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Open Baffle Mark Audio project

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Richardl60 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Feb 2017 at 7:27am
Highly rigid a very good point in the design.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Feb 2017 at 7:42am
I cut the new rear supports yesterday using a larger block but had to remove the guard from the saw & took it very slowly (pleased to report that all my limbs still seem to be in place). 


In between household duties this weekend I will paint these/attach the speaker terminal blocks and continue to araldite/clamp the main side braces - the bottom and middle one on each speaker are 9.5mm total thickness, the other pair are single thickness.

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Andrew
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2017 at 1:47pm
Things progressed slowly over the weekend as I had other priorities but after several hours work last night, here is the latest update.

All side braces trimmed, bonded together (when double thickness) and remaining bolt holes drilled - these still need a final spray finish. Rear uprights were blocked in place with pieces of timber to maintain height with the baffles & threaded inserts have been drilled and screwed in place.


Now wider material is being used for the rear uprights, speaker binding posts now fit on the back of these as can be seen in the bottom picture below.

Both frames are now completed & loosely bolted together. Over the coming days, all of the aluminium side braces will be removed, sanded down and re-sprayed black. Then the frames can be fully assembled with the correct washers & locking nuts





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Andrew
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 2017 at 6:55pm
That looks great Andrew, fine work.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 2017 at 6:51pm
Finished the build late last night and have done an initial indoor measurement & calibration this afternoon.

Completed rear frames: 15" drivers were mounted to their baffles prior to fitting, the Alpairs were added to the fronts after this picture was taken. I'm pleased that all the holes & threaded inserts lined up correctly & the weight of the Beymas did not pull things out of alignment.

Cabling connected (everything is GSP Spatia, including some 'internal' wiring that I bought from John C a couple of years ago):


Side view of a completed speaker:


Proprius amps powering the Alpair 7s @ frequencies above 2khz:


Initial readings taken in the centre of the room (each speaker moved to this position with some basic sound absorbtion). The mic was re-aligned to each driver during measurement, in this pic, the midrange Alpair 12. Crossovers are at 250hz 16th order and 2khz 20th order, both linear phase.


Raw data for the two speakers, measurements in-room as shown above, not perfect but OK to get me started.
LH:


RH:


Impulse response was reasonably clean until 10.7ms with a small floor reflection affecting the reading. This means that the data is reasonably accurate down to around 120hz so I have only corrected from 150hz to 6k for now. 

For comparison I have shown an outdoor measurement of my older OBs below this which is 'anechoic' to 31ms (corrupted only by tiny ripples after that). I plan to do a similar outdoor measurement of the new speakers sometime in March or April, weather permitting. They will be on a 1m high platform above the lawn & nothing to create significant reflections.





..& here's frequency response after group delay, time & phase alignment 150hz - 6khz. The uncorrected excursions from the upper response of the Alpair 7s are caused by predominantly ceiling reflections as these are very tall speakers - outdoor measurements will resolve that later. Although bass extends fairly flat to around 50hz, the room reflection at 10.7ms would affect a calibration & I know from previous experience that this would add a nasal quality which is completely absent from a typical OB speaker:


So, I guess the real question is, how do they sound so far? 

Very good indeed - not too dissimilar to my other OB speakers but with faster and more open bass, well integrated with the transient dynamics of the midrange which is what I was aiming for. These drivers also have quite a long way to go before they have completely loosened up. I have time aligned both existing subs to 40hz with 4th order LR crossovers, still noticeable if I switch them out. 

Overall this setup sounds absolutely huge in both height and width & even though I am not tampering much with the Alpair 7 / Proprius response at this stage I must say the treble is already lovely sounding (Boris Blank Anthology FLAC album being used for setup which is very clean, dynamic and well mastered ) . These have a way to go but already I am getting probably 80-90% of the result I believe I can achieve later and with a free weekend ahead there will be plenty of opportunity to listen....
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Andrew
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 17 Feb 2017 at 8:55pm
Impressive again Andrew keep up the good work.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 18 Feb 2017 at 9:23pm
Thanks again for sharing this Andrew.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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