The often neglected tweak: speaker rake angle

I still have a pair of Magnat Transpuls from 1982 in one system. They have a wood base that angles the speaker cabinets upwards a bit. I reversed the bases many years ago when they went up on higher stands. You "might" be able to see from this photo. These are the Magnat TP 45's. I guess you just gotta do what you gotta do sometimes

 

Thing with my house if that the floors are not level and things shift a bit if a storm comes through or seasons change. I can use a laser pointer to get things dead on, but I don't want to redo every month.

 

Expansive clay soil?

 

Quad ESLs benefit greatly from adjusting their tilt forward of backwards, as well as their height off the floor.

 

The foundations is pretty steady. Hundred-year-old house though, with lake winds and large snow loads through the winter.

 

Many speakers (or their review tests) do have test plots that show you the off-axis response curve - horizontally. It is not "beaming" (which is a term used for the transition where the piston size becomes a factor in larger drivers) but the expected and desired directionality in HF transducers that is being measured.

First type: multiple 2d plots, On-Axis, vs 15 and 30 degree off-axis response:


Second: 3d plots at multiple axes:


Third: Polar plots (seen more with mics, because 360 degree info is useful):


You can get some sense of how "off" your sound is when your speakers are pointed straight ahead instead of at your ears. Modern speaker design considers the total output of the driver, which may make them seem brighter when heard on-axis directly in near-field.



BTW, the piston effect (beaming) of large drivers has it's own cancellation lobes, but these are mostly mitigated in multi-way crossover designs:


For example, in a 5.4" effective piston area of a 6.5" driver, ka=1 is 800Hz. It's ka=5 response at 4kHz crossover is similar to the directionality of a tweeter.

The crossover cancellation plot I previously posted has to do particularly with the spacing between low and high frequency drivers, and the area of the two drivers. A typical crossover on a typical two-way speaker does give such a plot as depicted, with asymmetrical cancellations above and below, which also depend on the distance (not pictured in those plots).

Of course, knowing the full axial frequency distribution of a driver, we can then computer model the response of arrays of them in a room...

 

Or like my friend, whose TV/cabinet/speakers centerline goes approximately 2/3 of the way through one of his couch cushions?!? Glad I read your post, I swear when I go over to hook up his TV I'm going to re-center everything.

 

Nice post! And those in particular was the curves I want to know where did they come from? Is that a studio/desk/little man at the bottom?

 

Oh, no, actually it was these curves I asked about originally

 

I've seen some expensive speakers firing directly into the side of a couch.

 

Those particular ones come from Excelsior Audio Design. They have several articles that have pretty plots, such as "Optimizing loudspeaker directivity through the crossover region".

There's another article that I am not able to find again on the web, which had wonderful 3d plots of the cancellation nulls from driver interactions in the crossover frequencies.

 

I'm gonna try angling my bluetooth speaker.....

 

I should've mentioned in my original post that my experiments were inspired by this thread:

Speaker Asylum: Iron Chef Speaker Set Up Protocol by tubesforever

He refers to a Leonard Cohen song by Rob Wasserman, featuring Jennifer Warnes called "Ballad of the Runaway Horse"



When I achieved optimal angle, the double bass in this song became tighter and more pronounced. Further, I could detect more "inner detail" what some might simply refer to as resolution.

I didn't use the above-linked setup technique from start to finish, but I did reference the song for some of the other setup parameters as well. When it's best, everything in the song just sounds correct, the bass and vocals have the greatest separation of depth in the mental image, and Jennifer's voice will have an eerie realism.

 

Amateurs. I can hear a difference at 1/32 of a degree.

 

The manual for my speakers (Gibbon 88's) say the best results are achieved when you can barely, but clearly, see the top of the speaker from the listening position. I tend to agree. I had to tilt forward by raising the rear spikes a bit to reach this point. Wasn't a big difference as far as adjustment, but was a significant difference in sound.

 

Really? You un-liked my post on the basis that your physics don't agree with the spefic situation in my own personal listening space? Whatever have I done to offend? And...what on earth gives you the right to even BE offended that I've arrived at my own solution? Is my latitude out of line with your longitude? Am I perhaps an unacceptible distance from the nearest Amoeba? Is the azimuth of my avatar contrary to West Coast Standards, hah?

Smells like personal issues that don't even apply here. Double roll-y-eyes.

 

Someone once described Golden Ear Tritons as "ear drills" when pointed on-axis - a very fitting description IME. It's best to simply set up speakers however they sound best to the listener, experimenting is a must with any speakers in any room IMO.

 

So, four thousandths of an inch. (1 degree = 17 mils, divide by 4). Maybe four sheets of heavy duty aluminum foil. Got shims?

You might be full of prunes.

 

No more so than those who hear drastic differences with cables or DACs. I suppose I can just use their default response: have you tried it for yourself?

 

It cannot be done. Not in my home. Let’s think about this.

Do you believe the floor of your listening room is level from end to end within a thousandth of an inch or less, in any direction? If not, all your measurements are skewed. Any wood products anywhere in the structure? Because boards vary in thickness and straightness by massive amounts, with the errors accumulating as you assemble them. Ever seen framers heaving a wall into place while it’s nailed together before it snaps back to the shape it wants to hold? We’re talking full inches at some point. No house is even close to square— not to support the tolerances you quoted. And wood constantly loses moisture, causing homes to settle day by day, over the years, by vastly greater distances. Things move. Cracks open up in wallboard. Mine creaks impressively in the night.

I might be missing something. I understand some people are gifted with fabulous hearing I will never experience. But this is truly amazing, bewildering even, to me.

Does the sound improve throughout the room, or must you listen from the precise center position to experience it?

 

Anyone need instructions on how to split foil into 2 equally thick sheets?

Seriously,OP. How did you measure the amount of tilt? And what did you use to tilt the speakers? Just a few sheets of paper?

 

I'm not sure what you're getting at here. Are you struggling to understand how I measured the tilt? My speakers are on spiked stands. The floor is a concrete slab. I get that home construction lacks precision, but that has little to do with what I'm referring to. If the room warps, it might happen next week or next year, so be it. I'm simply trying to achieve the best sound I can get today. I may not even be in the same house next year.

Regardless, a fraction of an inch can make a difference when it comes to phase issues and room modes. Whether one can hear it is debatable. I believe I hear it, even with small adjustments and it seems others here have had similar experiences. The intent of this thread is to merely suggest that others experiment with rake angle, not to debate precision of measurements or room warping. 0.004 inch is quite visible to the naked eye, so I don't understand why this number is so confounding for you. One can estimate a 1/4 degree with a hardware store level. When you hang a picture frame, do you call it good as long as the bubble is within the lines, or do you try to center that bubble? If it's the latter, then surprise!, you're nitpicking over fractions of a degree.

As mentioned earlier in this thread, it's called a "machinist's level," and it's capable of far greater accuracy than 1/4°

 

OK. Color me skeptical. I just tried to do some trig for the first time in 40 yrs, and it seems that at 10ft from the speakers, the change in the aim of the speaker would be about ½ inch. I don't even know how one could do an ABX test because it would be so hard to reproduce that exact head/ear position.

Not saying rake doesn't affect sound, but ¼ degree?

 

So I suppose a half inch at the listening spot will have absolutely no effect on tonal balance or bass? There's so many variables with ABX testing that even perceived differences between components can be doubted. I won't deny that it could just be in my head, but ever since my speakers have been set at their current position, I've had no desire to tweak anything, and most music has a perfect tonal balance. I find myself thinking more about the music than SQ. I made multiple fine adjustments to arrive there. Maybe you're one who doesn't fuss over precision? That's fine by me. I'm meticulous by nature -- some would say "nutty." Maybe I am just "full of prunes," as so eloquently suggested by @TheSixthBeatle

If you adjust rake angle and perceive an improvement then great, if not, that's fine too. It's not as though I'm suggesting you spend hundreds on some esoteric cables or voodoo stones. It costs nothing to try. Congrats on being able to do trig calculations 40 years later.