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Any reason JL didn't go with a passive radiator design in the F113?

post #1 of 47
Thread Starter 
Going a few years back, there has been multiple huge threads comparing the JL F113 with the SVS PB13 Ultra. The consensus seems to be that the PB13 provides more output down low, which is confirmed with 2M GP measurements.

There is no doubt the JL F113 delivers incredible output for its size, especially considering it is a sealed design. However it does still suffer from lower bass output in the 20Hz range.

Here's a hypothetical question: Why didn't JL do a passive radiator design for the F113? The PB13 gains 10-12dB of output near tuning point. From what I've read, passive radiator are pretty much ported alignments. So if passive radiators were added, tune it at around 20Hz, the JL would gain 10-12dB near its tuning point. It would eliminate the need for EQ boost down low, and be an absolute output monster. If we assume 10dB output gain from passive radiators, the (hypothetical) F113 would have almost 115dB from 20Hz and up , beating the PB13 in output across the entire spectrum, but in a much smaller box.

What do you think?

Gear mentioned in this thread:

post #2 of 47
Some don’t think much of PR and am sure JL had it’s priorities in sink regarding what they were trying to accomplish.
post #3 of 47
While a PR can appear to be a floppy cone that just sits there and randomly resonates, reducing sound quality, that is not how it works. A PR functions in virtually the same manor as a port. A port functions by having the air mass inside of the port resonate with the air spring of the enclosure, the diameter and length or the port combined with the enclosure volume determine the frequency of resonance. A PR cone size is functionally the equivalent of a port of that diameter, and the mass of the PR equals the air mass of a port the equivalent length. The box volume (air spring) couple to the size/mass determine which frequency the PR will resonate at. The only limits to a PR is how much suspension travel it has, the main down side is using an uneven number of PRs can cause the cabinet to rock. PRs are also extremely expensive compared to the cost of PVC pipe. Benefits are they're silent, even at their limits. The signal will not compress unless the PR hits its limits. There isn't an unwanted resonance higher in frequency like a port has. Internal sounds can not escape. Most importantly, you can tune a small cabinet low without issue.

My guess for JL is they make more money with a sealed box
post #4 of 47
Think about this, just from a design and performance standpoint:

PRs pretty much equal a ported cab design. The first loudpseakers were sealed, remember the term "acoustic suspension"? I do.

Later comes ported cabinets. To take advantage of air movement from both sides of the woofer driver. Yields greater dbs (efficiency), or sound levels.
This always has intrigued me, a sealed cab equals sound or air movement from just the front face of the woofer driver.
Ported cab yields air movement from both the forward and rear movement of the driver = more volume. But isn't the sound from the rear or port an echo? secondary sound versus a sealed cab design? What about the timing of this secondary sound, versus the original sound?

Clearly speaker manufacturers went to ported cabs to enhance the bass production. Also the ability to "tune the enclosure" to specific frequency.
It just seems to me a sealed cab would be more accurate, especially when your talking about reproducing recorded acoustic instruments like the double bass or grand pipe organ, or the cello. Non-electric instruments.

But from the latest GTGs where the Captivator and Submersive were demo'd, and a few other ported cabs, results indicated almost no one could pick or "call" ported or sealed in the blind auditions. So that throws a huge wrench in my thinking.
And I have owned both sealed and ported subs, currently a Rythmik FV15HP. And Brian Ding (Rythmik) has stated the sound signature between his sealed and ported subs is minimal. And I put a lot of faith in Brian, his ears. He designs and executes his products. He is an electrical engineer. He is a really smart guy imo, and honest and straight forward.

My brain says sealed subs must be more accurate, especially from a timing or latency aspect. But the well trained or experienced ears say otherwise. And the mere act of sound reproduction does include direct and some reflected sound, such as in a live performance. Reflected off the walls, the furniture, the people, whatever is in the hall or room. Sure some is absorbed too.

So we can conclude that a live performance of acoustic instruments, the most delicate in detail, include both direct and reflected sound waves to our ears. This is probably why no one can "call" ported or sealed in true blind testing with any accuracy.
post #5 of 47
Quote:
Originally Posted by polizzio View Post

Think about this, just from a design and performance standpoint:

PRs pretty much equal a ported cab design. The first loudpseakers were sealed, remember the term "acoustic suspension"? I do.

Later comes ported cabinets.
Ported designs go back just as far as sealed, and while all acoustic suspension cabs are sealed, not all sealed cabs are acoustic suspension. For that matter today you can hardly find a true acoustic suspension cab.
What it boils down to is driver specs and desired cabinet size and response, none of which was quantified until Theile/Small in the 1960s. Today we use whichever alignment that gives what we want for response given the constraints of the cab size we want to use and the specs of the driver we want to load it with. As for PRs, they're primarily used when a duct with the same resonant frequency would be too long to fit into the desired cabinet size.
post #6 of 47
I thought about rewording my post after posting to something like.. some don’t think to much of PR, ported or sealed for that matter (take your pick) but then just let it stand. biggrin.gif
post #7 of 47
It's all good Steve, I know that perception still exists among audiophools. Sometimes I like to ramble off stuff like that just so I dont forget it.
post #8 of 47
People generally like smaller and attractive in subs. JL's formula is small, sealed, attractive well finished, and substantial on board amp power.
Edited by polizzio - 7/24/13 at 10:23am
post #9 of 47
Quote:
Originally Posted by steve nn View Post

I thought about rewording my post after posting to something like.. some don’t think to much of PR, ported or sealed for that matter (take your pick) but then just let it stand. biggrin.gif

Discussion is good, we learn from it. I am.

Its just kind of sad when discussion dwindles into insults or innuendos. And many times context is really lost in just printed type.
post #10 of 47
Quote:
Originally Posted by Jay1 View Post

It's all good Steve, I know that perception still exists among audiophools. Sometimes I like to ramble off stuff like that just so I dont forget it.

Hey J. go on over to DIY, I left a little question for yuh! cool.gifbiggrin.gif
Edited by steve nn - 7/24/13 at 8:25am
post #11 of 47
Quote:
Discussion is good, we learn from it. I am.

^^+1 Yes I do too.. much to learn. smile.gif
post #12 of 47
Quote:
Originally Posted by Bill Fitzmaurice View Post

Ported designs go back just as far as sealed, and while all acoustic suspension cabs are sealed, not all sealed cabs are acoustic suspension. For that matter today you can hardly find a true acoustic suspension cab.


Quite interesting reading: (from wikipedia - loudspeaker enclosure)

"Before the 1950s many manufacturers did not fully enclose their loudspeaker cabinets; the back of the cabinet was typically left open. This was done for several reasons, not least because electronics (at that time tube equipment) could be placed inside and cooled by convection in the open enclosure.
Most of the enclosure types discussed in this article were invented either to wall off the out of phase sound from one side of the driver, or to modify it so that it could be used to enhance the sound produced from the other side. However, a few designs have ventured in a different direction, attempting to incorporate the natural acoustic properties of the cabinet material rather than deaden it, and shape the cabinet so that the rear can remain open and still provide good bass response with limited comb filtering.

Sealed cabinet
The loudspeaker driver's moving mass and compliance (slackness or reciprocal stiffness of the suspension) determines the driver's resonant frequency. In combination with the damping properties of the system (both mechanical and electrical) all these factors affect the low-frequency response of sealed-box systems. Output falls below the system's resonant frequency (Fs), defined as the frequency of peak impedance. In a closed-box, the air inside the box acts as a spring, returning the cone to the 'zero' position in the absence of a signal. A significant increase in the effective volume of a sealed-box loudspeaker can be achieved by a filling of fibrous material, typically fiberglass, bonded acetate fiber (BAF) or long-fiber wool. The effective volume increase can be as much as 40% and is due primarily to a reduction in the speed of sound, and not to the popular misconception of a change in operating conditions from adiabatic to isothermal. The enclosure or driver must have a small leak so internal and external pressures can equalise over time, to compensate for barometric pressure or altitude; the porous nature of paper cones, or an imperfectly sealed enclosure, is normally sufficient to provide this slow pressure equalisation.

Acoustic suspension or air suspension is a variation of the closed-box enclosure, using a smaller box to exploit the almost linear air spring which results. The "spring" suspension that restores the cone to a neutral position is a combination of an exceptionally compliant (soft) woofer suspension, and the air inside the enclosure. At frequencies below system resonance, the air pressure caused by the cone motion is the dominant force. Developed by Edgar Villchur in 1954, this technique was used in the very successful Acoustic Research line of "bookshelf" speakers in the 1960s-70s. Although no longer popular in commercial designs,[citation needed] the acoustic suspension principle takes advantage of this relatively linear spring. The enhanced suspension linearity of this type of system is off-set by rather low efficiency. Drivers for these designs rely more upon the enclosure characteristics than typical drivers, and most modern woofers are not well suited to acoustic suspension use.


Bass reflex
Also known as vented (or ported) systems, these enclosures improve low-frequency output, increase efficiency, or reduce the size of an enclosure, using cabinet openings or passive radiating elements to transform and transmit low-frequency energy from the rear of the speaker to the listener. They deliberately and successfully exploit the principles of the Helmholtz resonator. As with sealed enclosures, they may be empty, lined, filled or (rarely) stuffed with damping materials. Port tuning frequency is a function of cross-section and length. This enclosure type is very common, and provides the maximum deep-bass output for a given enclosure volume. Malcolm Hill pioneered the use of these designs in a live event context in the early 1970s. Vented system design using computer modeling has been practiced since about 1985, when researchers Thiele and Small first systematically applied electrical filter theory to the acoustic behavior of loudspeakers in enclosures. While ported loudspeakers had been produced for many years before computer modeling, achieving optimum performance was challenging, as it is a complex sum of the properties of the specific driver, the enclosure and port, because of imperfect understanding of the assorted interactions. These enclosures are sensitive to small variations in driver characteristics and require special quality control concern for uniform performance across a production run."


I don't remember open back speakers, clearly before my time (pre 1950s). I do remember sealed speakers, and the AR "acoustic suspension" reference. I was quite young but my brother in law had a pair of the early bookshelf ARs. The reference dates above also supports my assertion that mass produced bass reflex or ported cabs came later after sealed cabs.
post #13 of 47
Quote:
Originally Posted by polizzio View Post

The reference dates above also supports my assertion that mass produced bass reflex or ported cabs came later after sealed cabs.
Wikipedia is hardly definitive. This one dates to 1930:
http://www.aes.org/aeshc/docs/recording.technology.history/images3/thuras-pat01.jpg

It wasn't the first.
post #14 of 47
There must be a reason why most of the expensive subs are sealed... I think the designers are figuring that the buyers are looking for more accurate and tighter bass than lower frequency...
post #15 of 47
Quote:
Originally Posted by Jon S View Post

There must be a reason why most of the expensive subs are sealed...
It's the least expensive cabinet design to construct. Never forget the almighty profit margin.
Quote:
I think the designers are figuring that the buyers are looking for more accurate and tighter bass than lower frequency...
Sealed cabs are no more accurate or 'tight' than any other. Consumer perception that they might be would influence some manufacturers as to what they will market.
post #16 of 47
Quote:
Originally Posted by Bill Fitzmaurice View Post

It's the least expensive cabinet design to construct. Never forget the almighty profit margin.
Sealed cabs are no more accurate or 'tight' than any other. Consumer perception that they might be would influence some manufacturers as to what they will market.

+1
post #17 of 47
Quote:
Originally Posted by Jon S View Post

There must be a reason why most of the expensive subs are sealed... I think the designers are figuring that the buyers are looking for more accurate and tighter bass than lower frequency...

Ha ha.. That's funny biggrin.gif Some of the funniest posts are the most serious posts imo.
post #18 of 47
What is really funny is at the latest GTGs featuring the best of the best in true high performance subwoofers of our day and true blind testing, no one could reliably pick "ported or sealed". Subs like a pair of submersives and a pair of captivators, to name a few. And these were guys who have auditioned many of the best, playing the same source materials, in the same environment.

So much for these descriptive adjectives frequently used like tight, accurate, fast, slow, tactile, articulate, warm.........yada yada.

Go read it for yourself. Its in the GTG links here on AVS. Archaea'a GTG I believe. Gotta love blind testing smile.gif the only way to fly.
post #19 of 47
There are real and substantial differences between sealed and ported. Sound quality, in a controlled test with properly set up subs, in the designed bandwidth of the sub, there wont be much difference.

The problem is that a lot of people don't compare properly. I see this all the time here.

Take, for example, the recent proliferation of the Klipsch RW12 in the forum. These are ported subs tuned to about 25hz. Well, I keep seeing reports of output down to 20 hz and below.

Yes, I'm sure they are making some sort of noise (and probably shortening the service life of the woofer) as the enclosure loses control of the woofer.

So this guy gets a hold of a Fathom, plays his test disc, and is overwhelmed by how clean and tight it sounds. My God! These sealed subs are awesome wink.gif

It is awesome when you aren't spewing 100 percent harmonics out a four inch hole. And so the myth is born.

There are valid reasons to chose either type, but they have more to do with your overall plan and direction for your system than anything else.
post #20 of 47
BTW the Fathom doesnt use a PR because that would make it a reflex design, just like ported, with all the size requirements that come with it.

IMO, as peoples budget goes up, their tolerance for fridge size boxes mixed in with high budget furniture goes down.
post #21 of 47
Quote:
Originally Posted by Tack View Post

BTW the Fathom doesnt use a PR because that would make it a reflex design, just like ported, with all the size requirements that come with it.
The advantage to a PR is that it's smaller than reflex. The net internal volume of the cabinet is the same, but the gross internal volume of the PR can be much smaller, as a PR takes up less room inside the cab than a long ducted port. A sealed cab that gives the best possible result in a sealed cab with a specific driver can be substantially smaller than either a reflex or PR that gives the best possible result with the same driver, but those best possible results will usually be with a considerably higher low frequency cutoff for the sealed than a reflex or PR.
post #22 of 47
Quote:
Originally Posted by Bill Fitzmaurice View Post

The advantage to a PR is that it's smaller than reflex. The net internal volume of the cabinet is the same, but the gross internal volume of the PR can be much smaller, as a PR takes up less room inside the cab than a long ducted port.

Agreed.

Quote:
Originally Posted by Bill Fitzmaurice View Post

but those best possible results will usually be with a considerably higher low frequency cutoff for the sealed than a reflex or PR.

True, but that can be manipulated with a combination of hardware, power and filters. But "it is what it is" once you specify your tune in a reflex design.
post #23 of 47
Quote:
Originally Posted by Tack View Post

Agreed.
True, but that can be manipulated with a combination of hardware, power and filters. .
To some extent. But if you must employ, for instance, 6dB of EQ boost to realize the same LF response as a VB or PR that will require twice the driver excursion, and four times the power. Not that it can't be done, the Bag End ELF is one example, but as is always the case with speaker design there's no such thing as a free lunch, what you save in one way you will pay for in another.
post #24 of 47
Quote:
Originally Posted by Bill Fitzmaurice View Post

To some extent. But if you must employ, for instance, 6dB of EQ boost to realize the same LF response as a VB or PR that will require twice the driver excursion, and four times the power. Not that it can't be done, the Bag End ELF is one example, but as is always the case with speaker design there's no such thing as a free lunch, what you save in one way you will pay for in another.

mmf! I never thought of that..
post #25 of 47
Yeah, there is no free lunch like the man said..........there is a huge difference between a Klipsch RW-12D and a JTR powered Captivator smile.gif
post #26 of 47
Quote:
Originally Posted by polizzio View Post

Yeah, there is no free lunch like the man said..........there is a huge difference between a Klipsch RW-12D and a JTR powered Captivator smile.gif

Ha ha.. Who in the world would state as such? Maybe this post pertains to another post I was just involved in?? I might have my answer. biggrin.gif
post #27 of 47
Quote:
Originally Posted by Tack View Post

BTW the Fathom doesnt use a PR because that would make it a reflex design, just like ported, with all the size requirements that come with it.

IMO, as peoples budget goes up, their tolerance for fridge size boxes mixed in with high budget furniture goes down.

There are ways to optimize a driver for deep extension in a tiny reflex enclosure, in fact many drivers like that exists. A mid/high Qts, with a very low Vas tends to do the trick. This type of driver is impossible to port without using a slot that ends up taking up as much or more volume then the woofer its self requires, leaving you with an overall box that isnt as small as you thought you were getting. Enter a PR, now we can simply heavily mass load a cone until it reaches the desired tune, with a miniscule effect on cabinet volume. Of course you need the correct PR for the application, but something like flat to the 20hz range from a 1 ft3 box is definitely possible.


Oh, and you can still shape the response of a reflex design with EQ/DSP, you just have to account for port velocity or PR excursion, as well as the active driver's excursion of course.
post #28 of 47
Quote:
Originally Posted by steve nn View Post

Ha ha.. Who in the world would state as such? Maybe this post pertains to another post I was just involved in?? I might have my answer. biggrin.gif

I seriously don't know what your talking about? another post? I was being somewhat sarcastic in my statement about the klipsch and jtr smile.gif
post #29 of 47
Quote:
Originally Posted by polizzio View Post

I seriously don't know what your talking about? another post? I was being somewhat sarcastic in my statement about the klipsch and jtr smile.gif

Yes I know that, sorry for thinking out loud pertaining to another thread. cool.gif
post #30 of 47
Quote:
Originally Posted by Jay1 View Post

There are ways to optimize a driver for deep extension in a tiny reflex enclosure, in fact many drivers like that exists. A mid/high Qts, with a very low Vas tends to do the trick. This type of driver is impossible to port without using a slot that ends up taking up as much or more volume then the woofer its self requires, leaving you with an overall box that isnt as small as you thought you were getting. Enter a PR, now we can simply heavily mass load a cone until it reaches the desired tune, with a miniscule effect on cabinet volume. Of course you need the correct PR for the application, but something like flat to the 20hz range from a 1 ft3 box is definitely possible.

Well, I was speaking in general terms but you're right about the small PR. A 1 ft³ PR box will be no output monster, but you can have something that's flat to tune in a small box I guess. Depends on your goals.
Quote:
Originally Posted by Jay1 View Post

Oh, and you can still shape the response of a reflex design with EQ/DSP, you just have to account for port velocity or PR excursion, as well as the active driver's excursion of course.

Yes you can, above tune. There's nothing to be done below that.

I'm not trying to correct you, I just don't want anybody to get the wrong idea and sack their driver. " Dood I got 124db at 10hz from my PB12!" wink.gif

Speaking of DSP, I always wondered why JL kills the output on the Fathom at around 20hz. They have a good amount of amp and a beefy driver and they pretty much cut the legs out from under it.
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