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-   -   Amphion, ATC, Gethein, Focal, cabinet design (https://www.gearslutz.com/board/high-end/1064138-amphion-atc-gethein-focal-cabinet-design.html)

petergel 27th January 2016 11:56 PM

Amphion, ATC, Gethein, Focal, cabinet design
 
According to Genelec at 3:20 www.youtube.com/watch?v=eO8zcbfZDwk sharp cabinet edges maximizing diffraction. How Amphion, ATC, Yamaha, Gethein, Focal, etc manage to get away with this?

Henrik Hjortnaes 27th January 2016 11:59 PM

Amphion's use a waveguide on the tweeter. That alone eliminates edge diffractions.

ddageek 28th January 2016 03:49 AM

It's all about construction/ sonic priorities. ATC is all about the drivers, simple box and crossover. Almost any cabinet will exhibit some diffraction .
Best thing you can do is listen to some speakers and find what works for you and figure out from there what's important to you.

jlaws 28th January 2016 08:12 AM

As has been mentioned, diffraction occurs on just about any cabinet. Also, it's not the only thing to worry about. Other things like phase/time alignment, distortion, etc all play a part in how a speaker sounds so it's a matter of choosing your priorities. This is almost like the sealed/closed cabinet argument. Each has its merits, which is why different speakers can sounds different despite having similar specs on paper. There are huge advantages to having dsp for time alignment, a huge waveguide on the front for the tweeter/mids and a concentric design like on the genelec 8351s, but there are other approaches to achieving a good result. I'm not a speaker designer by any means and I'm sure one will fill in the rest of the details, but the important thing is you can't take what's said in one product's marketing against other products because they will of course emphasize the strengths of their product and downplay the weaknesses. It's best to test each set of speakers.

dinococcus 28th January 2016 08:12 AM

Understanding Cabinet Diffraction

Understanding Cabinet Diffraction — Audioblog

Henrik Hjortnaes 28th January 2016 08:41 AM

Quote:

Originally Posted by jlaws (Post 11659865)
As has been mentioned, diffraction occurs on just about any cabinet.

Baffle edge diffraction is negligible when using a properly designed waveguide for the tweeter (or the higher frequency driver).

Furthermore, placing a tweeter dome "outside" of the enclosure and centered on the baffle (same distance to the sides and top) will create even more artifacts from diffraction.

So it's pretty easy to visually point out the manufacturers that care about these details and those that don't. Bevelled edges will help reduce diffractions, but is not really needed when the tweeter design and placement has been optimized.

ISedlacek 28th January 2016 09:38 AM

Interesting then why Genelecs sound as they sound :) (when everything is perfect in their opinion)

pentagon 30th January 2016 08:14 AM

Quote:

Originally Posted by petergel (Post 11659055)
According to Genelec at 3:20 www.youtube.com/watch?v=eO8zcbfZDwk sharp cabinet edges maximizing diffraction. How Amphion, ATC, Yamaha, Gethein, Focal, etc manage to get away with this?

ATC uses fillet edge baffle trims for sometime now (>3-5 years?) on the large speakers. This was a change from the "sharp edge" that existed prior. However there's more to speaker cabinet design than edge diffraction.

bcgood 30th January 2016 08:30 AM

I'm sorry, I can't take any speaker seriously that has a bass port in the back

Enlightened Hand 30th January 2016 04:15 PM

@ bcgood - The Genelec 8260 represented itself as an excellent speaker system that I've auditioned in my space. It also gets a lot of love from actual users. I suspect they're doing a few things right despite the port in the back. -

Whatever the case the answer to how certain cabinet designs work with whatever edges has more to do with everything the speaker offers as a trade off. It's impossible to reasonably judge a speaker system's quality based solely on one design element. It has to all work together to effectively reach the design goal.

If there was one "right" design then that would be the only design serious manufacturers would make. And I bet there would be a lot fewer manufacturers.

Henrik Hjortnaes 30th January 2016 08:37 PM

Quote:

Originally Posted by bcgood (Post 11665349)
I'm sorry, I can't take any speaker seriously that has a bass port in the back

Why is that?

ddageek 2nd February 2016 04:28 AM

Quote:

Originally Posted by bcgood (Post 11665349)
I'm sorry, I can't take any speaker seriously that has a bass port in the back

Why ? At the tuned Freq it is acting as an omni radiator unless it's soffit mounted.

Petrus 2nd February 2016 10:59 AM

Quote:

Originally Posted by bcgood (Post 11665349)
I'm sorry, I can't take any speaker seriously that has a bass port in the back

Some companies take a calculated risk of alienating ignorant customers to serve better those who know better.

gt_jumper 2nd February 2016 11:27 PM

Quote:

Originally Posted by bcgood (Post 11665349)
I'm sorry, I can't take any speaker seriously that has a bass port in the back

The 8260a is rear ported, it's a well received monitor as far as I'm aware. I'm sure there are others, the genelec was just off the top of my head.

John Willett 2nd February 2016 11:35 PM

Quote:

Originally Posted by ddageek (Post 11672316)
Why ? At the tuned Freq it is acting as an omni radiator unless it's soffit mounted.

:lol:

All loudspeakers (with the exception of the Geithain K-series) are omni-directional radiators at low frequencies.


There is an explanation of Geithain's cardioid monitors HERE

bcgood 3rd February 2016 01:28 AM

Quote:

Originally Posted by Petrus (Post 11672751)
Some companies take a calculated risk of alienating ignorant customers to serve better those who know better.

Ironically you're the one who is ignorant.. cooge

bcgood 3rd February 2016 02:13 AM

By their own nature, resonant systems cannot start and stop instantly. Ported speakers stagger two resonances, one from the driver and boxed air and another from the boxed air and port, in order to achieve their bass output, a more complex case than an equivalent sealed box. This causes increased time delay (increased group delay imposed by the twin resonances), both in the commencement of bass output and in its cessation. Therefore a flat steady-state bass response does not occur at the same time as the rest of the sonic output; rather, it starts later (lags) and accumulates over time as a longish resonant "tail". Because of this complex, frequency-dependent loading, ported enclosures generally result in poorer transient response at low frequencies than in well-designed sealed box systems.

Another trade-off for this augmentation is that, at frequencies below 'tuning', the port unloads the cone and allows it to move much as if the speaker were not in an enclosure at all. This means the speaker can be driven past safe mechanical limits at frequencies below the tuning frequency with much less power than in an equivalently sized sealed enclosure. For this reason, high-powered systems using a bass reflex design are often protected by a filter that removes signals below a certain frequency. Unfortunately, electrical filtering adds further frequency-dependent group delay. Even if such filtering can be adjusted not to remove musical content, it may interfere with sonic information connected with the size and ambiance of the recording venue, information which often exists in the low bass spectrum.

Whether or not the effects of these in a properly designed system are audible remains a matter of debate. A poorly designed bass reflex system, generally one that is tuned too high or too loosely, can ring at the tuning frequency and create a 'booming' one-note quality to the bass frequencies. In effect, this is due to the port resonance imposing its characteristics to the note being played, and is grossly exacerbated if the port resonance coincides with one of the resonant modes of the room, a not unusual occurrence. In general, the lower in frequency a port is tuned, the less objectionable these problems are likely to be.

If undersized, a port may also generate "wind noise" or "chuffing", due to turbulence around the port openings at high air speeds. Enclosures with a rear-facing port mask these effects to some extent, but they cannot be placed directly against a wall without causing audible problems. They require some free space around the port so they can perform as intended. Some manufacturers incorporate a floor-facing port within the speaker stand or base, offering predictable and repeatable port performance within the design constraints.

Port compression is a reduction in port effectiveness as sound pressure levels increase. As a ported system plays louder, the efficiency of the port reduces, and distortion emitted by the port increases. This can be reduced by port design, but not totally eliminated.



References

Thiele, A. N., "Loudspeakers in Vented Boxes: Parts I and II," J. Audio Engineering Soc., Vol 19, No. 5, May 1971, pp 382-392 (Reprinted from a 1961 publication in Proc. IRE Australia).
Small, Richard H., "Vented-Box Loudspeaker Systems, Part I: Small-Signal Analysis", J. Audio Engineering Soc., Vol 21, No. 5, June 1973, pp 363-444.

jlaws 3rd February 2016 05:12 AM

Yes, there are advantages to sealed enclosures, but I don't think anyone believes it's the only way to make a properly designed speaker. Certainly I don't think anyone should disregard a speaker based on where its port is...If you think that's the case, maybe you should email Genelec and tell them that they've been doing it all wrong. Maybe they'll offer you a job.

Petrus 3rd February 2016 07:02 AM

Quote:

Originally Posted by bcgood (Post 11675019)
By their own nature, resonant systems cannot start and stop instantly. Ported speakers stagger two resonances, one from the driver and boxed air and another from th………..

I did read this through, and I did not find any mention of back facing ports somehow affecting the sound in a negative way (as long as there is enough space to breathe). Often there is more space for larger ports on the backside. Genelec designs their reflex ports very carefully and professionally, with symmetric flare and ample diameter. All you write is well known to all of us, or at least should be, this is a professional site after all.

So what was your point?

While acoustic suspension alignment certainly is theoretically the best practical design, we should realize that people are NOT choosing their speakers first and foremost for absolute quality, but for the best bang for the buck. First they have to decide how much to spend, then find the best solution for the available amount of money, and space. As bass reflex alignment gives more bass from the same size box (about 1/2 octave), more SPL from the same size box and drivers (5 dB more), less distortion and requires much less amplifier power for the same SPL levels, The great majority of monitor designs are ported. They simply offer more for the same amount of money a closed box would do, there is simply no other reason for their popularity. I recently read a review of a splendid closed box speaker with 1500W of amplification and 4x6.5" woofers which goes to 20 Hz, costing 10000€, with maximum SPL at the lowest frequencies around 95 dB. One 12" woofer in well designed ported enclosure produces 105 dB with 250W and costs 80% less. Not a fair comparison price wise, but shows that kind of difficulties (costs) one faces if one demands sonic purity from a full range monitor.

Timesaver800W 3rd February 2016 09:28 AM

personally I don't like the rear firing genelec ports one bit.. they're good speakers for the money... (now excluding the dsp stuff.)

bcgood 3rd February 2016 04:23 PM

The Amphion design is one of the best I've heard and I get to hear a lot of high end speakers in a professionally designed studio..

Sealed box + passive radiator = much greater accuracy
A ported box always has uncontrolled pressure changes and turbulence inside the cabinet which lead to decreased resolution - especially in the midrange - preventing a balanced audio signal from being reproduced optimally. The One15's sealed cabinet design results in a dramatic improvement in midrange resolution and bass accuracy, while also loading the room in a more controlled and predictable manner. Essentially a speaker cone, surround and basket without the motor, Amphion's rear-mounted passive radiator moves in perfect synchronization with the front woofer, ensuring that the distance from the front of the cabinet to the rear is always the same and that the balance of air in the cabinet is maintained. This results in a much tighter, even response in the low end of the spectrum, guaranteeing more accurate translation to just about any playback system. A passive radiator is not the same as a rear port, and is nowhere near as sensitive to placement near a rear wall.

Petrus 3rd February 2016 06:56 PM

@ bcgood : Passive radiator design is a variation of bass reflex, and the passive radiator has the same out-of-phase problems as a reflex tube has; radiators do not move in phase with the woofer. Maybe less turbulence inside the enclosure, but passive radiators have their own problems, so it is also a compromise.

So I find it quite funny that you dismiss speakers with rear facing ports, but praise designs with rear facing passive radiators, when they actually work identically.

There are 3-way designs which have a rear or down facing woofer, and they can be just as good as any other design variation, as long as the crossover point to woofer is low enough.

If you are truly interested in loudspeaker design and theory, get the Book: http://www.amazon.co.uk/High-Perform.../dp/0470094303

Would save us from some agony here on Gearslutz.

Enlightened Hand 3rd February 2016 06:59 PM

It's just a trade off.

A port done well doesn't introduce any significantly audible problems. But it will measure less well than a well done sealed enclosure in the time domain. But why does that matter?

I used to be all about sealed and nothing else. Until I heard really well done ports. Then I started to realize that a speaker system is a collection of decisions that compete with each other for optimal performance.

There is less room for error when designing a ported enclosure in such a way as to not detract from the overall performance of the system. But it can be, and is, done well in several cases. To take a stance on the quality of a speaker system based on the design ethos is unreasonable in my opinion. I have to listen to the things and decide if the measurements reconcile with what I need to hear. Sometimes they do. Sometimes they don't.

bcgood 3rd February 2016 07:24 PM

Yes it is true, everything is a set of compromises in speaker design. I personally cringe anytime I see a rear port because a lot of people will put those speakers right near a wall in a room that is already not very good which tends to cause even more problems..

These designs are not identical and even though they may share some similar attributes the end results are different.

Anyways, just my taste. I'm bowing out of this thread.

js230 3rd February 2016 07:44 PM

Frankly, when you have thousands of great mixes done on ported speakers like B&W, ATCs, and Questeds, the discussion is a little academic.

Unless you're talking about a perfectly tuned mastering room ideal, even as plenty of great masters too have come out of less than ideal rooms, done on B&W 800/802s, ATCs, and Quested H208/3208s.

Like said above, what's important is the synergy of components, which include a properly sized and tuned cabinet, crossover compromises, silk dome or metal tweeter preference, accurate rather than large bass target of speaker designer coinciding with engineer's sense of bass balance, near-field and mid-field bloom, console or stands, and so on.

Ported speakers are more sensitive to placement. But so do full range sealed speakers like Duntechs essentially need a room designed around them, if we're talking ideal performance throughout their range, even if placement for accurate bass is easier than with ported speakers.

Amphions are not sealed speakers like NS10s, but they have tight bass that translates well, case in point.

Audiop 4th February 2016 10:43 AM

Quote:

Originally Posted by dinococcus (Post 11659866)
Understanding Cabinet Diffraction

Understanding Cabinet Diffraction — Audioblog

Ok but with some errors where he is confused about max or min diffraction and diffraction vs reflection.

Audiop 4th February 2016 10:55 AM

Quote:

Originally Posted by ddageek (Post 11659541)
Almost any cabinet will exhibit some diffraction .


Actually one can argue that ALL boxes have diffraction.

It's just a matter of which frequency the transition from 4pi to 2pi radiation take place.

So just because the design is such that time domain and frequency response problems are minimized or eliminated does not mean that the box no longer diffracts.

The bigger the front baffle, the less sound energy in total are being diffracted and the lower the frequency when full diffraction happens.

Audiop 4th February 2016 11:02 AM

Quote:

Originally Posted by John Willett (Post 11674691)
:lol:

All loudspeakers (with the exception of the Geithain K-series) are omni-directional radiators at low frequencies.

Not at all dear John. :-)

May I suggest a visit to the informative site of mr Linkwitz?

There are lots of cardioid and dipole LF-speakers in the world.

Audiop 4th February 2016 11:10 AM

Quote:

Originally Posted by Enlightened Hand (Post 11676705)
It's just a trade off.

A port done well doesn't introduce any significantly audible problems. But it will measure less well than a well done sealed enclosure in the time domain. But why does that matter?

I used to be all about sealed and nothing else. Until I heard really well done ports. Then I started to realize that a speaker system is a collection of decisions that compete with each other for optimal performance.

There is less room for error when designing a ported enclosure in such a way as to not detract from the overall performance of the system. But it can be, and is, done well in several cases. To take a stance on the quality of a speaker system based on the design ethos is unreasonable in my opinion. I have to listen to the things and decide if the measurements reconcile with what I need to hear. Sometimes they do. Sometimes they don't.

Good post!

John Willett 4th February 2016 12:17 PM

Quote:

Originally Posted by Audiop (Post 11678313)
Not at all dear John. :-)

May I suggest a visit to the informative site of mr Linkwitz?

There are lots of cardioid and dipole LF-speakers in the world.

I know about dipoles, of course, but was not thinking about electrostatics in this instance.

I do know about PA loudspeakers that are cardioid - but we were talking about studio monitors in this thread, not PA loudspeakers.

And if you are referring to a website, it would be nice to post the link so I can find it. ;)