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Talk but not walk?

Hi Guys

This isn't meant to start a fight, but it is important to on lookers. As a qualifier, I have my own audio forum where we report on audio issues as we empirically test them. It helps us short cut on theories and developing methods of listening. We have a wide range of systems and they are all over the world adding their experiences to the mix. Some are engineers, some are artist and others are audiophiles both new and old. One question I am almost always asked while I am visiting other forums, from some of my members and also members of the forum I am visiting is, why do so many HEA hobbyist talk theory without any, or very limited, empirical testing or experience?

I have been around empirical testing labs since I was a kid, and one thing that is certain is, you can always tell if someone is talking without walking. Right now on this forum there are easily 20 threads going on where folks are talking theory and there is absolutely no doubt to any of us who have actually done the testing needed, that the guy talking has never done the actual empirical testing themselves. I've seen this happen with HEA reviewers and designers and a ton of hobbyist. My question is this, why?

You would think that this hobby would be about listening and experience, so why are there so many myths created and why, in this hobby in particular, do people claim they know something without ever experimenting or being part of a team of empirical science folks. It's not that hard to setup a real empirical testing ground, so why don't we see this happen?

I'm not asking for peoples credentials, and I'm not asking to be trolled, I'm simply asking why talk and not walk? In many ways HEA is on pause while the rest of audio innovation is moving forward. I'm also not asking you guys to defend HEA, we've all heard it been there done it. What I'm asking is a very simple question in a hobby that is suppose to be based on "doing", why fake it?

thanks, be polite

Michael Green

www.michaelgreenaudio.net


128x128michaelgreenaudio
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elizabeth
6,726 posts
 

'technical facts'.. There were NO technical facts in your post to 'comprehend'.. Just lots of quasi-rants. And the one true fact: You do not like planar speakers. Then the attack on MG, and your scathing words, oddly also apply to YOUR OWN ARGUMENT. "Going sideways' Which for YOU is arguing about a particular design of speaker, and has zero to do with MG's discussion, but serves you with a way to rant on about stuff which in the context of the thread have no meaning. Mainly because you do not like the guy, and just are searching for anything to whine about. And finally no one would expect anyone to own equipment they do not like.  
LOL
bdp24's avatar
bdp24
4,908 posts
 

One thing I can contribute to this discussion happens to be where the subjects of planar loudspeakers and technical facts (at least those posited above by kosst) overlap. Though they are my over-all preferred design, there are very valid objections to be made against planars (as kosst has done), and reasons to not like them. That’s fine.

But there were some statements made about planars that are simply not true:

1- ESL’s and magnetic-planars should not be grouped together in terms of the load they present to the power amp. ESL’s have an impedance profile that varies wildly as a function of frequency (fancy term ;-), magnetic-planars (Magneplanars, Eminent Technology LFT’s) do not. ESL’s are an extremely capacitive load, magnetic-planars an almost purely resistive one. Consequently, ESL’s and magnetic-planars present very different challenges to power amps. That’s why Roger Sanders makes two versions of his Magtech amp---one for ESL’s, one for magnetic-planars.

2- Planars interact with the room in very different ways than do non-planars (or, more accurately, non-dipoles), but some of those ways are actually advantageous. For instance, as a result of their line source behavior, dipoles interact less with the room in terms of ceiling and floor reflections, a potentially good thing. Additionally, because of the cancellation to either side of a dipole (where the front and rear wave meet out-of-phase), planars create less side wall reflections, and the eigenmodes created by the room width dimension are less excited by a planar than by a non-planar, both again a potentially good thing.

However, the rear wave of planars presents a number of challenges to users. To prevent comb-filtering (too complicated to go into in depth here), planars need to be well away from the wall behind them. Three feet has long been considered the minimum, but that has been found to be insufficient, five feet being much better. Five feet creates a 10 millisecond delay between the front and rear wave (sound travels at roughly 1’/ms)---5’ from the rear of the speaker to the wall, 5’ from the wall back to the planar. 10ms is considered the minimum time required between two acoustic events for them to be perceived as separate events, rather than a smeared single one. The rear wave reflection itself can be dealt with either by absorption or diffusion, or a combination of both. A "too lively" room may benefit from absorption, a "too dead" one from diffusion.

elizabeth
6,726 posts
 
(added ten minutes later: sorry about this rant. I just had to.. But it is nothing to do with the topic, other than thinking for yourself instead of just parroting other’s notions.)
I would comment on the 10ms delay thing.. If one ONLY looks at the single line (instead of endless ones all way) from the back directly behind the speaker. But the reality is the waves travel away in all directions. So my 20.7 being 42" nearest, and 58.5" (they are angled in a lot) farthest from direct back wall line, are actually an infinite variety of distances! The shortest being 45" from actual tweeter location, varying up to about ten feet to the opposite side back wall! I just take issue with using a single measurement, then claiming it is the theory answer. Well it is not. The distance of reflection is changing all across the back wall as the reflections of the sound hit all along the wall and bounce every which way..
Now I do have to say perhaps the ’main’ reflection is the angle from the rear of the speaker to the wall to the space between the speakers at the listener... However the percentage of the total surrounding sound from that tiny little line is pretty small. (if you calculate the actual space, vs all the space as a fraction.. Maybe 0.25% (guessing) of all the sound from the back.. and IMO is lost in the mix. So the made up rule of five feet is just that made up to fit a theory, which theory used in the rule of five feet... IMO is wrong. So the distance planar speaker should be from the back wall... may be anywhere from a few feet, to whatever sounds good... relying on made up theory is not good unless you think it through yourself. Way too often it is just repeated malarkey someone thought made sense.PS the ’five feet’ seemed to suddenly appear just a few years ago. Prior to that everyone was 2 to 3 with 3 being considered best. Then, suddenly the 10ms thing popped up and the five feet became the suggested distance. all based on the theory of 10ms and the first reflection. and nothing to do with actual use Like someone invented it and it suddenly became popular... Just whining.. feel free to "harrump" in disgust that anyone would dare to challenge a theory.
geoffkait's avatar
geoffkait
14,147 posts
 
Rather than just guessing, I don’t know why people don’t adopt a sure thing. The out of phase track on Test CDs like the XLO Test CD is just the ticket for finding the absolute best locations for any speaker in any room. And with any level of room treatment, from zero to $20,000. As you improve room acoustics over time the track will allow you keep track and find the best locations as you progress. It’s fool proof. Hel-loo! Trying to calculate or guesstimate or move a little/ listen a little will not work. They will provide only local maximums. You need a guaranteed method. Trial and error methods are like trying to solve x simultaneous equations in x + n unknowns.

Don’t be a cube, rube. Go ape! 🦍
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