# Taming the NEO8



## Patrick Bateman (Sep 11, 2006)

In this thread I'll illustrate a few ways to tame the BG Neo 3 and Neo 8.

This post might be a little confusing, *so if you want to cut to the chase, read the last half.*










Here's a frequency response measurement of the BG Neo 8. In the measurement, we see a big strong peak at 12khz.

*What's interesting about this peak is that it doesn't appear to be a resonance.*

This is important, because it means that the peak at 12khz won't "ring". When a device rings, the sound is delayed in time, and "ringing" in the time domain sounds very obnoxious. (Basically, if you have a driver that rings, you want that ringing to occur outside of the passband.)

Dynamat Coin Demonstration - YouTube

This video from Dynamat shows what ringing sounds like, and how damping can reduce it.









Justus Verhagen from diyspeakers.net posted this cumulative spectral delay plot from the NEO8, and it seems to confirm what I suspected - the NEO8 doesn't "ring." *If it did, you'd see a big ridge in the CSD at 12khz.*

At this point, I hope I've established that *the BG Neo 8 does not ring.*

So what the heck is making that peak?​
My first hunch was that the peak was due to geometry. Basically, that the sound radiating from the edges of the Neo 8 was summing in phase on axis, and creating that peak at 12000hz.

If this were true, I would expect that the peak at 12000hz in the Neo 8 would be dependent on distance, and that the Neo 3 would exhibit the peak at a frequency about 20khz.

For instance, if you measure a Neo 8 at a distance of one meter, the sound from the edge of the diaphragm arrives at the microphone 0.0118 milliseconds later.

That's not enough time to create a peak or a notch, or at least not one that's audible.










Just to double check my theory, I did a sim of the BG Neo 8 in ARPE. The ARPE doesn't show the peak on axis; though it *does* show the off-axis dip at 12khz.

So what the heck is making that peak?​








Let's take a look at the BG Neo 3. If the peak in the NEO 8 was due to it's geometry, we'd expect the Neo 3 would be flat.

Unfortunately, *the Neo 3 shows the same peak as the NEO 8, only it's a bit higher in frequency and not as severe.*










Here's Saurav's measurements of a dipole Neo 3. His measurements show a peak at 15khz too, consistent with Danny's measurements.




So, once again, *what the heck is causing that peak?*




















Here's my hypothesis:

The peak in the Neo 3 and the Neo 8 is due to three things. First, the size of the holes in the faceplate. Second, the spacing of the holes in the faceplate. Last, I believe the drivers would have rising response on-axis if it wasn't for the holes.


Here is the math on my theory, if anyone is curious. The BG Neo 8 behaves like 48 drivers in an array. (This is due to the holes.) *In an array, two drivers will sum on-axis if their spacing is within one-quarter wavelength.* The holes in the Neo 8 are approximately 0.64cm apart. So when the Neo 8 is playing a wavelength that's 13281hz or lower, the sound emitted by the holes sums.

Here's the math:
_speed of sound / distance / 4_
= 34000cm per second / 0.64cm / 4
= 13281hz[/i]​
As the wavelengths get shorter and shorter, the sound emitted from the holes begins to sum destructively. Basically, the spacing of the holes creates a low pass filter that starts at 13281hz.

Where things get REALLY complex is that there are 48 holes in the Neo 8! For instance, one hole will sum constructively with it's neighbor, but DESTRUCTIVELY with a hole that's further away on the faceplate. So the upper frequency limit is about 13khz, unless you covered up 47 of the 48 holes. (If only one hole was playing, there would be no constructive or destructive interference.)










Which brings us to the NEO 3 PDR. I believe the improved response of the NEO 3 PDR is due to two things:

First, the NEO 3 has less than half as many holes as the NEO 8. Less holes means less interference, and less interference means the effect of that interference is less pronounced. *Note that the interference is due to geometry though; the fundamental reason that both the NEO 3 and the NEO 8 begin to rolloff around 14khz is due to the spacing and size of the holes IMHO. The QUANTITY of holes just makes the problem worse.*

The second thing that improves the response of the NEO 3 PDR is simple. The felt that covers up some of the holes eliminates the output at high frequencies, and THAT cuts down on interference.





OK, that was a long post, I hope this makes a little sense.





Now that we've established that the size, spacing, and quantity of holes in the NEO drivers affects their response, we now know how to improve it.

The first idea is obvious - cover up some of the holes! This is exactly what BG does in the PDR versions. It's too bad the matrix isn't 5x5 instead of 4x5. *Ideally, we would progressively cover up the holes.*

In other words, if the NEO 3 had a 5x5 faceplate, we would leave the center hole uncovered, then put some damping around a 3x3 ring in the center, and more damping in a 5x5 ring on the outside.









Picture a felt or foam bullseye, that's cone shaped. As the depth gets thicker, the felt or foam reduces high frequencies further and further.









VMPS does something similar with their flagship speakers; if you want to look up the patent it's 7835537

Another thing you could do is replace the faceplate, and use smaller holes. For instance, if the holes were spaced 0.35cm apart, the rolloff would begin at 24000hz instead of 14000hz. This seems like a no-brainer; I'm not sure why this isn't done.

Anyways, hope that gives you some food for thought. I believe it's possible to improve the high frequency response of the NEO 8. Some would suggest doing this with a crossover, *but it is better to do it mechanically.* This is because taming the peak mechanically improves the polar response and improves the power response. Fixing the peak in the crossover network only improves things on-axis.

I took my pics from the following threads - thanks to Danny Ritchie, [email protected], and Justus Verhagen for their measurements.

Bohlender Graebener Ribbons - Page 3 - diyAudio

HTGuide Forum - Getting back to my OB design...

Siegfried discovers added dimension


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## rawdawg (Apr 27, 2007)

"Less holes means less interference, and less interference means the effect of that interference is less pronounced."

So, how would it measure if the faceplates were removed?

Edit: I just re-read. Rising response over the entire range?


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## cvjoint (Mar 10, 2006)

Patrick Bateman said:


> Another thing you could do is replace the faceplate, and use smaller holes. For instance, if the holes were spaced 0.35cm apart, the rolloff would begin at 24000hz instead of 14000hz. This seems like a no-brainer; I'm not sure why this isn't done.





rawdawg said:


> "Less holes means less interference, and less interference means the effect of that interference is less pronounced."
> 
> So, how would it measure if the faceplates were removed?
> 
> Edit: I just re-read. Rising response over the entire range?


Guys...there are magnets behind the faceplate. You take it off or make the holes bigger and the magnet will still cover the diaphragm. 

Otherwise, good read. My .02 is to get the non PDR regular versions and don't cover anything. It will cripple output and consequently distortion will go up at any power level. In turn, you may gain a bit flatter top end response but up there you are in the beaming region anyway. Imo the Neo8 should not be used without a tweeter and the Neo3 can be bested dispersion wise by other much easier options. 

Why not a line array of Neo10s flanked by Airborne narrow planars? Or heck, just get the large BG elements, no headache and possibly better results with a single speaker.


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## whoever (Nov 21, 2008)

From what I understand he is considering using it as a faux axial driver, Suitable midrange cone, for bandpass mid in Unity horn. - Page 55 - diyAudio post #543


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## minbari (Mar 3, 2011)

cvjoint said:


> .............Why not a line array of Neo10s flanked by Airborne narrow planars? Or heck,* just get the large BG elements*, no headache and possibly better results with a single speaker.


are you refering to the RD48,50,75, etc? I am seriously considering those


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## cvjoint (Mar 10, 2006)

minbari said:


> are you refering to the RD48,50,75, etc? I am seriously considering those


Yep, those are optimized to take over from 200hz up. I played with the Neo10 dipole and that ruined every project I had in mind for cone midranges. They are just that good. 

The Neo8 has been completely scooped by the Neo8s. This size planar has an awkward range to begin with, due to beaming it's not much use without a tweeter and the bottom doesn't extend low enough to be used outside the telephone band. But the Neo8s finally gets a diaphragm that caters to the size of the Neo8 but covers the relevant frequencies with ease. Neo10 crosses even lower which may not be all that important if you have several Neo8s. At the end of the day why go through the trouble of using multiple Neo8s and 10 when you can just buy the one piece elements? 

If you are really baller buy several RD elements and orient them in a cylinder so as to get a 360 coverage. The more you have, the larger the cylinder, the better the output and distortion. You would also change from a dipole setup to bypole. The back of each RD will be sealed in an optimum wedge box by design. This is what I would do with unlimited money, best of everything. Sit it on the top of an AE 10" passive radiator setup that digs down to 20hz flat without EQ and cross at 200hz. Simple, yet terrifyingly capable. Enlarge the cylinder as much as your pocket book allows lol.


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## Patrick Bateman (Sep 11, 2006)

rawdawg said:


> "Less holes means less interference, and less interference means the effect of that interference is less pronounced."
> 
> So, how would it measure if the faceplates were removed?
> 
> Edit: I just re-read. Rising response over the entire range?


I wish I knew! I've put my money where my mouth is, and have placed an order for a pair of Neo8s. I have some of the Monsoon Planars already; if I can find a couple hours this week I'll try and get my Arta setup running again.

I really can only guess what the effect of a waveguide will be on these, so it's time to do some measurements.


























The graphs above are Danny Ritchie's measurements of a VMPS home speaker that uses one of these Monsoon Planars. *In the measurements, you can see the polar response is truly bad around 4khz.*

But a lot of people like these speakers which means one of two things:

#1 - people have tin ears (possibly)
#2 - people can't detect problems in polar response (not likely)
#3 - getting the phase response correct is so important, it can make a speaker with terrible frequency response 'good enough' to live with (quite possible)

If you want to read more about the VMPS, and the drama that ensued when these tests were published, just google around, it's on audioasylum and audiocircle

http://www.gr-research.com/vmps626r.htm

It's quite an interesting discussion, because it covers a lot of the things that I've been pondering in audio for the last year or two. Particularly the important of well behaved phase, and how UNimportant frequency response and distortion are. I have a pair of the Monsoon ribbons, and the response is terrible, and they audibly distorty. But despite all that, I can listen to them for hours on end. In fact, I've taken some flack because I keep using the Monsoons to replace the satellites that you get with 'regular' computer speakers. (Basically I have three or four stereos at the house, with the 'reference' system in my bedroom and a couple more stereos in the family room and in the kitchen. In fact, the system in my kitchen probably gets used more than my megabuck reference rig.)


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## thehatedguy (May 4, 2007)

I would have sent you a couple of Neo-8Ss if I had known you were wanting to play around with some...or got you better than retail pricing on the regular Neo 8s from PE.

The Neo-8S is a really nice speaker, if I had the room, I would have went with the Neo-10 off of the bat...but I didn't.

But I am also liking the path I am going down right now with the Neo-8Ss replacements.

The only thing about the B&G speakers I don't like is the sensitivity seems to be lower than what is published. They would be a good candidate for a horn to pick up some sensitivity in the low end.


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## rugdnit (Dec 24, 2007)

Cripes... Anyone notice that the price of neodymium finally caught up? I went to purchase and the Neo3PDR was $30 more. The Neo8 went up $25 bucks a piece as well. Really stewing on the Neo10 or the Neo8S. I could fit the Neo10, but I am concerned how much they will stick out. I have large Pillars, but the Neo8S would be a stealthier fit. 


CVJ-- How has your testing gone with the Neo10?


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## cvjoint (Mar 10, 2006)

rugdnit said:


> Cripes... Anyone notice that the price of neodymium finally caught up? I went to purchase and the Neo3PDR was $30 more. The Neo8 went up $25 bucks a piece as well. Really stewing on the Neo10 or the Neo8S. I could fit the Neo10, but I am concerned how much they will stick out. I have large Pillars, but the Neo8S would be a stealthier fit.
> 
> 
> CVJ-- How has your testing gone with the Neo10?


Good enough that Im willing to forget cone mids ever existed: http://www.diymobileaudio.com/forum...cal-advanced/125188-oh-you-know-bg-neo10.html


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## thehatedguy (May 4, 2007)

Want a used set of Neo-8Ss?


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## barracuda777 (Mar 4, 2009)

thehatedguy said:


> Want a used set of Neo-8Ss?


If they are PDR ones, I'm interested sir!!!


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## thehatedguy (May 4, 2007)

No, they are the Neo-8S version.


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## whoever (Nov 21, 2008)

barracuda777 said:


> If they are PDR ones, I'm interested sir!!!


The Neo8S is BG's top of the line for that size driver, Neo8, Neo8pdr, Neo8S
Here is some info on it

http://www.audax-speaker.de/index.p...view&index[shop_articles][category]=4&lang=en

just click on the english setting and scroll down to the Neo8S


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## barracuda777 (Mar 4, 2009)

thehatedguy said:


> No, they are the Neo-8S version.


You've got PM sir.


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## bconline (Apr 13, 2012)

thehatedguy said:


> No, they are the Neo-8S version.


Still have the Neo8s' for sale?


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## barracuda777 (Mar 4, 2009)

I'm asking too..........again.
I' still interested!


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## thehatedguy (May 4, 2007)

I do, I just haven't had time to pull the other one out and list them up and stuff. I have 3 total.


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## bconline (Apr 13, 2012)

thehatedguy said:


> I do, I just haven't had time to pull the other one out and list them up and stuff. I have 3 total.


barracuda777 asked first, so I'll give him first shot at em.

How much do you want for a pair?


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## barracuda777 (Mar 4, 2009)

PM send dear hatedguy.


bconline, thanks!


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## bconline (Apr 13, 2012)

barracuda777 said:


> bconline, thanks!


It's only fair. Let me know if you don't buy them.


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## barracuda777 (Mar 4, 2009)

Bconline:
Updating, i bought Jason NEOs. I can't wait to play with. I hope you can find some BG soon.
I owned a pair of NEO3pdr in my car and i lovedthem.


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## Patrick Bateman (Sep 11, 2006)

bconline said:


> It's only fair. Let me know if you don't buy them.


Danny Ritchie at GR Research has a big stock of NEO 8s, and he has them in a lot of unique configurations that aren't available from other vendors.

Whenever possible, I try to send my business his way and recommend him to other people, because he's very knowledgeable and gives back to the community with his designs.

Danny has been using the BG drivers in his speakers for close to a decade, so I think that's how he's able to get BG to make custom versions for him.


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## rugdnit (Dec 24, 2007)

Patrick Bateman said:


> Danny Ritchie at GR Research has a big stock of NEO 8s,* and he has them in a lot of unique configurations that aren't available from other vendors.
> *
> Whenever possible, I try to send my business his way and recommend him to other people, because he's very knowledgeable and gives back to the community with his designs.
> 
> Danny has been using the BG drivers in his speakers for close to a decade, so I think that's how he's able to get BG to make custom versions for him.




I only saw the std version on his site. I would really like to do the NEO10, but not sure I can work it in. What other configurations are the NEO8 available in?


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## whoever (Nov 21, 2008)

rugdnit said:


> I only saw the std version on his site. I would really like to do the NEO10, but not sure I can work it in. What other configurations are the NEO8 available in?


Get the Neo10. Wait for it, its worth it. If you cannot fit it there is the Neo8S


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## Fast Hot Rod (Apr 19, 2007)

rugdnit said:


> I only saw the std version on his site. I would really like to do the NEO10, but not sure I can work it in. What other configurations are the NEO8 available in?


I have only seen info on the Neo8 and Neo8 PDR. Here's a link that describes their performance:

http://www.k4revenge.com/Mat/new/bgneo8pdr.pdf

I'm curious about the Neo8 PDR's performance for use as part of a center channel of a 7.2 home theater system. Maybe run a pair of 7" or 8" drivers for the low end, then have the Neo8 PDR take over at 1,500~2khz?


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## rugdnit (Dec 24, 2007)

I'm aware of the of NEO8 and NEO8PDR as well as the NEO8S. Was just curious what the other variations were.


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## bconline (Apr 13, 2012)

barracuda777 said:


> Bconline:
> Updating, i bought Jason NEOs. I can't wait to play with. I hope you can find some BG soon.
> I owned a pair of NEO3pdr in my car and i lovedthem.


Thanks for letting me know that you worked out a deal. Tell us what you think of the NEO8S after you try them out. I'm curious to know how they compare the regular NEO8.

I'm using the NEO3PDR in a home build. Very sweet upper end. I was also using the NEO8 and am thinking of switching to NEO8S or, better yet, NEO10.


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