Axiom Home Page Forums General Discussion Technical Questions Ian (or Alan), question about VP150 design/layout

I think it is important to remember when listening for buzzing and crackling noises that the speaker is going to reproduce whatever information or noise may exist in your entire system right back to the original recording. This goes to every wire connection, solder joint, antenna hook up, ground wire, and electrical component through the whole system. If the speaker is the culprit then the noise will be mechanical in nature, which generally means that crackling type sounds are not the speaker. A mechanical noise will generally seem to add an overall distortion to the sound at volume levels that are definitely below clipping. This is usually pretty easy to notice when listening to music. For jkohn's particular issue with the VP150, there seems to be something wrong here for sure. We would be happy to bring your VP150 back to our lab for a thorough test and either fix your problem or least be able eliminate the VP150 as the source of the problem. There is absolutely no way with the power you have that there should be any distortion from the center channel, unless of course you are running into clipping. The VP150 can take the 200 - 300 watts you are powering it with no problem. In fact I run my own with more power than 300 watts and our power tests are done on the VP150 with a 620-watt amplifier. Please contact us directly at the toll free number 866-294-6688 or at advice@axiomaudio.com and we will look after all the details for you.

Going to the original post that started this thread. There seems to be quite a bit of confusion over how identical parts interact with each other (the two tweeters) in a room environment. The comment about comb filtering is a red herring. This effect can be measured in anechoic environments but it is not an audible reality in the room. If it were we would have all dumped stereo a long time ago and would be listening to mono again. The off-axis lobing effect of the tweeter and woofer is a reality in the down-axis measurement of all speakers that use a tweeter above the woofer, and does create an interesting dilemma with center-channel design because this phenomena now exists in the right and left off axis in a WTW layout. As to how big an issue this is in the real world is best determined by double blind listening tests. It is audible, especially when seated far off axis from the TV, but always surprised me as to the how slight the effect in the room is when compared to the measurements. A testament to the importance of the family of measurements as opposed to the single axis you are directly seated in. The VP150 driver layout does eliminate this issue altogether by effectively not having this particular axis no matter your seating position. The result is excellent, and it has been proved out in our double-blind listening tests. In fact it was so impressive we actually changed the VP150’s driver array to this layout mid-stream from a WTWTW layout.

I'm having a similar problem with my M30s. I would occasionally notice a buzzing sound out of my right speaker. I tightened down the wire connectors and also tightened the screws, but the sound is still there. While listening to a Peter Gabriel CD, there was a particular song that kept causing the buzziness. The sound was most noticeable from the back, coming out of the port. I eventually found that as I was turning the speaker, to hear where the sound was coming from, it would actually quiet down and even go away as I would turn the speaker over. Tapping on the sides of the enclosure seemed to have quieted it down, but it is still there when upright. It definitely sounds like there is something in the enclosure that is vibrating at certain frequencies. I have both speakers upside down now and that seems to have temporarily fixed the problem.

Other than the occasional vibration sound, the speakers do sound good, especially with high quality recordings with a nice dynamic range. I hate to have to go through the trouble of returning them, but if the sound continues after I put them upright, I'll have no choice.

This is my concern, that the noise sounds mechanical, a definite buzzing right after a musical note. It is not an electrical type crackle or anything that sounds wire related.

I figured that the speakers should easily take the power my receiver feeds it so i know that the volume thing should not be the issue esp. not at 75% of max. I am well away from the clipping zone.

I will give Joe a call today i guess and see if he can hear it through the phone. After listening again last night, i'm positive that 2 of the woofers (low one on the left and mid one on the right) both make the noise.
A friend is coming over today who knows a bit more and can confirm for me it is definitely a mechanical issue or not.

Thanks Ian. I hope this all works out. I really do like the speakers a whole ton.

So here's a whole new question, perhaps a new thread, who does these double blind test at the lab?
People off the street?
University students hired for a day?
Because i think it would be really fun to visit Ottawa someday, drop into Axiom and sign up for an afternoon of blind listening testing.
Can just anyone do that or do you have to be a certain height to get on the ride?

here's my reply on everything in this thread:

1) I have the Diana Krall DVD in DTS, and I do NOT hear a crackling/buzzing sound out of the center.

2)I have occaisionally heard strange sounds out of all my speakers, but they were only repeated by playing the exact source material, therefore, the source is at fault

3) your Outlaw, what ohm switch do you have it at? 8 or 4? According to Outlaw, a 6 ohm speaker should have it at 8, I believe, but I'm not sure.

4)Fifth Element - Superbit is good for reference, as is the Nine Inch Nails live DVD in DTS, and that crappy Star Wars movie. The pod race scene is just excellent in audio.

5) 5 channel audio is loud, I only like it when not critically listening, and just listening for loudness. Otherwise 2 channel beats it anyday. I'm not the biggest fan of DPL2, maybe i need to get used to it.

6) do NOT try to make your VP150 play any deep bass. Mine's cut off at 80 and it sounds better like that. Set to Large, it distorted, especially at loud volumes.

Good luck with your difficulties with your centers

Well, last night I re-did the cable connections and also checked the screws on the center woofers and tweeters. For every driver there was at least one screw that could stand to be tightened. However on one of the tweeters two of the screws would not tighten down at all no matter how much you turned them, apparently the threads are stripped which concerns me somewhat.

By the time I did all this my wife was in bed so I didn't get to re-check for the sound issues. I'll do some more listening tomorrow and if the problem persists I'll contact Axiom to see what we can do.

Ian,
Just curious about the lobing you (and other reviewers) refer to. Can you either describe what this effect sounds like or give a short (astrophysics type dissertation) description on what is happening with the frequency interaction?

Thanks!

Randyman