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"The secret of big speakers"

hvbias

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I've been thinking about replacing my Harbeth SHL5 in my living room with some speakers that measure better and are objectively higher fidelity but still small enough ala Harbeth size that they are not intrusive looking. These will be separate from the major big horn DSP assault I am taking for the dedicated listening room. So I've been naturally looking at D&D and Kii.

I came across this on their website:

Kii’s mission for the THREE was to break the sonic mould of compact speakers. Powerful small speakers with deep bass have been around for a while now but none so far sounded like a big speaker. The THREE is built to fix that.

Basic acoustics tells us that a classic box speaker only directs sound towards the listeners from the midrange up while bass frequencies are radiated all around. The frequency where this change happens depends on the size of the box front (the “baffle”). The smaller the baffle, the higher the frequency at which bass is still radiated all around instead of directed towards the listener.

That in short is why big speakers have so far delivered much more precise timing and detail in the bass and low mids than small speakers: the room gets less chance to interfere. And that is what Kii has now managed to make a compact speaker do.

I'm curious to know what members thing of this paragraph. Scientifically sound or clever marketing?

I might have started a thread on this here early on when the forum started or someone else did. Having speakers that can reproduce the scale of a large orchestra as well as big tone of a concert grand has been one of my goals. The best speakers I have heard do this I described here. Now those speakers would go against what Kii are describing above as the bass would have been more directional than what they are referring to as big box speakers, (I assume they mean speakers like large Wilsons or Magicos, etc) yet that horn system was still the best at creating a "big speaker sound" and the closest I have heard to accurately reproducing the size of something like a full orchestra Mahler symphony or a well recorded concert grand from the further away mics in Carnegie Hall.
 

andreasmaaan

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I think there's something in it with regard to the midrange, but I question the idea that big speaker give the room less chance to interfere in the bass. To stop a conventional box speaker radiating omnidirectionally below 200Hz would require a baffle many times wider than any home audio speaker.

I also think they're glossing over the fact that big speakers play louder and with less distortion, which IMO is probably the more important factor.
 

Purité Audio

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It would be easier if you just heard a pair in your room than trying to describe how they sound or how they compare.
Both have a wide even dispersion, the sound from both fill the room , my very tall horns obviously add more height to the image because they are so tmuch taller.
Try a pair of either and report back!
Keith
 
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hvbias

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It would be easier if you just heard a pair in your room than trying to describe how they sound or how they compare.
Both have a wide even dispersion, the sound from both fill the room , my very tall horns obviously add more height to the image because they are so tmuch taller.
Try a pair of either and report back!
Keith

I do intend to. This thread was more of a starting point to discuss the science behind "big speakers", and I leave it open if people want to discuss subjective impressions as well as long as it's not too far off the thread topic.
 

Fitzcaraldo215

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I've been thinking about replacing my Harbeth SHL5 in my living room with some speakers that measure better and are objectively higher fidelity but still small enough ala Harbeth size that they are not intrusive looking. These will be separate from the major big horn DSP assault I am taking for the dedicated listening room. So I've been naturally looking at D&D and Kii.

I came across this on their website:

Kii’s mission for the THREE was to break the sonic mould of compact speakers. Powerful small speakers with deep bass have been around for a while now but none so far sounded like a big speaker. The THREE is built to fix that.

Basic acoustics tells us that a classic box speaker only directs sound towards the listeners from the midrange up while bass frequencies are radiated all around. The frequency where this change happens depends on the size of the box front (the “baffle”). The smaller the baffle, the higher the frequency at which bass is still radiated all around instead of directed towards the listener.

That in short is why big speakers have so far delivered much more precise timing and detail in the bass and low mids than small speakers: the room gets less chance to interfere. And that is what Kii has now managed to make a compact speaker do.

I'm curious to know what members thing of this paragraph. Scientifically sound or clever marketing?

I might have started a thread on this here early on when the forum started or someone else did. Having speakers that can reproduce the scale of a large orchestra as well as big tone of a concert grand has been one of my goals. The best speakers I have heard do this I described here. Now those speakers would go against what Kii are describing above as the bass would have been more directional than what they are referring to as big box speakers, (I assume they mean speakers like large Wilsons or Magicos, etc) yet that horn system was still the best at creating a "big speaker sound" and the closest I have heard to accurately reproducing the size of something like a full orchestra Mahler symphony or a well recorded concert grand from the further away mics in Carnegie Hall.
The explanation sounds like it might be a little backwards to me. Rather than affecting the woofer, I think the bigger baffle helps the midrange driver go lower in frequency, resulting in a potentially lower crossover frequency and possibly less audible distortion at the top of the woofer’s comfortable operating range. It also allows the use of a bigger woofer with a lower useable upper frequency range.

Me? I think subwoofers are best anyway. They have independent placement flexibility for best sound without compromising imaging. They can or should be biamped, ideally with digital xovers or bass management. They can be used in multiples for best evenness of bass and to reduce room modes.

So, my next system, if there is to be one, will have smaller speakers all around with multiple subs. Especially in Mch, like me, I think big speakers are disproportionately more expensive than smaller ones plus subs, due to big speaker cabinet sizes. I think internal bracing needs to be much better in a large cabinet if it contains true LF capabilities. Then, also think of bulk, shipping, etc.
 

Cosmik

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I think there's something in it with regard to the midrange, but I question the idea that big speaker give the room less chance to interfere in the bass. To stop a conventional box speaker radiating omnidirectionally below 200Hz would require a baffle many times wider than any home audio speaker.

I also think they're glossing over the fact that big speakers play louder and with less distortion, which IMO is probably the more important factor.
I thought this was done and dusted..?

The Kii and the D&D don't need a big baffle because they send out cancellation 'waves' from the rear drivers and/or vents to simulate the effect of a big baffle with a small box, resulting in the following plot:


image4.thumb.jpeg.4996cc40d7bcb53399e0665cafdb7c83.jpeg


The D&D may be even better (slightly different frequency axis range, though):
image3.thumb.png.9127e48eb9f659c6cf6edc3457846eb4.png


The Kii THREE’s produce a “big” color free sound that belies their size. Along with constant directivity to low frequencies, make these speakers just about perfect sound reproducers.
https://www.computeraudiophile.com/ca/reviews/kii-three-loudspeaker-review-r735/

I may have been labouring under is misapprehension recently. I thought everyone knew this..?

And as regards distortion, the Kii Three reputedly uses motion feedback, so it can play louder with less distortion than a conventional small speaker - up to a limit where it starts to back off on the bass 'intelligently'.
 

andreasmaaan

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I thought this was done and dusted..?

The Kii and the D&D don't need a big baffle because they send out cancellation 'waves' from the rear drivers and/or vents to simulate the effect of a big baffle with a small box, resulting in the following plot (for the D&D, but the Kii is similar I think):

image3.thumb.png.9127e48eb9f659c6cf6edc3457846eb4.png



https://www.computeraudiophile.com/ca/reviews/kii-three-loudspeaker-review-r735/

I may have been labouring under is misapprehension recently. I thought everyone knew this..?

And as regards distortion, the Kii Three reputedly uses motion feedback, so it can play louder with less distortion than a conventional small speaker - up to a limit where it starts to back off on the bass 'intelligently'.

I think you've misunderstood my post ;)

I'm responding to the paragraph quoted in the OP.

Read this again:

Basic acoustics tells us that a classic box speaker only directs sound towards the listeners from the midrange up while bass frequencies are radiated all around. The frequency where this change happens depends on the size of the box front (the “baffle”). The smaller the baffle, the higher the frequency at which bass is still radiated all around instead of directed towards the listener.

That in short is why big speakers have so far delivered much more precise timing and detail in the bass and low mids than small speakers: the room gets less chance to interfere. And that is what Kii has now managed to make a compact speaker do.

And then my response:

"I think there's something in it with regard to the midrange, but I question the idea that big speaker give the room less chance to interfere in the bass."

Is it clear what I'm responding to? Kii's final paragraph implies that "big" speakers radiate differently in the bass than "small" speakers.

No conventional home audio box speaker is big enough to be anything but omnidirectional in the bass. This was my first point.

My second point was that, contrary to Kii's claim, "precise timing and detail" is about more than a speaker's radiation pattern.

None of this is to detract from the Kii speakers themselves, I'm simply pointing out errors and half-truths with regard to their statements.
 
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DonH56

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For directionality it depends on where you define "bass" and where Kii applies compensation. For other speakers, baffle size, number and position of drivers, phasing etc. all play a part. The room will always be in play below the Schroeder frequency and for fundamental room modes irrespective of the speaker size (assuming the speaker reaches low enough, natch).
 

KSTR

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And as regards distortion, the Kii Three reputedly uses motion feedback
To my knowledge it doesn't, do you have a reference?
Another product where Bruno Putzeys was involved does, the Grimm Audio "DMF" subwoofer.
Kii Three has pure current drive on the midrange (confirmed info) and (probably) mixed-mode feedback on the woofers, that's what I got from several posts from Bruno and also that are natural/logical choices for advanced designers of active speakers. If they had true motional feedback they would surely advertise it, wouldn't they?
 

Cosmik

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KSTR

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Ah, I see.... that diagram is prone to cause confusion, I would think it's just a scrambled way of depicting the mixed-mode feedback, the feedback is based not on output voltage alone (as in conventional amps) but also current is measured and factored into the feedback. I see no true sensor-based motional feedback and also no signs of the use of the voice coil itself as the motional sensor... which can be done with quite elaborate techniques but seldom has a true advantage.
 

Cosmik

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Ah, I see.... that diagram is prone to cause confusion, I would think it's just a scrambled way of depicting the mixed-mode feedback, the feedback is based not on output voltage alone (as in conventional amps) but also current is measured and factored into the feedback. I see no true sensor-based motional feedback and also no signs of the use of the voice coil itself as the motional sensor... which can be done with quite elaborate techniques but seldom has a true advantage.
There's more about it here:
A second neat idea that the Kii Three employs, and one that seems to have passed by most manufacturers of active speakers, is not one of Bruno’s but was described by Dr Malcolm Hawksford of Essex University in a paper presented to the Audio Engineering Society in 1989. The technique goes by the name ‘current drive’, and involves placing a small resistor in series with the driver and using the voltage measured across it (which will be proportional to the current flowing through the driver voice coil) as a feedback signal. In a conventional arrangement, an amplifier will deliver any amount of current required to make the output voltage follow the input voltage. A current drive amplifier, however, will compare the input voltage with the measured output current and adjust the output voltage to make sure they track. So, now, the output current depends only on the input voltage and not the load. The amplifier delivers any voltage required to make the output current track the input voltage. The primary advantage of current drive is significantly reduced distortion, especially that caused by non-linearities in a driver’s magnet/voice-coil system.
As the article describes, all the bass drivers share a common sealed enclosure - that's very neat, I think. The feedback described above may be a vital part of making that work - I would guess.
 

Cosmik

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...I'm simply pointing out errors and half-truths with regard to their statements.
Just the opposite, surely. If baffle size only influences the mid range response, but their speaker actually achieves control of the bass, then they are playing down their own achievement!

But I don't think they are making an error; it's just that their version of big may be bigger than ours. They say on their web site:
The THREE’s ability to direct bass is comparable to, but much better controlled than that of a traditional speaker several meters wide.
 

KSTR

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@Cosmik, current drive and mixed-mode feedback have beed around for many years, and I've always promoted it and used it in some products I designed.
Actually, it compromises the detail that you mention a bit, as the drivers do react a bit more to the internal sound pressure that they would with standard voltage drive. But the influence is deterministic and can be easily EQ'd out.
We're getting quite a bit off-topic now, do we have a Kii Three thread where this discussion should move to?
 

andreasmaaan

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Just the opposite, surely. If baffle size only influences the mid range response, but their speaker actually achieves control of the bass, then they are playing down their own achievement!

But I don't think they are making an error; it's just that their version of big may be bigger than ours. They say on their web site:

Come on Cosmik, this paragraph is not written about a theoretical several metre wide speaker ;) It says:

That in short is why big speakers have so far delivered much more precise timing and detail in the bass and low mids than small speakers.

Since big speakers don't do this any differently from small speakers (unless they are stadium-sized line arrays which nobody has in their homes nor has in mind when reading this document), the statement is wrong.

It also says:

That in short is why big speakers have so far delivered much more precise timing and detail in the bass and low mids than small speakers.

The box size certainly plays a part in this in the midrange (only), but is not even the main factor let alone the reason "in short".

I'm very much pro-Kii but this is a silly marketing document that exaggerates and is factually inaccurate. The angle seems to be "let's appeal to people who wouldn't buy Kii Threes because they're prejudiced against small speakers. What can we say to convince them?"
 
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hvbias

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The angle seems to be "let's appeal to people who wouldn't buy Kii Threes because they're prejudiced against small speakers. What can we say to convince them?"

That is what I thought as well, but then again I am terrified of small speaker sound so they were playing right into my fears ;)

I obviously need to hear the Kii and D&D for myself as it is now when I see photos of them in rooms the synapses in my brain just don't connect and I think can these really reproduce concert hall like sound?

Since we have some Kii and D&D owners here, maybe I should start another thread where I offer to send them a file of a really good symphony recording and they say what it sounds like? That would also keep this thread on track.
 
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