I always understand that the sealed enclosure has a better transient response than the vented enclosure and may be in the top position compared to other enclosure types.
Recently, my friend, who is a fan of the transmission line system, told me that the TL gives overall better performance than the sealed enclosure. He described that the TL won't produce any emphasis on the bass like the sealed system, no matter how well designed it is, and the TL gives a better transient response.
Unfortunately, when I tried reading Vance Dickason's cookbook, there was little information in the TL chapter compared to the sealed and vented chapters.
All in all, Is my friend correct?
Recently, my friend, who is a fan of the transmission line system, told me that the TL gives overall better performance than the sealed enclosure. He described that the TL won't produce any emphasis on the bass like the sealed system, no matter how well designed it is, and the TL gives a better transient response.
Unfortunately, when I tried reading Vance Dickason's cookbook, there was little information in the TL chapter compared to the sealed and vented chapters.
All in all, Is my friend correct?
It's possible to build transmission lines you'd find comparable to closed. Until alignment tables were formulated I'd guess transmission lines were one of the most widely interpreted enclosure types. Perhaps as reflex were before reflex alignment tables told builders to keep their volumes and port dimensions within constraints.
So find out how your friend developed this view.
So find out how your friend developed this view.
The amount of airspace damping in a TL has a determitive affect on the low frequency alignment.
A TL is a box with one dimension significantly larger than the other 2. Usually with a hole. This gives it an impedance response like a reflex with 2 large bumps plus a number of smaller ones as one goes up in frequency that are caused by the quarter-wave resonances.
One usually adds at least sufficient damping to (mostly) kill the upper ripples and one ends up with a response that looks like a reflex. Transient performance should be similar. Response is usually lower than a reflex due to the aid of the quarter-wave resonance.
At the other end of the spectrum is stuffing until aperiodic with any impedance peaks (mostly) flattened. This can have transient performance better than sealed (ref Perkins). Roll-off is slow.
extreme: Take it further and you plug the line and get a sealed box of some sort).
So given there are more degrees of freedom in a TL than a sealed box you have to be much more specific than TL to get a simple answer.
dave
A TL is a box with one dimension significantly larger than the other 2. Usually with a hole. This gives it an impedance response like a reflex with 2 large bumps plus a number of smaller ones as one goes up in frequency that are caused by the quarter-wave resonances.
One usually adds at least sufficient damping to (mostly) kill the upper ripples and one ends up with a response that looks like a reflex. Transient performance should be similar. Response is usually lower than a reflex due to the aid of the quarter-wave resonance.
At the other end of the spectrum is stuffing until aperiodic with any impedance peaks (mostly) flattened. This can have transient performance better than sealed (ref Perkins). Roll-off is slow.
extreme: Take it further and you plug the line and get a sealed box of some sort).
So given there are more degrees of freedom in a TL than a sealed box you have to be much more specific than TL to get a simple answer.
dave
The transients are related to LF roll off: 2th order, 3th order 4th order and so on. The steeper, the more ringing.
But that is too simple: to summarize all the above: until Thiele and Small appeared on the scene, the general idea was that the various types of LF loading were -sort of- mutually exclusive.
Thiele and Small plus the development of LF simulation software have shown that the various types of LF alignments are actually a continuum: dependent on the way of tuning and dimensioning a reflex enclosure can almost be tuned as closed box (Cordell) a TL can be tuned as a reflex and so on. With e.g. filter assisted alignments even a closed box can be tuned as a 4th order standard reflex.
Furthermore , the continuum allows software that is basically designed for Horn design (e.g. AJHorn, Hornresp) is also capable of closed box or reflex enclosures: at the end of the day it is all a matter of parameters.
But that is too simple: to summarize all the above: until Thiele and Small appeared on the scene, the general idea was that the various types of LF loading were -sort of- mutually exclusive.
Thiele and Small plus the development of LF simulation software have shown that the various types of LF alignments are actually a continuum: dependent on the way of tuning and dimensioning a reflex enclosure can almost be tuned as closed box (Cordell) a TL can be tuned as a reflex and so on. With e.g. filter assisted alignments even a closed box can be tuned as a 4th order standard reflex.
Furthermore , the continuum allows software that is basically designed for Horn design (e.g. AJHorn, Hornresp) is also capable of closed box or reflex enclosures: at the end of the day it is all a matter of parameters.
This can be the case if the incompressible resonance of the line is designed to be well below 20 Hz and only the low frequency output from line is used to enhance the bass with all compressible resonances effectively damped in the line. However, it is common to use incompressible resonances at frequencies above 20 Hz to enhance the bass output in which case it becomes debatable.
Having said that the low frequency transient response of a speaker is normally irrelevant compared to the much worse transient response of the room. If the drivers are of adequate size for low frequency reproduction (e.g. 10-12" cones) ported speakers can have their resonances and poor transient response at frequencies down towards 20-30 Hz where they have no practical effect on sound quality. This is not necessarily the case with small ported 5" midwoofers with resonances at significantly higher and more audible frequencies. So if you have a 5" midwoofer with parameters appropriate for a TL it may work well (apart from being large and complex which possibly defeats the point of using a small 5" midwoofer in the first place!).
Transient response is best without addition of a resonance system like bass reflex or transmission line. The more the resonance is damped the more the total system will act like a closed system with a significant leak (low Ql).
Note that a sealed system transient behaviour is dependent on the Qt , the theoretical ideal is 0.707, primarely influen ed by box volume for given driver.
Putting the Qt on 0.9 or so will measurable give a small increase above res freq, but sound more bassy/boomy.
The box itself can also influence what we hear.
Bottom line, it all depends on your personal impression which you will like best.
Note that a sealed system transient behaviour is dependent on the Qt , the theoretical ideal is 0.707, primarely influen ed by box volume for given driver.
Putting the Qt on 0.9 or so will measurable give a small increase above res freq, but sound more bassy/boomy.
The box itself can also influence what we hear.
Bottom line, it all depends on your personal impression which you will like best.
Depend on the criteria. For your friend better extension in the bass, yes a TL does better. The TL is the box has the least boxy sound although you have mid-range resonance to deal with. The closed box is the box with more boxy sound.
For you : Transient response, a closed box does better.
No definitive response for your question. Question of choice to get the best result according to your constraints.
For TL see Martin J King site, an amazing work.
For you : Transient response, a closed box does better.
No definitive response for your question. Question of choice to get the best result according to your constraints.
For TL see Martin J King site, an amazing work.
I'm afraid your friend is wrong, unless he can indicate exactly what he means -perhaps there is some unusual characteristic he's referring to but wasn't specific over. A sealed box with a Qtc of 0.5 is usually defined as 'critically damped' with minimal ringing (slightly questionable terminology but popular); being a well-damped alignment by definition it doesn't have any 'emphasis' (i.e. excess gain) in the LF. No system Qtc < 0.707 does.
I suspect he is confusing sealed boxes with poorly designed (not necessarily a given) traditional reflex enclosures; Bailey's original Wireless World article, almost entirely useless as it is for design purposes beyond copying exactly what he created, illustrated reduced ringing compared to those via an impulse response generated by exploding wires.
Going back to either side of 1970 when my father was buying speakers sealed box units seemed to be all that was around. I recollected vented being boomy being mentioned. He eventually bought AR's known at the time for accuracy. Curiously A3's sounded better to me compared with some of their larger stuff. The strange shaped ones often used in opera houses were good too. Size of the 3's suited so bought. An independent test showed that the bass boost switch worked and the room is expected to boost this end on sealed enclosures.
He had also owned some warfdale sealed unit's. Shelf mountable sized volume probably similar to the AR3's. The difference in sound from the AR's caused me to think of the term warfdale sound. I'd guess transient response relates to this and a number of other brands were similar.
Around 20years ago I wanted some speakers for a holiday home. Didn't want to spend much and found some secondhand warfdale lasers. 3 way units with stands to help the bass response. Vented. Bought with some misgiving but they turned out to be pretty good. As they were initially connected to an amp with a bass boost switch the response gave me earache not that the excess bass was that noticeably. No signs of the warfdale sound. The name came about as they started using lasers for cone analysis.
I suspect the message is things move on and aspects like transient response depends on what speakers are bought. DML's are interesting in this area
but can have other "problems".
He had also owned some warfdale sealed unit's. Shelf mountable sized volume probably similar to the AR3's. The difference in sound from the AR's caused me to think of the term warfdale sound. I'd guess transient response relates to this and a number of other brands were similar.
Around 20years ago I wanted some speakers for a holiday home. Didn't want to spend much and found some secondhand warfdale lasers. 3 way units with stands to help the bass response. Vented. Bought with some misgiving but they turned out to be pretty good. As they were initially connected to an amp with a bass boost switch the response gave me earache not that the excess bass was that noticeably. No signs of the warfdale sound. The name came about as they started using lasers for cone analysis.
I suspect the message is things move on and aspects like transient response depends on what speakers are bought. DML's are interesting in this area
but can have other "problems".
That's actually a very easy topic. Transmission line and reflex GAIN significant low frequency level, 6-10dB. And they achieve that with a resonant system.
Helmholtz or lambda 1/4 tube ... both are resonators. Efficiency and (impulse) response depends on the Q of your system - you don't gain that much level for "free".
A closed volume doesn't add anything to the response of the driver (ok, it rises the Q of the over all system). So it's more or less impossible to get better transient response with a resonant system then a closed system with low Q (0,5-0,6).
Nevertheless - these resonant systems also have their pro's (less excurison, less THD, more max level, higher sensitivity without EQ), but sound quality is normaly not one of them.
Helmholtz or lambda 1/4 tube ... both are resonators. Efficiency and (impulse) response depends on the Q of your system - you don't gain that much level for "free".
A closed volume doesn't add anything to the response of the driver (ok, it rises the Q of the over all system). So it's more or less impossible to get better transient response with a resonant system then a closed system with low Q (0,5-0,6).
Nevertheless - these resonant systems also have their pro's (less excurison, less THD, more max level, higher sensitivity without EQ), but sound quality is normaly not one of them.
A closed box resonance consists of the mass of the cone assembly and the stiffness of the suspension + trapped air volume. It is a resonance which can be used to increase output.
A line can increase output by delaying the output of the rear radiation until it is in phase with front and adds constructively. This is not resonant. Resonances can be added to the line to increase output but they are optional.
The closed volume modifies the free air resonance of the driver. It get's higher in frequency and Q. That's the inherent resonance you have with a speaker anyways! Just make your volume big enough to keep Q in the wanted area.
Your thought experiment about a line is nice - but it's ALWAYS a half open pipe. Look at the pattern of peaks and dips and the impedance of the driver in an undampened line (which shows the working principle - dampening just modifies and brings additional losses into the game).
Your thought experiment about a line is nice - but it's ALWAYS a half open pipe. Look at the pattern of peaks and dips and the impedance of the driver in an undampened line (which shows the working principle - dampening just modifies and brings additional losses into the game).
Not exactly. 'Transmission Line' was always a hazy term at best and even from the get-go in audio was essentially used to describe partially resonant lines; it's since (like it or no -I don't but we're never going to get shot of it) become used as a catch-all synonym for pretty much any quarter-wave design, spanning the gamut from heavily damped max-flat impedance types to resonant designs where the eigenmodes are used as an alternative to Helmholtz to load the LF. In the former case the damping is there to suppress output & flatten impedance; in the latter it's used, usually in conjunction with other acoustical design elements (mass-loading, offset drivers, termini etc.), to attenuate the unwanted harmonic modes while preserving the fundamental.
A "quarter wave design" is simply a pipe which is on one end closed and the other end open. This gives a resonance at 1/4 of the wavelength. The PRINCIPLE of it is the resonance.
For getting it work in an HiFi context you need to dampen it cause it has a lot of unwanted side effects. But this doesn't change the principle behind it - a resonance of the pipe.
You can also make good sounding bass reflex constructions when you don't let them resonate to much. The same with transmission line. And still a closed box setup is less resonant (if not done really brutal). Independed of what sound you prefer. (I regularly find that people are used to some resonance and they miss some "boom" with a precise system)
For getting it work in an HiFi context you need to dampen it cause it has a lot of unwanted side effects. But this doesn't change the principle behind it - a resonance of the pipe.
You can also make good sounding bass reflex constructions when you don't let them resonate to much. The same with transmission line. And still a closed box setup is less resonant (if not done really brutal). Independed of what sound you prefer. (I regularly find that people are used to some resonance and they miss some "boom" with a precise system)
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Transient response is straightforward to evaluate from the relevant transfer functions and if this is done there is no ambiguity about what is what. I would suggest the main reason we have threads like this is because people opt not to do the homework, build both and are then not on top of what is going on when they have a listen. And so it continues. Perhaps we need a reliable source of information to point at when people have questions like this? There is of course vast amounts of unreliable information to point at on the web which is likely part of the problem.