A Broad Discussion of Speakers with Major Audio Luminaries

[Neadych]

I'm talking about scale.
Is it possible to achieve with a small system, at a short distance and in a small room, what a large system can achieve at a long distance in a large room? Something similar, but on a smaller scale. After all, a smaller system requires fewer resources and costs less. Mini-hi-end, if you like)

 

[NTK]

Speculating on his meaning here. For a small speaker to play a 50Hz note at the same SPL as a larger speaker, the swept volume needs to be the same, and therefore more cone excursion for the smaller speaker. This means it needs to move "faster". What effect this has on the wavefront - I have no idea. I don't think I have ever read anything that says there is a difference. @NTK?

The acoustic pressure waves that we hear from loudspeakers (i.e. those that hit our eardrums and bodies) are elastic waves, not bulk fluid motions. The bulk fluid displacement (the wind) caused by the moving woofer cone goes down exponentially with distance from the diaphragm surface, the so called "hydrodynamic nearfield".

I'll use ripples in a pond as an analogy. When you drop a boulder into the middle of a pond, a surface wave will spread radially outward. There will be some bulk water displacement outward near where the boulder is dropped. However, if there is a floating ping pong ball some distance away (e.g. > ~20 diameters of the boulder), the ping pong ball will just be moving oscillatorily up and down, and not moving away.

Therefore, the actual "bulk" fluid velocity at the cone surface has little direct relationship with the acoustic pressure it radiates to the farfield. It is the volume velocity (= surface area × cone velocity) that matters. (To be pedantic, the acoustic pressure is directly related to volume velocity multiplied by frequency.)

With regard to how much the air particle displacement would be in the farfield, below is from "An Introduction to Acoustics" by S.W. Rienstra & A. Hirschberg. At 140 dB SPL 1 kHz (exceeding the threshold of pain), the air particle oscillation amplitude, δ, is only 80 μm. At 140 dB 20 Hz, the displacement amplitude would be 4 mm (= 80 μm × 1000/20), which would be much smaller than the cone surface displacement.

The book also points out an interesting point that, at our threshold of hearing at 1 kHz, the average "acoustic particle displacement" is in the subatomic length scale of 0.01 nm (= 0.1 Å) and can go down even smaller at higher frequencies!

 

[Fredygump]

It is not that difficult to measure, but most of what is discussed here are FFTs, steady state tones, and SINAD.
Other than organ music and Mongolian throat singers, most music is a lot about attack, transients, and impulses.

If you have a very expensive and specialized piece of gear, then yes, it is easy to measure because the machine does the work for you. But if you don't have the right gear, the results will be limited by your gear and inaccurate!

This is the video by Amir that I was referencing. He is explaining what "actual" peak loudness is and how it is much higher than we might expect.

 

[j_j]

Sorry! I thought I understood something, but it's clear now I did not haha

We've all been there. When one does research, one finds this out rather more often than one might prefer.

 

[j_j]

It is a good idea, as well, to remember that in a loudspeaker with any kind of crossover, each driver's impulse response is limited not only by the driver response,but also by the bandwidth that the crossover feeds it. Hence in an impulse like a tympani hit,the goal is to get the total of all the drivers to look like an frequency-shaped impulse, which will then decay into a set of ring tones, which for percussion are not generally harmonic.

There is a mega-boat-load of complexity in single tympani hit.

 

[Duke]

Is it possible to achieve with a small system, at a short distance and in a small room, what a large system can achieve at a long distance in a large room?

In some ways maybe so, but not in all ways.

For instance, there are benefits which arise from the longer reflection path lengths (and therefore later reflection arrival times) of larger rooms.

Imo some loudspeaker types are more "small room friendly" than others, but personal preferences and priorities play a role.

If you're serious (to the point of spending money) about getting a small room to sound more like a big room, I think it would make sense to hire a professional acoustician.

 

[Fredygump]

You had a three-way system with a low crossover frequency, but now you have a regular system with a high crossover frequency.
The low crossover frequency allows for a subwoofer, but the high crossover frequency does not.

What listening distance are you listening from?

I can understand that it's better if the distance is greater.
Is there an advantage to listening from a short distance?

I have DIY speakers that are not really comparable to anything you would buy, so don't worry about my crossovers.

Buy the speaker that you like, and don't worry about the size of the room. The big speaker will work just fine in a little room. The idea that you should buy a small speaker for a small room is a myth, and all the people I trust say it is BS.

The character of the sound will change depending on your listening distance. Changing the size of the speaker isn't a variable in that equation!

 

[Neadych]

You have a very optimistic statement. Send your speakers to Amir so that we can see them. It is obvious that an 8" speaker will overload when working at a long distance and at a high level of 100 Hz. It will become easier for it if it is cut at 300 Hz.I am referring to the principle. If the distance is short and the room is also small, is it necessary to purchase the largest, most powerful, and expensive speakers to achieve the best sound in that space?I do not want to proceed to listening, let alone purchasing, until we have clear numbers.

 

[dagfinn]

I'm talking about scale.
Is it possible to achieve with a small system, at a short distance and in a small room, what a large system can achieve at a long distance in a large room? Something similar, but on a smaller scale. After all, a smaller system requires fewer resources and costs less. Mini-hi-end, if you like)

No. One 6,5" 8340 driver will never achieve the same as 2x15" or 2x18", and not only at max SPL. No matter how close you sit or size of room. Even going from 6,5" to 8" there will be an audible difference, particularly in the range up to 200-300Hz or so. But from there, the situation changes, a 5" mid reaches far, particularly given a waveguide loading. My experience comes from realtime ABC setup using 4", 5 1/8", 6,5", 8", 12", 2x12" and 2x15" speakers from Genelec, with and without subs.

Even the 8361a is better with W371a, according to those who have them. Why is that, you think? Which part of the 8361a does the W371a substitute and improve?

 

[Thomas_A]

I think the ”fast bass” myth from small drivers come from their limitations of low bass and less room effects below 100 Hz.

 

[Holmz]

If you have a very expensive and specialized piece of gear, then yes, it is easy to measure because the machine does the work for you. But if you don't have the right gear, the results will be limited by your gear and inaccurate!

That section that starts about 23:00 in, shows peaks and average.
One can just do it all in the digital domain with the numbers.

Getting back to real life, on could use a microphone and digitise that to measure what the system did relative to the input, which was quantified in the bits.

This is the video by Amir that I was referencing. He is explaining what "actual" peak loudness is and how it is much higher than we might expect.

There are reams of speed sheets that show the crest factor of various kinds of music and specific tracks.
13dB was pretty common for rock before the loudness wars.
And 20+ dB was common for classical.

At a crest factor of 20dB, that 1W RMS becomes 100W peaks.

 

[Sokel]

Added to that is if the "small" speaker is a 2 way design, and the "large" speaker is a 3 way or 4 way, then the mids and low frequencies should be more clear on the large speaker, assuming the crossovers are designed well to split the workload.

I've had some experience taking 2 way speakers and adding stereo subwoofers, essentially turning the 2 way speakers into "big" 3 way speakers. Doing that always improves the midrange, I suppose by reducing IM distortion. Using a subwoofer typically means a crossover of 100hz, but in my current project I'm finding crossing the midrange as high as 300hz is a significant improvement over 100hz.

That will only work if mains and subs are co-located, tightly, like using the subs as stands and respecting the 1/4 wavelength rule, measured outside with spins, etc, the works.

In general, as midbass chest hit is one of my vices, what I KNOW listening to a gazillion of gear is that apart from driver size this kick is directly comparable with VC size and motor strength. And you can have it even from speaker that does not go lower than 40's, easily, subs don't matter there. Only what I described along with some decent real estate.

I'll let you do the math.

 

[goat76]

Does this critical distance have any application outside of a studio?

Of course it does. For example, it enables you, as the listener, to better distinguish the three-dimensionality of the recorded room acoustics with reduced acoustic interference from your listening environment, allowing you to hear more details from the recording itself.
The higher ratio of indirect sound you perceive at a longer listening distance can only degrade those finer details in the recording, as the listening environment's reflections only "sees" two sound-generating sources (the two loudspeakers), and can't make a distinction between the separated sound sources and the reflective directions in the actual recording, which can only lead to a blurring effect on the perceived overall sound.

When sitting inside the critical distance, you will mainly hear the recorded sounds as the main thing, which the two loudspeakers are "projecting" to your ears as a single unified stereo image, and the indirect sounds from the listening environment will then act as a secondary diffuse sound, adding envelopment without interfering too much with the recorded stereo image.

 

[Neadych]

No. One 6,5" 8340 driver will never achieve the same as 2x15" or 2x18", and not only at max SPL. No matter how close you sit or size of room. Even going from 6,5" to 8" there will be an audible difference, particularly in the range up to 200-300Hz or so. But from there, the situation changes, a 5" mid reaches far, particularly given a waveguide loading. My experience comes from realtime ABC setup using 4", 5 1/8", 6,5", 8", 12", 2x12" and 2x15" speakers from Genelec, with and without subs.

Even the 8361a is better with W371a, according to those who have them. Why is that, you think? Which part of the 8361a does the W371a substitute and improve?

Thank you. I think the woofer unit replaces the 8361 woofers, which is both a relief and a disappointment.

 

[Thomas Lund]

This is the video by Amir that I was referencing. He is explaining what "actual" peak loudness is and how it is much higher than we might expect.

It is important to distinguish between peak and average level, like Amir does. However, Loudness is a perceptual property of an audio signal when it is reproduced acoustically and listened to. "Peak loudness" in this context is therefore not the right term, and it does not cover the various peak level measurements explained later.

Please also note how an average SPL of 90 dB actually can cause temporary as well as permanent hearing loss (HL). It is only a question of the amount of time one is listening. HL is more associated with sound energy ("sound exposure") than sound power ("SPL").

See attached, showing sound exposure safety limits in adults [WHO, EU]. The baseline in children is 5 dB lower. US OSHA is dangerously outdated, and does not reflect the last 40 years of clinical research.

 

[j_j]

Remember that as you move back, you become closer to the same distance between drivers. The summation of all the driver outputs changes as a result.

US OSHA is dangerously outdated, and does not reflect the last 40 years of clinical esearch.

This bears repeating. Often.

 

[dagfinn]

Minor gripe, "immersive" means "fully enclosed in a diffuse field". Let us remember that.

Trying to understand your gripe. "Diffuse" is not at all how I prefer to hear stereo, or what makes stereo emotionally or perceptually "immersive" for me. Obviously two different definitions that may apply to the same theme.

If you measure the physical size of the waveguide of a 1039a, (or other big master monitor), you'll find it to have about the same diameter as a 15" woofer cone. I believe this decides the dimensions of soundfield created. At 2-3m, the speaker dominates and I do feel physically "immersed" at 75-80dB SPL (which equates to 96db SEL). The illusion appears in front, and between the speakers as it would in real life, and it does so with extreme fidelity. Add the dispersion and dynamics of woofers, and the illusion is stunning. Particularly live performances, with the added rawness and venue interactions. Even bad recordings sound real, and monitors like this will expose the problem(s).

Remember that as you move back, you become closer to the same distance between drivers. The summation of all the driver outputs changes as a result.

Yes, and the further you go the poorer the imaging becomes, until it sounds like mono (if the room is long enough) - since both ears can hear both sides equally and crosstalk is 100%. So an equilateral triangle in near or midfield is optimal, as I hear it.

Here's the 1039a, if it matters.

My typical levels, here with SEL.

 

[Blueprint]

Sure, but nothing else is ever equal. A bigger driver will generally have a bigger motor.

In any case, I've never understood this "transient" business. The driver has to move fast enough to produce a certain frequency. If it doesn't do that relative to the signal it's being fed, it either produces nothing, it produces the right frequency with reduced amplitude, or it produces the wrong frequency (aka distortion). Is there something else?

Completely agree with this.

All of these things people speak of, transients, ‘fast’ bass, ‘tight’ bass, all of this is measurable in the frequency domain. If you have a woofer that measures flat, the perception of ‘fast transients’ is likely the absence of sub-bass.

 

[Neadych]

Many people use much more modest speakers at 4 meters, but they obviously won't achieve the enveloping effect at that distance.
What's your room size?

 

[audiofooled]

Remember that as you move back, you become closer to the same distance between drivers. The summation of all the driver outputs changes as a result.


This bears repeating. Often.

Intrachannel summation, interchannel summation, phase summation, response linearity with regards to peaks?

And, on the other hand, cochlear dynamics, auditory compression, frequency vs. time resolution with regards to actually perceived loudness. Can the complexity of reproduced, say, percussion, leave us subjectively oblivious of the true peaks delivered by small vs. big systems and what are the metrics for the perceived dynamics? Average SPL measured can be misleading, no?