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Old 21st July 2003, 09:07 PM   #1
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Default What to do with BG Neo8PDR?

I just saw that these are at PE for $52.50. I've seen threads on these before, but nothing really caught my eye, as I plan to go passive.

I'm looking for a recommendation on how to apply these to a 2-way. The manufacturer's spec sheet recommends a crossover in the 500-700Hz range. This opens up a wealth of designs, maybe crossing over directly to a small sub driver? Or maybe an MTM is better because they spec 92.5dB SPL? Any advice, including "stay away" is welcome.
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Old 21st July 2003, 10:20 PM   #2
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I've read on the forums where they say this driver lacks
top end.

Research madisound.com forum too, I think you may find
some tips there also.
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Old 22nd July 2003, 05:01 AM   #3
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Default The 8PDR

Hi Leadbelly,
I have a pair of the Neo8PDR's. I was also very worried about the large HF peak above 10Khz and the subsequent rolloff.

I use it in dipole mode in an active two way system ( on trial).
The Neo8 is crossed over at 600Hz with a -12db per octave crossover and the woofer is crossed over also at -12db at 600Hz.
The woofer is a 12 inch Peerless( classic range) in a sealed box with Qtc just under 0.7. The Peerless sounds remerkably good even when rolled off at 600Hz. The sensitivity levels have to be matched. This is easy as the system is active.

My observations:
It doesn't sound like a normal boxed speaker.
It surely has better mid range than a boxed speaker. The HF is there all right and the HF peak does not seem to show itself as bad sound. In fact I cannot say that there is a nasty peak just by listening to it.
I like it and my Mission701's ( upgraded) now sound bad in comparison.

Sometimes I feel that there must be more BITE in the HF but I do not miss it most of the time. Transients are very good and mids are particularly good. The crossover is crucial and I think more work has to be done in this area.
The sound also seems to have a sense of depth that I have not heard the same way in a boxed speaker. I think the rear reflected sound has much to do with this. This sounds good.

For the price I think it is a good buy. If things are ironed out more eventually it will be a "great buy".

The best listening position is a bit confined due to the planar configuration. Not too bad however.
But off axis the sound does not seem to crash as the rear signals combine with the frontal signals and room reflections to produce a very good listenable sound anywhere - unlike boxed speakers.

Conclusion:
May not be the greatest driver you can get but certainly a driver that can produce very good results and a sound that you probably can never get tired listening to. It's really very easy on the ear. I have been listening to it for long periods of time and keep discovering sounds I never heard clearly on other speakers. A planar dipole is "different". Get yourself a pair. You can use a Vifa P21W as a bass driver. I plan to use a TL Vifa P21W eventually.
Of all the 8 inch drivers ( in this price range) it seems to behave best in the crucial 500 to 700 Hz range.

In the picture the Neo8 is standing on the Mission 701. The Neo8 baffle is 14 x 10 inches. I also tried the Mission 701 as the woofer
( active crossover) and it isn't any better than the Peerless. Bass is of course much worse than the Peerless.

cheers.
Attached Images
File Type: jpg neo8-test.jpg (32.0 KB, 351 views)
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Old 22nd July 2003, 03:35 PM   #4
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Default LR crossover

I forgot to mention that my ultimate aim is to use a Linkwitz Riley 24 db per octave crossover. The tweeter will probably need only a -12db one to give an overall -24 db. But the Q will have to be looked at closely as it should result in an overall Q of 0.5 .
This way we can go a bit lower on the tweeter than a Butterworth filter will permit.

The woofer will also benefit with a -24 db slope. Mine is currently
-12db and I think the sonics will get even better than it is now.
I am driving these units with a Hybrid Mosfet power amp.

Has anyone been trying these things as single units ? Most people are using them in arrays.

Cheers.
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Old 22nd July 2003, 07:13 PM   #5
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ashok,

Why did you choose not to use the notch filter BG recommends? Does it make the HF dropoff worse?
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Old 23rd July 2003, 05:02 AM   #6
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Default The notch filter

Hi Leadbelly,
I did consider using the notch but decided against it for the moment because :

1. B&G said that in normal use the HF peak is not a problem - not really audible .

2. The notch flattens the peak but there is an expected slight roll off further up. This most likely will not cause any audible problems.

3. I believe that to keep the passive components as few as practically possible contributes to better sound.

4. Without a long listening spell ( a few months at least ) it will be hard to say if the stock speaker is acceptable or not without additional filter components.

5. The driver has to break in well before any fiddling is done otherwise you will get lost. As you keep changing components the drivers will be changings its own sound. You have to wait !

6. Due to the scattering and reflections in the room the peak should even out at the ear - differently in different rooms. I have an average room with a reasonable amount of absorbent curtains and furniture and the neo8 sounds good. Like I said earlier , it might not be razor sharp but is very clean and clear. The sound is effortless and nicer than boxed speakers.

I will post more results as soon as I make the changes. I will also make some measurements in the room and try to post the response graphs. I am also very keen on getting this done. Unfortunately I have to attend to work that keeps the 'funding' going !

If I were asked to say in one line if I recommend the Neo 8, I would say " If you like scintillating highs in preference to very clean unboxed mids , then the Neo8PDR is not for you ". Remember that you can always add a super tweeter IF you want to but you can never clean up the mids if it's not OK to start with.
Cheers,
Ashok.
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