Bohlender&Graebener Neo 8 Magnetostat

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Dimensions are 86"x9.5"x16". The baffle is 1.5" MDF. The enclosure is heavily braced. One brace per driver. I used Black Alsphat Saturated Felt on all surfaces except the baffle. Same with Grey Convoluted Open Air Cell Acoustic Foam. Veneer is African Bubinga. Internal wires are QED Silver Anniversary. Total cost of the project: around $3000 Canadian which is not much in U.S. currency ;)
 

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Hey now

Tomahack,
Be-aaaa-utiful job, I would be scared to put a watt through those. I am about an hour away from you, right on the Canadian border in Northern Vermont, about a mile into the woods on a dead end private road.
Thanks for the crossover info. How are those neo 8's mounted?

I cannot bear to raise the crossover frequency, so have been experimenting with an asymmetrical cross at 4-600 hz with 48db/oct on the neos and 24db/oct on the Peerless csx. I have settled on an MTM design with the 10" peerless wired in parallel. I thought this would bring the sensitivity of the woofers from 88 to 94db, which would match the neo's 93db nicely, but didn't coun't on the rear radiation from the dipole, which increased it to 100db! I am also using a Marchand cross...eerie.
Last night I sat about 4 feet away from them in my cellar with about 20 ft behind them. These speakers dissapear, and set a firm, wide image well behind them. On track 13 of big head todd and the monsters' Midnight radio ( all 2 track digital live), the guitarist was sitting about 12-15ft in front of me.
The Peerless composite sandwich cone is very smooth, yet with 9mm x-max, four of them can shovel some serious air in a dipole, and bass is satisfying without the subs. A freinds wife is buying these for him this christmas, and I am now looking at the 28" ribbons for my own speakers!
 
Thanks diypole!

If you happen to go to Montreal, let me know. The Neo8 are wired by pair in parallel and then the four pairs are in series for a total impedance of 8 ohms. The HDS are tapered. Driver 1,2,3 in series (24ohms), driver 8,9,10 in series (24 ohms), driver 4,5 in series(16ohms), driver 6,7 in series(16ohms). The four groups are paralleled (total impedance of around 5ohms).

I will probably try a lower Xover frequency when I will have the time. Something like 1000Hz. Are you satisfied with the treble extension of the Neo8 above 12kHz with only one driver? What are you using as a source and electronics?
 
And if you should come to vermont, let me know also.
I am still in cellar mode, where I am ALLOWED to tinker with unfinished (not pretty yet) stuff after the kids go to bed, LOL. I can't wait to hear these up in the main system for a while before they go, but for now I am just feeding them with an old rat shack cd player and early eighties kenwood amps(makes what they are doing even more impressive). I will build 4 x 50 watt amps so that my freind can afford an active version, probably Marchandelec.com kits for the convenience and value.
What are those rails you have mounted the neo's on? Those things are going to be a be-atch to flush mount, I will have to make a template for the router. Also, are you getting any hot spots off the window? Using any absorption behind the neo line, or is closing the drapes enough? Even with some distance behind them, I have to use absorption on the cellar wall so images are not pulled to highly reflective areas.
Have you put the neo's on the outside to better time align the cones with the ribbons? I probably won't be able to reply until tomorrow, as the connection at the university where I work is so much faster than home. Once again, excellent job.
regards, Jason
 
The rails you see on the photo are aluminum "L" shape. I'm using heavy drapes to block reflections so I don't have any hot spots from the window. I tried both sides but found that putting the Neo8 line outside of the enclosure improved imaging and soundstage. I'm in fact really impressed by how wide they image. Wider than 180 degree on some recording. My biggest problem right now is a hole in the 100Hz region. Any suggestions?
 
Don't mind notch filters, but filling holes is another matter. What are you crossed to under 50hz? These drivers are 3db down at what-70-80hz? Raising the cross might be the only solution...:bawling:
I am pretty satisfied with the treble extension for the type of recordings that I enjoy. My freind, however, has a rather large collection of 70's and 80's rock on cd! The lack of treble extension might help:xeye:
After looking at your line, I think I will try putting the neos slighltly to the outside of the center of the 2 peerless to improve time alignment between the cone and planar.
BTW-Listened to Clapton unplugged last night with just a 6db cross at 800hz-the guitar sounded so right. I miss those box resonances :D
Regards, Jason
 
Hi tomahack

If you don't cross over to a sub (which could as well cause this) then your hole at 100 Hz might be due to speaker placement/room acoustics (does the center frequency of the hole change when you move them back and forth ?) or do they show this hole also when measured outdoors ?


Reards

Charles
 
phase_accurate:

I moved the speaker one more foot away from the back wall and the hole dissapear along with a nasty peak at around 50Hz.

dypole:

I use 2 Shiva's in a 200 liters ported enclosure under 50Hz.
F3 for the midbass is 41Hz anechoic. Regarding treble extension, my line is flat up to around 15Khz. Enough for me and my cats! Have you heard of the DBX driverack? May be it could replace the Marchand Xover. Nice to have a digital equalizer also.
 

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Tomahack,
Glad that was easily solved, what a great place. Although I love dipole mid-bass/bass for it's lack of interaction with the room, I can't get that close to the back wall. I have not heard of the DBS driverack, thanks for the tip, I will check it out.
41hz- hey now:cool: Jason
 
baffle size?

I got a few of those and tested them using a wine carton as a sealed enclosure - absolutely mind boggling!!!

Now I have some more and I'm getting ready to to some woodworking. I prefer going to a sealed enclosure (no wall reflections to worry about), but I am also open for an open baffle :)

What I am pondering right now: should I go for a wide baffle for LF boost? Or rather a narrow baffle to minimize edge reflections which would screw up the temporal resonse?

Does this matter at all, i.e. isn't the driver so directional that it doesn't see the baffle edges anyway? If so, does it make a difference whether the grille is flush with the wood or whether the baffle works as a shallow horn?

Puzzled,

Eric
 
Neo 8's

They are in my current reference system and will be for the forseeable future. Used them for about 8 month's. Among the best sound that I have heard short of a Quad, Maybe equal if you treat them properly. Check out the BG site for a proper notch filter they tend to get a little raged on the top end without it. My highest reccomendations.

Mark
 
Neo8 and a TL

What would you guys think of using a Neo8 with a Vifa 8inch (P21W...) in a TL enclosure ( or even a 10 incher) . Would you think that a TL is better than an open baffle dipole crossed over at about 200Hz with a 24 db LR electronic crossover ? The units will be biamplified of course.

My current plan was to use the Neo in an open baffle above the woofer. The baffle is to extend its natural low frequency response a bit. The crossover will be selected later. It will have to have a combined response ( acoustic +electrical) to give a 24db LR slope.

Thanks,
Cheers.
 
Hey guys, glad I found this Thread, I am thinking of building these myself. I think it is the newest version of the Alpha LS mentioned earlier.

http://www.gr-research.com/AlphaLS/Alpha.htm

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Anthony
 
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