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Offline Simon Briggs  
#141 Posted : 01 April 2009 13:15:42(UTC)
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zonepress wrote:
Let the record show that today is April 1st.
Laugh


BigGrin

Hence my slightly snarky remark Smile but only 40mb!!
Offline Simon Briggs  
#142 Posted : 01 April 2009 13:21:21(UTC)
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In all seriousness as has been pointed out this has turned into a bigger project than originally envisaged, there are so many options to explore and several that I quite like.
Perhaps what I could do is offer some options and ideas based on my favs, probably by next April BigGrin
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#143 Posted : 01 April 2009 13:44:30(UTC)
zonepress

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Aren't you making this too hard? No need. Just start jotting down your thoughts at random. My elaboration will be, as can be expected, eloquent and erudite. Or, as dcathro might put it:
dcathro wrote:
irrational and pointless
Sumer is icumen in!
Offline Martin Colloms  
#144 Posted : 09 April 2009 14:59:45(UTC)
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zonepress wrote:
darkmatter wrote:
Agreed, I will put something together Smile
It took all of two months, but the overworked and unappreciated darkmatter was kind enough to email me a hefty 40 MB PDF file chock full of equations, differential and otherwise, LSPcad simulations, anechoic measurements and the like.
It will take me a while to digest and start presenting all this material to the forum.



While we are doing the equations and all that, I have been refreshed on the subject of loudspeaker dynamic range and the variation of distortion with level .

The new Wilson Audio MAXX III , in review , is providing some further teaching on the subjective benefit of large radiation areas and low distortion , provided of course that the device works satisfactorily as a whole.

Premature compression and distortion in smaller speakers is a way of life, and those that legitimately use them are so adapted and forgiving.

My reference speaker is not so small , has an 11 inch nominal bass unit and runs 87dbW, but you can get it to limit and indeed its purest sounding cruising level is perhaps 5dB below the maximum possible.

Nevertheless going to the 150 litre bass bin , 11 inch and 13 inch bass units in parallel and the power shared twin mid units, at 91 dB sensitivity, of the MAXX III is a refreshing experience, seemingly unlimited maximum level, and very little change in innate timbre with level, only what goes on in your ears. It readily delivers those high levels where the ear shows a shift in perceived pitch, yet remains subjectively unforced. Measurement shows very low distortion over the frequency range.

Its great when you can get it , and may help to inform those thinking of building a speaker. Do not neglect issues of sensitivity, power handling , distortion , they may count more for realism and listening satisfaction than the result of a slavish attention to a nominally smooth frequency responses.

Martin C
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#145 Posted : 09 April 2009 15:35:57(UTC)
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Martin Colloms wrote:
My reference speaker is not so small , has an 11 inch nominal bass unit ... Nevertheless going to the 150 litre bass bin , 11 inch and 13 inch bass units in parallel
Stands to reason. For bass there is no getting around the need to move large volumes of air to and fro. The bottom line is that a radiator of more than twice the effective area of another will need to move less than half the distance to displace the same volume. This means that all the nonlinearities inherent in the radiator (magnetic flux, suspension mechanics etc) will be excited to a considerably lesser degree. The same holds true of a large vs. small box and the inherent nonlinearity of the volume of air trapped therein. This does not negate the need for a large Xmax. The Xmax is there to add a "safety" margin, just like a very fast car that can do 200 mph: the idea is not to drive at 200 mph, but to make 100 mph easy.
Sumer is icumen in!
Offline Simon Briggs  
#146 Posted : 09 April 2009 20:39:14(UTC)
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This has always been my approach to speaker design. The largest sub I have built so far was ~ 250 Litres, used a 21" bass unit and 16Hz was a doddle BigGrin
Offline Simon Briggs  
#147 Posted : 09 April 2009 20:42:17(UTC)
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Interesting that Maxx uses a 150 Litre Encl. I remember the X1 had 135 Litres and 15"+ 13" ?
User is suspended until 09/12/2283 19:47:11(UTC) zonepress  
#148 Posted : 17 April 2009 16:40:54(UTC)
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In the course of my reading, I came across an excellent paper in two parts by U. Horbach and D.B. Keele (aren't all Keele papers excellent?), which can be downloaded from Keele's own website in PDF format:
http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2007-09%20AES%20Preprint)-%20Linear%20Phase%20Digital%20Crossover%20Flters%20Part%201.pdf
http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2007-09%20AES%20Preprint)-%20Linear%20Phase%20Digital%20Crossover%20Flters%20Part%202.pdf

I'm not going to go into the particulars of the digital crossovering they propose, but focus on one aspect of the paper, which is particularly enlightening.
They are investigating the concept of a columnar speaker with very tightly controlled vertical directivity, what they call "constant beamwidth".
In essence they are taking the basic "D'Appolito" configuration (one tweeter between two mids, or MTM) to its extreme by adding woofers and subs on each end (say an "SWMTMWS" scheme).

They base their discussion on this invaluable table:
UserPostedImage
which portrays various patterns of directivity exhibited by two idealized point sources separated in space by varying fractions of their working wavelength.

By splitting up the audio band into smallish segments (each allocated to a suitable driver pair) and calculating the required distance for each driver pair, they aim to produce a speaker that emits a finite cylindrical wavefront approximately as tall as the speaker itself, and minimize boundary interactions with the floor and ceiling:
UserPostedImage
I recall seeing several speakers with similar layout of late, although I don't know to what extent they are actually based on Horbach and Keele's work.
UserPostedImageUserPostedImageUserPostedImage
This layout also reminds me somewhat of the concept behind Quad's concentric stators, except squished from sideways.
Sumer is icumen in!
Offline Martin Colloms  
#149 Posted : 27 April 2009 16:36:17(UTC)
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Duntech comes to mind regarding driver formation but Keele is doing something very different .



Ulrich Horbach and Don Keele have shown just how good the theory can get.

I quote :

'Ideally one wishes to achieve flat, frequency independent amplitude responses at any measured point in space'

'A common design practice is to accept non-ideal behaviour , such as interference due to path length differences in multi-way speakers , as unavoidable, and then try to optimise the sound quality by modifying crossover parameters- a process commonly known as voicing . '

One implementation is six way active with dsp crossovers, full time alignment , and high order crossovers this array speaker suggests exquisite control of vertical and lateral responses to achieve a lower frequency colouration for the room driven acoustic.



For this benefit to deliver higher fidelity, all the rest must be in place, nice sounding drivers, fine power amps , hi res crossover filters, quiet power supplies, resonance fre, low diffraction enclosures;

have I forgotten anything ?

BTW, recent advances in passive crossover alignment are in a few cases delivering superior off axis responses, some achieved by painstaking voicing.


Martin C


Offline Simon Briggs  
#150 Posted : 27 April 2009 16:58:34(UTC)
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Yes particularly the bigger models that Duntech made the Soveriegn 2001 and the later Dunlavy designs fromthe same designer, particularly the Reference VI which used 2x15" 2x8" 2x5" 2x 1 1/4" and a 3/4" tweeters.
Offline Simon Briggs  
#151 Posted : 27 April 2009 17:01:49(UTC)
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Martin Colloms wrote:
Duntech comes to mind regarding driver formation but Keele is doing something very different .



Ulrich Horbach and Don Keele have shown just how good the theory can get.

I quote :

'Ideally one wishes to achieve flat, frequency independent amplitude responses at any measured point in space'

'A common design practice is to accept non-ideal behaviour , such as interference due to path length differences in multi-way speakers , as unavoidable, and then try to optimise the sound quality by modifying crossover parameters- a process commonly known as voicing . '

One implementation is six way active with dsp crossovers, full time alignment , and high order crossovers this array speaker suggests exquisite control of vertical and lateral responses to achieve a lower frequency colouration for the room driven acoustic.



For this benefit to deliver higher fidelity, all the rest must be in place, nice sounding drivers, fine power amps , hi res crossover filters, quiet power supplies, resonance fre, low diffraction enclosures;

have I forgotten anything ?

BTW, recent advances in passive crossover alignment are in a few cases delivering superior off axis responses, some achieved by painstaking voicing.


Martin C




Scared That describes nearly the Active full range successor I hope to propose next year to my "Slam" project which I completed now 9 years ago.
Offline ashleym  
#152 Posted : 04 May 2009 12:37:47(UTC)
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Here are some more loudspeakers using the TAD drivers but with a very conventional looking cabinet..........

http://www.swissaes.org/nl/aes_newsletter_80.pdf
Offline Simon Briggs  
#153 Posted : 26 September 2010 15:45:24(UTC)
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My two ideas remain fundementally the same

1/ small two way system (sealed box)

2/ larger system again probably a sealed box system

A few additions to the melting pot, field coil units probably out of my price range at present but they look ideal to satisfy my goals, anyway this will be a good project for the Winter.
Offline darkmatter  
#154 Posted : 20 December 2016 12:32:35(UTC)
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Originally Posted by: Martin Colloms Go to Quoted Post
DM will have to work hard to define the design and try to exclude the noise from all our suggestions.

Thiel and KEF have been working towards coincident, time aligned driver systems with proprietary drivers. The Quad gets there as of right.

Avalon is more time coherent than most with low diffraction narrow enclosure forms , tilted back to align the bass mid and treble start positions relative to the listener.

The resulting system CSD is particularly good, thanks to careful control of the effective driver working ranges. With these designs it is the attention to such detail which impresses.


My instinct for an enthusiast is a sealed box three way with a form narrowing with height, a true 8ohm impedance, , ie two of the '5ohm' bass drivers in series probably 220mm SEAS , .

probably the 160 mm Scan pulp cone wide range mid and a DXT soft dome tweeter.

We could try and firm up device type numbers from this broad suggestion.

Martin C


Been asked about wide dispersion pattern tweeters, is there a soft dome equivalent of this unit?

http://www.seas.no/index...7tbcdgb-dxt&catid=45

http://www.seas.no/image...dfdatasheet/dxt_seas.pdf



Offline darkmatter  
#155 Posted : 25 December 2016 13:29:54(UTC)
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Another project of mine will be based upon a large high performance 3" soft dome midrange

ATC and Volt come to mind, the ATCS M75-150s and the Volt VM752

Still investigating these!
Offline Shadders  
#156 Posted : 25 December 2016 13:38:43(UTC)
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Hi,

The Volt and ATC units are very expensive. Any reason for using these? They are sealed units, whereas others are generally open.

Regards,

Shadders.
Offline darkmatter  
#157 Posted : 25 December 2016 13:43:23(UTC)
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Originally Posted by: Shadders Go to Quoted Post
Hi,

The Volt and ATC units are very expensive. Any reason for using these? They are sealed units, whereas others are generally open.

Regards,

Shadders.


Yes having heard both they have an excellent performance bettering many of the cone drivers I have used, and they meet with my design brief particularly as they are sealed back as well.

Regards,

DM Smile
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