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Thread: My personal Open Baffle speaker project

  1. #11
    Join Date: Feb 2011

    Location: Red Rose Country

    Posts: 153
    I'm Colin.

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    Quote Originally Posted by rubber duck View Post
    Thanks Colin, that's good to know. And I imagine it will be an easy load as well?
    Yes. That is one of the design goals.

    Bass driver transformer core inductors should arrive Monday next week, I already have all the other components, so I should have the 3-way filter built early next week and can report back initial listening review. I'll invite Chris (Stratmangler) around to give feedback. Watch this space..........

  2. #12
    Join Date: Feb 2011

    Location: Red Rose Country

    Posts: 153
    I'm Colin.

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    The Transformer core inductors finally arrived from Germany earlier in the week



    I have just finished the 3-way XO'ers temporary lash-ups for testing purposes for when Scott and Chris come over this afternoon. Should be an interesting tweaking of the filters session. To add to the mix I have also the 2-way modified XO that Scott designed for the Coax drivers as standalone speakers that on the baffles and without any added bass help do sound rather good but as one would expect lack bottom end extension but nevertheless are an engaging listen.

    As an aside earlier in the week I did try the twin 15" drivers driven direct with no filter and they are surprisingly good. The spec sheet states the FR for these drivers is F3-4000Hz and I don't doubt this listening to the drivers alone. This suggests to me that they will work rather well in a 2-way configuration replacing the 2-way coax driver with a horn loaded compression driver. Depending how this 3-way configuration set-up works out I reckon this could be worth further experimentation. I have in mind a rather nice Monacor 1.4" compression driver (MRD-300) that when coupled with their MRH-300 mid-high range horn has the capability of a 1kHz - 20kHz FR and the driver a recommended minimum XO of 1.2kHz. This however, will require a slightly larger central baffle to accommodate the horn, so a complete new speaker build.

    I'll report back later our initial listening findings and any fine tuning mods.

  3. #13
    Join Date: Feb 2011

    Location: Red Rose Country

    Posts: 153
    I'm Colin.

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    Well Sunday afternoon proved to be a very fruitful and successful afternoon.

    I have to give my thanks to Scott for coming over from Hull even though he was not well. However I think he left feeling a lot better in himself than when he arrived, thanks perhaps to Lynn's home cooked pastry's and good few Stepsils to calm his evil chesty cough and sore throat.

    Chris (Stratmangler) had hinted previously he knew we had a good speaker from the initial experiments with playing the 15" units full range without a XO and also playing the coax driver mounted on the finished baffles and using Scott's modified 2-way XO that resulted from my taking the test baffles over to David's Huddersfield Sunday gatherings. The end XO is a combination of using the modified coax filter with the bass filter element of Scott's first attempt 3-way filter. This gave a very cohesive and engaging sound but, though the lower bass was present it was a little muted in the mix. This was solved when Scott suggested we make the capacitor in the bass shunt CR a much smaller value. Five minutes with the soldering iron and the cap was changed and hey presto bass definition solved.

    Apart from this the demo of driving the bass units direct with no filter convinced Chris and Scott they would work very well as a 2-way when coupled with a quality compression horn tweeter. I suggested the Monacor 1.4" compression driver and horn that would require a larger central baffle (it would have to be increased in size from 300 high to around 330mm to accommodate the horn). This would require a complete new speaker frame build. Scott then suggested a 1" Celestion compression horn driver and a matching mid-high range horn as a better option that from the manufacturers published data sheets and FR plots he preferred and would also fit perfectly on the existing size 300mm high baffle. So all I need to do is buy a pair the drivers and make up a couple new centre baffles that will bolt straight on the existing frames. This should also have the advantage of being more efficient, pushing the efficiency into the upper 90's dB and the XO should also (in theory) be simpler. So that's the next stage of development for these speakers.

  4. #14
    Join Date: Nov 2008

    Location: Valley of the Hazels

    Posts: 9,139
    I'm AMusicFanNotAnAudiophile.

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    It was a very fruitful afternoon, and Scott's input was invaluable.
    The elements for a really good speaker were already in place, it's just that the various elements weren't quite gelling.
    A bit of alchemy happened, and base metal became gold.
    It could have gone the other way, and we'd have created purest green, but thankfully it wasn't the case.

    Various bits of music were played, basically trying to trip the speakers up, and we didn't once have cause to wince.
    Eventually the "torture track" (Metallica - S&M - Nothing Else Matters) was retrieved from its hiding place, and for once I actually enjoyed it.
    As far as I'm concerned that counts as a result.

    If they weren't so big I'd be after a pair ...
    Chris



    Common sense isn't anymore!

  5. #15
    Join Date: Feb 2013

    Location: North Yorkshire

    Posts: 129
    I'm Mark.

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    Hello Colin,

    I have read this post with great interest and congratulate you on creating such a great set of speakers, which look the 'bis' too.

    Looking through your photos I was however more than intrigued with a particular image I spotted (which was incidental to the focus of the photo): And hope you can tell me more.

    Your ninth photo is a view of the whole assembly but what caught my eye was the black & white photo montage picture on the wall above your rack.
    It shows various instruments, central to which is the badge that can be seen as "Laurinat & Co Berlin"........ is this a picture you created yourself or is it one from a commercial source ?

    The significance for me is that as I type this I am sitting next to Mrs. vt's piano, which was made by Laurinat & Co, Berlin !!

    The World is made up of such amazing coincidences and I can't believe having spotted this in a post about DIY OB speakers

  6. #16
    Join Date: Feb 2011

    Location: Red Rose Country

    Posts: 153
    I'm Colin.

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    Quote Originally Posted by Vinyl turner View Post
    Hello Colin,

    I have read this post with great interest and congratulate you on creating such a great set of speakers, which look the 'bis' too.

    Looking through your photos I was however more than intrigued with a particular image I spotted (which was incidental to the focus of the photo): And hope you can tell me more.

    Your ninth photo is a view of the whole assembly but what caught my eye was the black & white photo montage picture on the wall above your rack.
    It shows various instruments, central to which is the badge that can be seen as "Laurinat & Co Berlin"........ is this a picture you created yourself or is it one from a commercial source ?

    The significance for me is that as I type this I am sitting next to Mrs. vt's piano, which was made by Laurinat & Co, Berlin !!

    The World is made up of such amazing coincidences and I can't believe having spotted this in a post about DIY OB speakers
    Hi Mark,
    Thanks for the interest in this thread. I started it as I believed these OB speakers could be a DIY project for all you budding speaker builders. When the development side is complete I may offer them as a kit of parts - drivers, fixings, XO components etc. with a set of plans for the home constructor to make the side cheek frames, bases and a set of baffles. However for those that just wish to source their own drivers and fixings just a set of plans. However, these are still in the development stage and from this weekends gathering and feedback from Nick Gorham and a couple of other good mates I need to make the side cheeks, frames deeper to bring up the lower bass which will also mean new bases as well. So they are a few weeks off being finished. I also learned that OB's need to be at least 1.5m away from any rear wall and some wall treatment/high frequency damping wall panels is really a requirement to fully integrated speakers with the current driver configuration.

    Now as to the large picture mounted on the wall I bought this from 'The Range' multi-store in Rochdale. We happened to be passing the store on a shopping trip for other things and my wife suggested we pop in to see if they had a couple of table lamps for my then new music room. It was whilst browsing for lamps I spotted the picture and as thought what a perfect montage for my music room. I also found a couple lamps so a very fruitful diversion thanks to the missus.

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