Sealed versus ported boxes in a 2-way speaker?

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hiesteem

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Honestly? I have had them all. Linn Isobaiks (huge) Quad 57’s AE1’s PMC’s and Big Transmission line ( not PMC).  Too many more to mention ( I am very old😀) Speakers are very room dependent.  In a small room only a sealed box will do.  Bigger rooms were you can get ported floor-standers away from back walls and side walls will work well. That’s it.
Yes, pretty much what I was going to say. All speakers are room dependent. Least that's my experience.

 
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tuga

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Yes, pretty much what I was going to say. All speakers are room dependent. Least that's my experience.
I completely disagree.

Yes, all speakers (or the sound they produce) will interact with the room but speaker performance is an independent issue.

It doesn't make sense to believe that because rooms create havoc in the bass and sub-bass it doesn't matter how well the speaker performs in that range.

.

But I would like to again underline that even though sealed is theoretically the most accurate and thus best technology it is ultimately down to implementation.

Just like 3-way is also theoretically better - it has higher performance potential - than 2-way but we still have to look at the individual design. (and horns should be at least 3-way + bass bin)

 
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hiesteem

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I completely disagree.

Yes, all speakers (or the sound they produce) will interact with the room but speaker performance is an independent issue.

It doesn't make sense to believe that because rooms create havoc in the bass and sub-bass it doesn't matter how well the speaker performs in that range.

.

But I would like to again underline that even though sealed is theoretically the most accurate and thus best technology it is ultimately down to implementation.

Just like 3-way is also theoretically better - it has higher performance potential - than 2-way but we still have to look at the individual design. (and horns should be at least 3-way + bass bin)
Yes I agree with you Tuga.  implementation of design is very important. I have got a pair of speakers here now, Ruark equinox. I love their mid range but I know I will never get them performing how I know they can sound because my room is 11ft wide & 21ft long. The speaker needs to be completely in free space. That's its design. I don't care because they image like an orchestra and the mids are 😍.

However the only way to release their potential is to put them in free space, in which case they would substitute as foot stalls!

 

zeta4

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That is obvious in the measurements of the PSB speaker I posted earlier.

But I do see bass reflex as a form of trickery, clever but lower-fi than a cone that is directly controlled by an amplifier. The resonant sound is not any different to what we get when we blow across the mouth of a bottle.
But a closed box is also a form of trickery, its to prevent dipole cancellation between the front and rear of a driver. But by doing that you introduce a resonant system with the mass of the driver reacting with the spring formed by the trapped volume of air. As you know this forms a high pass 2nd order filter with the advantages youve shown. However even this can adjusted to give different resonant Q,s which in turn will give different sonic results.

I think its inaccurate to say that a ported design is always "lower fi" than a sealed box. For example a damped QB3 (Quasi Butterworth 3rd order) alignment can be a very good compromise. This can give you the size advantages of a ported box with a better transient response. It all depends on the actual design of course.

 
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DomT

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I wasn't expecting you to confuse the goal of sound/music production with that of reproduction of recorded sound/music... I'm disapointed. :minikev:
I think the point that is being made is that of basic physics 

 
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DomT

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I completely disagree.

Yes, all speakers (or the sound they produce) will interact with the room but speaker performance is an independent issue.

It doesn't make sense to believe that because rooms create havoc in the bass and sub-bass it doesn't matter how well the speaker performs in that range.

.

But I would like to again underline that even though sealed is theoretically the most accurate and thus best technology it is ultimately down to implementation.

Just like 3-way is also theoretically better - it has higher performance potential - than 2-way but we still have to look at the individual design. (and horns should be at least 3-way + bass bin)
Yes and no. Not all speakers are designed with the same design goals and so whilst there may be ‘technical superior design’ of a speakers bass response it is not always what the speaker designer wants to achieve. This is why Rogers and ATC sound so different in the bass region but both speakers have their fans.

 
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lindsayt

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...Just like 3-way is also theoretically better - it has higher performance potential - than 2-way but we still have to look at the individual design. (and horns should be at least 3-way + bass bin)
Have you auditioned the 2 way horned plus bass bin Altec Model 19's?

Or the 2 way co-axial horn plus bass binned Altec 604's?

Or any other variations on the 2 way horn plus bass bin theme?

If so, what did you think? If not, on what are you basing your assertion that horns should be at least 3 way?

 

tuga

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Have you auditioned the 2 way horned plus bass bin Altec Model 19's?

Or the 2 way co-axial horn plus bass binned Altec 604's?

Or any other variations on the 2 way horn plus bass bin theme?

If so, what did you think? If not, on what are you basing your assertion that horns should be at least 3 way?
What I have audiotioned or not audiotioned doesn't matter, it will mostly express my preference. But I did convert a pair of Opera Consonance Barque M12 one-way horn + bass bin into two-way horn + bass bin if that is of any interest...

Narrow directivity waveguides with gain, also known as horns, cannot cover more than 3-octaves (see why here). More ways not only addresses the "honking" sound issue but also the problem of directivity mismatch "flare" which can be seen in the plot below at around 3kHz.

The ideal horn speaker will have constant directivity down to (at least) the mid-bass (taking into account that one would need a huge horn for low-bass duties).

Since the Uno XD is 2-way + 2x 10" woofers croossed at 300Hz, the directivity widens early because it is using cones for the upper-bass and below, and as I'm sure you know cones and domes have narrowing directivity as the frequency increases. A pair of woofers has the advantage of producing a narrow pattern but it is still not ideal.

10-UNO-hor-1024x683.jpg


https://www.fidelity-online.de/avantgarde-acoustic-uno-xd-messungen/

The Duo Mezzo is better in that regard (taking the constant directivity to a lower frequency) but will still show the flare where the horn mid crosses to the horn tweeter. The flare would be eliminated by adding an extra horn/way.

avantgarde-uno-xd.jpg
avantgarde-duo-mezzo-xd.jpg


 
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tuga

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Yes and no. Not all speakers are designed with the same design goals and so whilst there may be ‘technical superior design’ of a speakers bass response it is not always what the speaker designer wants to achieve. This is why Rogers and ATC sound so different in the bass region but both speakers have their fans.
Sorry, there is a topology which more accurately reproduces the signal/music - sealed. But I agree that it may not produce the best results in all applications or set-up conditions, of for all budgets. To make matters worse there aren't that many drivers available that are fit for a sealed cabinet application.

You cannot compare different speaker models, less so if they're from different manufacturers. I see the speaker as a means to reproduce the recording as accurately as possible. I don't care for designers who do not wish to achieve accurate transduction. I'm not saying that they shouldn't exist, only that personaly they're off my radar.

The BBC Research Department had accuracy as goal. They did the best they could give the design brief (light, cheap, easy to repair) and the measuring equipment of the day. They designed and built an anechoic chamber, came up with a few innovative measurements and measurement tools, R&D'ed cabinet and cone material. Today they'd have come up with a digital all-in-one active Genelec, Neumann or even a Dutch & Dutch. In fact I believe that's what they're using in applications where sound quality is critical (monitoring classical music). Rogers was born out of that wealth of research, as was Kef, Spendor and Harbeth, and now Stirling, Graham and Falcon.

This has nothing to do with preference. People like all sorts.

 
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tuga

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I think the point that is being made is that of basic physics 
It's a dumb point, and @andrew s is a sensible and knowledgeable chap, hence my surprise.

The goal of a loudspeaker is to transduce the signal as accurately as possible (that's high-fidelity). That signal can be a pipe organ, a cello, a human voice, a kettle drum, cymbals. It makes no sense trying to equate a speaker to an instrument. Horns don't soun more like horns, and if they did then they're :td:

 

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Unfortunately for some folks they can't / wont consider that other opinions are just as valid as their own...and indeed might just contribute to assembling a system which actually sounds very good?  The key word here is  "sound" and our own interpretation of it.  If listening to an excellent interpretation of music, that came from behind curtains & could not be identified, some would struggle with their analysis ? This could indeed be construed as a distraction (by some) especially if you you can't identify  the "Funk" in music anymore 😀 

It takes all kinds, and diversity is what keeps things interesting imo ...but an obvious intolerance (constantly) to anything outside of ones sphere is sad.  Enjoyment & sharing others enjoyment is good... snuffing it out is not.  

Enjoy the Wknd !

 
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tuga

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But a closed box is also a form of trickery, its to prevent dipole cancellation between the front and rear of a driver. But by doing that you introduce a resonant system with the mass of the driver reacting with the spring formed by the trapped volume of air. As you know this forms a high pass 2nd order filter with the advantages youve shown. However even this can adjusted to give different resonant Q,s which in turn will give different sonic results.

I think its inaccurate to say that a ported design is always "lower fi" than a sealed box. For example a damped QB3 (Quasi Butterworth 3rd order) alignment can be a very good compromise. This can give you the size advantages of a ported box with a better transient response. It all depends on the actual design of course.
It's all a compromise, I agree. But some topologies are more compromised.

With a closed box the amplifier is controlling the woofer, with bass reflex the box "farts" at a give tuning frequency. Ultimately it depends on implementation and also listener expectation/preference.

 
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tuga

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@DomT in regard to your comment about application, it is interesting to see that many studio monitors are designed with flexibility in mind, usually in the form of a Boundary (tone) control (or EQ) which allows the user to position the speakers closer or farther from the front wall.

3series-mkii-back_z_3_700x700.jpg


 

andrew s

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It's a dumb point, and @andrew s is a sensible and knowledgeable chap, hence my surprise.

The goal of a loudspeaker is to transduce the signal as accurately as possible (that's high-fidelity). That signal can be a pipe organ, a cello, a human voice, a kettle drum, cymbals. It makes no sense trying to equate a speaker to an instrument. Horns don't soun more like horns, and if they did then they're :td:
I was being ironic as your blowing over a bottle was a (damning) analogy using a crude instrument as the example.

From a physics perspective I suspect an infinite transmission line would be the best loading for a conventional speaker.  I don't see how a sealed box can avoid the back reaction on the speaker from modulating the presure of the enclosed air.

But I take the general point about reproduction v creating sound being different. Although,  fundamentally the physics is about modulating and transforming one form, or another, of energy into sound waves. It's the objective that's different. 

Regards Andrew 

 

tuga

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From a physics perspective I suspect an infinite transmission line would be the best loading for a conventional speaker.  I don't see how a sealed box can avoid the back reaction on the speaker from modulating the presure of the enclosed air.
I'm confident that the internal pression is taken into account in the design (and probably why sealed cabinets require different driver characteristics from ported or open-baffle ones Qts).

As for the infinite transmission line, nearly perfect absorption can be achieved with tappering and damping, as per this prototype of B&W's "snail" design:

OlqLuen.jpg


 

uzzy

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I think nearfield monitors with front slot ports would be ok for such use.
Aye but the BBC designers didn't .. deep bass was not on the agenda most of all it was made for monitoring speech I would suggest (in a van for outside broadcasts the majority of which would be news and outside documentaries etc 

 
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andrew s

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I'm confident that the internal pression is taken into account in the design (and probably why sealed cabinets require different driver characteristics from ported or open-baffle ones Qts).

As for the infinite transmission line, nearly perfect absorption can be achieved with tappering and damping, as per this prototype of B&W's "snail" design:

In my student days I built some transmission line speakers using the classic 3 KEF drivers.  It was in the days when hi fi mags published DIY designs.

Too long ago to remember what they sounded like but recall being pleased with them unlike my wife who thought they were too big.

Regards Andrew 

 
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Fergus

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I agree with @lindsayt that the small 2-way is probably the most compromised of topoloies and thus that with the least performance potential. The combination of a long-excursion midwoofer with a highish port tuning frequency is a recipe for disaster.

Yet it's what most of us have to live with for practical reasons... To make matters worse current speakers with larger woofers and/or 3-ways are less common and quite expensive.
I use Neat Motive 2s which are very slim and small two way ported speakers but they sound fantastic to my ears

 
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tuga

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I use Neat Motive 2s which are very slim and small two way ported speakers but they sound fantastic to my ears
That is what matter most. :^

(and now you're free to worry about the important things, such network switches and USB cables :p )

 
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Pedro2

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I now own Hedd actives and you can choose ported or sealed (there are bungs and DSP settings to accommodate both). I’ve tried both. I prefer sealed.