It sounds like you guys had a great time, and learned a lot.
I appreciate you guys taking the time to post your views too. It really helps us. Customer feedback goes a long way.
The A/B comparisons are great too. It helps motivate us to produce the best products that we can.
I am sure VMPS appreciates it too.
Sounds like there were likes and dislikes across the board.
We learn that there is no one speaker for everybody and that the room interaction can make or break a combination.
One set of technical questions were asked by JoshK that I will try to answer.
I really find the statement that the Neo8's peaked output in the range in question to be able to be combed flat. According to the white paper the comb effect from a ribbon or planar is minimal (IIRC within 3 db, and the Neo8 has much more than 3db peak). The two just seem to be in opposition. Now maybe I am missing something here, but if not I really question whether the alphas have a flat response in the highs as suggested.
Good question Josh.
If you look at the Neo 8 frequency response you will see rising response that peaks at about 13kHz then rolls off at the top end.
http://www.partsexpress.com/pdf/264-712s.pdfIf you use one of them, you have to use a notch filter to attenuate the peak.
If you use two of them playing together you get no gain in the higher frequency ranges (above 16 to 18kHz) because of the limited vertical response.
But as frequency decreases, the output overlaps and you get gain in the lower ranges.
By the time you have eight of them in a line, the output level is much higher at the bottom end (around 500 to 800Hz) and falls down to the higher ranges where output is less.
What was a peak at 13kHz is now been pushed out a little further into the 15 to 16kHz where it drops off about 4 to 5db and then extends out to 40kHz.
The output level in the lower areas then has to be pulled down by the network to equal the output level at the top.
You then get a flat response to 15kHz or so then the roll off.
Now keep in mind that the playing surface is 1.25" wide. So off axis response will roll off more quickly in the higher frequency ranges more quickly than a narrow ribbon tweeter.
Looks like the Alphas were set up firing nearly straight into the room and the listener was about 10 degrees off axis.
This positioning will see a roll off in the highs that is greater than if they were turned straight at the listening position.
My measurements that far off axis match the roll offs you guys measured in the top octave too.
Toeing them in should pick the output at 20kHz up about 3db or more.
This will lessen the width of the sound stage slightly but also minimize side wall reflections too. Images will be a little more focused but not as large too.
It's give and take.
Side wall reflections could be the cause for a little extra energy in the 10kHz region too. Towing them in might take that away too.
Because the RM-40's are a point source at those frequencies they should have much less room interaction at 10kHz and may not have a peak there at all.
The Alphas will load the room quite differently there.
The room can simply cause a lot of problems and it sounds like this was a tough one.
By a "real" ribbon, I meant something that would extend output to 20khz. You wouldn't even have to change much on the Alpha's, just plop a tall line ribbon next to the BG array and set the crossover at 10hz. The crossover could take care of that bump in the low/mid treble, and the line tweeter would give output to 20khz at least (and maybe furter, although I doubt anyone could hear it, or that it would matter much).
Pros and cons to that too.
One, it would add a lot of cost to the bottom line and it would be a lot more expensive.
Secondly, crossing drivers that high can cause more problems than the they fix.
You would then have a real narrow sweet spot because moving off axis one way or another would then cause the overlapped area of the drivers to cause large dips in the response just below and just above the crossover points in the neighborhood of 20db.
A 120db per octave crossover might make it work though.
I would rather have a slight roll off in the top and an even response over a wide area.
A real solution would be a line of Neo 3's like what was used in the Epiphany line.
These extend the top end all the way out very smoothly, but it takes three of them to equal the length of one Neo 8 and it would add a lot to the price too.
It is all give and take again and how much it is worth to you.
The sibilance observation may or may not be speaker related.
Capacitors can be a cause if they are not burned in.
I heard Gary Dodd's Alpha LS's a day before Xi-Trum did and there were no (ZERO) sibilance issues. I have not heard any such problems with them like that any other place either.
But, the day after Xi-Trum heard them at Gary's, he (Gary) hooked up a brand new pre-amp (zero hours on it) and he noticed some obvious sibilance until it burned in.
If there is anything in the system that causes it the Alpha's will show it off and not cover it up.
There is something else in the system causing that and it can be corrected.
Were any Bybee's used in the system? I have heard them elevate sibilance several times.
Are those Parasound amps pictured? That could be a cause too.
Keep working with it and I am sure it can all get dialed in.
Thanks again.
