Sealed versus ported boxes in a 2-way speaker?

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pmcuk

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We have some excellent threads going on 2-way speakers, and part of the discussion is around sealed versus ported boxes.

The discussion ranges from the BBC LS3/5a which is a very small sealed box to the ATC SCM11 which is 20 litres in external dimensions. 

If we consider "bookshelf" 2-ways to have a mid-bass from 135mm to 150mm could the discussion include floorstanders with similar units? 

Some have stated that they will not use ported boxes for sonic reasons. Others are more open to persuasion. 

There is a huge knowledge of 2-way speakers here, so what are you guys finding on this issue?

 

JANDL100

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Oh no - I've got 4-way speakers in my main system. Does that mean I can't post here?  :(

They are ported. And they are keepers. 

I've had sealed box, too. And some of those were really good. 

Honestly, ported / non-ported. It's an argument about a misconception imo. You can get excellent examples of both types that will give huge amounts of entertainment. 

 

pmcuk

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Haha..... yes, once you go above 2-ways the picture does change. 

The easy answer is, as you say, that there are good and bad examples of both. But a sealed box remains an ideal for some. For the BBC I imagine they wanted the speakers to be used in confined spaces including up against walls, though a front port would have been possible with a different design. So presumably a sealed box was thought to have virtues. For ATC a sealed box was a design decision, and they are pretty good at designing speakers. So the question is a valid one.

Here's an interesting site to read up on this:

https://audiojudgement.com/sealed-enclosure-closed-box/

 
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Jules_S

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These are my personal observations and they are subjective only (cover your ears, @tuga 🤣) because I possess neither the equipment nor knowledge to take meaningful measurements! I expect there will be many different viewpoints expressed here. All the speakers I've owned have been 2-way, to the best of my knowledge.

My first "proper" hi-fi speakers were Monitor Audio 14's - a sealed enclosure. I preferred them to all their ported contemporaries I heard at the time, both floorstanding and stand mounted, but as I was very new to audio and naive to boot I couldn't say if that was purely about the bass or the overall presentation. I enjoyed them very much though and thought they were nicely balanced for the rest of the system, and most importantly, were musically communicative. I did fil the bottom enclosure with sand though, which I though made an improvement. Whether that was down to increased stability on a carpeted floor, or because when it was empty the enclosure caused some resonances I don't know,  but it did "tighten" the bass a little. They're still a warm and cuddly style of delivery though.

After those I went through a variety of designs of ported and 1/4-wave transmission line (which is a type of port, I suppose) and have now come back to a speaker with a sealed enclosure, albeit rather different in fundamental principle, being a hybrid ESL, so only the bass is "sealed". Although the additional "heft" of a ported design is sometimes useful, I found that the bass quality can suffer, inasmuch as it presents as a little bit "soft" or loosely-defined, lacks some definition and can be a bit sluggish, affecting music that relies strongly on rhythm. I've also experimented with partially-covering the ports which was not successful - firstly it undoes the benefits of having the port in the first place, and secondly gives the sound a "closed-in", restrictive feel, as though one were listening with a head cold.

TL I felt was a more successful approach, retaining the precision, definition and drive of the lower registers while providing some useful augmentation. I think it's a shame that there are so few commercially-available examples of this type, maybe there are some bigger and fundamental flaws to the principle that I don't know about? I very much liked my Castle Harlechs, and the earlier PMCs that a few people on here seem to dislike - I'm talking about models such as the FB1, DB1 etc, not the "Twenty-x" stuff.

Now I'm back with a sealed enclosure but with much bigger drivers than I've ever had before. They are providing all the additional "grunt" that I could possibly want in my current room, plus bringing back that control in the bass that was previously missing. There's still work to do to treat the room's worst effects but I'm sure that once done, I will have the right balance of qualities - both extension and precision. Out of choice I wouldn't go back to a ported design now I don't think - I'm sure that it's possible to get some great results with the right design, but I am happy where I am now.

 
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lindsayt

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Low efficiency slimline ported 2 way speakers are the work of the devil, sound quality wise.

I've also heard tiny 2 way low efficiency acoustic suspension speakers that sounded pants - relatively speaking.

When it comes to which is least worse out of tiny low efficiency 2 ways: sealed or ported? What a Hobson's choice!

With this genre of speakers it's a case of aiming for something that fits with your lifestyle, that is affordable and listenable.

For a cunnning plan, go for 12" or larger woofers and then you can go 1, 2, 3, 4 or 5 ways with a chance of good sonic results for the money...🦊

 
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tuga

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In theory a sealed cabinet will reproduce the signal more accurately but as usual it depends on implementation.

In a 3-way configuration there a better chance that the bass reflex will produce a negative audible impact (one-note bass, softened transients) because it is more likely to be tuned to a lower frequency.

How the system is tuned/damped will also impact the result: over-damping will reduce de output amplitude but be more accurate.

If I’m not mistaken passive resonators behave more or less like ports. They might be less compromised.

A true TL has to be extremely long (a 50Hz wave is 7 metres, 1.75m for 1/4 wavelength). Most TL speakers are not TL and I think that they behave more like a long port or a port at the end of a long tunnel.

 
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MartinC

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The various 2-way speakers I've owned have all been ported. If used without a subwoofer I'm doubtful there are any 2-way sealed models that I'd really consider due to bass extension and output limitations. With a sub would be a different question though.

 

tuga

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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.

 
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Minicoupeman

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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.

 

uzzy

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All conjecture - the BBC designed the LS35A to fit in a van for outside broadcasts . no way could you ideally site a speaker with a port to work properly and they were not overly concerned with deep bass but more mid rang quality.

I have had in my lifetime sealed boxes (Marantz 4G and Gale 401), transmission lines (PRO9TL) and ported speakers (Systym 931 which were designed by the boys at Art and are LS35A sized with a port, and my current Art Impressions .. and in the garage for my son a Pair of Timewindows 3 a kind of Transmission line/Port hybrid).   With all of these speakers I have never had a problem with one note bass or lack of bass definition .. I prefer the Systym 931 to the LS35As, I prefer the transmission line to the Gale 401 (it was in effect a 401 in a transmission line sharing the same mid range driver) and the Art Impression trumps them all.

At the end of the day it is down to design and placement in my books and perhaps for selling the stuff for so long I have an open mind or should I say open ears (as they are the things I like to keep happy).  Just remember all speaker designs are a compromise and to not have a closed mind just determine your choices by how they sound. 

 
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DomT

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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 suppose that it depends on what “least performance potential means”. I have a pair of Harbeth P3ESRs on a shelf over my desk as the Harbeth SHL5 would have been too big for that space.

I chose ATC SCM 11 rather than a bigger speaker a) because my Audio Research amp puts out *deep* bass and b) because I have a room node. So my choice of the SCM11 was optimised for the room that it was to be used in. A much bigger speaker like my SHL5 was seriously compromised in that room.

As always it depends on what the needs of the user are.

 
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Lawrence001

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All conjecture - the BBC designed the LS35A to fit in a van for outside broadcasts . no way could you ideally site a speaker with a port to work properly and they were not overly concerned with deep bass but more mid rang quality.
I think nearfield monitors with front slot ports would be ok for such use.
 

tuga

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I suppose that it depends on what “least performance potential means”. I have a pair of Harbeth P3ESRs on a shelf over my desk as the Harbeth SHL5 would have been too big for that space.

I chose ATC SCM 11 rather than a bigger speaker a) because my Audio Research amp puts out *deep* bass and b) because I have a room node. So my choice of the SCM11 was optimised for the room that it was to be used in. A much bigger speaker like my SHL5 was seriously compromised in that room.

As always it depends on what the needs of the user are.
I agree. I was speaking in terms of overall performance but you may have other constraints which may limit what you are able to use. My sitting room is 3.4 x 3.6 metres, in theory I could get larger speakers and make them work but I'd need a room all to myself.

Each topology has a particular performance potential, and some topologies have more potential than others but not all will fit our requirements or budget, and whether that potential is fullfilled depends on how the design has been implemented. And higher performance does not always equate to a more enjoyable listening experience.

 
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jobseeker

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I wonder just what the ratio of ported to non-ported speakers currently available is, in the general market. I’m guessing a lot more people out there are likely to have ported than non-ported. Though I have absolutely no evidence for that 😀  I can’t recall ever owning a sealed-box speaker, over many years. I wonder how that happened. I have used several large speakers in a small room to great success - probably more so than with small ones.

 
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tuga

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I wonder just what the ratio of ported to non-ported speakers currently available is, in the general market. I’m guessing a lot more people out there are likely to have ported than non-ported. Though I have absolutely no evidence for that 😀  I can’t recall ever owning a sealed-box speaker, over many years. I wonder how that happened. I have used several large speakers in a small room to great success - probably more so than with small ones.
Here's a thread about sealed cabinet speakers:

 

tuga

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This topic need a few graphs. :D

Here we can see that alhough the port manages to keep the response flat down to a lower frequency the sealed cabinet produces more extension (the port peaks at the tuning frequency but the response falls abruptly below that):

209PSBfig5.jpg


PSB Imagine B, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with complex sum of nearfield woofer and port responses plotted below 300Hz (blue), and with woofer response with port closed (red).

https://www.stereophile.com/content/psb-imagine-b-loudspeaker-measurements

 

zeta4

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I think the main reason for ported speakers is to get a lower bass extension from a smaller box than with a sealed one. These are more domestically acceptable and so have become popular.  However to get this it has to use two resonant systems ie driver/box and port/ box. There's a lot of ways these two can work together, for example different port tuning and you can get it right or wrong in my opinion. There's been a lot of work done on this subject over the years to help designers avoid some of the pitfalls so as usual its more about how a particular technique is used rather than the technique itself.

 
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tuga

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Here we see that the sealed cabinet goes quiet when the signal stops (Yamaha NS10), but the ported's output/resonance lingers on and decays at a much slower rate (Tannoy A600):

4LDpcZS.png


iDQsmTm.png