Evidence-based Speaker Designs

[ctrl]

And how would you recognise dip is coming from floor bounce?

You can calculate the floor bounce (see "Testing Loudspeakers" by Joseph D'Appolito) or simulate it (e.g. VituixCAD) - This gives you a first clue.

You can repeat the measurement with a sufficiently large "obstacle" or sound absorber on the mirror point of the floor bounce and observe whether the result changes significantly in the respective frequency range.

 

[QMuse]

You can calculate the floor bounce (see "Testing Loudspeakers" by Joseph D'Appolito) or simulate it (e.g. VituixCAD) - This gives you a first clue.

You can repeat the measurement with a sufficiently large "obstacle" or sound absorber on the mirror point of the floor bounce and observe whether the result changes significantly in the respective frequency range.

I see, thank you. And then after you identify it, do you correct for it with EQ or not?

 

[ctrl]

I see, thank you. And then after you identify it, do you correct for it with EQ or not?

To be honest, I've never been particularly concerned with the floor bounce. Should I ever have the feeling that there is a significant lack of sound level in the relevant frequency range, a closer examination would be in order - call me an ignoramus, but for me, floor bounce is one reflection among many.

One should perhaps try to avoid that all possible first-order reflections (front, back, floor, ceiling, side walls) have identical propagation times differences

 

[QMuse]

One should perhaps try to avoid that all possible first-order reflections (front, back, floor, ceiling, side walls) have identical propagation times differences

How would you avoid that? With speaker positioning or..?

 

[ctrl]

How would you avoid that? With speaker positioning or..?

First of all, there's probability on your side.
... and then there are tools like Amray that calculate the delay for each reflection (for floor and ceiling just enter another simulation).

 

[andreasmaaan]

What I asked is whether using a short sweep the measurement will show the floor-bounce cancellation?
In my experience it does but I could be doing something not quite right.

It should be visible, unless swamped by other reflections. In this case, assuming it's the first reflection, it may be possible to isolate it by windowing to a time just before the arrival of the next reflection.

Smooth off-axis response is important in wide-directivity speakers because of the precedence effect

I think this may be a slight misunderstanding of what the precedence effect is, which is only about perceived direction of sound.

Why is floor bounce different? Why is a reflection which creates a dip in the perceived balance at th listening spot not objectionable (or downright offensive)?

I don't think we have strong evidence that floor bounce does create a dip in the perceived tonal balance, although I'm open to the possibility. Do you have some evidence to share?

And I'm not saying that floor bounce is different. Indeed, it seems to be you who are saying it should be treated differently from other reflections, if I'm not mistaken?

the listener will perceive the combined balance direct and reflected sound as one.

Yes, in terms of direction of arrival. In terms of perceived tonal balance, it's more complicated.

The paper is not free, but it seems to be dealing with "speech reinforcement". Can you be more specific on its relevance?

Listeners were asked to draw the perceived frequency responses of a number of test systems they listened to in rooms. The responses they drew tended to match the on-axis responses of the speakers, rather than the in-room responses.

 

[QMuse]

Yes, in terms of direction of arrival. In terms of perceived tonal balance, it's more complicated.

Perceived tonal balance is seen when measuring with MMM.

 

[Jon AA]

The centre frequency of the primary cancellation null is dependent on the height of the driver and the listening distance, but it tends to be too low in frequency for rugs, even heavy ones, to make any appreciable difference.

I think it varies too much to generalize quite like that. Especially for those with a decently long listening distance, there are many driver layout combinations on speakers that'll put the cancellation in the 500-800 Hz range, where the Toole recommended 40 oz felt underlay for a rug will be decently effective.

 

[andreasmaaan]

I think it varies too much to generalize quite like that. Especially for those with a decently long listening distance, there are many driver layout combinations on speakers that'll put the cancellation in the 500-800 Hz range, where the Toole recommended 40 oz felt underlay for a rug will be decently effective.

Well I did say "tends to"

Out of interest though, could you be more specific about the kind of felt underlay you're talking about?

 

[RayDunzl]

Sounds are never, and hear I mean literally never, composed mainly of harmonics.

It is not uncommon for the second and/or third harmonic of a sound to be at a higher SPL level than the fundamental

Experiment:

Here is the spectrum of my voice singing "Oh".

Fundamental about 120Hz.

Equal contribution from second and third harmonics.

That was easy.


My "whistle" is somewhat unexpectedly pure, though:

Whoa.

Figured a little "pitch pipe" I had in the drawer would have a strong clean fundamental...

But nooooooooo....

 

[andreasmaaan]

It is not uncommon for the second and/or third harmonic of a sound to be at a higher SPL level than the fundamental

Experiment:

Here is the spectrum of my voice singing "Oh".

Fundamental about 120Hz.

Equal contribution from second and third harmonics.

View attachment 64136

That was easy.


My "whistle" is somewhat unexpectedly pure, though:

View attachment 64137


Whoa.

Figured a little "pitch pipe" I had in the drawer would have a strong clean fundamental...

But nooooooooo....


View attachment 64138

The pitch pipe looks more or less like a sawtooth waveform.

Can you get a graph of it in the time domain?

 

[RayDunzl]

The pitch pipe looks more or less like a sawtooth waveform.

Can you get a graph of it in the time domain?

 

[andreasmaaan]

View attachment 64148

Kind of, lol...

Thx

 

[tuga]

The church bell also has harmonics that are very high in level but only the second sustains considerably:

 

[tuga]

A flute (intersting dispersion chracteristics, definitely not as directional as the horn family but still tricky to mic):

 

[Senior NEET Engineer]

What would really help are measurements of a set of speakers in a room, after and before room treatments. If the speaker as been reviewed here, even better.

My experience so far as been: studios mostly LEDE with toons of treatments, non // walls and so on, studios which are Dolby certified and residential places with none or very few treatments.

It is not super clear to me which one is "better". They sound different, ok with that but do we have a preference? I get used to any situation quickly.
Except when mastering, I do not care too much.

New speakers with great directivity integrate very well in normal rooms without treatment. Bass is well compensated with subwoofers and you can easily get excellent crossover now. Taming treble is easy too. You can play a bit in the time domain but it is not clear it is easy to detect (and I really would like to believe I hear a difference between my time aligned speakers with XO and a basic EQ).

Please show some figures and people will be more receptive.

What are the main differences you notice in untreated domestic rooms vs. LEDE model rooms?

Personally I can't stand the sound of rooms without acoustic treatments. Either too dead or too live.

 

[Bjorn]

@Bjorn
Could you please tell us how far away from the horn the microphone was? And at what height was the microphone and the horn?

1 m distance and the different heights were: 0 (floor), 50, 65, 85, 110, 130 and 160 cm.

Need to measure at more distances but the experience from living rooms is that the floor bounce is greatly minimized. Here's are two measurements from one room with wooden floor and no ceiling treatment. No EQ ("room correction") in listening position was used. Crossover to a subwoofer at 100 Hz.

Distance 2.7 m and height 97 cm, 1/12 oct. smoothing:

Distance 3 m and height 97 cm, 1/12 oc. smoothing:

 

[ctrl]

1 m distance and the different heights were: 0 (floor), 50, 65, 85, 110, 130 and 160 cm.

Need to measure at more distances but the experience from living rooms is that the floor bounce is greatly minimized. Here's are two measurements from one room with wooden floor and no ceiling treatment. No EQ ("room correction") in listening position was used. Crossover to a subwoofer at 100 Hz.

Distance 2.7 m and height 97 cm, 1/12 oct. smoothing:
View attachment 64215

Distance 3 m and height 97 cm, 1/12 oc. smoothing:
View attachment 64216

Thanks for the frequency response measurements.

Now there is still one thing missing, the height of the midrange horn. If I had to make a guess based on your measurements, I would guess the center of the horn mouth at about 60cm high.

 

[Bjorn]

Thanks for the frequency response measurements.

Now there is still one thing missing, the height of the midrange horn. If I had to make a guess based on your measurements, I would guess the center of the horn mouth at about 60cm high.

Not quite.

Picture of a prototype:

 

[Biblob]

Not quite.

Picture of a prototype:
View attachment 64353

Nice thing about this is you can place your TV in the horn, if you're not listening to music. Benefits the WAF greatly.

Joking aside, I'm curious how it would sound compared to a more ordinary floorstander.