Much more compact and practical, with the additonal benefit of reduction of the impedance peak which an undamped infinite line will not.
dave
Does this question actually lead to some practical knowledge for the task? And if so...what are you trying to point out? You asked me what I meant by backwave. I said its the sound wave coming from the backside of the driver.
Incorrect, but from your dialog I think you know that this true already.
- Think in practical terms of loudspeaker enclosures..."In short, because lower frequencies have a higher transmission coefficient for most building materials. You could be quite advanced and solve for the transmission coefficients based on the actual molecular physics involved using kinetic theory. Notice that ultrasound also penetrates most materials easily; so it just happens that treble frequencies, like 5k-10k, are near the vibrational modes of many common molecules, while frequencies above and below don't."
Source Why can bass travel through walls so easily? | Physics Forums
Interesting stuff about 5k-10k...
The watt (symbol: W) is a unit of power.
The loudness button? lol. Spectral energy distribution in music is, generally speaking.....closer to neutral, on the 1/3 octave scale. Yes. Some music is bass heavy or mid heavy etc etc... generally speaking, when I master music, I want an even spectral balance
e·ven
/ˈēvən/
flat and smooth.
lin·e·ar
/ˈlinēər/
arranged in or extending along a straight or nearly straight line.
Excuse me for not making myself clear. Lets back up. I said that shortening effective panel dimensions via bracing raises the resonant note and Q, and I compared the higher Q of the panel resonance to a high Q filter. So what happens here is that the spectrum width of the note is decreased, like a high q filter, and thus, less perceivable...Planet10 explained it already here Enclosure design - Exactly what is required?
I understand you now, hopefully the I've made myself clear now as well.
Semantics....I just mean that there is no considerable... noticeable.... effective.... pressure variation, coming out of the terminus.... as Planet10 confirms "Aperiodic midTLs attempt to completely absorb the rear radiation." Calling it a midTL, only, is a little biased...I personally wanted that response for my subwoofer. My perspective is biased on TL's in general, I know am not dead on right, but I am closer than most....for the original TL designs (and I say original loosely...maybe early is a better word), this was always the goal, and in reference to "Build a TL, stuff it until the port is completely silent. This system behaves about the same as a closed box" about the same, equals, not the same, but after I studied TL for a while guess what I came to the conclusion of....I'm building a closed TL, not a vented one lol, and here is where TL still comes out ahead of a basic rectangle box completely open inside. The trend still remains, a closed TL will have lower resonant energy, in connection to the aspect of channelling the back wave though a line of a heavy damping material. The longer the line, the greater potential for absorption with the use of damping material....if I recall, I was saying it is wise to understand this aspect, while building any enclosure.
In the words of the wise...the different enclosures have a different set of compromises. It wise to see where and how these different compromises come about, in that you may be able to add bits and pieces of one style to another...in order to exacerbate and effect...as I have done with an design of an "improper" half wave line... "improper" that it is tuned to a note I would not exactly have purposely chosen, yet there are no undesirable side affects of this choice and the desired affect of further decreasing resonance IS achieved, which is basically, a win.
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I thought about that for a second....then I was like ooooooooooh lol. Hmmm.... I serendipitously ended up with my sub design have each driver aligned to force cancellate...my goal was really just to find a way to get the output of 2 drivers on one plane... without pushing the dimensions larger.....guess that it is a blessing in disguise
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@Camplo
I wouldn't discourage you in your search to perfection. Only stating a TL is just as good an alternative to other solutions simply isn't true. It's design is much harder and requires a lot of trial and error, be it in real or with the aid of BEM software. Certainly when any form of mass loading of the line enters the equation things become complicated. Other solutions are much simpler to predict.
Your assumption that you need a full, half or quarter wavelength to get damping materials like mineral fibers or foam to work on that specific frequency hasn't been backed up by measurements or by any theory, at least to my knowledge. You need air movement for it to work, but not necessarily a wave. In your solution the open end of the TL can be closed and you won't notice the difference. What you might consider is that the actual construction of the line behind the driver could add mass loading components or other artifacts that influence the response of the driver in the enclosure. Happens a lot in TL designs, but this has nothing to do with (real) transmission lines.
Your quote from Physics Forum: I think this is funny. In a past long ago at the acoustics lab of my university we never came to such conclusions about ultrasound. Mass law, bending waves et cetera yes, but ultrasound? By the way. 5-10k disqualifies as ultrasound, I don't have to tell you that. And molecular resonances occur, but they seem to lead to absorption, rather than transmission. That aside, we're talking megacycles here.
I wouldn't discourage you in your search to perfection. Only stating a TL is just as good an alternative to other solutions simply isn't true. It's design is much harder and requires a lot of trial and error, be it in real or with the aid of BEM software. Certainly when any form of mass loading of the line enters the equation things become complicated. Other solutions are much simpler to predict.
Your assumption that you need a full, half or quarter wavelength to get damping materials like mineral fibers or foam to work on that specific frequency hasn't been backed up by measurements or by any theory, at least to my knowledge. You need air movement for it to work, but not necessarily a wave. In your solution the open end of the TL can be closed and you won't notice the difference. What you might consider is that the actual construction of the line behind the driver could add mass loading components or other artifacts that influence the response of the driver in the enclosure. Happens a lot in TL designs, but this has nothing to do with (real) transmission lines.
Your quote from Physics Forum: I think this is funny. In a past long ago at the acoustics lab of my university we never came to such conclusions about ultrasound. Mass law, bending waves et cetera yes, but ultrasound? By the way. 5-10k disqualifies as ultrasound, I don't have to tell you that. And molecular resonances occur, but they seem to lead to absorption, rather than transmission. That aside, we're talking megacycles here.
It might seem that I am suggesting to build a TL, which I might have indirectly (and sarcastically)...you are reading into things a little too much, there isn't even a connection between 5-10k to ultra sound in that guys quote....
I point to TL as a way of exposing what an enclosure is capable of, with certain traits...those traits can be transferred to other enclosures without them being a TL.
Bracing that breaks up the internal dimension and channeling of the sound energy into damping material is probably all one needs to take away.
I point to TL as a way of exposing what an enclosure is capable of, with certain traits...those traits can be transferred to other enclosures without them being a TL.
Bracing that breaks up the internal dimension and channeling of the sound energy into damping material is probably all one needs to take away.
As long as it doesn't influence things in a detrimental way, as I've stated. There is no open end of a TL, there are vented transmission lines and closed transmission lines.
I do not point to any specific frequency but open up hornresp, and you will see that damping material is more effective in a line, than not in a line. If anyone has ever measured an aperiodic TL, is we tend to call it here, there is your measurements and its old news by now.
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Yes there is, though the whole quote breathes so much vagueness to me that I'm going to skip that forum altogether 😉
Probably. Filling the enclosure with good absorption has proven to be very effective and above all enough, the need for lines is absent.
Furthermore, an internal volume in a CB or even a BR behaves like a reasonably simple air spring that loads the diaphragm, damping materials do not change that very much. Changing the simple (linear) acoustic load on the diaphragm to a complex one that isn't easily predictable seems not logical, certainly when folding the line brings further issues. It may be fun, though.
With a modern modeler in the hands of someone who knows what they ar edoing there is no more trial & error than in building a BR enclosure. This statement starts to stray from reality when one is working towards aperiodic as we do not yet have sufficient coefficients for the damping as density increases beyond what we have real measured data for.
And on the subject of an aperiodic box being essentially the same as a sealed box, there is some small amount of real-world data that disputes this.
dave
Lol it’s funny you should say that, I was thinking that your technical expertise was probably causing you to be annoyed some of the untechnical presentations in my responses but non the less...I’m at work right now can’t reply to full extent.
Bump, does the basket of abass or mid driveris transmiting vivration into thefront panel or is it only mainly theback wave, please?
The cabinet is vibrated primarily by the drivers. The internal air pressure can become significant at the lowest frequencies for something like a subwoofer in a small sealed cabinet (for example). At the frequencies of the cabinet resonances the only significant forcing will be from the driver/s for reasonable cabinet designs.
Thank you Andy for that input.
So we can all agree that an important part of a cabinet design is to damp that vibrations at the coupling meeting between the driver and the cabinet. So Young modulus could be primarily chose for the coupling material between the driver baskett and the cabinet and or front plate (thinking about Dynaudio high end models with decoupled front plates) ?
Is there ring with such material to tie the driver on the front plate....rubber ring being the best if I remember my reads about Young modulus and damping ? Then decouple the small front plate where the driver is coupled with a further high damped barrier (glue, rubber, isolation pads, etc) to the main cabinet? Spring mass spring model ?
So we can all agree that an important part of a cabinet design is to damp that vibrations at the coupling meeting between the driver and the cabinet. So Young modulus could be primarily chose for the coupling material between the driver baskett and the cabinet and or front plate (thinking about Dynaudio high end models with decoupled front plates) ?
Is there ring with such material to tie the driver on the front plate....rubber ring being the best if I remember my reads about Young modulus and damping ? Then decouple the small front plate where the driver is coupled with a further high damped barrier (glue, rubber, isolation pads, etc) to the main cabinet? Spring mass spring model ?
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It depends. The frame+magnet of a sub/woofer typically benefits from the addition of the mass of the cabinet in order to reduce the movement caused by the reaction to the moving mass of cone+air. The mass of the frame of a tweeter on the other hand is usually sufficient compared to the moving mass. A midrange is debatable. Some opt for isolation whereas I would lean more towards isolating the midrange cabinet but with a rigid connection to the driver. The pros and cons are close.
If you opt for isolation then that means something like rubber grommets because the resonant frequency of the driver on the soft mounting needs to be at least a decade or so below the lowest frequency of the driver. A softish gasket may place the resonance in the passband and make things worse.
I didn't wholly follow what you were suggesting.
Hey, trade offs...good to know. My first post before was about to know the part coming from the basket and the part coming from the back and front waves on the cabinet. We have to know the level of each... sort of.
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No new insights though. Driver-enclosure decoupling came up in the late ‘70s, early ‘80s, iirc. I think Linkwitz even paid attention to this in his Wireless World publications. And we’ve seen magnet fixation in commercial designs for decades now. KEF RR104/2 comes to mind here. And this shouldn’t surprise us, research on enclosures has been extensive through the years. Fortunately, it has become nit-picking even for us DIY-ers. Iin normal listening conditions even a mediocre enclosure design does hide it’s flaws and only compared directly to good designs will fail. But how many of us can and will go that length?
[Edit]The Wireless world articles still reside on Linkwitz’ site. A must-read for a lot of us here, the thoroughness of the designs will stun many. And this was 1978.
[Edit]The Wireless world articles still reside on Linkwitz’ site. A must-read for a lot of us here, the thoroughness of the designs will stun many. And this was 1978.
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Kef 107 Ref, Kef 104/2 Ref... Nice Loudspeakers, the isobaric chip board cabinets with coupled woofers design iirc and top quality finition were even better than the drivers themselves... sota quality and pairing... Just don't understand one not try to do the same with modern drivers... well the price and difficulty maybe... poor margin with nowadays standard I surmise...😱
Britanic class at its best😎
Britanic class at its best😎
The woofers in the 104/2 were not isobarik, they were bandpass and one of the 1st commercial use of push-push mounting to actively cancel reaction forces.
dave
dave
oups... thanks, indeed the space between the two drivers is not sealed, there is a port...
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Context confines a discussion to what's important. It reduces misunderstandings. Not including it when expected can cause problems.
Eg, in a pure theoretical look at TLs the concept of bracing does not exist, yet when building a TL the brace is important and somewhat unique. If you simply said you learn bracing by studying TLs, someone might say that bracing has nothing to do with a TL, it has to do with box construction.
Further, and it's good that you got into hornresp, if such a tool were to include effects like the TL bend resonance or modes in more than one dimension then I'd like the option to turn those calculations off to keep development focussed at one stage, another example of context.
I referred not only to the woofers, the midrange units had magnet assemblies fixed to the back of the enclosure in order to decouple the drivers from the baffle. Smart engineering.