New Axiom VP180

[AJinFLA]

So I take it the comb filtering issues will be audible and have a negative impact on performance?

Possibly. Depends on who is listening .
It's a rather odd arrangement for a center. Would be interesting to see some polar mapping done for the VP180 like Dr Geddes does.

cheers,

AJ

 

[fredk]

Its funny how people always want for there to be only one right answer, one best speaker...

When I did marketing we always paid attention to 'checkpoint features'. Those things people really thought they wanted, but never used. I'm not saying there is no validity to the vertical mid/tweet arrangement, just that people (or marketers) convince themselves of all kinds of things that are not relevant.

 

[GirgleMirt]

That looks like a horrible design to me... Did Axiom explain anywhere why they chose such a weird design?

 

[MinusTheBear]

That looks like a horrible design to me... Did Axiom explain anywhere why they chose such a weird design?

The design is to match the driver complement of their flagship M80 tower to allow horizontal placement. If you don't like the two tweet design on the M80's, you won't be to fond of this center.

 

[GirgleMirt]

The design is to match the driver complement of their flagship M80 tower to allow horizontal placement. If you don't like the two tweet design on the M80's, you won't be to fond of this center.

Wow and 700$ too! Why not put the two tweeters vertically then instead of horizontally? I'm trying to visualize how the current design would work with the mentioned comb filtering, and I really don't see how this design makes any sense...

I'm not quite sure about the double tweeter of the m80, but other speakers, quite rare though, have been using them... Dynaudio C4 for example, so they must not be all that bad, and if they're positioned vertically, seems a lesser evil to me than horizontal. But going back to the center, where horizontal off axis is quite important, that center design just looks as bad as the VP150 center... It's something I really don't get. I've seen quite a bit of negative VP150 comments, and quite a few seemed to recommend the VP100 instead (regular MTM design). Now, they go with some kind of monster center with some really strange design... Just seems weird...

I can understand the marketing department wanting the exact same driver design as the m80, but they shouldn't have the final word on design...

 

[MinusTheBear]

Wow and 700$ too! Why not put the two tweeters vertically then instead of horizontally? I'm trying to visualize how the current design would work with the mentioned comb filtering, and I really don't see how this design makes any sense...

I'm not quite sure about the double tweeter of the m80, but other speakers, quite rare though, have been using them... Dynaudio C4 for example, so they must not be all that bad, and if they're positioned vertically, seems a lesser evil to me than horizontal. But going back to the center, where horizontal off axis is quite important, that center design just looks as bad as the VP150 center... It's something I really don't get. I've seen quite a bit of negative VP150 comments, and quite a few seemed to recommend the VP100 instead (regular MTM design). Now, they go with some kind of monster center with some really strange design... Just seems weird...

I can understand the marketing department wanting the exact same driver design as the m80, but they shouldn't have the final word on design...

From a marketing perspective the public relations on their VP150 is pretty poor because of the 2 tweeters. Outside the Axioms fans the VP180 will have that similar vibe to folks. Something like a properly designed W T/M W center would fit the best of both worlds from a marketing perspective and performance standpoint.

 

[autoboy]

How can you be so concerned about comb filtering in a center, but don't mind recommending a phantom center or listening to music in stereo?

Isn't it the same concept?

From all accounts of the VP180 I have heard, the speaker sounds great. They sound very much like their M80 tower speaker, which would also suffer from comb filtering but both the vertical AND horizontal space since they have two tweeters and you always run at least two of them in stereo.

And how about their QS8 surround speakers that fire 4 drivers in completely different directions, likely causing all sorts of comb filtering. I have a pair and they sound great as surround speakers with a huge sense of spaciousness.

 

[bigbassdave]

I'm a bit suprised at all the low expectations. I love my m80's duel tweeters and all. I also love my qs8's. My vp150 is not perfect but overall I think its a pretty nice little speaker. Hopefully we will get a review of the 180 from one of the audioholics staff so we can see how they feel. I would love to hear this thing. For me the design doesn't mean it will or will not sound great it simply has me intrigued.

 

[AJinFLA]

Isn't it the same concept?

No.

How can you be so concerned about comb filtering in a center, but don't mind recommending a phantom center or listening to music in stereo?

Because our brains process/perceive them differently. In the case of the stereo sources, we are programmed to use the phase shifts to localize the source, to essentially tell "where it is", even though there may be significant changes in the amplitude (FR) from the combing, we "hear" only very slight shifts in the tone and timbre of the source.
When the combing occurs directly at the source itself, from essential the same point in space, then we easily hear the combing/amplitude ripples in the form of shifts in tone and timbre.

From all accounts of the VP180 I have heard, the speaker sounds great. They sound very much like their M80 tower speaker, which would also suffer from comb filtering but both the vertical AND horizontal space since they have two tweeters and you always run at least two of them in stereo.

You are conflating two separate issues.
"What you/other like" (subjective) and "What is physically occurring/audible" (objective and verifiable).
You like the sound - fine, no arguments (purely subjective preference).
Because you like the sound, combing is audibly innocuous - verifiably false (objective).

And how about their QS8 surround speakers that fire 4 drivers in completely different directions, likely causing all sorts of comb filtering. I have a pair and they sound great as surround speakers with a huge sense of spaciousness.

Because that is exactly what you want in a surround....low localizable/spaciousness .

cheers,

AJ

 

[autoboy]

Still don't know what is different between a stereo speaker set playing content that is exactly the same between the speakers, and a center channel that is essentially two speakers laying on their side. (objective)

Yeah, there's a difference when the content is different between the two stereo speakers, but most of the sound from a stereo set is duplicated between the two speakers which would create the comb effect, just as Axiom describes in their blog.

And, as Axiom describes, my head is not a microphone. I have TWO mics spaced some distance apart and ears that shape the sound entering them.

 

[Paul_Apollonio]

Still don't know what is different between a stereo speaker set playing content that is exactly the same between the speakers, and a center channel that is essentially two speakers laying on their side. (objective)

Yeah, there's a difference when the content is different between the two stereo speakers, but most of the sound from a stereo set is duplicated between the two speakers which would create the comb effect, just as Axiom describes in their blog.

And, as Axiom describes, my head is not a microphone. I have TWO mics spaced some distance apart and ears that shape the sound entering them.

Autoboy is right in his concepts. Whenever you have two speakers making the same frequencies simultaneously (or close to it) you will get comb filtering. The difference is that in stereo, by the time the two sound fields meet, they are direct sound in combination with a great deal of reflected sound. When you use separate speakers (drivers) producing the same frequency range in CLOSE proximity, now you have created a situation where the direct sound of one is close in space and amplitude to the direct sound of the nearby driver. When the distance between acoustic centers (of the respective drivers) is close to or larger than the size of the wavelength (speed of sound/frequency), then the addition of the two is going to be different at different angles and in the immediate surrounding spaces. Those distances can differ by only a few inches as you move across the horizontal or vertical axis. Those few inches of difference in path length equate to a phase shift. Remember if you are in phase, (0 or 360 degrees) you add 6db. 90 or 270 degrees off, you add 3db. If you are 180 degrees off, for equal amplitudes, you can get a nearly complete null at this angle. As you walk across the horizontal axis, the dips move along the frequency scale, up and down. When viewed on a linear frequency scale, the nulls look like evenly spaced teeth in a comb, hence the name comb filtering. If these dips are narrow enough (close spacing of drivers relative to the shared frequency range) then they are hard to hear because real world signals (ie, musical instruments) have LOW Q's, or, in other words, span a LARGE range of frequency information. The narrow dip can be ignored, as this is the same thing that happens without multiple drivers as a result of reflections from nearby surfaces in rooms. USUALLY, those room effects are more random than drivers spaced apart on the same baffle. Flat speakers are not flat in your room, unless you listen in an anechoic chamber. I have, and let me tell you, it is not a musical experience.

I hope that sheds SOME light.

 

[AJinFLA]

just as Axiom describes in their blog

What "blog"?

I hope that sheds SOME light.

I'm pretty sure you've confused him some more .
Let me add to it .
If you were to listen to the VP180, by itself, in the far field, it would be fairly easy to hear (pink noise, human voice, etc.) the changes in timbre (from the combing), as you moved laterally.
...However (Sean, are you reading )...this would not be a typical end user situation, i.e., you would normally be listening to the entire MCH soundfield, which would make it more difficult to perceive such an individual source non-linearity (plus who the heck gets up and keeps moving around during a movie)....so there is a "it depends" caveat. Would it be audible to some under very specific (LCR ch mastering, etc.) circumstances...yes. Would it be a deal breaker for most, under most circumstances...no, probably not.

cheers,

AJ

 

[autoboy]

My head moves around during a movie by a few inches, maybe up to a foot as I squirm around. I'm a bit hyperactive.

The higher the frequency, the smaller distance between the combs and I would likely be able to hear them if I squirmed around in an anechoic chamber. But, i watch in a room with walls that reflect and smooth the response, and our hearing is not as good for higher frequencies (see Bose for proof) so is it much of an issue in the real world? You would also hope that Axiom placed the drivers in the enclosure and tuned the crossovers such that it would minimize any combing effects. I was concerned about combing when I bought my Axiom VP100 which is a D’Appolito array instead of the strange VP150, but now I'm looking for a system for my brother's dedicated home theater and I have my eye on the VP180 and a pair of the incabinet M60s.

From the Axiom message boards, the customers seem to be incredibly happy with their new speakers. That could be just because they are fanboys or they could be swayed by the fact that they are playing with new stuff so I'm trying to see if the dialog will be intelligible in different seating positions since that is my brother's top priority. The fact that it is a full range center for $700 is definately a big plus in my book, and I've been very happy with my setup of M60s, VP100, and QS8s.

His theater build is here. It's pretty impressive design wise. We're trying to keep the budget from blowing up too much with expensive audio gear.

http://www.avsforum.com/avs-vb/showthread.php?t=1152809

 

[fredk]

Autoboy. You are right to ask what the real world effects of comb filtering are. Arguing theory is fine, but it only gives you theoretical results. The best thing you could do is, for the cost of shipping a speaker, order one and compare for yourself.

I know from a couple of posts on the Axiom forum that they went through a number of different driver configurations, and this is the optimum configuration they came up with. As mentioned in a previous post, to put the tweets/mids in a vertical alignment you would need to make the VP180 about 20" tall. That is not a practical configuration for a center.

 

[Midwesthonky]

Fascinating thread! I appreciate all aspects of the various positions posted and thank you to everyone that has posted.

Here's my pennies: I suspect the Axiom guys that upgraded to the VP180 are used to the sound produced from the VP150. As such, to them, the fuller sound of the VP180 is very pleasant. I am an owner of a VP150. In my echo chamber of a room, I am very happy with the VP150. It is a HUGE improvement over my old speaker and the dialog is substantially easier to hear and understand. That was a primary requirement that has been fully met.

In a dedicated home theater room with proper sound panels, I may not be so pleased. For those guys who have such an arrangement and a finicky ear, I suspect the VP180 is not the right approach for them. I also suspect the type/genre of movie that is mostly played will also have an effect on the perceived performance. Those woofers will probably make a good impression for action/adventure movies.

Does anyone run type speaker setups that they change depending on the movie genre?

 

[GirgleMirt]

My head moves around during a movie by a few inches, maybe up to a foot as I squirm around. I'm a bit hyperactive.

Your head movement isn't really the problem, it's mostly for those listening off axis.

I don't think you understand quite well the notion of comb filtering. Here's what seems to be a fairly good explanation with some examples, http://forum.ecoustics.com/bbs/messages/34579/572305.html

Basically, as you said, even with 2 channel you'll get some, BUT, it's not a reason to put two tweeters sideways on a center channel, which will cause comb filtering which would not be there had there been one single tweeter, or two tweeters placed vertically. In case of 2 tweeters placed vertically, comb filtering would happen vertically instead of horizontally, which would be a lesser evil since people sit at pretty much the same height, but they don't all sit 0 degrees in front of the center.

When you talked about an MTM, ok, if you're talking about about a center placed horizontally, you'll get comb filtering with the two woofers... But if you're talking about MTM mains, then the comb filtering happens vertically and there's little comb filtering horizontally. Also, I believe that since the wavelength of the frequencies produced by the woofers are longer than the ones produced by the mids, the comb filtering might be less of an issue here. (That's just a guess though, not an expert in the field...)

You mentioned phantom center, this works great if you're sitting in the center, but if there's many listeners sitting off axis from center, then center is usually better...

The higher the frequency, the smaller distance between the combs and I would likely be able to hear them if I squirmed around in an anechoic chamber. But, i watch in a room with walls that reflect and smooth the response, and our hearing is not as good for higher frequencies (see Bose for proof) so is it much of an issue in the real world? You would also hope that Axiom placed the drivers in the enclosure and tuned the crossovers such that it would minimize any combing effects.

Why put 2 tweeters sideways and then try to minimize combing effects? This makes very little sense since using one tweeter would eliminate this! Besides, they can't really eliminate it... It just makes very little sense to put two tweeters like this... Like a huge "faut pas"... Placing two tweeters like that will create issues...

Two images which illustrate it:
http://www.olympus-ims.com/data/Image/theroy/InterferencePattern.jpg
http://homepage.mac.com/planet10/forum/comb-filter-diagram.gif

Now take a single tweeter, or sound source:
http://paphysicalscience.wikispaces.com/file/view/SoundWaves.jpg/77617045/SoundWaves.jpg

Which will be cleaner? MTM speakers, (not centers), are different because you're sitting on axis from a vertical standpoint. So fact that there's comb filtering with the two woofers doesn't really matter (the whole point of an MTM!) since your ears are at the same level as tweeter and equal distance of the two woofers. For a center, it's a compromise to place it horizontally, but in best case scenario it should be sitting vertically like your L/R and not horizontally, but not many can accommodate this arrangement. But designing a humongous center with TMMMT just seems like a ridiculously bad idea... Seems like a very bad design, like I said, I can't really understand it.

People will tell you best is 3 identical fronts. So messing up your center by giving it a ridiculous TMMMT, which is quite dissimilar from your L/R, makes very little sense to me from a technical standpoint... Is it a killer, means it'll suck and all that? No, but it's most probably not as good as it could have been, and just seems like the design starts off from the wrong foot... Well, or they have different priorities, sensitivity, max output, etc...

 

[fredk]

like I said, I can't really understand it.

Unless you can climb inside the head of the designer, or the designer is willing to share all his design criterion, it will be difficult to understand.

People will tell you best is 3 identical fronts.

How many of these people that tell you this actually have this setup? Thats the issue. Center channels are a trade off. Most people live under aesthetic constraints that are met by sub optimal center channel designs. I strongly suspect that esthetic's were part of the design criterion.

Even I, with my mancave, could not fit a third M80 in as a center. Well, I could have put it upside down over my display hanging from the ceiling, but I only know one guy crazy enough to do that.

It just makes very little sense to put two tweeters like this...

How many people would buy a 20" tall center, regardless of how it sounded?

Product design is almost never about delivering the most technically competent solution. Its about building something more people will buy given their requirements and constraints.

 

[GirgleMirt]

But like I said, since most people will sit horizontally off axis from the center, and not vertically, so it would have made more sense to put the two tweeters vertically than horizontally.... so if (x/x) means vertical position, having WM(T/T)MW would have been better than WTMMTW...

Take NHT: http://www.nhthifi.com/Center-Channel-Speakers , Paradigm, JMLabs, etc... Vertical to reduce comb filtering betweent tweet/mid... Logical design! That's the way 2ch. or L/R speakers work...

You know, yes, as I've said, the center placed horizontally is a compromise, but putting the two tweeters sideways like that can't even be called a compromise, because there's no apparent advantage to it... Yes, a horizontal center is the compromise, but you should try to make the best out of it... A weird woofter/tweet config like Axiom's doesn't seem to have any advantage, only disadvantages... Or if there's some advantages to be had, I don't think anyone has mentioned what they are...

Btw, I'm aware the article quoted in previous post is by Axiom, and he says that it's not 'big issue', but it's definitely measurable (10dB variance!) and so audible, so its makes his points fairly irrelevant or flawed... (brain dealing with it and all)

 

[MinusTheBear]

Based on their previous center designs I doubt they tried any driver complement with the tweeters placed vertically over the mids with the VP180. My guess is the WTMMTW driver complement probably won out to TWMMWT and WM T/T MW. Again, why can't Axiom bring to market a W T/M W design? A W T/M W makes the most sense for the majority of their product line.

 

[GirgleMirt]

My guess is the WTMMTW driver complement probably won out to TWMMWT and WM T/T MW.

Why would WTMMTW win over WM(vertical TT)MW? Again, he says that it might be perceived as additional spaciousness, but I don't see this winning over the vertical tweeters... His own measurements showed the significant adverse measurable effects of the comb filtering... So how could this be better?