Fractions matter

May 16, 2021
 by Paul McGowan

In yesterday's post, we looked at long wavelength bass notes—some exceeding 50 feet in length. Today, let's have a look at their shorter cousins, high frequencies.

Where bass frequencies are typically multiple feet in length, higher frequencies are generally in inches or fractions of an inch. 1kHz, for example, is right around 1 foot, while 10kHz is a little more than an inch.

When it comes to system setup what makes these frequencies challenging is their very short wavelength. You can imagine toeing in or out one channel's speaker a "skosh" and making a very big sonic difference.

The short wavelengths of higher frequencies are one reason I have long been an advocate of relying upon the off-axis response of the system for best imaging (as opposed to pointing tweeters directly at your ears). In my setups you'll almost always notice the left and right speakers are nearly without toe-in, pointing instead almost straight ahead. The energy distribution of the off-axis response is much smoother and less prone to laser-like problems we get when we rely instead upon a perfect triangulated setup of speakers.

Fractions matter when it comes to higher frequencies but one can mitigate some of this specificity by relying instead upon speakers with excellent off-axis response.

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19 comments on “Fractions matter”

  1. Paul do you think you would really also choose this extreme non-toe-in positioning if you could lower the level of your tweeters where you perceive them too bright in a toe’d-in position?

    I think, unless your speakers react very differently to toe-in (non-sensible in terms of imaging) than most other conventional, ribbon or planar speakers, you must sacrifice a lot of imaging quality to have your favored treble tonality and the wide, but less deep and focused soundstage that usually results from hardly any toe-in.

    In my opinion using toe-in to control tonality can’t be a good way, as one always makes one characteristic worse to better the other. To have both (optimal tonality and optimal imaging) snap-in would be just pure luck and very unlikely.

    For me, recommending to vary speaker toe-in for tonality reasons is like recommending to vary cartridge adjustment (VTA/SRA) for tonality reasons. It works to a minor extent, but it puts off proper cartridge adjustment for imaging and tracking, which is the main purpose of VTA/SRA adjustment.

  2. My NHT 2.9 speakers were designed to sound best when toed in and I don't have to toe them in since the front baffle is angled in at the right amount of toe in. I can point the speakers straight ahead and they are naturally toed in. The speakers are obviously also in mirrored image. This angled baffle also serves to help eliminate internal standing waves that would be worse in a perfectly rectangle enclosure.

  3. I found that my best 3D holographic imaging home audio set-up (1993 - 1999) had virtually no loudspeaker toe-in (1" SEAS aluminium dome & 8" TPX mid/bass with phase plug)...but that could've been for any number of reasons.

  4. So, do you recommend no toe-in for the Magnepan 3.7i. If not, what placement do you recommend. I have Mye stands with 50 lbs of sand loaded on each speaker. Thanks for your advice, JS

    1. I just had to reset my system up because of a move and I have 3.6 R’s.
      In my last residence I followed Magnapans directions and toed them in approximately 5° and they sounded really good. Only issue was that imaging was not rock solid but more than acceptable.

      When I moved into my new residence I set my system up and toed in about 5° to be amazed by how much better every aspect of the imaging became. After a few days of listening I decided to tow the speakers another 2° or so almost like nothing at all and everything locked into place. The sound that I am getting in my new listening room now is spectacular. Thanks for the help with this set up Paul. Your set-up disk from Octave works like a charm. I didn’t want to go against the manufacture’s directions but in my case their recommendations we’re not the best.

    2. Paul's generalization that the response is smoother off axis is true with Magnepan, but otherwise Magnepan speakers make for an interesting case. The tweeter section needs to be slightly farther back from one's ears than the mid/woofer section for proper time alignment. The toe-in is determined by whether the the user sets the speakers up with tweeters on the inside or the outside. If inside, quite a lot of toe-in is necessary for time alignment. The tweeters will need to be aimed to cross in front of the listener.

      With tweeters outside, where I prefer them, the tweeters can be aimed to the outside of the listener's shoulders. Depending on the listening distance, this will time-align the driver sections and also produce smoother response in the crossover region (upper midrange, low treble).

  5. Some speakers are voiced to sound best toed in with tweeters pointed at or just outside of your ears. Try as I might with other set ups, my Wilsons are designed that way. When I try to angle them out it creates all sorts of distortions that can't be avoided with other room set up adjustments.

    1. If you have Wilson's that have the micro adjustments of the tweeter and mid-range then you must toe them in. That is how they are designed.

  6. With RAAL ribbon tweeters (very wide off-axis horizontal dispersion) in a quasi near-field listening setup, I have my monitors toed-out 5 degrees. Acoustic W-H-D Soundstage is huge (extends well beyond room boundaries), but still provides pinpoint imaging and proper placement of vocalist, instrumentalist and full ensemble genre. With eyes wide open, the monitors Still totally disappear!

  7. So let's do a little geometry and trigonometry. My speakers are Magico S7's which have a 1" dome tweeter. I started of with the usual equilateral triangle with each side being nine feet. With the equilateral triangle all of the angles between the adjacent sides of the triangle are 60 degrees. If you were to toe-in the speaker so that the front baffle is perpendicular to the line from the speaker to the listener that would be a 30 degree angle between the line connecting the two speakers and the line formed by the front baffle. I refer to this as a full toe-in because to toe-in the speaker anymore than this would cause the tweeter to be directed away from the listener.

    After playing around with listening position and speaker toe-in the equilateral triangle morphed into an isosceles triangle with a 9 foot base and two 11 foot sides between the listener and the speakers. This changes the angle between the two speakers from 60 degrees to 50 degrees. This means the angle between the 9 foot base of the triangle and the 11 foot sides is 65 degrees. That implies that the full toe-in angle is now 25 degrees.

    I measured my toe-in angle and it is 20 degrees which is 4/5 of the full toe-in angle. This gives me very good imaging and what I perceive as good even frequency response. I try not to adjust my speaker position to see if I can fine tune the sound because the speakers are 300 lbs. each and every time I suggest adjusting the speaker position I can see my wife's composer go from relaxed to very tense.

      1. Theo, The S7's feet are designed so that the actual foot ( in my case M Pods ) can be replaced with a supplied castor. You can use these for major moving or shipping. They are, however, pretty useless for fine tuning the position to get the best sound. So if I want to move them 3" or 4" I basically have to pretend I am back playing HS football and I am trying to block a 300 lb. tackle. 😮

    1. The Magico S7’s are a hell of a speaker. Phenomenal inner detail retrieval. I’m wondering what electronics you’re using to power these beauties

      1. stimpy2, Before I talk about amps, may I ask who is stimpy1?

        I use to have all c-j amps and I still use a c-j GAT S2 preamp and a TEA1b S3 phono preamp. For the first year that I had the S7's I used my old c-j Premier 12 monoblocks to drive the S7's. It sounded good, but I knew I wasn't getting all the bass that the S7's can do so I started looking for something with a lot more power. My search turned up a used Constellation Audio Hercules II stereo power amp that a dealer was selling at a small fraction of its original price. He had been using it as his in house personal reference amp.

        The Hercules II just took total control of the S7's. The bass is powerful, controlled and there is no strain. or distortion no matter how loud I want to play the music ( at my age I do not get too crazy about blasting the Stones late at night ).

  8. Straight on for me. Only yesterday, I finally succumbed to my friend's urging to eliminate the 10-degree toe-in of my Revels. Wider soundstage and no loss of imaging, so why was I so stubborn ? Because the manual recommended pointing the speakers to the listening position. This hobby demands lots of experimenting.

  9. Hi Paul,
    Thank you again for stimulating the audio community to get the best from their SYSYEMS. My experience with in-room placement and speaker layout is similar to yours. I have taken out the tape measure and blue tape for position optimization many times. Sometimes, I leave the blue tape on the carpet for years. Limitations of room decorum, seating position(s), acoustics, room shape and size are always difficult (even in dedicated rooms).
    This toe-in and tilt has an interesting effect on the overall presentation. Compensation for me is often more about first surface reflection(s). This would be to the sides of the speakers, behind the listener and between the speakers. As we know, the first surface reflections can be managed by diffusion or absorption.
    After compensation is made, listening begins with many musical pieces. Adjustment for toe-in (for me) begins with the loudspeaker straight ahead listening for the center blend as we begin toe-in. I tend to set this up for a primary forward seating position. While I have a second row of raised seating there often is a REALLY good seat behind the front row. My rooms are very large meaning we do not sit on top of the speakers.

    It may take months of listening before you settle on a specific toe-in (or none).

    The tilt of the loud speaker(s) is really dependent upon seating position. If you think I'm wrong, stand for a while, transition to a chair, then to the floor while listening. Tonal balance and sound stage often change. My friends universally agree this is more personal than absolutely important. My desktop speakers are tilted up (~2 degrees).
    Sincerely,
    Leg_one

  10. To toe-in or not to toe-in. That is the dispersion and frequency response of the speakers question.

    Showing REW in both settings would have clarified the answer. I presume that the IRS may be a little too bright exactly on axis and the "spinorama" provides a better Harman frequency response off axis.

    Data matters. Science matters.

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