very interesting.
Hans
Offline Martin Colloms  
#36 Posted : 01 January 2009 18:12:50(UTC)
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There has been some discussion about available DIY drivers and test results reported for example by Linkwitz.

It is worth noting that many of the high end speaker makers do not use standard drivers , they specify specials which meet the specific need of their design criteria.

Thus general results for an Accuton ceramic driver may not relate to the version used for example by Avalon, or Focal tweeter used by Wilson Audio, nor how it behaves in a particular design under specific acoustic loading and crossover filtered conditions.

Special proprietary features may include magnet modifications, suspension compliance and linearity alterations, lead out and termination , impedance and first resonance, diaphragm cone selection and damping , matched resonance and sensitivities, and special surrounds.

Some high end speakers are special because they really are special.

Martin C

Offline Simon Briggs  
#37 Posted : 01 January 2009 18:24:18(UTC)
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The above makes it all the more of a challenge for a rank amateur like me, to achieve the excellent results craved for when only stock drivers are available.

This is half the fun for me and makes one more resourceful.

DM Smile

Edited by user 02 January 2009 00:14:03(UTC)  | Reason: Not specified

Offline Martin Colloms  
#38 Posted : 02 January 2009 18:31:31(UTC)
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The amateur, if he does not go off the rails, has an opportunity to better tune the outcome to his taste and room accoustic, on the assumption that all loudspeaker systems are imperfect and thus are to some degree a product of the taste of the designer.

Then

1. Reconciling the large room/ small room issue

2. Reconciling the rigid brick-concrete room versus open plan drywall issue

3. Do you go for perfection in integration, micro detail, stable neutral timbre?

4. Or demand lifelike dynamics , scale and authority , with good timing , which may compromise 3. to some degree?

The amateur now has low cost tools to design and calibrate which professionals would have admired 25 years ago.



What do you value , and in what order, in the list of sound quality characteristics?

The sky is the limit..............

Martin C

Iston  
#39 Posted : 11 January 2009 14:04:43(UTC)
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Cemil wrote:
Martin Colloms wrote:
the enclosure still accounts for 60 to 70% of the sound quality, through secondary radiation from the panel walls.



The Magico Mini 2, with its over-the-top cabinet shows just how important a good enclosure is.


I couldn't agree more. I made my first speaker cabinets. They were 4 cubic feet; had sand-filled sides and baffle, with the tops, bottoms, and backs made of a sandwich of plywood - glued and screwed together. I used 2 by 2 as reinforcement. Originally they has a distributed port, but converting them to infinite baffle made little difference (they were also well and truly stuffed. With just 12 watt valve amplifiers these reproduced plucked double basses better than anything else I've had up until a fairly recent substantial upgrade.

But, 4 cubic feet is rather a big beast ...
Offline Simon Briggs  
#40 Posted : 11 January 2009 16:21:43(UTC)
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Iston wrote:
Cemil wrote:
Martin Colloms wrote:
the enclosure still accounts for 60 to 70% of the sound quality, through secondary radiation from the panel walls.



The Magico Mini 2, with its over-the-top cabinet shows just how important a good enclosure is.


I couldn't agree more. I made my first speaker cabinets. They were 4 cubic feet; had sand-filled sides and baffle, with the tops, bottoms, and backs made of a sandwich of plywood - glued and screwed together. I used 2 by 2 as reinforcement. Originally they has a distributed port, but converting them to infinite baffle made little difference (they were also well and truly stuffed. With just 12 watt valve amplifiers these reproduced plucked double basses better than anything else I've had up until a fairly recent substantial upgrade.

But, 4 cubic feet is rather a big beast ...


Interesting, what drivers did you use?

DM Smile
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