Axiom Home Page Forums General Discussion Home Theater VP150 Calibration Problems

Jason:

Ian has measured my VP150 and says all is well with it, so I don't think a new VP150 will resolve my issues. Thanks for the suggestion, though.

In reply to:

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However, in my environment, I noticed a very significant drop-off in output as I moved off axis, one that I heard with my ears. The meter just confirmed it.

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But you specifically stated this occurred when calibrating with pink noise. As i iterated to previously, this is partly an artifact of pink noise and secondly, this will occur with any horizontal centre.
Does this equate to the same 'sound' during a test tone playback or real music?
Not that i've heard and certainly not measured with an SPL. Play a song in DPLII such that the centre channel is being used and then do your SPL test from left to right. I can just about guarantee the results will not be the same as you measured with pink noise.
Keep in mind that your original measured values were 2-3dB which is at the marginal range for human perception as significantly different volume (this number seemed to increase as your later posts came along, i don't know how). If the right and left channels are working and placed for optimum performance, you should not detect any dropoffs or suckouts.
If you do not like the VP150 for this sound, then logically you should not buy towers either since they have the same 'problem' just in a different plane. Someone posted an article recently about the omnidirectinal Beolab5 speakers. You could always give them a try.

As for the design concept, everyone has different ideas for what sounds good as a speaker and not all use measurements like Axiom at the NRC. Many design speakers off the top of their heads based on principles they know, and everyone wants to have something unique. Very few companies like to copy each other, but note how recently many companies have jumped on this multi-directional driver dispersion idea like the QS8s. Sometimes the concepts take time to catch on and be accepted.
Maybe there is a company that does have the best centre channel design for off-axis response.
Who knows?
But from what i've seen so far, many centre channels are very simple. Usually one or two drivers and that's it. I find this style to have a real point source for sound such that localizing the near exact position of dialogue is distracting as it comes from above or below the viewing screen. I think this is far more a negative property compared to the VP150 shift in response by moving left or right 4 feet or more. The distance to ones listening location from the main/centre channels will greatly alter such perceived sounds.

Hi,

Thanks, Joema, for the mention and link to Floyd Toole's white paper. It was Floyd who first demonstrated to me (back in the late '70s) the effects of comb filtering and the limitations inherent in 2-channel stereo playback.

Tony, ALL speakers at the front of a room produce comb filtering and uneven response as a result. It's yet a further liability of stereo listening and is quite audible using pink noise as a test signal. The explanation is too long to go into at length here but while it's audible with pink noise, it's not a significant factor that seriously undermines our enjoyment of music, movies, or even stereo playback, nor is it identifiable using music as a test signal. (Music has a wonderful masking effect of tiny and even large distortions.)

Plus I believe you had your VP150 stuck in an entertainment center, correct? I would suspect that the interference effects of the EC would have the potential to significantly alter the dispersion of the VP150 and introduce some of the anomalies you seem to find with it. A speaker with a smaller enclosure might be less affected, which might explain why you aren't finding the same effects with the smaller M2i on its side.

All of that said, I would point out that the stereo illusion and that with multichannel is always compromised to a greater or lesser degree. What is astonishing is that with neutral, transparent, and accurate speakers like Axiom (and some others) that the movie soundtrack soundfield reproduction with 5.1 or multichannel music is so convincing and enjoyable much of the time!

Given the vagaries of listening rooms, furniture and the like, it's a hopeless and frustrating odyssey trying to find the "perfect" center channel. There isn't one. But the VP100 and VP150, when properly set up, deliver a convincing and seamless soundstage and intelligible dialog for a reasonable number of listeners in most average rooms.

Regards,

Tony, one more item: if you want a higher degree of off-axis capability you could investigate speakers specifically designed for this. One brand I've heard is Mirage, another Canadian company. http://www.miragespeakers.com

I auditioned the Mirage Omnisat and Omni 60 several times. Moving around the room, the stereo image wasn't affected as much as traditional direct radiating speakers. However the tradeoff was an overall sound I didn't like -- diffuse, blurred, and spread out, even when on axis. In A/B testing with direct radiating speakers I greatly preferred them over the Mirages. Other people love the Mirage sound.

My M60/VP150/QS8/VTF-3 config are the best speakers I've heard at any price, so naturally I'm satisfied with them. If there's an abnormal off-axis problem, I haven't heard it. However 95% of my listening is 1 or 2 people, directly on axis, so I wouldn't be affected by it even if it existed.

Hi Alan:

This odd (to me) behavior was noticeable even after I took the VP150 off the shelf (it's not really a cabinet) and placed it where the left speaker was (essentially free space). I noticed the exact same behavior, so I doubt it was the placement.

The other center I have on hand (an NHT M5) uses a three way arrangement ( two woofers flanked by a centrally located midrange with tweeter above or below the midrange, depending on placement) and I neither heard (nor measured) any such frequency or output aberrations. Now, if you guys are telling me that these aberrations are inaudible with music or movies, that's fine. But I would be interested to see the NRC measurements of the VP150 on axis and off-axis to see if what I'm hearing shows up in as measured anomalies.

"But you specifically stated this occurred when calibrating with pink noise. As i iterated to previously, this is partly an artifact of pink noise and secondly, this will occur with any horizontal centre."

It does not occur with my NHT M5, nor did it occur with the CSW MC500 I once owned, both 3 way centers.

I keep trying my best to NOT read any more of this thread. To no avail. I'm glad so many people are happy with the VP150. I'm sorry Tony is not.

Now, go to the beer thread.

If you didn't post to it, Tom, you wouldn't help to keep it alive. No need to be sorry I'm not happy. I'm glad everyone is happy too. I'm also happy, just not with the VP150. I am very happy with the M2i: absolutely amazing value and a good sounding speaker, irrespective of price or listening axis!

Tony, have you tried using one of your M2is as a center? Be interesting as a point of comparison.

Yes I did and it sounded pretty good. Problem is though, that it's too tall for my cabinet and doesn't work so well on its side.