Evidence-based Speaker Designs

[andreasmaaan]

I got that part and I have wav file on my NAS.
How do I do IM measurement with it?

Ah, I misunderstood.

Play the WAV file from your NAS and then use the RTA window in REW to observe the output as picked up by your mic.

I'm not sure if REW can calculate the IMD automatically or if you need to do it yourself.

 

[ctrl]

Isn't pretty much all of that cooked into my EQ for LP?

No, the distortion of your speaker could be less than measured at 4m distance if your room and its objects cause additional distortion.

The distortion of your speaker could be significantly higher than measured at a distance of 4m, if in the worst case the phase shifts caused by the reflections increase the fundamental tone on average and e.g. reduce the third harmonic distortions by cancellation.

 

[andreasmaaan]

But aren't my drivers also radiating into half-space as rear-space radiation is funneled into TL tubes? I mean, you cannot simply absorb rear side radiation - you have to channel it somewhere.

The rear radiation of the drivers is out of phase from the front radiation. The TL tubes delay this output so that a useful portion of it comes out in-phase.

But none of this changes the fact that the baffle is of a finite size and that this size is small relative to the largest wavelengths the speaker reproduces.

 

[QMuse]

Ah, I misunderstood.

Don't you worry, I'm old enough to know how a floppy disc looked.

Play the WAV file from your NAS and then use the RTA window in REW to observe the output as picked up by your mic.

I'm not sure if REW can calculate the IMD automatically or if you need to do it yourself.

I don't think it knows how to calculate it, harmonics distortion looks ok but THD number is meaningless.

 

[QMuse]

No, the distortion of your speaker could be less than measured at 4m distance if your room and its objects cause additional distortion.

The distortion of your speaker could be significantly higher than measured at a distance of 4m, if in the worst case the phase shifts caused by the reflections increase the fundamental tone on average and e.g. reduce the third harmonic distortions by cancellation.

Wouldn't the same thing happen with pink noise which I use when measuring response at LP, in which case I wouldn't get flat FR?

 

[QMuse]

The rear radiation of the drivers is out of phase from the front radiation. The TL tubes delay this output so that a useful portion of it comes out in-phase.
of this changes the fact that the baffle is of a finite size and that this size is small relative to the largest wavelengths the speaker reproduces.

True, but that doesn't change the fact that drivers are radiating only in half space. As soon as you attempt to take rear radiation away you will change the phase, and you have to let it somehwere out. How would a "true" infinite baffle design look like?

But none of this changes the fact that the baffle is of a finite size and that this size is small relative to the largest wavelengths the speaker reproduces.

Isn't that true for every speaker design? You can't really make infinite baffle, can you?

 

[andreasmaaan]

True, but that doesn't change the fact that drivers are radiating only in half space. As soon as you attempt to take rear radiation away you will change the phase, and you have to let it somehwere out.

They are not radiating only into half-space. At wavelengths that are large relative to the dimensions of the baffle, they are radiating into full space.

How would a "true" infinite baffle design look like?

Obviously, in practice impossible. But,for all practical purposes, built into/onto the wall

 

[QMuse]

They are not radiating only into half-space. At wavelengths that are large relative to the dimensions of the baffle, they are radiating into full space.



Obviously, in practice impossible. But,for all practical purposes, built into/onto the wall

Wall would also reflect some LF so even in that scenario they will not be radiating half space.

According to your definiton of infinite baffle such speaker doesn't exist.

 

[andreasmaaan]

According to your definiton of infinite baffle such speaker doesn't exist.

Ofc not. Infinity is after all rather large

But in practice any speaker in which the baffle is large relative to the wavelengths the speaker reproduces / the room it's in (ie when the baffle is a whole wall) is classed as infinite baffle.

 

[QMuse]

Ofc not. Infinity is after all rather large

But in practice any speaker in which the baffle is large relative to the wavelengths the speaker reproduces / the room it's in (ie when the baffle is a whole wall) is classed as infinite baffle.

As such speakers are very rare no wonder Wiki sticks to their definition of infinite baffle.

 

[andreasmaaan]

As such speakers are very rare no wonder Wiki sticks to their definition of infinite baffle.

Hmm, the definition implied in the article on TL speakers is not really the standard definition, nor is it necessarily the definition used elsewhere on Wikipedia.

I think it would be fairer to see that an ideal TL enclosure behaves like an IB in some respects.

 

[QMuse]

Don't you worry, I'm old enough to know how a floppy disc looked.




I don't think it knows how to calculate it, harmonics distortion looks ok but THD number is meaningless.

View attachment 64807

Maybe IMD works only when signal is played by generator and not with file. @JohnPM , is that so?

 

[Thomas savage]

So minimise driver distortion used crossovers to navigate frequency errors and think about the enclosure and how that interact with the room. People spend loads of money on room treatments but a speaker enclosure is in your room and it's big.

Think about the sound coming out the back of ya speaker, think about how pure the off-axis sound is as that's where the limits of drivers are and what separates true sound from reproduced sound.

more important than any other design preference, a speaker has to be played in a room that people live in, or if it's design dependent and there's no other way tell people what they have to do to their room in order to achieve the best performance.

Did I miss anything?

 

[QMuse]

So minimise driver distortion used crossovers to navigate frequency errors and think about the enclosure and how that interact with the room. People spend loads of money on room treatments but a speaker enclosure is in your room and it's big.

Think about the sound coming out the back of ya speaker, think about how pure the off-axis sound is as that's where the limits of drivers are and what separates true sound from reproduced sound.

more important than any other design preference, a speaker has to be played in a room that people live in, or if it's design dependent and there's no other way tell people what they have to do to their room in order to achieve the best performance.

Did I miss anything?

Wow! Have you been teacher's liebling in school, sitting in the first row?

 

[Thomas savage]

Wow! Have you been teacher's liebling in school, sitting in the first row?

No I've had 4 cans of DIPA, a bottle of wine and half a bottle of vodka.

It's not a big issue you have to make something predictable ie a speaker interact with environment , a room , so you have to make compromises and that might ultimately lead to a less perfect speaker but applyed to a non perfect room dynamic = better performance these are design trade-offs.

That's what the Harman research was all about not the ultimate speaker in isolation but the mean average what works best in people's rooms.

Please correct me if I'm wrong.

 

[QMuse]

No I've had 4 cans of DIPA, a bottle of wine and half a bottle of vodka.

It's not a big issue you have to make something predictable ie a speaker interact with environment , a room , so you have to make compromises and that might ultimately lead to a less perfect speaker but applyed to a non perfect room dynamic = better performance these are design trade-offs.

That's what the Harman research was all about not the ultimate speaker in isolation but the mean average what works best in people's rooms.

Please correct me if I'm wrong.

I think you're right.

P.S. What is DIPA?

 

[Thomas savage]

I think you're right.

P.S. What is DIPA?

Double IPA , 8%( insert look out emoji)

 

[andreasmaaan]

No I've had 4 cans of DIPA, a bottle of wine and half a bottle of vodka.

THIS is what puts you head and shoulders above other authority figures.

 

[QMuse]

Double IPA , 8%( insert look out emoji)

Double India pale ale?

 

[QMuse]

THIS is what puts you head and shoulders above other authority figures.

Oh please don't flatter him as he will become impossible to handle.