Ported vs. sealed (here we go again)

[Steve F]

From the Cat Dragged in LST thread:

Hi Jerry,

What great replies!  First of all, I, too, didn't realize that speaker companies who built vented enclosures paid too much attention to small air leaks; however, I can see where it could give a problem.  I think what Steve is referring to regarding the "their lower 3dB down points" is the lower fc of many vented designs, but the 24 dB/octave rolloff below resonance in vented vs. the 12 dB/octave in acoustic-suspension designs.  Thus the vented design obviously rolls off very rapidly below resonance compared with a/s designs.  Vented designs are certainly more efficient, and I agree about the ported designs' tendency to exhibit "one-note bass," and although there is usually plenty of punchy low-frequency energy, it always seemed (to me at least) muddy or less well-defined than sealed systems, but there were some exceptions.  If one is listening to a lot of jazz with kick drum or orchestral music with big orchestral bass drum, organ or electronic music with lots of low-frequency energy, the acoustic-suspension system seems to have a significant advantage.  Ported or vented systems do just fine with probably 90% of all recorded music, especially rock or popular music.  But overall, I think acoustic-suspension systems are much cleaner than vented systems in reproducing fundamental energy, usually with flatter response and lower harmonic distortion, but many will argue that some vented designs that are certainly excellent as well.

I'd written about this topic in great length (over 1500 words--about four pages) back in 2002. I guess it's time to summarize that post again now, so here goes.

 

Yes, the “tuning frequency” of a correctly-designed vented speaker with a woofer of appropriate T-S parameters will allow it to reach a lower -3dB point for a given enclosure size compared to a sealed speaker of the same size. In the early 90’s timeframe, for instance, the PSB Alpha was reaching, say, -3dB in the low 50’s Hz compared to our sealed Boston Acoustics HD5, which was down 3dB at about 65Hz. That was terrifically audible in a retail A-B demo comparison.

 

 

The fact that the HD5 had more output at 30 or 35Hz because of its 12dB/oct rolloff compared to the PSB’s 24dB/oct rolloff was essentially meaningless, for two reasons:

  1.     They were both so far down in level at 30Hz (these were small 5 ¼” 2-way bookshelf speakers for about $200/pr. at the time) that it didn’t matter at all if one was down 15dB and the other was down 24dB. Neither had any impactful output down there, so the HD5’s sealed “advantage” was no advantage at all.

    2. These were speakers that would be used to play popular music in stereo, where the lowest bass content in the program was in the 40-60Hz range. The PSB just sounded so much “fuller” and richer than the HD5. The fact that the sealed HD5, 7 and 8 were getting killed at retail was the driving factor that lead to the CR Series that replaced them being ported speakers.

Which leads us to the next big point: It’s waaaaaay past time to totally debunk that tired old cliché about “Ported speakers are boomy and one-notey and ‘thick’ sounding compared to the ‘fast, tight’ sound of acoustic suspension speakers.”

 

 

That may have been true in the ‘50’s and ‘60’s, but only because designers didn’t have fully fleshed-out T-S parameters and modern computer modelling to work with. So, ported speakers were hit-or-miss, “cut-‘n-try,” etc. A lot of shooting in the dark.

 

 

Not any more. I defy anyone to listen to a really excellent Aerial or B&W or KEF or Legacy Audio—name a good company, your choice—and tell me that their bass isn’t excellent.

 

 

It is excellent. “Tight, crisp, well-defined, fast, articulate, musical, muscular, athletic, accurate, natural,” etc. Pick your adjective. Pick your music.

 

 

Sealed had a huge advantage when design practices were unsophisticated, because the acoustic suspension design principle enabled designers to optimize a truly excellent system by jockeying and adjusting only a few variables. Presto: Combine 17Hz Fs, high compliance, 1.7 cu.ft. enclosure and you get 3a bass. Duck soup.

 

 

But to build and test dozens of variations of woofer parameters, port length, port diameter, vent shape, vent location, etc., etc. and come up with an optimized vented design was just not practical in 1966.

 

 However, it is now. Press a button and see 12 vented design options in a second. Press the button again and see another 12. You couldn’t build and measure 24 of them in 1966. Now you can do it in an hour.

 

 

So, you can now get that lower -3dB down point and get bass that’s all the above good things. Why do you think nothing’s sealed any more? Don’t misunderstand my point—the 7, 4x, 2ax, 3a, et al. had—and have!!—terrific bass. It just that now there’s no barrier to getting great bass from ported designs, with their advantages, but without the drawbacks of 50 years ago.

 

 

Steve F.

[Aadams]

2 hours ago, Steve F said:

So, you can now get that lower -3dB down point and get bass that’s all the above good things. Why do you think nothing’s sealed any more? Don’t misunderstand my point—the 7, 4x, 2ax, 3a, et al. had—and have!!—terrific bass. It just that now there’s no barrier to getting great bass from ported designs, with their advantages, but without the drawbacks of 50 years ago.

Interesting.  How small is a ported design that is 3db down at 35hz?  They used to be at least as large as a washing machine and sometimes 2 washing machines.

[Steve F]

The BA CR 9 8-inch two-way, barely larger than a 4x, was dead flat to 40Hz. Dead flat. Deeper than the 10-inch 2ax/5. Just good modern ported design, nothing magic. Oh, designed in 1994, so this is nothing new. Computer-aided ported designs have been great for a loooong time.

Steve F.

[Aadams]

This is good info. Thanks for the insight.  I took a quick peek at some current ported models to check for low end response.  It looks like there is some kind of logarithmic rule in effect.  To get the last 20 cycles below 40 the ported enclosures turn into towers that are comparable to AR9s but down to 40 cycles or so ported designs can be quite accommodating and convenient. This changes my outlook on what I might use in certain applications.  Thanks Steve.

[owlsplace]

6 hours ago, Steve F said:

1.7 cu.ft. enclosure and you get 3a bass.

1.5 cu.ft.

3 hours ago, Aadams said:

used to be at least as large as a washing machine

folded horn not vented design ... the original Klipschorn patented in 1946:

One watt RMS produces a 105 decibel per meter sound pressure level (SPL) ... As the only speaker in the world to be in continuous production for 60 years, the Klipschorn has remained relatively unchanged since its inception." from https://en.wikipedia.org/wiki/Klipsch_Audio_Technologies#The_Klipschorn

I'm still not giving up my beeswax

Roger

[onplane]

10 hours ago, Steve F said:

So, you can now get that lower -3dB down point and get bass that’s all the above good things. Why do you think nothing’s sealed any more? Don’t misunderstand my point—the 7, 4x, 2ax, 3a, et al. had—and have!!—terrific bass. It just that now there’s no barrier to getting great bass from ported designs, with their advantages, but without the drawbacks of 50 years ago.

Steve F.

Steve, thanks so much for your very interesting post. (I either missed or forgot your 2002 post.  I mean, that was 14 years ago!)

In any event, I appreciate you taking the time to share with us how and why the market changed.  I've noticed that not only are the high end systems today all vented or reflex, but most of them now have powered woofers. I can see the logic in this as it allows the multi-channel home theater receivers to easily drive the remaining mids and tweeters.  

A good friend of mine purchased a pair like this last year and the price exceeded $6K.  While I can see the value in having a woofer per channel, I really can't see having the powered woofer inside the box.  I mean, once the plate amp goes (and it will), what a mess you have! Especially, if your speaker company is no longer in business.

My sense is the better alternative are those systems where the mid and tweeters are housed together, but also offered are companion sub-woofers.  Hopefully, the companies that sell these "sets" have figured out how to match the units so that there are no glaring frequency holes or 'poles'.

Returning back to the vented vs sealed, I admit that my sample is very small.  I have a vented AR sub-woofer + KLH vented satellites and a pair of vented JBL's (6.5 inch woofer about the size of an AR4x).  Neither of these vented systems can reproduce the notes of a double bass clearly like my sealed AR's and of course, neither, of these systems are "high end" nor were they ever advertised as such.  So my comparisons might NOT be fair.  (Both of the vented systems are about 10 years old.)

Steve, I never really understood the theory behind vented systems.  I understand the idea is to use the "back wave" and add it to the wave propagating from the front of the woofer. Thus, a major increase in efficiency!  Problem is you can't use that back wave immediately, because it is 180 degrees out of phase with the front wave. So, via the ports you attempt to store the wave for a half cycle and then ... release.  If I have this right (and that's a BIG if), it would seem to me that this system is ripe for distortion.  I mean, any time you are adding waves together all kinds of "stuff" can and will happen.  The AS front only propagating system seems orders of magnitude simpler and more direct.  

Like Tom mentioned, there are a ton of fundamental instrument note frequencies in the range of 150 to 700 Hz.  Steve, do the vents continue to add the back waves over this entire range?

I suppose it's possible that any distortion added by ports is masked by all of the other distortions caused by these vibrating things we call speakers. 

Regards,

Jerry

PS:  Velodyne's top of the line subs are all sealed boxes:

http://velodyneacoustics.com/subwoofers/digital-drive-plus-18.html

 

[iso]

5 hours ago, onplane said:

 

Steve, I never really understood the theory behind vented systems.  I understand the idea is to use the "back wave" and add it to the wave propagating from the front of the woofer. Thus, a major increase in efficiency!  Problem is you can't use that back wave immediately, because it is 180 degrees out of phase with the front wave. So, via the ports you attempt to store the wave for a half cycle and then ... release.

 

As far as I understand phase response of 3rd order (vented box) is worse than 2nd order (acoustic suspension).  But I think that at f3 there is still 90 degree phase shift when using acoustic suspension principle? Best LF alignment should be 1st order alignment if phase sihft is the one and only consideration... and I believe that this is open baffle, electrostatic or other design that does not have cab to boost woofer resonance. There is still some phase shift due to the woofer resonance even effect of cab has been removed. 

Kimmo

[Jeff_C]

I tend to agree with the sentiment of Steve F's OP.

When I bought AR speakers 4 decades ago, I recall ported competitors gave away their design (as ported) by the sound in the bass region. IMO the quality of the bass was inferior to Acoustic Suspension designs, regardless of the generally lower -3dB point for ported designs. More modern ported speakers which have the benefit of computer aided design and tools do not seem to give away their ported design. The fact that they can generally reach lower -3dB points whilst delivering a quality sound in the bass region, made it inevitable that ported designs would dominate the modern speaker market place.

One thing that puzzles me though is that Tom Tyson has referred to Julian Hirsch of HH Labs having tested the AR-16 frequency response as 30Hz to 15kHz + or - 2.5 dB. Those figures seem to 'best' modern small ported designs by some margin. (The AR-16 is sized like an AR4x).

See Tom's last message in this thread. Unfortunately the pdf files are no longer accessible.

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1568-ar-16-resurrection/#entry58139

 

[iso]

10 hours ago, owlsplace said:

1.5 cu.ft.

folded horn not vented design ... the original Klipschorn patented in 1946:

One watt RMS produces a 105 decibel per meter sound pressure level (SPL) ... As the only speaker in the world to be in continuous production for 60 years, the Klipschorn has remained relatively unchanged since its inception." from https://en.wikipedia.org/wiki/Klipsch_Audio_Technologies#The_Klipschorn

I'm still not giving up my beeswax

Roger

High sensitivity and SPL, good bass extension, low distortion is something that one can not simply get from modestly sized cab... this is scientific fact. If your focus is in sensitivity you simply lose bass extension ... if your focus is in bass extension you loose sensitivity or have to use bigger cab... if you look at CBS-Lab test of AR-LST  you can see that you need 100 watts to reach similar 105 dB SPL that Klipschorn will get from 1 watt. This does also mean that when feeding Klipschorn with 100 wpc amp you will get something like 125 dB peak capability. 

So being big or small... acoustic suspension, ported or horn... you always have pros and cons, you simply can not get all the goodies at the same time. 

Kimmo

http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_other/cbs_laboratories_report_on_/cbs_laboratories_report_on__7.html#previous-photo

[Aadams]

It looks like the big change is ported systems can be very good these days but other than that things are still the same.  If one wants to merely hear the symphonic bass drum a small ported box works but if one wants that visceral hit then you get a big box, or a use a powered subwoofer.  12" AR classics are looking better all the time for certain types of music.

[tysontom]

On 10/24/2016 at 2:43 PM, Steve F said:

From the Cat Dragged in LST thread:

Hi Jerry,

What great replies!  First of all, I, too, didn't realize that speaker companies who built vented enclosures paid too much attention to small air leaks; however, I can see where it could give a problem.  I think what Steve is referring to regarding the "their lower 3dB down points" is the lower fc of many vented designs, but the 24 dB/octave rolloff below resonance in vented vs. the 12 dB/octave in acoustic-suspension designs.  Thus the vented design obviously rolls off very rapidly below resonance compared with a/s designs.  Vented designs are certainly more efficient, and I agree about the ported designs' tendency to exhibit "one-note bass," and although there is usually plenty of punchy low-frequency energy, it always seemed (to me at least) muddy or less well-defined than sealed systems, but there were some exceptions.  If one is listening to a lot of jazz with kick drum or orchestral music with big orchestral bass drum, organ or electronic music with lots of low-frequency energy, the acoustic-suspension system seems to have a significant advantage.  Ported or vented systems do just fine with probably 90% of all recorded music, especially rock or popular music.  But overall, I think acoustic-suspension systems are much cleaner than vented systems in reproducing fundamental energy, usually with flatter response and lower harmonic distortion, but many will argue that some vented designs that are certainly excellent as well.

I'd written about this topic in great length (over 1500 words--about four pages) back in 2002. I guess it's time to summarize that post again now, so here goes.

 

Yes, the “tuning frequency” of a correctly-designed vented speaker with a woofer of appropriate T-S parameters will allow it to reach a lower -3dB point for a given enclosure size compared to a sealed speaker of the same size. In the early 90’s timeframe, for instance, the PSB Alpha was reaching, say, -3dB in the low 50’s Hz compared to our sealed Boston Acoustics HD5, which was down 3dB at about 65Hz. That was terrifically audible in a retail A-B demo comparison.

 

 

The fact that the HD5 had more output at 30 or 35Hz because of its 12dB/oct rolloff compared to the PSB’s 24dB/oct rolloff was essentially meaningless, for two reasons:

  1.     They were both so far down in level at 30Hz (these were small 5 ¼” 2-way bookshelf speakers for about $200/pr. at the time) that it didn’t matter at all if one was down 15dB and the other was down 24dB. Neither had any impactful output down there, so the HD5’s sealed “advantage” was no advantage at all.

    2. These were speakers that would be used to play popular music in stereo, where the lowest bass content in the program was in the 40-60Hz range. The PSB just sounded so much “fuller” and richer than the HD5. The fact that the sealed HD5, 7 and 8 were getting killed at retail was the driving factor that lead to the CR Series that replaced them being ported speakers.

Which leads us to the next big point: It’s waaaaaay past time to totally debunk that tired old cliché about “Ported speakers are boomy and one-notey and ‘thick’ sounding compared to the ‘fast, tight’ sound of acoustic suspension speakers.”

 

 

That may have been true in the ‘50’s and ‘60’s, but only because designers didn’t have fully fleshed-out T-S parameters and modern computer modelling to work with. So, ported speakers were hit-or-miss, “cut-‘n-try,” etc. A lot of shooting in the dark.

 

 

Not any more. I defy anyone to listen to a really excellent Aerial or B&W or KEF or Legacy Audio—name a good company, your choice—and tell me that their bass isn’t excellent.

 

 

It is excellent. “Tight, crisp, well-defined, fast, articulate, musical, muscular, athletic, accurate, natural,” etc. Pick your adjective. Pick your music.

 

 

Sealed had a huge advantage when design practices were unsophisticated, because the acoustic suspension design principle enabled designers to optimize a truly excellent system by jockeying and adjusting only a few variables. Presto: Combine 17Hz Fs, high compliance, 1.7 cu.ft. enclosure and you get 3a bass. Duck soup.

 

 

But to build and test dozens of variations of woofer parameters, port length, port diameter, vent shape, vent location, etc., etc. and come up with an optimized vented design was just not practical in 1966.

 

 However, it is now. Press a button and see 12 vented design options in a second. Press the button again and see another 12. You couldn’t build and measure 24 of them in 1966. Now you can do it in an hour.

 

 

So, you can now get that lower -3dB down point and get bass that’s all the above good things. Why do you think nothing’s sealed any more? Don’t misunderstand my point—the 7, 4x, 2ax, 3a, et al. had—and have!!—terrific bass. It just that now there’s no barrier to getting great bass from ported designs, with their advantages, but without the drawbacks of 50 years ago.

 

 

Steve F.

I'd written about this topic in great length (over 1500 words--about four pages) back in 2002. I guess it's time to summarize that post again now, so here goes.

>Yes, the “tuning frequency” of a correctly-designed vented speaker with a woofer of appropriate T-S parameters will allow it to reach a lower -3dB point for a given enclosure size compared to a sealed speaker of the same size. In the early 90’s timeframe, for instance, the PSB Alpha was reaching, say, -3dB in the low 50’s Hz compared to our sealed Boston Acoustics HD5, which was down 3dB at about 65Hz. That was terrifically audible in a retail A-B demo comparison.  —Steve F

Well, no argument that for a given speaker enclosure size, it's easier to design a lower -3dB point in a vented system than a standard, optimally designed  sealed system.  "Optimally" in the sense that there are practical limitations and tradeoffs in the proper design of a sealed woofer (or any type of system, of course).  However, it all comes down to the laws of physics, in which there  is a trade-off of efficiency, linearity,  power-handling capability and other factors in determining the bass resonance frequency for any woofer system.  That is to say, down to a point, there is a practical—but not necessarily physical—limitation to setting bass resonance if you are willing to juggle with the parameters.  The "practical" system designer uses a combination of factors that gives good bass performance with low distortion and good durability, etc. 

The best example of this is the quite small The Smaller Advent Loudspeaker—AR-6 in size—about half the volume of full-size, 1.8 cu. ft. The Advent Loudspeaker, yet the small Advent has a fc of around 43-45 Hz, same as the large Advent, a third octave lower than competitive speakers such as the AR-6 or even the AR-2ax/AR-5, with -3dB at 48Hz.  This meant that the small Advent had a -3dB point of approximately 35 Hz, very low for such a small speaker system.  Henry Kloss wanted deep bass from a very small speaker, so he applied the so-called "Hofman's Iron Law" (simply a white paper quantifying, in simple terms, the well-known physics of sealed-box speaker design) and juggled the woofer's parameters, free-air resonance, cone diameter and damping, etc., to get a very low resonance. 

The trade-off in the Small Advent was very low efficiency (sensitivity) of the speaker, low power-handling capability and higher harmonic distortion.  I have a pair, and I speak from experience.  The speaker has very low efficiency and relatively low power-handling capability.  It was designed as a 4-ohm speaker to take advantage of modern solid-state amplifier's high current at low impedances, but it stressed some amplifiers.  It didn't sell particularly well with a sensitivity 2-3dB lower than the big Advent or other comparable speakers in its class, but it could go very low. 

The trade-offs weren't particularly appealing, and the speaker was not a sales success.  For the relatively few music-lovers who liked organ music played at fairly low volumes in an apartment or in a small room, this speaker did fine.  It's simply a matter of physics.  Compared with an AR-6, the Small Advent is significantly "punchier" and more potent-sounding with its lower fc, but it also sounds more "strained" than the similarly sized AR-6.  The latter has greater excursion capability and lower harmonic distortion, possibly accounting for perceived differences.

With a vented system, of course, the designer can use a combination of woofer parameters and vent size and length, tuning the system for the desired low frequency—down to a certain point, of course.  Below cutoff, of course, there is no protection for the excursion of the woofer cone, and vented systems with very low resonance frequencies are vulnerable to over-excursion, bottoming, excessive distortion or "chuffing" in the port, etc.  

>That may have been true in the ‘50’s and ‘60’s, but only because designers didn’t have fully fleshed-out T-S parameters and modern computer modelling to work with. So, ported speakers were hit-or-miss, “cut-‘n-try,” etc. A lot of shooting in the dark.

>Which leads us to the next big point: It’s waaaaaay past time to totally debunk that tired old cliché about “Ported speakers are boomy and one-notey and ‘thick’ sounding compared to the ‘fast, tight’ sound of acoustic suspension speakers.”

 

>Not any more. I defy anyone to listen to a really excellent Aerial or B&W or KEF or Legacy Audio—name a good company, your choice—and tell me that their bass isn’t excellent.

>It is excellent. “Tight, crisp, well-defined, fast, articulate, musical, muscular, athletic, accurate, natural,” etc. Pick your adjective. Pick your music.

>Sealed had a huge advantage when design practices were unsophisticated, because the acoustic suspension design principle enabled designers to optimize a truly excellent system by jockeying and adjusting only a few variables. Presto: Combine 17Hz Fs, high compliance, 1.7 cu.ft. enclosure and you get 3a bass. Duck soup. —Steve F

I have owned several vented speaker systems over time, a Altec Lansing (604), University (315) and even a Jensen SS100 system.  In the 1990s, I purchased a pair of B&W 801 Matrix II speakers (made famous by wide studio-monitor use, especially at London's Abbey Road).  Just as Steve says, the earlier vented woofers tended to have some alignment issues—hit-or-miss—designs that did cause the sound to be less natural.  Actually, the co-axial Altec 604s were fairly smooth and unobtrusive by 1950's standards with good bass down into the 60-50 Hz range, and the speakers could pound out very high volume levels quite effortlessly!  The University 315 was easily one of the better co-axial designs, too, using the famous old theatre C-15W woofer as the low-frequency component, and this speaker performed well down to around 50 Hz or so.  The Jensen SS100 I owned was very carefully designed factory-built enclosure, and the bass response was really quite smooth and unobtrusive, but not terribly extended below 50-60 Hz.  It was peak-free, however.

Altec Lansing 604Es

University 315

Jensen SS100

It is true, as Steve says, that the newer vented designs are excellent.  Consider my B&W 801s: this speaker had a very heavy, low-resonance 15-inch woofer and a stiff, heavily braced cabinet and finely tuned port.  With an optimizer module, which I used, the 801 could go to 20-25 Hz easily and effortlessly.  At one point, I had my AR9s, 801s with Bass Alignment Filter and KEF 107Rs with KUBE, all connected to an A-B switch for comparison in our family's 17' x 25' living room.  I was using my Threshold amplifier at the time.  This was only for a weekend, as my wife quickly made me disassemble the entire setup.  Therefore, I had the big vented 801 compared with the AR9's low-resonance dual 12-inch woofers, compared with the KEF's band-pass (half acoustic-suspension, half vented) 107s.  What I found was that all systems could pound out effortless low-frequency energy.  The KEF 107s would go the deepest with greatest output, followed by the 801s and then the AR9s, but this is what you would expect insofar as the AR9 was not equalized down to 20 Hz and below, whereas both the KEF and B&W were equalized.

B&W 801 Matrix IIs

Low-Resonance Matrix woofer

KEF R107s  

To me, the 801s have a slightly "heavy" quality to them.  There is no way to adjust this characteristic, and this was with the 801s pulled out about 3 feet from the front wall and away from the corners.  The AR9s were back against the front wall, as were the 107s.  A lot of this is related to damping of vented design vs. damping of a sealed box.  Of the three components of woofer damping for a vented system, acoustic damping is perhaps the strongest element with magnetic damping second and mechanically through the suspension of the woofer.  With a sealed system, magnetic damping plays a bigger part, but it is definitely easier to design an optimally sealed system than a vented system, since optimizing one parameter can sometime offset something else, resulting in more of a compromise.

The biggest problem with the vented system is the linearity of the suspensions, also part of the mechanical damping.  It is up to the mechanical stiffness of the spider and surround to determine the proper restoring force, and with modern systems, as Steve points out, great improvements have been made.  Plus, the lower in frequency the system goes, down to the port resonance, the smaller the woofer's excursion, reducing distortion.  Once below resonance, however, the vented-woofer's cone begins to make increasingly larger excursions and begins to enter into the non-linearity range.  The B&W's alignment filter cut-off helps prevent over-excursion, but I think this characteristic of a vented system is the source of a lot of unpleasantness at high output, low-frequency points. 

In one comparison, I played Peter Hurford's Mendelssohn Organ Sonata No. 3 in A Major, Argo 414-420-2.  On one band, the pedal note involves a 32' pipe resulting in a quiet, but very deep sub-20Hz clean organ-pipe tone.  The AR9 and the KEF 107 produced this pedal note effortlessly, even though there was air-chuffing sound coming out of the large slot on the top front of the 107.  The 801 also produced this note, but to me the speaker's woofer was now out of the linear range and didn't sound natural; in short, distortion was beginning to dominate.  Overall, the AR9 seemed to be the clear winner in clean, low-distortion bass output!

When playing jazz with lots of well-recorded drum kick-bass, all three systems produced very clean, realistic bass that could be felt as well as heard, and in this case, the 801s seemed the most potent of the three!  So therefore, while huge improvements have been made -- especially with regards to low-cost systems -- the vented systems of today still have some compromises in their design relating to the mechanical suspensions at very low frequencies below their normal cutoff frequency.  --Tom Tyson

 

[Steve F]

 

Tom makes many good points and his experiences with those three superb speakers back up the contention that with modern speakers, great bass is really a matter of design skill and execution, not the inherent advantages or disadvantages of a particular design approach.

I was simply pointing out that the old cliché of "ported speakers are always flabby, bloated and boomy compared to acoustic suspension" is no longer true.

the vented systems of today still have some compromises in their design relating to the mechanical suspensions at very low frequencies below their normal cutoff frequency.

Pick the speaker that fulfills the mission you have for it. I certainly wouldn't recommend a  6 1/2-inch 2-way vented bookshelf speaker if you like organ music with fundamentals below 35Hz. You can't EQ it, the woofer "unloads" below the system tuning, etc. But for popular music/jazz at moderate SPLs in a normal-sized room, without a sub? Sure, they'll be great, and assuming good design, they'll go lower -3dB than a sealed system of the same size.

If you need to carry a 4 x 8, don't buy a Miata. If you want to go darting around corners, don't buy a Honda Odyssey. But in the middle of these two extreme use scenarios, there are lots of great choices. Same with speakers.

Steve F.

[onplane]

8 hours ago, tysontom said:

Compared with an AR-6, the Small Advent is significantly "punchier" and more potent-sounding with its lower fc, but it also sounds more "strained" than the similarly sized AR-6.  The latter has greater excursion capability and lower harmonic distortion, possibly accounting for perceived differences.

 

At one point, I had my AR9s, 801s with Bass Alignment Filter and KEF 107Rs with KUBE, all connected to an A-B switch for comparison in our family's 17' x 25' living room.  I was using my Threshold amplifier at the time.  This was only for a weekend, as my wife quickly made me disassemble the entire setup.  Therefore, I had the big vented 801 compared with the AR9's low-resonance dual 12-inch woofers, compared with the KEF's band-pass (half acoustic-suspension, half vented) 107s.  What I found was that all systems could pound out effortless low-frequency energy.  The KEF 107s would go the deepest with greatest output, followed by the 801s and then the AR9s, but this is what you would expect insofar as the AR9 was not equalized down to 20 Hz and below, whereas both the KEF and B&W were equalized.

Tom, your last post was simply terrific!  Thank you, thank you, thank you!!

You clearly put some thought and effort into this post and the pictures .... my lord, they are BEAUTIFUL!!!

Your comment about your wife making you disassemble your test setup struck a chord.  You know how many speakers I have in our living room?  Zilch, nada, none!  My wife considers the living room her domain and I'm NOT allowed to "pollute" this pristine area.  Now, within reason I can pretty much do as I like in the family room, where we currently have seven speakers.

Your comment about "strained" also struck a chord.  Way, way back in 1968 or 1969 I happened to be with some friends in a HiFi shop as I was looking to buy some speakers for the my recently assembled Eico solid state receiver. (BTW the Eico receiver wasn't a bad unit at all.  It was similar in design to the AR amp in that it too had interstage transformers and direct coupled output. It was smaller and cheaper than the AR and only rated at 25 wpc into 8 ohms. One huge advantage was no transistors were soldered!  That is, they were all mounted in sockets for ease of testing and maintenance. That turned out to be not worth much, because I never had a problem with it for the 3 years I owned it.)

Anyhow, we were in this fairly large HiFi shop listening to a variety of speakers.  I was listening to AR's, KLH's, E-V's and some bookshelf Altecs.  I remember salivating over the AR-3a's, which I couldn't afford.  I ended up buying a pair of AR-4x's which paired very nicely with that little Eico.  

Anyhow, after I made my decision, the gentleman, who was so patient with me throughout my laborious comparisons, asked if I wanted to hear something "special". Of course I said, "Sure!"  He then took us into another huge room, where he had another pair of AR-3a's and a pair of these huge massive speakers he called Altec A7's.  These things were .... ENORMOUS!  

So first he fired up the AR's and we listened and they sounded great ... just like in that smaller room.  Then he switch in the huge Altecs and my goodness what a difference.  These "monsters" sounded wonderful!  By comparison, the AR's sounded "strained".  The A7's are a hybrid of a vented system, but with the addition of a low frequency horn.  Then on top, they had a multi-cell high frequency horn.  To this day, I haven't heard a speaker produce sound as effortlessly as these Altec A7's.  They are clearly in a class by themselves.

Now from a marketing standpoint, I'm surprised they were ever made in the first place!  I mean, the market for something that large and expensive had to be very small. As I said earlier, in spite of the terrific sound of the A7's, I still bought the AR-4x's.  I had a few minor "obstacles" in purchasing the A7's:

1.  I couldn't begin to afford one of them ... let alone a pair!

2. I couldn't pick them up

3. I had no way to transport them

4. I had no place to put them

Other than that, I would have been the proud owner of a pair of Altec A7's!

Seriously, I did learn something that day about trade offs in audio quality.  Size really does matter!

Regards,

Jerry 

 

[tysontom]

20 hours ago, onplane said:

Tom, your last post was simply terrific!  Thank you, thank you, thank you!!

You clearly put some thought and effort into this post and the pictures .... my lord, they are BEAUTIFUL!!!

Your comment about your wife making you disassemble your test setup struck a chord.  You know how many speakers I have in our living room?  Zilch, nada, none!  My wife considers the living room her domain and I'm NOT allowed to "pollute" this pristine area.  Now, within reason I can pretty much do as I like in the family room, where we currently have seven speakers.

Your comment about "strained" also struck a chord.  Way, way back in 1968 or 1969 I happened to be with some friends in a HiFi shop as I was looking to buy some speakers for the my recently assembled Eico solid state receiver. (BTW the Eico receiver wasn't a bad unit at all.  It was similar in design to the AR amp in that it too had interstage transformers and direct coupled output. It was smaller and cheaper than the AR and only rated at 25 wpc into 8 ohms. One huge advantage was no transistors were soldered!  That is, they were all mounted in sockets for ease of testing and maintenance. That turned out to be not worth much, because I never had a problem with it for the 3 years I owned it.)

Anyhow, we were in this fairly large HiFi shop listening to a variety of speakers.  I was listening to AR's, KLH's, E-V's and some bookshelf Altecs.  I remember salivating over the AR-3a's, which I couldn't afford.  I ended up buying a pair of AR-4x's which paired very nicely with that little Eico.  

Anyhow, after I made my decision, the gentleman, who was so patient with me throughout my laborious comparisons, asked if I wanted to hear something "special". Of course I said, "Sure!"  He then took us into another huge room, where he had another pair of AR-3a's and a pair of these huge massive speakers he called Altec A7's.  These things were .... ENORMOUS!  

So first he fired up the AR's and we listened and they sounded great ... just like in that smaller room.  Then he switch in the huge Altecs and my goodness what a difference.  These "monsters" sounded wonderful!  By comparison, the AR's sounded "strained".  The A7's are a hybrid of a vented system, but with the addition of a low frequency horn.  Then on top, they had a multi-cell high frequency horn.  To this day, I haven't heard a speaker produce sound as effortlessly as these Altec A7's.  They are clearly in a class by themselves.

Now from a marketing standpoint, I'm surprised they were ever made in the first place!  I mean, the market for something that large and expensive had to be very small. As I said earlier, in spite of the terrific sound of the A7's, I still bought the AR-4x's.  I had a few minor "obstacles" in purchasing the A7's:

1.  I couldn't begin to afford one of them ... let alone a pair!

2. I couldn't pick them up

3. I had no way to transport them

4. I had no place to put them

Other than that, I would have been the proud owner of a pair of Altec A7's!

Seriously, I did learn something that day about trade offs in audio quality.  Size really does matter!

Regards,

Jerry 

 

Hey Jerry,

The Altec A-7 story you told is very familiar!  It is actually somewhat of a "bait-and-switch" tactic that some audio dealers used.  

The A-7 VOTT is a wonderful sound-reinforcement or movie-theater type speaker, but it is less well-suited for home high-fidelity use.  Size does matter when it comes to high-efficiency speakers, for sure!  What I think you heard was the sheer acoustic output power and efficiency of the A-7 in comparison to the AR-3a.  The A-7 has an output sensitivity of nearly 98 dB at 1 watt, 1 meter, (about 3-1/2% efficient) whereas the AR-3a's sensitivity is around 84 to 85 dB at 1 watt, 1 meter, (approximately 0.75% efficiet).  That means that when switched from the AR-3a to the A-7 with a non-equalized switcher, the volume will go significantly louder, giving the A-7 a sense of sheer power and making the AR-3a appear to shrink into the background.  The same is true when playing both at very high levels: the A-7 can pound out nearly 7 acoustic watts of power on peaks of only 100-125 watts or so!  An AR-3a could never approach that level of acoustic output.  It would take several thousand watts into the AR-3a to get even close to that level of acoustic output, and distortion would be high, not to mention possible damage.  Power-handling capability is high on the A-7, too, with its large 3-inch diameter horn-driver and woofer voice coils, but it was designed to play loudly.

However, when comparing deep-bass capability, musical accuracy, dispersion and smoothness across the band, the comparison ends with the AR-3a -- much superior to the A-7 in terms sonic accuracy and low-frequency depth.  The A-7 has a bass -3dB point of around 55 Hz, whereas the AR-3a has a -3dB point of 35 Hz, and the AR-3a has considerable output down to below 20 Hz.  The A-7 has virtually nothing down that low.  Also, the A-7 is rated +/-10dB from 45-20kHz, which is not outstanding. 

This bait-and-switch tactic has been around for ages.  When I was in the service, I remember visiting a large Altec dealership out in El Paso, Texas.  He had all sorts of big Altec speakers, and out in the middle of the floor of the demo room was a single AR-3.  He was disparaging the AR-3 as being inferior to his bigger speakers in the showroom.  On top of it all, he had the level controls turned down, making the already reticent AR-3 sound rather pathetic in that company.  He played a jazz LP at my request, and out of nowhere the kick-bass sound (way down in output) coming from the single AR-3 out in the floor sounded cleaner and more powerful than the big Altecs!  I think this even surprised the showroom salesman!

In the end, it's probably better that you didn't get the A-7s, although I must confess that in college I had a girlfriend who owned a pair of A-7s.  I think they were purchased by a former boyfriend, of all things, and he moved out of town and never picked them up.  After a few beers, I could adjust to the sound. 

--Tom Tyson

 

[onplane]

1 hour ago, tysontom said:

Hey Jerry,

The Altec A-7 story you told is very familiar!  It is actually somewhat of a "bait-and-switch" tactic that some audio dealers used.  

The A-7 VOTT is a wonderful sound-reinforcement or movie-theater type speaker, but it is less well-suited for home high-fidelity use.  Size does matter when it comes to high-efficiency speakers, for sure!  What I think you heard was the sheer acoustic output power and efficiency of the A-7 in comparison to the AR-3a.  The A-7 has an output sensitivity of nearly 98 dB at 1 watt, 1 meter, (about 3-1/2% efficient) whereas the AR-3a's sensitivity is around 84 to 85 dB at 1 watt, 1 meter, (approximately 0.75% efficiet).  That means that when switched from the AR-3a to the A-7 with a non-equalized switcher, the volume will go significantly louder, giving the A-7 a sense of sheer power and making the AR-3a appear to shrink into the background.  The same is true when playing both at very high levels: the A-7 can pound out nearly 7 acoustic watts of power on peaks of only 100-125 watts or so!  An AR-3a could never approach that level of acoustic output.  It would take several thousand watts into the AR-3a to get even close to that level of acoustic output, and distortion would be high, not to mention possible damage.  Power-handling capability is high on the A-7, too, with its large 3-inch diameter horn-driver and woofer voice coils, but it was designed to play loudly.

However, when comparing deep-bass capability, musical accuracy, dispersion and smoothness across the band, the comparison ends with the AR-3a -- much superior to the A-7 in terms sonic accuracy and low-frequency depth.  The A-7 has a bass -3dB point of around 55 Hz, whereas the AR-3a has a -3dB point of 35 Hz, and the AR-3a has considerable output down to below 20 Hz.  The A-7 has virtually nothing down that low.  Also, the A-7 is rated +/-10dB from 45-20kHz, which is not outstanding. 

This bait-and-switch tactic has been around for ages.  When I was in the service, I remember visiting a large Altec dealership out in El Paso, Texas.  He had all sorts of big Altec speakers, and out in the middle of the floor of the demo room was a single AR-3.  He was disparaging the AR-3 as being inferior to his bigger speakers in the showroom.  On top of it all, he had the level controls turned down, making the already reticent AR-3 sound rather pathetic in that company.  He played a jazz LP at my request, and out of nowhere the kick-bass sound (way down in output) coming from the single AR-3 out in the floor sounded cleaner and more powerful than the big Altecs!  I think this even surprised the showroom salesman!

In the end, it's probably better that you didn't get the A-7s, although I must confess that in college I had a girlfriend who owned a pair of A-7s.  I think they were purchased by a former boyfriend, of all things, and he moved out of town and never picked them up.  After a few beers, I could adjust to the sound. 

--Tom Tyson

 

Hi, Tom!

Let me get this straight, you had a girlfriend who owned a pair of Altec A7's???   These things are massive!  What kind of a place did she live in ... a theater?  And for the most important question of all ... you didn't marry her???

WOW, when I think back to my girlfriends ... I had to buy all of them hifi sets!  Not a one had anything other than a record player. And you had a girlfriend who owned a pair of Altec A7's!  Damn ... life just isn't fair!

As for "bait and switch" that may well have been a tactic of this retailer, but he clearly knew that I wasn't a candidate for purchasing the Altecs.  Heck, as a college student, I couldn't even afford the 3a's.  

I know I took my own records to help in the selection process and at that time I was going through a J. S. Bach phase.  I suspect we listened to one of the Brandenburg's on the A7. Further, vaguely I recall the guy turning down the volume prior to switching in the A7's.  Of course there is nothing scientific here so that even with the volume control down, the A7's still may have been putting out a lot more SPL.

I don't believe SPL is the only difference in the sound between the 3a's and the A7's, however.  They don't sound similar to each other at all.  One of my friends on the ride home said something along the lines ... with good speakers you can close your eyes and envision the ensemble on a stage in front of you. With these Altecs, it's like the ensemble is 5 feet in front of you ... you feel like you can reach out and touch them. 

Maybe it's due to the horns (Altecs have both low and high frequency horns) and the way horns couple acoustic energy to air. Could also be the room.  Maybe A7's only sound good playing Bach.  I don't know, but we were all impressed.

I recently found on the net Altec's published response curve (see below).  Frankly, I don't understand how they could publish this. As I understand the A7, you are buying a system ... not a loudspeaker.  That is, you have to specify the cabinet (port up or down, HF horn inside port or on top).  Next, there are tons of options for the drivers that you must choose from.  Finally, even the crossover has a slew of options and you must specify the one you want.

Which brings me back to why would a HiFi retailer even have an A7 and a showroom for it? All I can guess is this particular retailer may have had a commercial side as well. Or possibly Altec forced them to do it.  I do know that he demoed Altec bookshelf units and they weren't bad speakers.  They weren't as cheap as the AR-4x's, which is what I choose.  My decision was based upon "bang for the buck", because I didn't have many bucks!

Tom, I think I read somewhere that the AR-4 series was the most popular in terms of units sold of all of the AR's.  Do I have that right?

 

Regards,

Jerry

   

 

 

 

 

[owlsplace]

Ro

22 minutes ago, onplane said:

Tom, I think I read somewhere that the AR-4 series was the most popular in terms of units sold of all of the AR's.  Do I have that right?

Sounds right to me with over 400,000 units produced.

The AR-3 series will perhaps be their most remembered speaker from the gilded age of stereo.

http://www.theabsolutesound.com/articles/the-12-most-significant-loudspeakers-of-all-time/

Roger

[iso]

6 hours ago, onplane said:

 

Maybe it's due to the horns (Altecs have both low and high frequency horns) and the way horns couple acoustic energy to air. Could also be the room.  

My experience is very limited with horns, but whenever I have heard what kind of LF-energy horns do produce, vented or sealed cabs are no match in solidity of it. As horn loading reduces all ready small excursion of big 15" woofer (there is no point of use smaller woofer in LF-horn) due to the superior coupling of acoustic energy to the air... distortion is quite small. Big horns do have similar problems like any big enclosures. Cab with 50 L volume is more prone panel resonances than 7 L cab and fridge sized horn is even more prone to resonances...bandwidth of horn is limited, so old 2-way horns do have other short comings too.

Kimmo

Quote

 

 

[Sonnar]

On 29/10/2016 at 1:56 AM, tysontom said:

Hey Jerry,

The Altec A-7 story you told is very familiar!  It is actually somewhat of a "bait-and-switch" tactic that some audio dealers used.  

The A-7 VOTT is a wonderful sound-reinforcement or movie-theater type speaker, but it is less well-suited for home high-fidelity use.  Size does matter when it comes to high-efficiency speakers, for sure!  What I think you heard was the sheer acoustic output power and efficiency of the A-7 in comparison to the AR-3a.  The A-7 has an output sensitivity of nearly 98 dB at 1 watt, 1 meter, (about 3-1/2% efficient) whereas the AR-3a's sensitivity is around 84 to 85 dB at 1 watt, 1 meter, (approximately 0.75% efficiet).  That means that when switched from the AR-3a to the A-7 with a non-equalized switcher, the volume will go significantly louder, giving the A-7 a sense of sheer power and making the AR-3a appear to shrink into the background.  The same is true when playing both at very high levels: the A-7 can pound out nearly 7 acoustic watts of power on peaks of only 100-125 watts or so!  An AR-3a could never approach that level of acoustic output.  It would take several thousand watts into the AR-3a to get even close to that level of acoustic output, and distortion would be high, not to mention possible damage.  Power-handling capability is high on the A-7, too, with its large 3-inch diameter horn-driver and woofer voice coils, but it was designed to play loudly.

However, when comparing deep-bass capability, musical accuracy, dispersion and smoothness across the band, the comparison ends with the AR-3a -- much superior to the A-7 in terms sonic accuracy and low-frequency depth.  The A-7 has a bass -3dB point of around 55 Hz, whereas the AR-3a has a -3dB point of 35 Hz, and the AR-3a has considerable output down to below 20 Hz.  The A-7 has virtually nothing down that low.  Also, the A-7 is rated +/-10dB from 45-20kHz, which is not outstanding. 

This bait-and-switch tactic has been around for ages.  When I was in the service, I remember visiting a large Altec dealership out in El Paso, Texas.  He had all sorts of big Altec speakers, and out in the middle of the floor of the demo room was a single AR-3.  He was disparaging the AR-3 as being inferior to his bigger speakers in the showroom.  On top of it all, he had the level controls turned down, making the already reticent AR-3 sound rather pathetic in that company.  He played a jazz LP at my request, and out of nowhere the kick-bass sound (way down in output) coming from the single AR-3 out in the floor sounded cleaner and more powerful than the big Altecs!  I think this even surprised the showroom salesman!

In the end, it's probably better that you didn't get the A-7s, although I must confess that in college I had a girlfriend who owned a pair of A-7s.  I think they were purchased by a former boyfriend, of all things, and he moved out of town and never picked them up.  After a few beers, I could adjust to the sound. 

--Tom Tyson

 

Tom, I have Altec Valencias with 416-8b woofers and upgraded drivers 802 8G and I know very well their sound . High quality very fast and clean bass but audible lows stopped very soon in comparison to AR 3's bass . The aluminum 802 8G Tangerine drivers have an extended response up to 20 Khz ( not so the Symbiotik 806 standard ) , but I have to use two additional JBL 's 075 toeing it, as shown in pics , 'cause of the very poor dispersion of the big 811b horn at high frequencies . High frequency driver  is not only much more sensitive than woofer ( 112 db vs. 98 ) but they are lighter in mass and very fast in transient response , faster than any woofer: and these differences are clearly audible . In AR classic speakers every loudspeaker , woofer, midrange, tweeter , has the same sensitivity and the audible results is a homogeneous,  well balanced and clean response . I have two AR 3 pairs , and while one pair has pots in working conditions, the pots in the other couple are gone. So , just to try , I decided to bypass the pots connecting midranges and tweeters directly , without attenuations: the tonal balnce is equilibrate and excellent , and to me this pairs sounds slightly better than the other pair with working pots . Altec and JBL vintage gears are impressive , but obsolete in sound , and a 416 or 515 needs a 9 cu.in. vented box for a correct reproduction of bass fundamentals: the unfair short horn of Altec A7 can support only the midbass region , and the short folded horn of Klipsch LaScala cuts everything under 100 Hz . Modern low efficiency vented designs suffers of phase distortions at very low frequencies and various kinds of " hiss " and noise by the port . So , I think a well restored pair of classic AR wins easily every competition to the ears of a very experienced and mature listener.  My best wishes , Adriano