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Open Baffle Mark Audio project
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KJFAudio View Drop Down
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Points: 119 		Post Options Post Options   Thanks (0) Thanks(0)   Quote KJFAudio Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2017 at 8:36am
Great work Andrew. I'd be inclined toward just using an minimum phase 1st order between the 12p and the bass drivers centred around the baffle step frequency. Using such steep filters especially at the bass end take a lot off correction power with FIR and assuming you have a limited amount of taps available they may be better spent on a little bit of judicious phase amplitide correction and save the rest for room correction. Don't you know how many taps there are to work with in the Deqx? Also as at the other end you are crossing between driver that are so similar in character you may find shallower filters are fine there too, the steeper filters will create stronger pre ringing which will continue ringing for a while.
UK/EU dealer for Mark Audio Drivers and Manufacturer of speaker kits
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Drewan77 View Drop Down
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Points: 1544 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jun 2017 at 2:01pm
I have finally reached the point where these speakers are 'finished' in their current configuration*. 

My immediate neighbours are on holiday so new calibration measurements have been taken outdoors & in spite of a few uncooperative birds (and an aeroplane!), I was able to run multiple long frequency sweeps which averaged out everything except the speakers. 

The raw anechoic response is completely flat +/-0dB @ 30hz- 9.2k & apart from a very narrow, high Q null @ 11.8k, it's +/-3db from 18k-25k (the limit of the M23 Earthworks mic). DEQX algorithms corrected phase, timing, amplitude & group delay across all drivers & frequencies. I never cease to be amazed by the resulting music from any speakers treated in this fashion.

The four 15" drivers have taken an age to loosen up and run in properly & I also changed the high end crossover settings, created new correction filters, made a few room adjustments and did a new in-room measurement/bass eq adjustment.

These are now almost unbelievably transparent, fast & full range with height, depth and (some) width to the soundstage. Voiced exactly as I want and no apparent room effects on any material that I have played or at any volume so far. Although I am obviously biased, Stefan will be calling in after the Cranage show so I can get a second opinion. 

Below are the listening chair plots (the room has naturally caused deviations from the outdoor measurements above, even allowing for acoustic & subtle bass eq treatment. Nevertheless the results are impressive, still almost 'flat' & they certainly sound great).

3-Way OB speakers:


Two subs:


Combined, final result (with time/phase aligned crossovers between both speakers/both subs):


* I would like to try these at some stage with my NEO3 ribbons instead of the Alpair 7s and also change the configuration to have one of the 15" panels at the top, with the mid/treble drivers nearer head height - easy to do with this design of OB. No real reason for this but it will be fun to do sometime - I loved the NEOs' which may just have a very slight edge on the Alpair 7s' - they certainly measure flatter, without that null & in fact corrected to +/- 0dB right up to almost 25k.
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KJFAudio View Drop Down
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Points: 119 		Post Options Post Options   Thanks (0) Thanks(0)   Quote KJFAudio Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jun 2017 at 5:25pm
Nice little write up, I'm really looking forward to popping in to see these.

Stefan
UK/EU dealer for Mark Audio Drivers and Manufacturer of speaker kits
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KJFAudio View Drop Down
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Points: 119 		Post Options Post Options   Thanks (0) Thanks(0)   Quote KJFAudio Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2017 at 8:45pm
I had the pleasure of going to Andrew's House last night to have listen to his speakers ( and look at some of his lovely art). It was quite late and was at the end of a long weekend exhibiting at Northwest Audio Show so I don't think my brain was quite as queued into the music flow as usual so my help probably wasn't as constructive as I normally try and make it, sorry Andrew.

Anyway, the speakers sounded great, the height and depth of the image really is astounding. Andrew has chosen his seating point to give him the best bass response and it really does sound very natural and believable, maybe at the expense of side to side imaging which does locate extremely well sitting slightly further forward but the bass does't sound quite as good. The integration of the sub bass to bass is I think the best I've heard. The integration of the rest is seamless as well as very very coherent.

I've heard quite a few customer builds since I started selling the Markaudio drivers but this one certainly had the largest scope, well done  Andrew.

Stefan
UK/EU dealer for Mark Audio Drivers and Manufacturer of speaker kits
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Drewan77 View Drop Down
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Points: 1544 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2017 at 10:31pm
Thanks Stefan, it was very good of you to come over after such a busy two days & I'm gratified that you were so positive about what you heard. It's all very well having other visitors enthusing about what they hear but I appreciate critical and experienced ears like yours (even if still recovering from the excesses of Saturday!) 
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Points: 1544 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2017 at 8:35pm
I mentioned in an earlier post that I may replace the Alpair 7s with the Neo 3 ribbons. 

After listening to music over an extended period, the response of the Alpairs didn't quite match my memory of the Neo's (which I had used in the previous OBs for several years). With vinyl, the astonishing & delicate percussion sparkle which I was used to via the Accession was missing so I bit the bullet and decided to change things.

Initially I planned to take outdoor calibration measurements on a dry day last week but by the time everything was set up in the garden, it had become too windy to get a clean response, even using 36 frequency sweeps per speaker (about 2 minutes) which averages out all rogue sounds like occasional birds/distant aircraft/exasperated wife etc. The wind became almost gale force by midday when I was ready so I abandoned that.

I set it up again yesterday, which was dry and wind free - with the added bonus that this followed several days of continuous rain, meaning the lawn was soft & wet, reducing possible floor reflections even though the speakers/mic were raised well above it. 






Twittering birds are scarce at this time of year too & I must say that the results were by far the cleanest I have taken. After letting DEQX do its thing 0hz - 20k with frequency, phase, crossovers, group delay and impulse, a second set of verification measurements gave the 'semi-anechoic' response below. This is genuine, not a fake! The Neo's are powered by a pair of Proprius at 3024hz/300dB to the Apair 12s & because the speaker is measured as a 3 way, the interface is corrected automatically and seamlessly. Proprius & ribbons seem like a real marriage made in heaven.

It's not just about measurements of course so this afternoon I started to listen to a selection of LPs and CDs. It sounds marvellous so far, the sparkle is back and the system really does sound remarkable. 

N.B. I apologise that I post far less frequently than previously - the system needs no further adjustment and retirement gives us the opportunity to spend a large part of the year away with the family/grandchildren overseas. I listen to more music but spend much less time behind a computer screen and that has to be a good thing!



Edited by Drewan77 - 29 Nov 2017 at 8:38pm
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Richardl60 View Drop Down
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Points: 1468 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2017 at 9:35pm
Very good!

Do you think that low temps or dampness may impact iron the drivers and therefore the results at all?
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