IME and IMO, the most important factor is the driver's Qts; the best overall results will be achieved if it's in the range of 0.35 to 0.5, although depending on other factors, a somewhat lower or higher value can give acceptable results. The larger Vas is, the larger the enclosure's volume will likely be necessary. The lower the driver's Fs is, the lower F3 will likely end up provided the line has adequate volume. Sd comes into play primarily in how wide the cabinet (line) needs to be. A TL won't care what the driver's cone is made of.
Paul
Paul
Correct, any point source driver can successfully be TL loaded over some gain BW, Fp, so the question should be 'what specs are best overall for a given gain BW and Fp?'
GM
GM is 100% correct but my comments about what to look for in a driver that would likely give good to excellent results in a TL come from the practical side. Other things being equal, the higher Qts is, and Vas, the larger the necessary box. Also, other things being equal, the lower Qts is, the higher F3 will likely be. So, like many aspects of speaker design, you'll have to make compromises; on box size or F3 or perhaps both, and I'd much rather choose a driver in the first place that has a high percentage probability of working really well without needing a 5 ft3 box or living with an F3 in the 50s.
Paul
Paul
There are too many variables and there are too many ways (equations) to achieve good result. Usually we have one or more fixed variable and solve for the other variables.
For example, one fixed variable is a driver on hand, and then next variable can be lowest frequency response or minimal box size or others.
But it is rarely the TL enclosure type as the fixed variable. I will surely avoid TL, if I haven't yet had any fixed variable.
But people might be impressed by a certain TL design and want to duplicate similar performance. So I think I will use Qts as the parameter to limit driver choice, as other has mentioned. And then may be sensitivity, because TL kills speaker sensitivity.
Absolutely wrong. A TL does not "kill sensitivity". The sensitivity is inherent to the driver, plus how you implement the TL design. In a tapered TL, for instance, if you stuff the TL at too high of a density and/or too much of its length, you will kill all of the output from the terminus, which will eliminate all of its contribution to the bass, but that's not the TL's fault.
Paul
Paul
Not so, as others have noted above. Since like any rear-load a transmission line only operates over a restricted BW, it only affects that BW (notwithstanding potential distortion if you so chronically over-stuff it that the high acoustic mass deforms the cone under dynamic loads). Equally, as also noted, if you design a TL with the objective of using its output to provide additional LF gain, and then stuff it to ~aperiodic levels, that's really not the fault of the box.
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interesting comments Scottmoose. Are you therefore saying that an aperiodic stuffed enclosure, potentially causes higher THD due to cone flexture? I would imagine that make many soft cone, stuffed TL, sealed box and horn advocates a little dismayed. I can see your logic, and in the persuit of low distortion reproduction, that realisation would seem to point to rigid coned, multiway systems, where all possible efforts are made to keep breakup flex totally out of band. If i am right in this assumption, then i am surprised that you are of this opinion, inview of my previous impressions of your preferences.
this is the driver lying around, which i want to put to use. spec wise, its Qts is very high to be considered for TL, but if i am ready to compromise upto 50 or 60hz, then will this driver give good results in TL? will Xmax of 6.5mm is helpful in this regard?
Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories
Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories
ah! The ws25e!
Very high Qts. This woofer is optimised for 'free air' open baffle or ripole use. Sealed box you will always have a bass hump. Vented box would be HUGE, but you could get it flat, but several hundred litres would be needed. In this respect a TL would also be enormous. Take a look at the visaton 'Orgue' and 'Grand Orgue' as they point to the most practical use for this driver. Same goes for the w20e8. Both are a cheap way into dipole bass In my opinion, anything else is impractical. Try it in a 8x4 sheet of ply, you will be surprised.
Very high Qts. This woofer is optimised for 'free air' open baffle or ripole use. Sealed box you will always have a bass hump. Vented box would be HUGE, but you could get it flat, but several hundred litres would be needed. In this respect a TL would also be enormous. Take a look at the visaton 'Orgue' and 'Grand Orgue' as they point to the most practical use for this driver. Same goes for the w20e8. Both are a cheap way into dipole bass In my opinion, anything else is impractical. Try it in a 8x4 sheet of ply, you will be surprised.
No, I'm saying that is a potential consequence of heavily over-stuffing a pipe. On occasion, it may follow that the quantity required for ~aperiodic behaviour and the near total flattening of the impedance load may be sufficient to deform a cone under dynamic load conditions, particularly with some relatively flexible types, but that is not the case in all, or even the majority of cases. Depends on the individual driver & pipe requirements. Like anything else, it's a question of needing to take all factors into consideration, or at least, try to cover as many as possible.
Rigid cones will ultimately be less likely to deform. However, we're talking about relatively unusual conditions, viz. pipes that have been extremely heavily stuffed which isn't often the case.
My preferences? A speaker I can ignore, frankly, and there aren't many of those. 99.999% of the speakers I design for forums etc. are for other people, not me, so they don't necessarily reflect what I happen to like, although they may reflect my opinion.
@ scott, id just got the impression you were a full range fan, perhaps that was my mistake after all. As for the OP question, would you have room for a TL using the W25E8? when last i tried a vented box for these, I needed a box volume of 400litres or more...and i cant see a TL being any smaller.
Is there any better objective?
It is how the response rolls off at low frequency that makes TL interesting, is it not? I think most box design objective have relationship with the low frequency performance.From all TL that I have seen, it operates more or less like introducing Linkwitz transform circuit, which can be understood if the sensitivity would be reduced.
My opinion is purely based on listening observation (not theory). So if you design TL speakers with different objective, can you mention what they are?
BTW, I'm curious. Have you ever tried to design the best speaker for the same driver, and put them in different enclosure (e.g. one in TL and another in vented/sealed) and listen side by side? How was your preference then?
A reasonable Xmax is worth having, although there is actually no universal standard. 10% distortion is commonly taken, but there are others. Q is over .707, so it will need considerable damping to be flattened out entirely. However, slightly more reasonably, here's a max flat impedance alpha TL for example:
56.716in long
58.28in^2 CSA
Driver tapped in 19in from throat.
Uniform stuffing density (polyester) 1.49 lbs ft^3.
The alphas are quick & simple boxes; you can better them in many ways but they work reasonably, and in this case, the prime object was simply to flatten the impedance.
A good wideband driver is an excellent choice for small spaces & nearfield apps., but I'm perfectly aware of their limitations. I often work with them because they make an interesting challenge.
Depends how you define 'better.' I prefer to say there are different objectives that vary depending upon requirements.
Not automatically, no. It can be, but this too varies. Another perfectly valid goal is to provide the flattest impedance that can practically be attained, as in the example above / below. By the strictest definition (rarely applied), that is exactly what an acoustic TL is: a box with the sole object of providing the flattest impedance. A third, often employed with MLTLs or lightly damped, high-taper pipes, is to use the QW resonance of the box to allow a lower F3 than might be possible with a BR.
To attain whatever the design goals may happen to be. I don't have any universal 'objective' since these necessarily vary depending upon requirements / circumstance.
Note that 'TL' has become something of a catch-all term which is often employed to describe boxes which in fact are almost the exact opposite of each other.
Not really, since that a/ implies the cabinet is an afterthought, and b/ that both enclosures have exactly the same design goals, which is rarely the case. When I design something, I establish the basic objectives first, and then decide upon the enclosure type based upon these criteria.
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what 'free air' means!?Very high Qts. This woofer is optimised for 'free air' open baffle or ripole use. Sealed box you will always have a bass hump. Vented box would be HUGE, but you could get it flat, but several hundred litres would be needed. In this respect a TL would also be enormous. Take a look at the visaton 'Orgue' and 'Grand Orgue' as they point to the most practical use for this driver. Same goes for the w20e8. Both are a cheap way into dipole bass In my opinion, anything else is impractical. Try it in a 8x4 sheet of ply, you will be surprised.
how about employing these woofers in MTM configuration in an OB something like Linkwitz's Phoenix (Dipole Main Panel). can i expect some bass down to atleast 60 hz this way?
We (almost) do this quite often, I design my style miniOnken, Scott designs TLs & horns, when Chris builds 2 for the same driver so we can compare. The goals of these enclosures are different, they both sound good (we don't talk about the ones that hit the fire during the monsson season), and one can hear that. Which works best for you, only you can decide. Each design has its balance of strengths & weaknesses.
Chris lives mostly with a set of Scott's speakers, Scott lives with a pair of ours. I have more of a round robin.
dave
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