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speaker measurements

Wharfedale Speakers

krishnamurthy

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I have seen very few manufacturers give the following measurements.

On-axis@0 degrees, Off-axis@30 degrees, internal volume in cft/litre.

How would these impact the performance of the speakers?
 

Fantastic

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As a user , those bits of information will not really help most users. On and off axis response is useful to designers to achieve a specified design target. Like for example speakers meant to be placed facing the user ( toe'd in) might have a flat response on axis. Of axis response will probably be tapered to reduce side wall reflections at HF.
Or on axis could be peaky HF which becomes flat off axis and the speakers are placed facing directly forward.
Room response is actually terrible to look at compared to anechoic response curves. Only if you average it out a lot will you get a reasonable smooth curve to "look at" on paper !
Just follow the manufacturers recommendation on how to place the speakers. Then move it around from there to suit your 'taste' or eliminate room problems. The given on axis and off axis response will look nothing like what they supply and will vary wildly from room to room.
Since all speakers could be measured in a 'standard room' an anechoic chamber , you can compare them with the on axis curve that you see so often in tests. But it will not tell you what will happen in your room ! Relatively speaking it will generally look disgusting in your room ! :)
Forgot about the cabinet volume. That is only required by the designer to design a box to suit the driver being used for the bass end. It doesn't help the user in any way . Neither can you do much about it except reduce it if you want to ! That will ruin the bass tuning and will certainly increase the roll off frequency ( less bass !).
 
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sdurani

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On-axis measurements tell you what you'll hear from the speaker. Off-axis measurements tell you what you'll hear from the room. In real life, the two are inseparable (by the time the sound reaches your ear, what you are hearing is a combination of direct sound from the speaker and reflected sound from the room).

Keep in mind that room reflections are typically reflecting the off-axis sound of a speaker (if you stand where the side wall reflections are, you'll be looking at the side of your speakers) If the off-axis measurement looks nothing like the on-axis sound, then the reflections will change the tone of your speakers when they combine with the direct sound on the way to your ear.

Speaker designers under the Harman umbrella (JBL, Infinity, Revel) go through great pains to make sure their speakers have consistent off-axis response, so that reflections don't alter the tonal characteristics of the speaker. Same with Kef.
 

keith_correa

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On-axis measurements tell you what you'll hear from the speaker. Off-axis measurements tell you what you'll hear from the room.
I think not. On-axis AND off-axis measurements tell you what you will hear from the speaker AND the room, both. Drivers radiate in all directions and some sound waves reach your ears/measuring device directly and some waves radiate off surrounding surfaces [off-axis waves] and reach your ears/measuring device. This is true for BOTH on/off-axis measurements.

Speaker designers under the Harman umbrella (JBL, Infinity, Revel) go through great pains to make sure their speakers have consistent off-axis response, so that reflections don't alter the tonal characteristics of the speaker.
Consistent with what? If you mean with different off-axis angles, then the heard/measured FR WILL change at different angles to the on-axis response - cannot be consistent.
Reflections WILL alter the frequency response [if this is what you mean by "tonal characteristics"] irrespective what the Harman guys do.

It's only that the Harman "family" measures and presents this measurement information differently from others.

What I said is true for measurements done in-room or in an anechoic chamber
 
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sdurani

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I think not. On-axis AND off-axis measurements tell you what you will hear from the speaker AND the room, both. Drivers radiate in all directions and some sound waves reach your ears/measuring device directly and some waves radiate off surrounding surfaces [off-axis waves] and reach your ears/measuring device. This is true for BOTH on/off-axis measurements.
Which is why I said: "In real life, the two are inseparable (by the time the sound reaches your ear, what you are hearing is a combination of direct sound from the speaker and reflected sound from the room)." Why did you leave that part out of your quote?
Consistent with what? If you mean with different off-axis angles, then the heard/measured FR WILL change at different angles to the on-axis response - cannot be consistent.
Reflections WILL alter the frequency response [if this is what you mean by "tonal characteristics"] irrespective what the Harman guys do.
Are you conflating "consistent" with 'exactly the same'? Consistent means in keeping with the on-axis response. For example:

Here is a speaker whose off-axis response is inconsistent with its on-axis response.


By comparison, here is a speaker that is more consistent (tweeter naturally rolls off as you move off-axis).


Reflections from the latter will sound much more like the direct sound than reflections from the former, thereby maintaining the tonal characteristics of the speaker.
 

keith_correa

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Which is why I said: "In real life, the two are inseparable (by the time the sound reaches your ear, what you are hearing is a combination of direct sound from the speaker and reflected sound from the room)." Why did you leave that part out of your quote?
Because I didn't disagree with what you said. I just disagreed with this:

Off-axis measurements tell you what you'll hear from the room.

And I understand your comment about the "consistent" on-axis response now since your pictures speak a thousand words :D
 

sdurani

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Because I didn't disagree with what you said. I just disagreed with this:
Even though both will blend by the time they reach the listener's ears, there are reasons to separate the measurements done on-axis and off-axis.

For example, off-axis measurements are useful in predicting how a speaker will behave in a room (high end home theatre designers rely on this to offer simulations to their clients). You can't get this information with on-axis measurements.

By comparison, on-axis measurements help during equalization, so the calibrator knows whether he's doing room correction or speaker correction.

This is only possible because off-axis measurements can tell you what you'll hear from the room while on-axis measurements indicate the direct sound from the speaker.
 
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