Polar response is not the key

[daftcombo]

because they stand out on dealer demos (listen to all that detail)

Absolutely true!

If that's the case, then to achieve a flat response at the listening position they need to be toed in, by an amount that can be seen from the polar diagram and anechoic on axis response

EQ correction also works for me (Shelving High).

 

[daftcombo]

Most speakers are designed so that the best possible response is obtained directly on-axis. So the answer is simple: the speaker should be facing the listener.

Is that so sure? Even with a flat on-axis response, do the two responses of the two speakers simply add and make a +3dB at all frequencies?

 

[sergeauckland]

Is that so sure? Even with a flat on-axis response, do the two responses of the two speakers simply add and make a +3dB at all frequencies?

Very much depends on the room. Even with two loudspeakers that are perfectly flat on-axis anechoically, and with good i.e. even off axis response, the in room response at the listening position depends then entirely on the room, how reflective it is, and at what frequencies, whether left-right symmetrical, and at LF, the room modes and their Q. The best that can be said in the absence of detailed measurements, is a room that feels 'nice' for everyday living and domestic noises stands a good chance of being benign for hifi reproduction

S.

 

[daftcombo]

Very much depends on the room. Even with two loudspeakers that are perfectly flat on-axis anechoically, and with good i.e. even off axis response, the in room response at the listening position depends then entirely on the room, how reflective it is, and at what frequencies, whether left-right symmetrical, and at LF, the room modes and their Q. The best that can be said in the absence of detailed measurements, is a room that feels 'nice' for everyday living and domestic noises stands a good chance of being benign for hifi reproduction

S.

Here is a measurement of my right speaker without EQ.
1) On axis, at 60cm.
2) At listening position.
(Left speaker is the same with a bit more bass.)

The speakers are toed-in so that they cross one meter behind my head (where is a wall).

What would you do?

 

[edechamps]

Very much depends on the room. Even with two loudspeakers that are perfectly flat on-axis anechoically, and with good i.e. even off axis response, the in room response at the listening position depends then entirely on the room, how reflective it is, and at what frequencies, whether left-right symmetrical, and at LF, the room modes and their Q. The best that can be said in the absence of detailed measurements, is a room that feels 'nice' for everyday living and domestic noises stands a good chance of being benign for hifi reproduction

Agreed. I would also add that I would expect distance to the speaker to make a significant difference here, because in the near-field one would expect more constructive interference (due to lower level of reflections), resulting in +6 dB summation, while in the far (diffuse) field, room reflections would become dominant and produce random (+3 dB) summation. (I'm not entirely sure about that last part. The precedence effect might complicate the reasoning.)

Above 2 kHz or so, the wavelength becomes so small that it's probably safe to assume the incoming wavefronts won't be aligned, hence random (+3 dB) summation.

At low frequencies (modal region), due to the dominant effect of the room, it's anyone guess what will happen - one would need to measure.

Come to think of it, this is an interesting question @daftcombo, because I would expect the answer to also be affected by "room correction systems" that try to also align the phase response at the listening position. If the phase response is aligned, then, below 2 kHz or so, one will get +6 dB constructive interference, while in a system without phase correction one would expect to get something closer to +3 dB random interference. This is interesting, because it brings up the question of "who is right". I wonder if one could argue that using room correction to align phase between channels at the listening position is "wrong" because (presumably) most production studios are not doing that in their monitoring systems, therefore you're not getting the intended result in terms of stereo summation. It's an interesting thought for sure.

 

[sergeauckland]

Here is a measurement of my right speaker without EQ.
1) On axis, at 60cm.
2) At listening position.
(Left speaker is the same with a bit more bass.)

The speakers are toed-in so that they cross one meter behind my head (where is a wall).

What would you do?

I find it difficult to tell what those graphs are saying given the extreme variations shown. Looking at the on axis 60cm graph first, I think there must be a measurement error somewhere as the variations are far too wide. If that's genuinely what your 'speakers are doing, you need new 'speakers.

My own 'speakers are +-1dB from 200Hz upwards, at 1m, and in room at the listening position, variations are around 5dB, with a gentle slope from LF to HF.

S.

 

[daftcombo]

I find it difficult to tell what those graphs are saying given the extreme variations shown. Looking at the on axis 60cm graph first, I think there must be a measurement error somewhere as the variations are far too wide. If that's genuinely what your 'speakers are doing, you need new 'speakers.

It's a pair of Epos K3 that I bought when I was a Hi-Fi newbie and when the "because they stand out on dealer demos (listen to all that detail)" effect worked full on my ears.
They sound good though, once EQed with a -6dB, Q=1 at 14 000Hz and with a room curve.

I corrected them based on those near-field on-axis measurements. Correcting them according to the listening position measurements didn't work. That's why I'm doubful about Dirac & other automatic correction software.
I have litteraly spent more than a hundred hours, making hundreds of measurements of every kind, on having them sound good in my room, which is wider than long and everything close to the walls.

 

[Kvalsvoll]

My main speakers have di-polar response above 200Hz or so.

Is that a flaw, or a difference?




Oh boy! Phase Response! I got a post for that, too...

My MartinLogans are in my typical room, and this is measured at the listening position (10 feet):

View attachment 26076

180Hz crossover point disrupts things a bit.

Dipole is of course no flaw. It is a choice. And they will sound different, because the radiation pattern is different.

 

[Juhazi]

daftcombo - your measurements look like having 500ms IG gating and 1/12 smoothing and very narrow y-axis selected. Still, nearield measurement sohw so much reflections that it is useless. Nearfield/quasi-anechoic measurements are really difficult to perform indoors, and with short IR gating you don't see what happens in bass.

Hera are my six years old measurements of a 2-way speaker on a stand - 1m and at spot. Top graph is with same settings as you have. Lower has wider y-axis, 1/3 smoothing and 12ms IR gating for nearfield measurement. Much easier to start using EQ now, me thinks!

 

[amirm]

Erm... Why are people engaging in a debate with someone that doesn't have basic knowledge of the subject?

It is useful for others who are reading as this is a very important topic.

 

[daftcombo]

your measurements look like having 500ms IG gating and 1/12 smoothing and very narrow y-axis selected

I've tried everything. 1/24 smoothing to 1/1 smoothing, with or without IR gating.
Here is the curve I finally imported to work in RePhase:

It is the 1/3 smoothing curved with [L=1ms ; R=30ms] gating.

As I explained in another thread, I didn't correct the magnitude below 300Hz because I don't think the measurements are reliable in that area. I tried various low-shelf filters because the bass was too much. I ended up with a 24dB/oct for both speakers. At 30Hz for the right one and 47Hz for the left one. I don't say that "47" would be spotted from 45 or 43 in an ABX, but still I like the result.

Also linking the impulse before smoothing.

 

[DDF]

...Even with a flat on-axis response, do the two responses of the two speakers simply add and make a +3dB at all frequencies ....

Given two perfectly identical speakers (in magnitude and phase), they will sum to +6 dB in SPL at one observation point perfectly equidistant from them both, in a reflection free environment. SPL=20*log("A") and "2A" = +6dB. Vary from 'perfect" on any of those attributes, and < 6 dB will result.

Add in room reflections and resonances, and difference between speakers increases again.

Finally, binaural hearing is different than a microphone at one location, so we don't hear things exactly the same way the mic would show it.

Here is a measurement of my right speaker without EQ.
1) On axis, at 60cm.
2) At listening position.
(Left speaker is the same with a bit more bass.)

The speakers are toed-in so that they cross one meter behind my head (where is a wall).

What would you do?

Following assumes 2 speaker stereo, no sub.

1. EQ the speaker for its response errors in the design:

• Measure your speakers somewhere you can take at least a 5 ms reflection free gate. This will only give you 200Hz resolution in the outcome but you only want broad based eq and generally not sharp eq anyway
• Measure on the listening axis, and at least at the two axes that represents a ray for the side wall bounces to the listening chair, and at least +/- 5 deg up or down. Measure at least 3' out from the baffle, more for a large speaker. Diffraction effects will not be fully accurately captured if you measure too close to the speaker.
• There are AES papers to help justify this and its also my personal experience that its often a good practice to toe in the speakers so they intersect about 2 to 3' in front of you. Define the listening axis as the speaker direction pointing at you with this toe in. For one, this gives you a better "average" of the diffraction response for a typical speaker with the drivers mounted center of the cabinet but it also gives a bit better representation of the speakers radiated room response
• DON'T EQ it perfectly flat for on the listening axis. Diffraction effect varies fairly appreciably in the mid range for even relatively small changes in the axis of observation and driver summing will change even within your +/- 5 degree window
• Start with EQ so its broadly flat (start with half or third octave averages) on the listening axis but if you see some consistent off axis irregularity (say a consistent peak) that you don't see on the listening axis, start with eqing about 1/3 to 1/2 of that peak out, even if it makes it a bit non-flat on axis. Avoid filling big holes unless they are consistent on and off axis. One common example in many speakers is that the crossover point features a dip off axis in the lower frequency driver (because it is more directional) followed by a peak in the higher frequency driver (because it will have broad dispersion in that range). It takes some skill and experience to get a good blend as possible. Sometimes, it helps to reduce on axis 1 to 2 dB just where the tweeter starts to take over.
• Doing more measurement points will give you more accuracy (the idea behind the "spinerama") but at least these 5 directions are a must IME.

2. EQ the speaker for your in room response at your listening position, but just below the room's transition frequency, usually ~ 250Hz. A very simple way to get close is to play 1/3 octave warble tones (the frequency varies up and down about an average) and use an RTA app and get it roughly flat at the listening position with both speakers playing. If you want to measure using REW and the like, OK, but use some frequency averaging (1/6 to 1/3 oct) because even minor changes in observation point can change the shape and center frequency of the peaks. Again, avoid filling big holes, focus on reducing peaks.

3. Apply some low frequency positive shelving below ~ 250Hz to target the Harman trained listener target attached.

4. Listen. The technique in #1 may sound bright if the room is highly reflective and the tweeter broad in dispersion. For example, you can take a long gate measurement of one speaker at a time, apply some smoothing (1/3 oct) and compare it to the upper response in the Harman trained listener curve and target that.

5. Pop a cold one, give it some extended listening to become acclimated to the new tonal balance. It will be different and that may be enough reason to not like it at first. We get used to the errors in our set ups and that skews initial impressions, at least until the listener "breaks in" with the new eq.

6. If still you don't like the outcome after a couple weeks, who cares if its "right" or not, tweak EQ by ear. Use measurements to try and find the areas that are still problematic.

7. Simplify the various Eqs into fewer settings that give the same result, if possible.

 

[daftcombo]

There are AES papers to help justify this and its also my personal experience that its often a good practice to toe in the speakers so they intersect about 2 to 3' in front of you.

Thank you very much for your extensive reply, that I'm in the process of reading.
About that very sentence, I've read the same thing under the pen of two competent people as well. It is far from being commonplace though.
Do any other person have experience with that positionning?

 

[DDF]

Thank you very much for your extensive reply, that I'm in the process of reading.
About that very sentence, I've read the same thing under the pen of two competent people as well. It is far from being commonplace though.
Do any other person have experience with that positionning?

NP, you're welcome and good luck with it.

Two of the immediate benefits of the toe in:
- usually places the worst case diffraction response off the "sweet seat" center listener axis
- broadens the "OK" listening area by giving right placed listener more highs from the left speaker and vice versa. This helps a bit to broaden the lateral listening area before all sound collapses to the nearer speaker

Of course this wouldn't work for an old Acoustat laser beam panel, but assuming typical dynamic drivers vertically in a baffle.

 

[Blumlein 88]

Thank you very much for your extensive reply, that I'm in the process of reading.
About that very sentence, I've read the same thing under the pen of two competent people as well. It is far from being commonplace though.
Do any other person have experience with that positionning?

I have often done this and find it helpful. Place the crossing axis about 3 feet in front of the listening position

 

[sergeauckland]

I have often done this and find it helpful. Place the crossing axis about 3 feet in front of the listening position

I understand this was first proposed by Hugh Brittain who was GEC's Head of Research, and in the UK is often referred to as the Hugh Brittain arrangement. I use it as it widens the sweet spot without seemingly affecting sharpness of image.

S

 

[Juhazi]

^It works if you have a rather wide triangle, wide separation between speakers. The other beneficial scenario is, when the room is narrow and you must place the speakers (too) close to side walls.

Technically, the previous means that because of the directivity
1) toe-in to cross in front of you adds crosstalk (hearing the left speaker's sound with your right ear, because more of the sound power projects to the right side and makes stronger reflections with long delay - and vice versa)
2) the side wall next to the speaker gets smaller fraction of sound power to get reflected with short delay

Other explanation is, that in most cases, especially with coaxial speakers, 5-15¤ off-axis respone is smoother and closer to "power response" than direct on-axis response.

So, "it depends" and you must try that with your own speakers in your own room. For this, just trust your ears!

 

[daftcombo]

Here is a measurement of my right speaker without EQ.
1) On axis, at 60cm.
2) At listening position.
(Left speaker is the same with a bit more bass.)

The speakers are toed-in so that they cross one meter behind my head (where is a wall).

What would you do?

I'm quoting myself to highlight this:
according to the "in room" plot, I have a bump between 600Hz and 2kHz. That is absolutely not the case for the speaker response, which can be seen on the "on-axis" plot.
And that's why I'm reluctant at giving too much consideration to the in-room measurements.

It seems just weird to me to accentuate speakers problems.

I have to try the toe-in with crossing in front of me to begin with.

 

[DDF]

^It works if you have a rather wide triangle, wide separation between speakers. The other beneficial scenario is, when the room is narrow and you must place the speakers (too) close to side walls.

Technically, the previous means that because of the directivity
1) toe-in to cross in front of you adds crosstalk (hearing the left speaker's sound with your right ear, because more of the sound power projects to the right side and makes stronger reflections with long delay - and vice versa)
2) the side wall next to the speaker gets smaller fraction of sound power to get reflected with short delay

Other explanation is, that in most cases, especially with coaxial speakers, 5-15¤ off-axis respone is smoother and closer to "power response" than direct on-axis response.

So, "it depends" and you must try that with your own speakers in your own room. For this, just trust your ears!

#1 The benefits I mentioned are actually independent of the triangle size.

#2 can actually be considered a drawback of toe in. The toe in makes the side wall reflection response less similar to the response on the listening axis due to the directionality of the larger drivers compared to the smaller drivers. I would expect this difference to be more audible the closer the driver is to the side wall due to the shorter time delay difference between the listening axis and side wall reflection. Btw I understand your logic in that less driver output is radiated at the wall and I used to think the same but it’s only true in the upper end of the drivers radiation and Olive and Tooles research convinced me this would be more coloured

 

[Blumlein 88]

I've done the crossing toe in mostly with panels, including long ago with the Acoustat laser beams. On those I actually aimed each speaker at the opposite ear. And this was mostly in a long narrow room with speakers near the walls, but panels aren't bothered as much by that.