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ashleym Offline
#61 Posted : 26 November 2010 10:44:03(UTC)
ashleym


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McSpeaker- Martin C geddit?

BNC- BMR and Cone

Then if the bass driver keeps growing, the Dominator, Terminator, Dreadnought and all the other macho style names.

LSD sounds good to me. ACID- all cone integrated drivers?

Its not really flowing at the moment, the Mat(t)s are doing better at the moment.
Martin Colloms Offline
#62 Posted : 26 November 2010 18:50:51(UTC)
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at the moment it is coded:

TRK

The Rhythm King !



Have provisional confirmation that Wilmslow will support the supply of parts and kits and the exclusive supply of the latest version of the time coherent planar driver is secured.

Will get under way on the design very soon now

MartinC
ashleym Offline
#63 Posted : 29 November 2010 22:48:33(UTC)
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That name is setting the bar high. We will need Kan and SBL owners to get reading for a rhythm sound clash!!

http://en.wikipedia.org/wiki/Rhythm_King

For a slice of dance music just before Acid House broke, Beat Dis, S-Express etc.
markus sauer Offline
#64 Posted : 15 December 2010 15:21:26(UTC)
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Given that this design is intended to use the CSS BMR, and as I received my copy of Vol. 4 No. 4 today (thanks, very interesting issue), may I just point out that while a BMR does indeed not have an electrical crossover, there is a crossover region where the behaviour pattern of the BMR changes from pistonic to modal. One can expect a rise of distortion in this region, and measurements performed on Naim's Ovator S-600 indeed indicate that a distortion peak exists at that "changeover" frequency (around 2 kHz on the unit in the S-600). The mixed reactions the S-600 has received may relate to the individual listener's sensitivity to that distortion.

I think one needs to be careful not to eliminate one set of problems by introducing another.

Edited by user 15 December 2010 15:22:04(UTC)  | Reason: Not specified

Martin Colloms Offline
#65 Posted : 15 December 2010 17:45:22(UTC)
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With respect Marcus

too many cooks !


I have auditioned the driver and I consider the merits outweigh the demerits.

The operating theory is fascinating where the output is not that from each mode as it progresses up the range but the sum of all the modes including the first or pistonic mode.

The time coherent output from piston range up is special, the Manger driver has it too at massive cost, and has some distortion too; when I last measured it pretty constant over the range , while the residual BMR distortion is narrow band and infrequently voiced. I have tried to subjectively identify it as a specific feature and so far I cannot.



It can sound nearer to a wide range ribbon or electrostatic

Note that there are several iterations of the BMR with detail build differences, and differences in resulting performance.


Kind regards

MartinC
markus sauer Offline
#66 Posted : 15 December 2010 18:30:42(UTC)
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Martin Colloms wrote:
With respect Marcus

too many cooks !


Always a possibility.

Quote:

I have auditioned the driver and I consider the merits outweigh the demerits.


Fair enough. I do hope I'll get a chance to listen to the design. Will someone take it to the Scalford show?
Matt Offline
#67 Posted : 18 December 2010 16:19:03(UTC)
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Has a decision been made about what type of bass unit and crossover will be used?
Martin Colloms Offline
#68 Posted : 19 December 2010 16:26:57(UTC)
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very early days, but likely a long throw high mass 8 inch , 8ohm nominal with a reference 85dB/W sensitivity to match the BMR.

sealed enclosure volume 35 litres, with allowance for the mid treble enclosure

this system with be easy to drive so valve amps of 20W up are candidates plus some decent solid states.


The crossover will not be textbook but will be voiced for a natural timbre from the system at its preferred location.

A good overall time response is an objective to match the intrinsic performance of the BMR.


The BMR units are delivered now and the enclosure is in the draft stage.

Martin C
darkmatter Offline
#69 Posted : 19 December 2010 16:29:50(UTC)
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Sounds good should offer bass in room to 35hz or a bit below that Smile

Edited by user 20 December 2010 14:53:00(UTC)  | Reason: Not specified

Matt Offline
#70 Posted : 20 December 2010 17:56:14(UTC)
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Martin Colloms wrote:
very early days, but likely a long throw high mass 8 inch , 8ohm nominal with a reference 85dB/W sensitivity to match the BMR.

sealed enclosure volume 35 litres, with allowance for the mid treble enclosure

this system with be easy to drive so valve amps of 20W up are candidates plus some decent solid states.


The crossover will not be textbook but will be voiced for a natural timbre from the system at its preferred location.

A good overall time response is an objective to match the intrinsic performance of the BMR.


The BMR units are delivered now and the enclosure is in the draft stage.

Martin C

Sounds great. Will it still have a 6ohm impedance?

Edited by user 24 April 2011 13:16:49(UTC)  | Reason: Not specified

Martin Colloms Offline
#71 Posted : 23 December 2010 17:09:03(UTC)
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could be nearer 8ohm, the bass is 8 and while the BMR is lower , by the time it is integrated in the system it could well reach 7-8 ohm overall .


MartinC
ashleym Offline
#72 Posted : 23 December 2010 21:31:36(UTC)
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Flipping Cotswold Sound Systems website, still nothing there for me to have a poke around to get an idea of the driver. I am thinking the speaker could be in the proportions of a Cabasse BORA but without the dreaded port.
Martin Colloms Offline
#73 Posted : 28 December 2010 17:54:05(UTC)
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While it is not the same make of driver Naim provide this White Paper to illuminate the subject.

http://www.music-line.bi...in/pdf/wp_ovator_bmr.pdf

MartinC
ashleym Offline
#74 Posted : 29 December 2010 12:11:53(UTC)
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Thanks for the link. It doesnt look too dissimilar to the Manger driver. I can see the advantages of the even-ness of how the BMR drives the room, I think this builds on the research from the Canadian National Research Council and others. So I dont know weather to expect a wide flat fronted speaker because of the controlled off axis response or not? What would be nice to see is the distortion figures to see if the driver remains linear at each end of its frequency response.
Martin Colloms Offline
#75 Posted : 29 December 2010 14:17:59(UTC)
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Manger uses a relatively soft diaphragm with substantial viscoelastic damping.

BMR uses a reinforced honeycomb cored plate where the expression of the few bending modes present is controlled using dynamic balancing.

If perfectly made the axial response remains flat even though bending modes , ie resonances, exist.

Manger and BMR do have good time responses in common, ie they are linear phase.
They both have that special quality of a near full range driver.

MartinC

ReneZ Offline
#76 Posted : 30 December 2010 10:44:05(UTC)
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Martin, you really know how to keep us dangling out there. Any info as to when it all might be revealed?? Cheers, Rene
Martin Colloms Offline
#77 Posted : 01 January 2011 10:19:51(UTC)
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Phase 1 approach and technical design will be in the jan -march issue

MartinC
ReneZ Offline
#78 Posted : 03 January 2011 11:59:05(UTC)
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Good one, thanks! And a Happy New Year to all!!
ashleym Offline
#79 Posted : 09 January 2011 11:29:37(UTC)
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Just got my issue 4/4 *ahem- a bit late renewing the subscription* and I have read the BMR article. Rereading this thread and it all makes a lot more sense. The magazine article makes note of the importance of the cabinet construction, I have found that tweeters etc often sound better when taken out of the main woofer cabinet- then I note from this thread Martin mentions there is a mid/treble part to the enclosure. This could be crucial and so it will be interesting to see what Wilmslow offer. Seeing what they do for the Fostex drivers I am feeling positive.

"The Labyrinth cabinets are supplied in four different options as shown below, all are fully CNC machined and rebated from 22mm MDF.

Flat-pack option:

Cabinets supplied as a self-assembly flat-pack in either plain mdf or pre-veneered mdf of your choice. Both options are fully machined and rebated which means that the components all slot together very easily, just needing to be glued with the 'Evo-stik Resin W' wood adhesive that is provided.

All the neccessary holes and rebates for the drive units are pre-machined so you can assemble the cabinets without having any wood-work skills."


There might be an issue with the finish of the cabinets. As cabinets are often voiced with veneer on the MDF shell we are limited to the what Wilmslow supplies. Yes they have a reasonable range but I havent seen the veneers in the flesh/wood. Could a bit of Sonus Faber come in here and leather be an option for the front panel? Colour to suit your decor and taste?

It would be nice to try to avoid any compensation components in the crossover outside the actual crossover itself. I feel it would be best to use the full range nature of the BMR and avoid anything unnecessary in the way of the signal. But again Martin mentions an interesting crossover, so do we expect to see some magic capacitors???

Finally, it looks like this could be one of the first speakers to market with the BMR and so I am sure CSS will want it to add to their reputation. Martin at the controls, apart from us lot let loose with drills and hammers- what could go wrong?
Martin Colloms Offline
#80 Posted : 09 January 2011 15:33:56(UTC)
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Our approach is to make it a simple and short as possible consonant with a smooth and accurate timbre/ tonal balance.

I have no fear of octave by octave tuning of what is essentially the acoustic power output of the system with regard to driver responses, enclosure diffraction, nearby boundary placement and preferred listening axis.

To hand we have the following variables to help us aside from enclosure stuffing variations.

1, The enclosure volume and resulting bass alignment

2. the make up of the low pass network , order, slope, lower mid balancing

3. the absolute level chosen for the mid treble

4. the high pass network , order, slope , , inherent equalisation

5. If required, gentle slope shift and , bandpass equalisation of the BMR driver in situ, in this enclosure.


Simplicity has it virtues, but in my view should not be at the expenses of a natural sound.

For simplicity you can neglect accuracy but must then go for high efficiency and superior dynamics to make sense of the trade in sound quality.

This is a different kind of speaker.

We are aiming for a low distortion , well timed , wall boundary monitor with extended bass , smooth power response and unusual time coherence.

We shall see how it sounds, not been done before.


MartinC
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