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Discussion Starter #1
I have been listening to my old "New Large Advent" speakers (with the Walnut finish) I have had for a very long time. I have had the opportunity to listen to lots of modern speakers, expensive gear such as B&W and a host of other slim ported (bass reflex) designs that have replaced most of the acoustic suspension models of old like the Advent.


I was surprised to find that, while the sound stage and midrange/highs are superior to my old Advents, the bass response is, in my opinion, inferior. Every ported speaker I have auditioned sounds boomy to me, complex and confused at the lower end of the spectrum. Even very high end speakers seem to have this problem. The thing is, I don't listen to pounding rock, but rather classical and movies. This is a real problem for me, I purchased a pair of Polks some years ago but they just do not cut it in the bass response.


I found these posts by inky blacks below in an earlier thread here that I find enlightening. So what is the consensus at AVS? I for one am now convinced that acoustic suspension are the only speakers worth buying for my taste. Why these ported designs are so popular I really don't understand. Yes they are louder, more efficient, but is that what fine audio is all about?


Are there good lines of acoustic suspension speakers around, with a good wood finish?


Thanks, Inky for confirming my observations. This is really quite a surprise to me, after all these years do we have

fundamentally defective [bass reflex] speakers ?


Reminds me of DLP, glad that is going down the tubes.


posts by Inky Blacks:


"Bass reflex speakers have tuned ports, where acoustic suspension speakers are sealed. Bass reflex speakers have port noise and less accurate cone control because there is no sealed air cushion that acts as a spring behind the woofer cone to keep it moving accurately in tune with the signal. All other factors being equal, acoustic suspension speakers have less distort than bass reflex speakers. That is why companies like Velodyne use only sealed subwoofers for their top of the line units that have distortion levels below 1% Many high priced bass reflex subs have distortion levels of 30% or more. Generally, the distortion of the big bass reflex speakers is less audible than the distortion of the smaller models which have higher frequency tuning of the ports. You hear the phase distortion inherent with the design in smaller speakers with higher tuned ports. With 12" woofers and the bigger bass reflex speaker boxes with low tuning points, the distortion is still there but you are less likely to hear it as much."


"Manufacturers use bass reflex because they think most people want a loud sound rather than an accurate sound. If you want good efficiency with a sealed system, you need allot of cone area and a little bigger box. To avoid bass reflex speakers, I buy small sealed satellite speakers and combine them with sealed subwoofers. There are very few, if any, full range stand alone sealed speakers made anymore, so you have to go with a sub-sat system to get all sealed acoustics."


"Nuts! Even in the 1960s Acoustic Research acoustic suspension speakers achieved 2% distortion levels at 35Hz at reasonable listening levels with a 12" cone. Compare that to the 30% distortion levels of the very expensive B&W 801 12" woofer system in a bass reflex enclosure. The sound (or noise) coming from the port is inherently distorted. Modern day bass reflex speakers are better than they use to be, but they all have port noise and they all have higher distortion levels than an acoustic suspension speaker of equal build and design quality. With bass reflex you are intentionally allowing more distortion in the name of greater output. Acoustic suspension speakers have lower THD (total harmonic distortion), not just better transient response. If you use a low QTC on a sealed system, you will never get "boom." Some designers build in a boom intentionally because some rock and roll and disco type people like it. Sure you can find bad speakers of both types, but in a contest between well made speakers of both types, sealed systems always win the sound contest because the port inherently causes distortion."
 

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Well I don't know that I agree with what was said concerning distortion and all that...I will say that most speakers today (maybe the ones you heard) are using little 6.5" woofers and trying to compete with your (probably) 12" woofer of the old speakers. So ported or not, those little drivers are disadvantaged. And it's much easier to screw up a ported design than a sealed. OTOH those 12" woofers you have probably have a high Fs and no bass under 50hz. If you can't hear something it won't be offensive...
 

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Mark, Inky Black makes a lot of vague, generalized statements without supporting data. Nothing is framed or anchored to a specific reference however I'm sure its suitable for him in part to justify his particular choices.
 

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Discussion Starter #6

Quote:
Originally Posted by Jack Gilvey /forum/post/14291747


Lots of strange ideas about reflex on the 'net. Always found this a good article:

http://www.hometheaterhifi.com/volum...ayporting.html

That is a nice article, but after reading it I conclude that it reaffirms the concerns I (and Inky) have about the design. The article states that:


1. Efficiency or extension is improved for a given speaker box volume with bass reflex. However, the design has a sharper roll-off of low frequency response. My old Advents can reproduce some pretty low frequency organ notes like SAINT-SAËNS organ symphony or Bass drums in Copland's works that are slop on the Polks and some other speakers I have tried out at the stores. So Bass reflex is all about smaller boxes and louder sound. The article states:

"For starters, there is the aforementioned roll-off inherent to reflex designs. A sealed enclosure still has significant output after its –3 dB cutoff frequency. In fact, that roll-off can complement room response to yield flat output far below cutoff. Ported designs can’t do that. On the other hand, if they go deep enough without the room, they don’t need to."


So for a given cutoff frequency, acoustic suspension will outperform bass reflex. You have to get a pretty large ported box to output at low frequencies, to compensate for an acoustic suspension output below its cutoff, so then all you have is better efficiency.


2. The article makes a point of reducing cone excursion to limit non-linearity of the magnetic field coupling in the speaker, thus:

"In addition, the loading of the driver by the reflex system, which limits excursion, also makes the active driver do most of its work in the more linear range of the motor. This equates to less distortion at and a little above the tuned frequency, and more potential output in the case of a port because ports have no excursion limits. That’s a pretty substantial benefit. Why doesn’t everybody do it then? Well, like everything, there’s always a cost."


This is where I depart. He claims less distortion above and below the resonance of the port, but what about the contribution at resonance, the boom that I hear so frequently? Whether from resonance or at other frequencies, my ears are telling me that the excursion non-linearity of acoustic suspensions is a minor issue and overwhelmed by the problems introduced by adding a port. Just because the Physics is correct on the excursion issue does not mean that the Physics is applied in a proper quantitative way to a particular problem.


So after reading the article, my conclusion remains that bass reflex is a way to get volume or bass extension out of a smaller thinner box. Any suggestions of speakers one can hear without boom is welcome.


What gives this credibility in my mind is that I stumbled upon this entirely by accident. I had low expectations for what I thought were a pair of outdated pieces of crap (the Advents) but after hearing even high end ported speakers I am surprised at the quality of low frequency reproduction. Now at the higher frequencies they are outdated for sure.


The 10" woofers in the Advent cut off at about 40hz but I can hear output below 30hz. So there is not less distortion because of a higher cutoff.
 

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And at what frequency is this boom occurring?
 

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That post is just a bunch of generalizations that don't accurately represent the true virtues of sealed vs. ported ... of course it's a lot more complex than this. There are counless ways to tune a ported system, and for that matter a sealed system as well. All produce different results, and then of course you have to mix in the myriad of drivers.


Generalizations like this do nothing to advance understanding.
 

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Back in the day, I had both the Larger Advents and AR3a acoustic suspension speakers. For their time , the bass was impressive....though they both required hefty amplifiers to achieve sufficient volume.


However, subwoofers were not all that common back then.


Today, even in my "stereo only" system which includes Rotel electronics and B&W speakers, I use a dedicated sub for the bass. This current 2.1 system has a far broader and deeper soundstage, as well as a more solid bass foundation (organ music especially) than anything I ever had back in the '60's or '70s.


Can't say that I've ever encountered any port noise that was able to interfer with the music.
 

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Quote:
Originally Posted by petergaryr /forum/post/14294741



Can't say that I've ever encountered any port noise that was able to interfer with the music.

Must not have Listened with any women in the house.



Besides, I prefer and always will, a bass-reflex speaker, which Is why I purchased a certain pair of brand new sony speakers which I well not mention the name of again because I'd be ostricized, the predecessor of this speaker was an Acoustic suspension model with ugly banana yellow cones and an ugly veneer.
I am glad they started using gray cone drivers instead. I am glad they changed the veneer.
 

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I remember a time when acoustic suspension speakers were quite common. Now they are rare. That should tell you something.

The bass on my old Boston A60s was clean and tight, but not very extended or powerful compared to modern speakers with similar cabinet size (and certainly not compared to bookshelves with 8" woofers, if anybody still even makes such things.)
 

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Discussion Starter #14

Quote:
Originally Posted by TurboFC3S /forum/post/14294568


Generalizations like this do nothing to advance understanding.

Generalizations are sought after in science and engineering precisely to advance understanding of individual phenomenon. One could never formulate laws without generalizations. In fact, one can see from reading the article that there are fundamental physical differences in the 2 approaches that prohibit the 2 from performing similarly. There are real differences, you cannot tune a port to match an acoustic suspension speaker.


The laws of Physics, generalizations mentioned in the article, certainly advance understanding of speaker performance.
 

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Discussion Starter #15

Quote:
Originally Posted by petergaryr /forum/post/14294741


Back in the day, I had both the Larger Advents and AR3a acoustic suspension speakers. For their time , the bass was impressive....though they both required hefty amplifiers to achieve sufficient volume.


However, subwoofers were not all that common back then.


Today, even in my "stereo only" system which includes Rotel electronics and B&W speakers, I use a dedicated sub for the bass. This current 2.1 system has a far broader and deeper soundstage, as well as a more solid bass foundation (organ music especially) than anything I ever had back in the '60's or '70s.


Can't say that I've ever encountered any port noise that was able to interfer with the music.

This is a step in the direction of Inky Black's approach, to use satellite and a subwoofer (are yours sealed or ported?). Now you do lose the directionality at low frequency this way, even though you are less sensitive to that at low frequencies it still is a factor.


So I might ask: Is it possible to construct a 2.2 system, 2 satellites and 2 passive (not powered) subwoofers below them? That could be one solution to the problem short of getting vintage speakers on ebay.
 

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Quote:
Originally Posted by mark_1080p /forum/post/14295671


Boom occurs at a low frequency dependent on the speaker.

Given some of the speakers you've mentioned, this sounds more like a room placement issue as well as a room that would benefit from treatment.
 

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Quote:
Originally Posted by oztech /forum/post/14291915


I have heard both good and bad of each design and believe that you can not judge all

by one.

++1. There are plenty of good examples of poorly built speakers in both camps. Comparing one to the other is virtually meaningless.
 

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Quote:
Originally Posted by mark_1080p /forum/post/14293543


My old Advents can reproduce some pretty low frequency organ notes like SAINT-SAËNS organ symphony or Bass drums in Copland's works that are slop on the Polks and some other speakers I have tried out at the stores. So Bass reflex is all about smaller boxes and louder sound.

Can you describe both of these speakers? Comparing vented vs sealed using two totally different speakers is hardly a good method. Also vented boxes tend to require bigger boxes than sealed.

Quote:
Originally Posted by mark_1080p /forum/post/14293543


So for a given cutoff frequency, acoustic suspension will outperform bass reflex.

For a given F3 that is true, BUT, the F3 will never be the same for a given woofer in a sealed and vented box. The F3 is typically much lower in vented box.

Quote:
Originally Posted by mark_1080p /forum/post/14293543


This is where I depart. He claims less distortion above and below the resonance of the port, but what about the contribution at resonance, the boom that I hear so frequently? Whether from resonance or at other frequencies, my ears are telling me that the excursion non-linearity of acoustic suspensions is a minor issue and overwhelmed by the problems introduced by adding a port. Just because the Physics is correct on the excursion issue does not mean that the Physics is applied in a proper quantitative way to a particular problem.

The physics are well developed and quite clear. The tradeoffs are well known and I would suggest actually reading about it and not rely on Inky's blanket statements and imprecise use of the word "distortion".
 

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Discussion Starter #20
Reading the above 2 articles, the conclusion is that transient response is marginally better for Acoustic Suspension and Bass Reflex can be tuned. But why go that way if you can do very well with Acoustic Suspension? With a big enough woofer, you can do very well and have the tight bass you simply cannot get (or at least I have not heard) with BR.


The Advents are simple 2 ways, but as I said their bass output is tight, punchy, in comparison to the rumblings and I hear with even expensive ported. It is ridiculously obvious, I stumbled upon it by accident not even looking for such a thing, like seeing banding on a Sharp LCD TV. I had every expectation that speakers I would audition these days would blow away the inexpensive Advents at all frequencies, but it is not happening.


I have no ax to grind, I'm just surprised this is how it is (to my ears anyway), and reading Inky's statements gives me a little bit of hope that I'm not totally off the wall with this observation. Yes I can read further but my observations were made without bias toward what should be happening.
 
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