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Old 3rd February 2007, 02:05 PM   #1
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Default BG-75 / ATC planar dipole construction

After living with heavily modified/rebuilt/aging Infinity RS II's for 25 years, I stumbled upon some BG RD75 planars at 1/2 price shipped to my door.. soooo... being an inveterate builder/tinkerer, I decided to retire the Infinity's to the home theatre..... and build some dipoles based on the RD75's , obviously influenced by the RSII design (and the Genesis 201 array box)
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Old 3rd February 2007, 02:22 PM   #2
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Default BG-75 / ATC planar dipole construction(cont.)

After doing extensive online research, I decided to cross over the BG's at 600 Hz to avoid stretching their capabilities, and augment the high end with a technics EAS10th-400 supertweeter and 2 peerless domes, one firing rearward w/ reverse polarity.

Click the image to open in full size.

Since I was running the BG's from 600 Hz up, I needed midbass drivers to fill in from the sub (seen in the corner) I'd built previously ( from 50 Hz - 600 Hz)...

Click the image to open in full size.

The best drivers i found (2 years ago) were 6 1/2" Peerless HDS

Click the image to open in full size.

as they had a very smooth response up to ~2K and fairly robust power handling.

I chose to build the cabinets from local 1" cherry boards, with 45 degree wings to add baffle width control for the dipole roll-off
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Old 3rd February 2007, 02:32 PM   #3
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Default BG-75 / ATC planar dipole construction(cont.)

As you can see above, I first mounted the dome tweeters facing forward around the supertweeter, but the vertical lobing was intrusive, so I reversed the upper's position (and wiring polarity) and that problem went away.

Click the image to open in full size.

The domes and the mid-woofers were higher sensitivity than the RD-75's (by at least 3 dB) so I connected them in series rather than parallel, which helped immensely (and provided an easier load to the amp.

Here are some more construction pics...

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Click the image to open in full size.

more to come
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Old 3rd February 2007, 03:04 PM   #4
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Fantastic job, the room your speakers are in looks beautiful too with all the huge windows looking out on to nature. I'd expect its pretty peaceful listening to music in that environment.

Do I see a swimming pool too? Git

Once again congrats.
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Old 3rd February 2007, 06:25 PM   #5
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Default BG-75 / ATC planar dipole construction(cont.)

Thanks, Shin.. your projects (prior & current) look pretty cool.

yup it's a pool, but the liner split after 14 years and needs to be replaced .. another project..

Some further construction details & pics...

this was how I cut holes b4 the jasper jig joined my tool box...
Click the image to open in full size.


and here's the (almost) completed mid-woofer mdf box w/bracing
Click the image to open in full size.

The main baffle is 1" cherry, which I purchased down the road from a guy who cuts boards from trees and sells to local woodworkers. I planed them from ~1 1/4" rough dimensions; each baffle is 4 pieces joined w/ biscuits and gorilla glue.
Click the image to open in full size.

Since I couldn't wait to see how they sounded, here's a test setup b4 some finishing...
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Old 3rd February 2007, 11:35 PM   #6
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Default Intermediate finished version to date

at any rate...

here's where they stand now...

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John L.
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Old 4th February 2007, 12:47 AM   #7
Tenson is offline Tenson  United Kingdom
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Did you build these a long time ago? Only, I'm sure I have seen that last picture a fair while ago.
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Old 4th February 2007, 01:06 PM   #8
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Quote:
Originally posted by Tenson
Did you build these a long time ago? Only, I'm sure I have seen that last picture a fair while ago.
I posted a few pics here and there since starting them 2/2005, but v-bro and ruddyama asked me to start a thread with construction details...

plus, they keep evolvimg....

you probably remember this pic... note the absence of the 25" ribbon/planars.. and the second sono-subwoofer..

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John L.
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Old 5th February 2007, 02:00 AM   #9
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Default neoplanar 25" upgrade

One reason I added the neoplanar was I got a pair for $175 each, they had pretty good specs, and , rather than adding 2 more midwoofers on the baffle (which I didn't need) I wanted more power handling for the midrange & upper freqs. (150wrms)

polar response (monopole)
Click the image to open in full size.

neoplanar freq. response (mfg. info)
Click the image to open in full size.

for comparison (maybe?) here's a high end pure ribbon spec.

RAAL 70-10
Click the image to open in full size.

and here's the sheet for the RD75's... (with notch filter@ 5Khz)
Click the image to open in full size.

all these are mfgs. representations, so the normal caveats apply.

However, all I can say is in this setup, the neoplanar/RD75 combo floats a rock solid image throughout the room; it's as if each instrument being played has its own speaker custom built for it... no smearing or interference between the various sounds. Sounds good from low levels up to, maybe, 106dB or so (I can't listen much louder anymore)

xover setup...
Click the image to open in full size.

John L.
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