Bohlender Graebener Planar in DIY design

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DannyBadorine

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Bohlender Graebener Planar in DIY design
« on: 25 Nov 2021, 02:25 am »
Getting the B&G to work in a baffle is difficult. I have been working on this for a while with Norman Tracy making the recessed baffle/Waveguides for me.  The bottom of this speaker is the same as the GR Research X-Statik.  The top in the picture has one M130 for mid range along with the B&G tweeter.  I am also working on one that has two M130's with the B&G tweeter in the middle (MTM) style.  Getting the top end to measure flat is a challenge and I compromised by allowing a large boost around 10KHz and up.  Most people don't hear much up there. What's interesting is that the 15 degree off axis measurement is really flat.  This speaker is revealing and sound as good as most speakers I've heard in people's homes.  I'm excited to finish it up.



Here is on-axis, 15 off and 45 off.


Here is the just the on-axis measurement


Thoughts and feedback are welcome!  I'm interested if anybody else has experience getting this tweeter to measure flat.



Rusty Jefferson

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Re: Bohlender Graebener Planar in DIY design
« Reply #1 on: 25 Nov 2021, 03:43 am »
That really doesn't look bad at all. The wide horizontal dispersion of the planer is resulting in that nice off axis response. It's pretty much saying "point the speakers straight ahead and don't listen on axis."

DannyBadorine

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Re: Bohlender Graebener Planar in DIY design
« Reply #2 on: 25 Nov 2021, 04:27 am »
That really doesn't look bad at all. The wide horizontal dispersion of the planer is resulting in that nice off axis response. It's pretty much saying "point the speakers straight ahead and don't listen on axis."
Yes!  I would like to get it flatter on-axis but there are so many challenges with how the planar responds to being in a box.  And even though the frequency isn't "ruler flat", the phase and waterfall charts are really good.  The GR drivers are really good for this.  Plus, I've seen speakers that are flat on-axis, but garbage off-axis.  So, I feel good about the big picture with this speaker.

SteveJewels

Re: Bohlender Graebener Planar in DIY design
« Reply #3 on: 26 Nov 2021, 12:09 pm »
Nice looking speakers!

This thread caught me eye as I am working on building cabinets for a pair of B&G RD75's. I never cease to be amazed at how they sound. I have a pair in my main system. They are OB with trapezoidal baffles.

Any insight you can offer on designing a cabinet would be greatly appreciated.



DannyBadorine

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Re: Bohlender Graebener Planar in DIY design
« Reply #4 on: 27 Nov 2021, 04:58 am »
I haven't ever used the RD75.  So, I can't offer much except the following:
Measure the driver in open air, then measure it in your baffle and see the difference.  That's going to tell you what your baffle is doing.  I made the mistake at first of assuming the baffle was causing some problems when it was really the problems inherent in the driver. 
I have yet to experiment with an open baffle design since I don't have a room big enough to accommodate one.
And that looks like a cool speaker that you're making.  Keep me posted on your progress!

Shives

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Re: Bohlender Graebener Planar in DIY design
« Reply #5 on: 30 Nov 2021, 08:10 pm »
Awesome man!!!

S Clark

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Re: Bohlender Graebener Planar in DIY design
« Reply #6 on: 30 Nov 2021, 11:50 pm »
Very nicely done.  And I love the choice of the M130 as the mid driver- smoother and easier to work with than any others in its class. 
 :thumb:
And I'd bet that bump at 120 is room related... it's a common attenuation for lots of rooms. 

DannyBadorine

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Re: Bohlender Graebener Planar in DIY design
« Reply #7 on: 1 Dec 2021, 02:20 am »
Very nicely done.  And I love the choice of the M130 as the mid driver- smoother and easier to work with than any others in its class. 
 :thumb:
And I'd bet that bump at 120 is room related... it's a common attenuation for lots of rooms.

Thanks man!  The final design will be shorter (I'm losing 6" from the baffle where it's blank).  The speaker was measured outside on axis of the tweeter so the bump is not room related.  I think it has more to do with me having the low woofers a bit too loud.  When I listened to it in the room (didn't measure it yet) the 120 didn't seem to be a problem and everything below it got much louder.  It was clean down to around 50Hz.  I will have the first version tri-amped with DSP so any problems will be easily dealt with.  My measurements above are 2nd and 1st order slopes on crossover points without DSP.  I will eventually make a passive version but I want to experiment with this one more before I settle on a final crossover.  That tweeter is really difficult to work with but it sounds great.