JTR Noesis 210HT speaker (review by Erin)

[ernestcarl]

I admit I don't fully understand the use of compression drivers in speakers like this that still have relatively weak woofers. My understanding is that a good 1" dome tweeter is capable of 120dB SPL, and midranges at least that much. And that's ignoring any increase from a waveguide.

Considering the downsloping FR of content, it seems to me that most compression drivers are unnecessary for output.

Presumably there is some other advantage but I don't know what it is.

How are the woofers weak? I would look at the powerhandling and other parameters. They may not be equally sensitive as the compression driver, sure, but that does not matter since you can push them pretty darned hard.

Besides high SPLs, the compression diaphragm seen here coupled with the horn waveguide and large bass drivers can help achieve a certain desired directivity fit or pattern control — usually much narrower to also maintain the volume level efficiency required for longer-distances in PA and sound reinforcement applications.

I’m finding it difficult to believe that there are a good many viable and equally reliable 1” dome tweeter alternative replacements that could survive the same kind of regular abuse that may be expected more out of these torture tested “pro audio” drivers.

There may be other reasons for prefering compression drivers other than high SPL and sensitivity, of course — the combo of coaxial horn loading and physical time alignment, perhaps? Personal preference? You’d have to ask speaker designers who utilize these drivers heavily and the customers who to choose to buy them.

But, yes, for most home audio uses… these may well be overkill.

*Mainly referring to the examples I provided and not specifically this “entry level” JTR speaker.

 

[Sancus]

How are the woofers weak? I would look at the powerhandling and other parameters. They may not be equally sensitive as the compression driver, sure, but that does not matter since you can push them pretty darned hard.

2x10" is not a lot of woofer in the context I'm talking about. I don't see them reaching 130dB SPL in the 100-200hz range, and that's what would be required to justify more than a dome tweeter here. So yeah, I say again: I don't see any reason for a compression driver due to SPL output here.

I mean, just to pull a random example, Genelec uses wave guided dome tweeters and 5" midrange driver in their main monitors all the way up to 2x12"/1x15" woofer setups designed for >120dB SPL. It's only when they hit 2x15" & 2x18" targeting >130dB they feel a need to add a second midrange and switch to a compression tweeter.

It does seem like there's some design pattern where a compression driver is used to make a 2-way with the output of a standard domes/cones 3-way, but I'm unclear on the benefit of doing that. Maybe it's cheaper? JTR doesn't even do that past this model anyways, they switch to 3-ways in every other model.

 

[Chromatischism]

The bigger compression drivers tend to play lower in frequency than domes, so they can cross lower to a large woofer to avoid narrowing woofer directivity.

 

[ernestcarl]

2x10" is not a lot of woofer in the context I'm talking about. I don't see them reaching 130dB SPL in the 100-200hz range, and that's what would be required to justify more than a dome tweeter here. So yeah, I say again: I don't see any reason for a compression driver due to SPL output here.

I mean, just to pull a random example, Genelec uses wave guided dome tweeters and 5" midrange driver in their main monitors all the way up to 2x12"/1x15" woofer setups designed for >120dB SPL. It's only when they hit 2x15" & 2x18" targeting >130dB they feel a need to add a second midrange and switch to a compression tweeter.

It does seem like there's some design pattern where a compression driver is used to make a 2-way with the output of a standard domes/cones 3-way, but I'm unclear on the benefit of doing that. Maybe it's cheaper? JTR doesn't even do that past this model anyways, they switch to 3-ways in every other model.

I do not know what JTR's exact reasoning is for choosing compression drivers over separate or displaced dome tweeter and midrange drivers in this particular model. And haven't really checked in more detail any of their higher models. But I would strongly presume there is a "house design" mould they are trying to adhere to -- also, similar high SPL driver parts accompanied with perfectly matching large waveguides aren't likely just something you can buy off the shelf or develop in-house without prior extensive expertise.

As for your last question, @Chromatischism provided a good answer. My first two examples of Fulcrum Acoustic speaker models provide engineering design philosophy and rationale in their own website... in the spec sheets there's also a list some possible real-world applications.

 

[Vladimir Filevski]

My understanding is that a good 1" dome tweeter is capable of 120dB SPL, and midranges at least that much. And that's ignoring any increase from a waveguide.

Impossible, on both accounts.

 

[fluid]

Impossible, on both accounts.

KEF did it with their KM1 in the eighties but it is unusual for sure
https://us.kef.com/pub/media/pdf/Professional_Series_Model_KM1_r.pdf

 

[Vladimir Filevski]

KEF did it with their KM1 in the eighties but it is unusual for sure
https://us.kef.com/pub/media/pdf/Professional_Series_Model_KM1_r.pdf

No, they didn't.
Please carefully read the fine prints: "Measured with third-octave tonebursts...".
Also, there is no distortion measurements for that SPL. It is easy to reach 120 dB with 30% distortion.

 

[fluid]

No, they didn't.
Please carefully read the fine prints: "Measured with third-octave tonebursts...".

I did, they are quoting peak SPL capability not long term sustained level so I don't see the problem with a tone burst.

Also, there is no distortion measurements for that SPL. It is easy to reach 120 dB with 30% distortion.

No but at 110dB 2nd and 3rd are listed as being 3.2% or less. You said it was impossible, there was no qualification of distortion level in your statement.

The tweeter was unusual in that it had a double magnet with 21,000 Gauss and ferro fluid. Laurie Fincham told a little story about it in one of Erin's videos and how difficult it was for them to make a dome get as loud as the design spec.

 

[Sancus]

Impossible, on both accounts.

KH420 3" midrange dome does >120dB across its entire range at 3% distortion, and about 118dB at 1% distortion. The Genelec 5" midrange cone with a tweeter cutout is not far behind.

It seems the tweeter maxes out ~115dB @ 3% at the low end of its frequency range. Of course, these aren't true maximums but within a distortion threshold. So it is clearly possible. And I doubt they're using the most capable tweeter out there, cost is still a factor even at this level.

I suspect the truth is more like "Yes possible with very good drivers, but too expensive for HT speakers that are trying to hit high SPL at a price point".

The bigger compression drivers tend to play lower in frequency than domes, so they can cross lower to a large woofer to avoid narrowing woofer directivity.

Yeah, I knew that. I was more wondering what the benefits of doing this are relative to a cone/dome 3-way with similar size woofer(8-10", say). The answer may just be that it's an alternative design with different compromises but not substantially different performance.

 

[Chromatischism]

And maybe a marketing angle as well.

 

[Vladimir Filevski]

KH420 3" midrange dome does >120dB across its entire range at 3% distortion, and about 118dB at 1% distortion. The Genelec 5" midrange cone with a tweeter cutout is not far behind.

Yes, but because I was replaying to this post

I admit I don't fully understand the use of compression drivers in speakers like this.... My understanding is that a good 1" dome tweeter is capable of 120dB SPL, and midranges at least that much. And that's ignoring any increase from a waveguide.

I clearly stated - it is impossible for a 1" dome tweeter (without waveguide) to reach 120 dB (at acceptable distortion levels, of course!), so obviously you need a compression driver and horn, or dome plus waveguide, for that. On the other hand, pro midrange drivers can easily reach 120 dB with low distortion, without waveguide.
Again - it was about his assertion that "we don't need pro drivers for 120 dB SPL" and "we don't need a waveguide". On the contrary!
By the way, KH420 dome midrange has waveguide!

It seems the tweeter maxes out ~115dB @ 3% at the low end of its frequency range. Of course, these aren't true maximums but within a distortion threshold. So it is clearly possible. And I doubt they're using the most capable tweeter out there, cost is still a factor even at this level.

True, dome tweeters without waveguide has maximum SPL at about 110-115 dB (with acceptable distortion level!) and that is short of 120 dB, so - impossible, just as I said! Of course, maybe there is some exception I am not aware of, it will be interesting to see such example.

 

[Chromatischism]

Regardless of the actual numbers, he's right that the bass driver tends to be the weakest link in the system.

 

[Vladimir Filevski]

No but at 110dB 2nd and 3rd are listed as being 3.2% or less. You said it was impossible, there was no qualification of distortion level in your statement.

Come on... it implies that the distortion level has to be acceptable.
In the old DIN standard there was 3% distortion limit for something to be called "hi-fi". 3% distortion limit is widely accepted for all max SPL testing.
110 dB (with 3.2% distortion ) is short of 120 dB, so sorry - it is impossible!

 

[fluid]

Come on... it implies that the distortion level has to be acceptable.

If you say what you mean instead of implying things that you don't say, communication is clearer. All the research I have read on distortion perception finds that THD as a metric is very poorly correlated with perceived sound quality. Keeping it as low as possible is a good engineering excircle but drawing lines in the sand at specific percentages and calling something "hifi" or not is not something supported by research which took place after the old DIN standard was made.

In the old DIN standard there was 3% distortion limit for something to be called "hi-fi". 3% distortion limit is widely accepted for all max SPL testing.
110 dB (with 3.2% distortion ) is short of 120 dB, so sorry - it is impossible!

It is your use of the word impossible that is inaccurate. This is not something that could not be done by a manufacturer if they wanted to but why would they. It is much easier to make a high sensitivity compression driver go insanely loud than it is to force 500 odd watts of power through a dome tweeter.

 

[Vladimir Filevski]

... THD as a metric is very poorly correlated with perceived sound quality. Keeping it as low as possible is a good engineering excircle but drawing lines in the sand at specific percentages and calling something "hifi" or not is not something supported by research which took place after the old DIN standard was made.

Yet, lines are still being drawn in the distortion measurements! Ask Amir, if you don't believe me!

In modern pro circles 3% THD is still accepted as the line which separates good from bad sound quality and 10% THD is the line for not acceptable sound quality:

It is your use of the word impossible that is inaccurate. This is not something that could not be done by a manufacturer if they wanted to but why would they. It is much easier to make a high sensitivity compression driver go insanely loud than it is to force 500 odd watts of power through a dome tweeter.

Instead of waiting for Godot (1" dome tweeter capable of 120 dB SPL with less than 3% THD), we have to accept the painful truth - there are no such tweeters on the market. Besides, 500 watts will fry any 1" dome tweeter in a second.
Maybe the only 1" tweeter capable of very high peak SPL is Peerless DA25TX00, but it needs 1585 W power to reach 120 dB/1m!

 

[Vladimir Filevski]

My understanding is that a good 1" dome tweeter is capable of 120dB SPL,

KEF did it with their KM1 in the eighties

Gotcha! Tweeter in KEF KM1 is T52 with 1.5" (38 mm) dome - it is not a 1" (25 mm) dome tweeter!
So, still no 1" dome tweeter on this planet capable of 120 dB! In other words -impossible!

 

[fluid]

Yet, lines are still being drawn in the distortion measurements! Ask Amir, if you don't believe me!

Drawing a line in a review to represent a percentage to allow for quick reference and comparisons is a good idea. The problem comes if that line is meant to represent a perceived sound quality.

In modern pro circles 3% THD is still accepted as the line which separates good from bad sound quality and 10% THD is the line for not acceptable sound quality:

Specifying a figure because it is achievable and practical is one thing, tying it directly to sound quality is where it falls down.

Gotcha! Tweeter in KEF KM1 is T52 with 1.5" (38 mm) dome - it is not a 1" (25 mm) dome tweeter!
So, still no 1" dome tweeter on this planet capable of 120 dB! In other words -impossible!

If you had qualified your initial impossible as you have now I wouldn't have wasted my time and server space responding.

Because something does not currently exist to meet your expanded definition does not mean it could not, just that there is no business case for making one as there are cheaper and easier ways of getting to that output and distortion spec.

A high sensitivity dome with sufficient excursion, motor strength and heatsinking would be hugely expensive to make and who would they sell it to...

 

[thewas]

Joachim Kiesler from ME Geithain mentioned once in an interview another SPL limitation source of a pure 1" dome tweeter without waveguide/horn:

"With a 25-millimetre dome tweeter radiating at 110 dB at one metre metres, you are already in the order of magnitude where air compression causes distortion. In this respect, there is physically nothing more that can be done to the loudspeaker. This is often overlooked. Due to the small surface area, you reach a point where the physics is exhausted and not the transducer. It is then of no use to increase the surface area, because then other problems arise, for example a higher directivity. It is possible to counteract this by using horn waveguides, but this again requires the acceptance of colouration due to short-term reflections. In principle, it is always a question of optimising what is available for this or that application."

Original source in German language (unfortunately the link is not working anymore): https://studio-magazin.de/Leseproben/MEG Bassniere.pdf

 

[Vladimir Filevski]

Drawing a line in a review to represent a percentage to allow for quick reference and comparisons is a good idea. The problem comes if that line is meant to represent a perceived sound quality.

Specifying a figure because it is achievable and practical is one thing, tying it directly to sound quality is where it falls down.

You are trying to negate more than 80 years of scientific evidence that the 3% is the limit for good sound quality. Old DIN standard is still valid in this regard, also many old science books. For example, see Fig. 12.43 on page 597 of "Elements of Acoustical Engineering" by Henry F. Olson (second edition, 1957) - for music signal perceptible THD is below 1%, tolerable THD is 1.5% and objectionable THD is 2%. Every single scientific paper till today proved this numbers, even specifying lower numbers - you can google those.
You can try yourself to see (hear) how easy is to detect 3% THD (-30 dB) in some music samples:
https://www.klippel.de/listeningtest/?v=3

If you had qualified your initial impossible as you have now I wouldn't have wasted my time and server space responding.

But you were the one who thought there is a 1" tweeter capable of 120 dB SPL - and in inability to show such an example, you gave an example for bigger 1.5" tweeter (which can reach maximum of just 110 dB with 3.2% distortion)! It is waste of everyone time and server space, indeed.

Because something does not currently exist to meet your expanded definition does not mean it could not,

My definition is not "expanded" - it would be silly to measure loudspeaker only for max SPL, without measuring % distortion. What is the max SPL limit of a loudspeaker - when it disintegrate itself?! As you can see, you must measure distortion too.
You don't have a single evidence or example whether some company can make 1" tweeter capable of 120 dB with less than 3% THD - that is only your wishful thinking. Waiting for Godot will more fruitful than waiting for your unicorn 1" tweeter capable of 120 dB to show off.

 

[Sancus]

Regardless of the actual numbers, he's right that the bass driver tends to be the weakest link in the system.

Yeah the fact of the matter is Genelec uses a 1" dome tweeter with 250W amplifier in a speaker with 2x12"(1234A) woofers that is designed to hit 125dB SPL in the midrange and 120dB below 100hz. And Genelec's specs are usually very accurate.

Of course I should have known that people would miss the forest for the trees and get bogged down in an unimportant argument about +/- a few dB. Thanks for those who posted useful responses at least.

just that there is no business case for making one as there are cheaper and easier ways of getting to that output and distortion spec.

It does seem clear that this is probably what it comes down to for technical reasons(ignoring marketing/aesthetics/etc). You can reach the same levels as this speaker with standard drivers, but the whole package is going to be much more expensive between the driver and amplification requirements. This speaker is only $2000 which is cheap for its output capability.