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Open Baffle Mark Audio project

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KJFAudio View Drop Down
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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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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.

Older than I once was, younger than I'll be
.............................
Andrew
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KJFAudio View Drop Down
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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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