 The HB Project and the Hans Beekhuiser channel are supported by Dali Loudspeakers in admiration of music. The secret about towing in Loudspeakers was a title I came across on the web. I can tell you there are no secrets, only things you don't know yet. Weapon yourself with knowledge and insight and secrets disappear. This video might already be a good start. The best source to start off with is the manual of your speakers and I'm very serious here. If there is a secret, it's a secret that a perfect loudspeaker doesn't exist. Every loudspeaker manufacturer has to choose his sets of compromises, workarounds and shortcomings when designing loudspeakers. If the development and the materials budget are tight, more compromises, workarounds and shortcomings will confront the designer. But even unlimited budgets will not free the designer fully from them. Depending on the compromises, workarounds and materials chosen, a design will have certain properties and these properties make the speaker behave in a certain way. So it's important to know and understand the consequences thereof. I'll give you some examples. Golden ear loudspeakers are designed to be pointed directly towards the main listening position. Dali loudspeakers are designed to be used without any towing, so with a baffle parallel to the back wall. Martin Logan electrostatic loudspeakers has to be pointed inwards to a degree you see the reflection of a torch pointed to the speaker on the diaphragm at about 30% from the inner side. The manufacturers will advise you on the, in their eyes, optimal placement in the manual, so read at least the chapter on placement. Not that you necessarily have to adhere to that. In the 80s I visited the late Alistair Robertson Aikman, the founder of SME, manufacturer of very fine high-end tone arms and turntables. In his legendary listening room he used two quad electrostatic loudspeakers per channel. One was pointing straight forward and the other was placed behind it and turned 90 degrees horizontally, so it radiated sideways. Not exactly what Quad advises but the results sounded fantastic. He did this since he had studied the acoustic behaviour of the speakers and his room and so found his optimum in loudspeaker placement. Just saying. Loudspeakers only have a fairly linear frequency response in one direction, often but not always on axis. When you get more and more off axis you see the frequency response rolling off towards the higher frequencies. You also often see strange dips occurring. I show you this behaviour of a costly studio monitor by Genelec since it performs very good where off axis response is concerned. As you can see there already is 1 dB loss from 700 Hz upwards at 15 degree angle. At 30 degrees it's already several dBs, at 45 degrees it's even 5 dBs at 1 kHz and even around 15 dBs from 3 kHz upwards. Again this is a speaker that has very good specs since it had to be sold to critical customers like Film Studios. Given the off axis behaviour it is very likely that these speakers need to be pointed towards the mixing position. The result will be that the sound that is reflected from the sidewalls will have far less high frequency energy. That's fine in a studio environment where the control room design takes that into account. But in a living room it might lead to either a dull sound if the walls dampen the high frequencies further. But it might just be perfect if you have reflective walls and provide some scattering to it. At the other end of the spectrum there are speakers that sound overly bright on axis like some dual concentric models. These should not be pointed directly at you of course. Here you should use clearly less towing or even no towing at all. As a result the amount of energy above say 500 Hz to the sidewalls will be higher having the room sound more vibrant. If you use panel loudspeakers like electrostatic and magnetic static loudspeakers, things get more complex. When you have a single panel, either electrostatic or magnetostatic, it is most likely the best to aim them straight at you. These panels generate all frequencies all over the panel. If you place the panels toe in like in this illustration, the sound will reach one ear, in this case the right ear, earlier than the other ear and this time misalignment will influence the sound. The time relations between the left and right ear are also distorted. This results in effect called lobing which can be seen in this plot diagram that shows the attenuation of axis over 360 degrees. This will heavily color the sound. That is clearly audible when you move your head sideways. For now we are interested in the behavior on the front of the loudspeaker, the upper half of this graph. When we look at the black line we see a cardioid behavior for 500 Hz, which is fine. At 1000 Hz and 2000 Hz, the green and blue lines, the cardioid is slightly more narrow but still fine. But at 4000 Hz, the red line, you see a 22 dB attenuation at 30 degrees. At 8000 Hz, the gray line, we see 17 dB's attenuation at 25 degrees. It might be clear that being at between 15 and 40 degrees of axis means you miss out a lot of the high frequency energy. Martin Logan uses curved membranes for their hybrid electrostats that, when placed correctly, will not suffer from this effect due to the curving. Quad uses another technology where the stator, the fixed part that holds the charge, is divided into rings. These rings receive the signal at different times. The inner ring gets the signal first, then slightly delayed the second ring and so on. This makes the panel act like a point source. In plain English, the panel is electronically made to behave as a panel that is curved in both horizontal and vertical direction. A third way, found in both electrostats and magnetostats, is to use a two-way setup. The original Quad Electrostat design has the high frequency panel in the middle with low frequency panels on both sides, which has impact on the dispersion of course. Hence the virtual point source in the newer designs. Other manufacturers use separate high frequency and low frequency membranes but then the high frequency membrane is on one side of the panel. Depending on the room and the area where the listeners are, the high frequency membranes can be placed on the outside or on the inside. Usually having them on the inside is preferred when a single listening position is considered ideal. For a fair to good stereo image of a wider area, they better be on the outside. By the way, there also is a limited number of cone loudspeakers that have an asymmetrical placement of drivers and they adhere to the same rules as the panel loudspeakers with a separate tweeter membrane. To give you an idea of what happens when you tow in a loudspeaker, I use a simplified drawing where this is a loudspeaker, this is an approximation of how the mid-lows are projected into the room, this the mids and this the highs. Please do realize that in real life there is a smooth transition from wide to narrow and not in three steps as drawn here. My drawing skills are limited unfortunately. Also realize that the mid-lows also cover the area of the mids and the highs and the mids also covers the highs area. Real low frequencies are radiated almost in all directions equally and are not influenced by towing in. How does the left loudspeaker in the stereo system function in a room? Let's define the top and sides of the screen as the walls and place the listener here. Behind him is the rest of the room. With no tow in and this dispersion the listener will hear the highs at a lower level than when the speaker is pointed directly at the listener. If the speaker is designed to be used like this, the high frequency energy will be correct for this position and the signal on axis will have too much high frequency energy. This is a handy way to get rid of distortion products since they will be in the high frequency range. Another advantage is that the direct sound and the reflected sound have about the same spectral balance which isn't bad since we will hear clearly more reflected sound than direct sound. On the left wall the mid-lows will be reflected over a large area while the mids are reflected over a slightly smaller area. On the right wall only the mid-lows will be reflected but since that wall is further away it will arrive at a later time and the level will be lower. When we tow in the speaker so that it is fully aimed at the listener reflections coming from the left wall will be drastically reduced and will be mainly mid-lows. Reflections now come mainly from the right wall. On the listening position the on-axis response of the loudspeaker is heard. If the loudspeaker was designed to be used this way the tonal balance will be fine. If it was designed to be used without tow-in it will most likely sound too bright. Of course you can vary between no and full tow-in to vary the brightness but it will have an effect on other things as well. If the sound of the left speaker is mainly reflected from the left wall as in the no tow-in situation it will widen the stereo image. If it is reflected mainly from the right wall it will narrow the stereo image. What exactly is the best for you not only depends on your walls but also on the taste and preference. The behaviour of the right speaker is of course the mirror of that of the left speaker. I just couldn't manage to do the illustration with both speakers illustrative enough. An easy way to find a good tow-in is to use mono-pink noise. There are many sources on the web on streaming services and in YouTube. Make sure it's a mono signal that it has long enough playing time. I used mono-pink noise on YouTube that plays for 15 minutes. The link is in the top right corner at the end of this video and in the description in YouTube. Hook up your laptop, tablet or smartphone to your amplifier. Turn down the volume on the amp and start playing the mono-pink noise file while you have the speakers in the tow-in position as advised in the manual. Now turn up the volume. Listen if the noise comes finely focused from the middle in between the speakers. If not, vary the tow-in of both speakers and listen again. If the speakers are not set up in a symmetrical situation you might try varying the tow-in of only one speaker. Think about how reflections behave by thinking how light would reflect if the walls were made of glass. Bipolar speakers, like panel speakers, radiate about the same acoustical energy to the front and the back. We've seen that most of these panels preferably need to be pointed at a listening position. Since these loudspeakers have a figure of eight polar pattern they do not radiate energy to the sides, not even the lowest frequencies. This means that there is little to no direct reflections from the sidewalls. But since the rear radiates the same sound as the front do, this sound is bounced back into the room at a fraction of a second later. How much later depends on the distance between the speaker and the back and sidewalls. I would certainly not place them closer to the back wall than 1.5 meters, five feet imperial. Having diffracting materials against the back wall wouldn't hurt. I used read mats behind my quad ESL 55s back in the 70s. Acoustically a fine solution but nowadays unacceptable for the aesthetics commission, I'm afraid. Loudspeaker placement starts with reading the user manual, then placing the loudspeakers using the suggestions it gives. After that you can further optimise the placement using trial and error and a bit of thinking about how the audio travels through the room. As far as throw-in is concerned, low frequencies are irrelevant. Use my two-step approach to loudspeaker placement I suggested in my video Loudspeaker Placement to get the lows right and learn more about the behavior of the mids and highs in the same video. Links at the usual places. For mids and highs you can really visualise the behavior using a torch and a mirror. By experimenting you can get the best out of your system. Let's say that by following the manual you might get 70-80% if your room isn't oddly shaped. The last 20-30% is up to you. Or your dealer of course, which brings us to the end of this video. The coming two weeks there will be no new video since I will try to reorganize all the videos in a way that they are accessed easier. There are now 375 videos on the channel and it's very hard to find a certain video from all those videos. But don't be afraid, I will be back. And if you don't want to miss that, subscribe to this channel or follow me on the social media so you will be informed when new videos are out. Help me reach even more people by giving this video a thumb up or link to this video on the social media. It is much appreciated. Many thanks to those viewers that support this channel financially. It keeps me independent and lets me improve the channel further. If that makes you feel like supporting my work too, the links are in the comments below this video on YouTube. I am Hans Beekhuyzen, thank you for watching and see you in the next show or on theHBproject.com. And whatever you do, enjoy the music.