# Satori upgrade: Bohlender-Graebener Radia 520i loudspeakers



## cvjoint (Mar 10, 2006)

Thanks to the friendly prices available for the Satori with Erin's groupbuy I was able to beef up my 520i. 

Here is where the group buy was:
http://www.diymobileaudio.com/forum...satori-6-mw16p-4-8-ohm-$140-each-shipped.html

I have recently transitioned into the home audio side of of things. The BG planars have been the only constant in every car sound system I build since 2007, and with that I figured I should look for a way to make them part of the home audio collection as well. 

Enter the 520i. I've been looking at the larger planar elements from BG and a way to get them nicely finished and as cheap as I can. Bill (the guy responsible for the Omnimic system) had his pair for sale, already build in OEM form, lavish aluminum baffle and all, and so there they are. Why DIY when it's cheaper and better to buy them already made? 




























Specifications, as stolen from Stereophile http://www.stereophile.com/content/bohlender-graebener-radia-520i-loudspeaker-specifications:
Description: Two-way, floorstanding, sealed-box loudspeaker with line-source ribbon upper-frequency driver. Drive-units: 50" by 1.1" planar-magnetic coaxial midrange and HF ribbon; two 6.5" cone woofers. Crossover frequency: 350Hz. Crossover slopes: fourth-order, Linkwitz-Riley. Frequency response: 70Hz-20kHz, ±6dB. Sensitivity: 88dB/2.83V/m. Nominal impedance: 4 ohms. Recommended amplification: 50-250W continuous, 300W peak.
Dimensions: 70.25" (1800mm) H by 7.75" (200mm) W by 2.75" (70mm) D. Base: 13.25" (340mm) W by 17.25" (442mm) D. Weight: 59 lbs (26.8kg).
Finishes: Black anodized aluminum tower, black or mahogany base.

With that said, being DIY in my ways, I've instantly taken them apart to see what the base drivers are like. I didn't recognize the brand so instantly I knew they can be upgraded! So here is what they are like inside:



















































My initial impulse was to drop two Scan Speak Illuminator 7"s in there instead of the OEM woofers, but there really isn't enough room in there. The cutouts are for two:
165mm OD
150mm ID
100mm depth


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## cvjoint (Mar 10, 2006)

I turned on the omnimic to get some testing done. Little known secret is that the Onkyo TX NR929 receiver can not only biamp speakers but has a full electronic crossover built in for the front speakers. I set the crossovers as follows:
Martin Logan push-pull subwoofer 70hz LP
Satori woofers 70hz HP - 500hp LP
BG planars 500hz HP

How did I set the 70hz HP on the Satori? I took the grille off the speakers and tested some heavy bass songs at what I consider loud. I started 50hz and went up until I stopped sensing the drivers are stressed. 70hz is all I could get away with. 

I picked the next crossover point of 500hz by looking at the harmonic distortion plots. 71db on the receiver is usually as loud as I get. I set it so that the planars never get stressed over 1% THD at 71db. You can clearly see from the distortion plots that the planars produce much higher THD than the Satori woofers. However, the planars sound much better than the woofers at low to medium output. I would run them down to 300hz ideally but they seem to strain crossed this low. 

Left channel frequency response









Right channel frequency response 









Left channel harmonic distortion









Right channel harmonic distortion


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## cajunner (Apr 13, 2007)

did you noticeably improve the sound overall with the switch?

the OEM drivers appear to be quite stout and purpose built to include high excursion and efficiency as their primary target, while the Satori appear to be all finesse and a smidge on the smooth in comparison.

that's just looking at the hardware however, since it's possible those OEM are just cheap banger offshore sourced jellybean design copies, and the move in a nice upgrade such as you have undertaken, (no small feat considering you had to buy 4 ) was highly advised and the speaker now has the voice of an angel, a particularly well spoken one...


"I rarely change out drivers in my bespoke home audio but when I do, I use Satori's, stay thirsty my friends"


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## 1fishman (Dec 22, 2012)

Looking forward to your results. What's the box volume? Im assume it's sealed.


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## Bmxnick101 (Dec 1, 2009)

Nice to see these put to use already. I was going to start my layout tomorrow. (Eight in the rear "doors" of my truck.


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## teldzc1 (Oct 9, 2009)

Nice work. Those Satori's look amazing. 

Sent from my SAMSUNG-SM-N900A using Tapatalk


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## t3sn4f2 (Jan 3, 2007)

Stereophile link for the 520i's is not working. Looks like there's a colon at the end of the link that doesn't go there.

Bohlender-Graebener Radia 520i loudspeaker Specifications | Stereophile.com


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## cvjoint (Mar 10, 2006)

I can't speak enough about how wonderful the neo magnets work in a small box, especially in a box this small, with a neo magnet so huge. 

The most improvement is in the motor force and the lower Q and lower resonant frequency achieved with such a beefy neo motor. The OEM drivers, while they did use a huge ceramic motor, they were still undermotored for the job. They sounded boomy and the resonance was clearly audible. With the Satori I get a seamless transition to the low distortion Martin Logan push pull subs. It is however true that overall output is largely the same. So I kept a high xover but now it simply sounds like it has better extension and transparent. 

The other sweet bit is the suspension. With the one of a kind spider this driver has the speaker achieves the same centering needed in the gap with twice the softness of a high end driver. The time domain resonse is outstanding compared to the stock units. Part of me also believes this suspension is as good as it gets rattle wise without push-pull. You get high excursion without a ton of motor force exerted on the cabinet, so less transmission of vibration to the floor board. A proper match to the planars and the sub I have.


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## cvjoint (Mar 10, 2006)

The box is sealed. I'll get the measurements soon. It's super small.


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