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In Reply to: RE: Just received my new BG NEO8's. posted by Cougar on July 12, 2016 at 08:12:47
Madisound have similar looking ones,
https://www.madisoundspeakerstore.com/ribbon-tweeters/audiopur-pla200-6-planar-ribbon-tweeter-200mm/
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of the BG Neo8's. These Audiopur Knock offs are made in China. Enough said!
but even though they look close their sensitivity are 3dbs. less than the BG Neo 8's. The price does make them look attractive but I will go with what I have used and know to be a fine product in the BG's.
Thank You for the link I appreciate it.
Wouldn't surprise me to find that the 3db better sensivity of the NEO8 is due to simply better and stronger magnets.
Too much is never enough
I looked at the FR sweeps and specs and I don't think the new Chinese ones will do the same as the Neo8's since they have a heavy resonance around the 300hz mark that is much less pronounced in the Neo8 in both FR curves and impedance sweeps. I would have tried it if the Neo8 were still off the market, but not when they are and have more useful performance.
Anyway Congrats on the delivery, now you need to raise these babies into a line array ... Good luck, and if you have questions I and others have worked with them before and can probably help.
Interesting, I didn't know about that. I'd thought they were identical.
Well, they are knockoffs. You pay less and you get less. They seem to have missed some of the tricks BG used when they put this driver design and manufacture together. But the specs and FR are significantly different and not in favor of the Chinese KOs.
Audiopur measurements, http://www.diyaudio.com/forums/planars-exotics/289716-bg-neo-series-back-parts-express-3.html#post4821939
That is better than the sweeps on Madisound's page (spec). Looks like they worked out the kink with the resonance peak at 300 hz both the FR rise (5-6db less) and the accompanying impedance rise (from double to just a blip) are much smaller in these scans than the original manufacturer's spec.
The odd order distortion is low even at and below resonance. I don't think the 2nd order distortion is significant above 500 hz and even order is acceptable even below resonance.
The rolloff is oddly 18db rather than the 12 db I recall from the Neo8.
Looks much more promising than the spec sheet.
The 800+ hz dip between the 300hz resonance and normal output above 1khz is a worry since at 10db it is still much deeper than with the Neo8, unless it evens out with a line array like the cavity resonance at 12khz then it would need to be rather heavily EQ'd to use below 1khz. On the Neo8 singles the dip is much less pronounced at 4-5 db and irons out in the line array to within my measurement error and is no more than 2 db.
but since the BG Neo 8's are back on the market I will just use what I have know to be some great drivers.
Thank You for the offer, I will definitely ask. This is my first DIY Line Array project so I will be learning as I go.
BTW, That Notch filter on the BG Neo 8 white paper. Is that for the peak around 12khz? When I use the Xover Pro software there is a peak around 12khz. There is nothing the software can do to reduce it since it will not do Notch Filters in the active software. It will help you design a notch filter but will not add or show it in the final design.
"but since the BG Neo 8's are back on the market I will just use what I have know to be some great drivers."
But we do not yet know for sure these new BG's are identical to the former ones. BG are said too be made in the Philippines. The Audiopur made in China. I think you know that made in China may not be all bad, most suppiers are located there these days. When it comes to magnetics, I think China is the only place to go for.
I built something similar using nine Neo8 PDR's and twelve Dayton Audio RS180's. You'll find two unexpected characteristics of a line array that will effect your design. First, you don't get a doubling of sensitivity with each doubling of the number of drivers in the tweeter array. With four Neo 8's the sensitivity will be about the same as with one Neo 8. Second, the standard crossover values that would be correct for a point source woofer are incorrect for an array of woofers. The increase of sensitivity that's caused by an array of woofers isn't linear across the frequency spectrum. Most of the increase occurs at the lower frequencies. This will effect the value of the crossover components. In the case of my array I used a second order woofer / third order tweeter crossover at 1khz. https://fredt300b.smugmug.com/Hobbies/Towers-of-Awesomeness/
Totally awesome design How did you handle the dipole bass? Did you EQ it? use the driver resonance against the dipole cancellation?
I will check out that site.
I do have Dr. Griffith's White Paper on Line Arrays and will be studying it. He also mentions a tapering technique to help with the near field listening to help with some issues in regular line arrays for near field listening. I think this from I read is for blending better of the drivers for near field listening.
The 12khz peak is a cavity resonance, the more drivers you stack vertically the less prominent the peak. I use 6 of them and it is just a small prominence <3db.
How many drivers in your array?
Also measure the array FR from a distance similar to your listening distance rather than the standard 1 m or close up. Also check out the 15 and 30 deg off axis responses.
4 Neo8's and 6 Silver Flute 6.5 drivers. This configuration gives me the perfect level match with these drivers. The Xover with be a 1kz 1st Order Butterworth. Sensitivity should be around 98-100db.
Thank You for the suggestions and info. I really appreciate it.
How well do you find that the cones match the sound of the Neo8's?
As audiofred noted, the output of the array only adds up at the bottom frequencies. You will not get 98db sensitivity, it will be over 91db but not by much. Adding further drivers to a line of 6 drivers or more will increase sensitivity slightly but more significantly will give you the option of crossing over at a lower freq.
Fortunately for you, the silver flute woofers will not add up that way either, so what you would obtain by a line of 6 will not be much more than what you get from the single driver - within the spec operating range. However, you will obtain much deeper bass extension and power handling..
Most significantly, by increasing the length of the Neo8 array you get more coherent line array performance, less of a resonance peak (8 or 9 drivers will eradicate it completely) and the option of crossing over closer to 200 hz, thereby hitting the holy grail of midranges - covering the entire fundamental and 1st harmonic range of female voice violin and the bulk of the non-bass instruments. This would also allow you to use 1st order filters.
PS Unless I missed it, you did not mention a tweeter The Neo8 does not disperse well enough into the top octave. It's FR also rolls off at 14khz. though it still has substantial output at 20khz. You will need at least a single ribbon tweeter in the middle of your array of neo8 or beside the array at the center. .
for this project. It would be good to use them and not let them just sit used.
I'm just puzzled that the BG NEO8's would need a tweeter. The line arrays Danny Ritchie LS9 design and some others have done with the Neo 8's don't use a tweeter in their designs. Maybe they used some sort of correction circuit in their xovers to help bump up those areas that roll off?
As far as the 1st xover point that can be adjusted. It's just a starting point that I choose since Danny Ritchie used a Xover at 1khz in his LS9 from what I read. But I was wanting do something lower.
I have one of those Virtual Crossover Box that I can change values on the fly and add components to it to help tweak any xover design I want to try. I has been a good tool to use and have saved me a lot of time and money in doing some xovers. :)
I will be using some software my buddy is sending me to take measurements once it's up and running and make the xover adjustments as need to help out any rough spots. I will be using Erse caps and Coils since I have got good results with them and they don't break the bank like the other expensive caps and coils.
Thank You for the info and advice. I really appreciate it.
Another thought, you can try using some commercial line array designs as a guide to driver placement if you are not doing full length lines. The Infinity RS2b is one to look at with the short mid and tweeter arrays besides each other. Another planar short line array is the VMPS RM30 and RM40 with the tweeter placed up top. I actually don't have an example of a commercial short array design with a center mounted tweeter in line with the mids so there is likely a good reason for that, most likely that most of what you hear from the array comes from the center drivers. So those can't carry different frequencies than the rest of the array.. .
The version of the Neo8 that does not need a tweeter is the PDR version as audiofred had used in his project. It has an acoustic lens that improves dispersion at the expense of low end extension and power handling. I think the LS9 was using that but I don;t know that with certainty.
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