I've also found that sometimes there's something non-obvious going on, and expectations based on inaccurate theory can be upset by observation.
One such case was where I had a pair of 10" woofers in sealed boxes, and I was experimentimg with changing the damping factor by adding 10 ohms in series. The amplifier was connected to a PC with a parametric equalizer with independently adjustable gain, centre frequency, and Q, and in both cases I could make precise corrections.
There was a resonant mode at about 40Hz, which appeared to be the speaker's natural resonance combined with some kind of room resonance. With the resistors in place, the amount of equalization actually had to be reduced: a shallower notch with less dB of attenuation and lower Q. Rather than rely on visual aids like frequency sweeps which can often bring meaningless results at such low frequencies, I relied on a music keyboard with a pitch-bend function to fine-tune the bass by hand to the level of a semitone.
The results went totally against some of the popular threads of maximising damping factor for 'tight', "non-boomy" bass, and led me to question what the heck people were referring to. Tight like a drum skin that goes 'ping'?
It didn't make sense because in theory there should have been more overhang and less control, leading to more resonance. But then I realised that the room was also an enclosed space with another air-spring, and that's what needed to be non-resonant, cone position be damned.
What sort of clarification are you after?
The short version is that there's no generic answer other than 'it depends on exactly what is being compared'. As-written though, what the OP was told was twaddle, as described above. But going through it again:
The only sealed boxes that 'produce any emphasis on the bass' are those with a Q > 0.707. By definition, those with a Q of < 0.707 don't (can't). An open TL can provide equivalent damping to a sealed box, until it eventually unloads 4th order, but that's the best it can manage.
Same again: it depends on what's being compared. For example, if you've a critically damped sealed box (Qtc =0.5) then that is already the optimum -you can't actually do better than that. You may be able to more or less equal it (until unloading) with an open TL or even a very low tuned EBS vented box alignment (in that case providing the programme material doesn't contain any frequencies at or < Fb) but that's all. A well-damped TL may be superior in this regard to an underdamped or less well-damped sealed alignment, but as noted this is circumstance dependent since TLs and their alignments vary just as sealed boxes and their alignments vary, so you have to know exactly what they are as generic terms like 'sealed' and 'TL' can't tell you anything by themselves.
For a truly crazy transmission line, Nelson Pass's El Pipe-O takes some beating https://www.firstwatt.com/pdf/art_elpipeo.pdf
The most telling sentence in that link is
"Funny things happen when your speakers are flat to 13
Hz. You have to be careful about your tone arm, your
windows, your neighbors, and your bowels"
The most telling sentence in that link is
"Funny things happen when your speakers are flat to 13
Hz. You have to be careful about your tone arm, your
windows, your neighbors, and your bowels"
Yeah I bet if alignment was similar, system Q similar between any box type, then any difference in sound would be from outside dimensions of the structure and how sound interacts with it and the room considering crossover, what happens inside the enclosure, how panels resonate and so on. Heat transfer and maximum SPL capability are some other considerations that might matter, as well as looks and positioning and stuff like this.
Sealed box is simple, but could lead to some "box sound" if dimensions cannot be optimized due to some reason, like other transducers needing to fit the same structure or get transducer to some particular height or something, or bandwidth being too great. Sometimes TL or other "elongated" structure could work better, but is more work, nothing wrong with that.
So, my logic says that choosing a box type is not determined by "bass" but the whole system concept, everything else in the system except bass. Exactly opposite as usual intuition that " for best bass use TL/sealed/ported/horn/whatever", which doesn't matter at all, any bass can be achieved with any of these, and only difference is what problems or issues happen elsewhere, as compromises on the midrange / size / looks/ wallet / schedule.
Sealed box is simple, but could lead to some "box sound" if dimensions cannot be optimized due to some reason, like other transducers needing to fit the same structure or get transducer to some particular height or something, or bandwidth being too great. Sometimes TL or other "elongated" structure could work better, but is more work, nothing wrong with that.
So, my logic says that choosing a box type is not determined by "bass" but the whole system concept, everything else in the system except bass. Exactly opposite as usual intuition that " for best bass use TL/sealed/ported/horn/whatever", which doesn't matter at all, any bass can be achieved with any of these, and only difference is what problems or issues happen elsewhere, as compromises on the midrange / size / looks/ wallet / schedule.
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TL enclosure is interesting for experimenting with meta absorbers. Below 1,5 meter long for 8" fullrange. Then we could try absorb lower frequencies so that closed box becomes functional matrix not just empty closure.
For sure, great fun 🙂 Thanks reminding, need to try some evening again, its few years since I played with stubs in hornresp 🙂
If you wish to compare closed box and TL the best reference is work done by Augspurger. In his articles, he gave alignment tables (based on driver TS specs) to make fully stuffed TL with same performance as closed box with Q=0,7
But, driver itself is criticaly damped at Q=0,5 and its possible, with larger TL volume, to extend the bass by 1/2 of an octave.
So, benefits are superior cone control, and lower F3. Also more uniform impedance.
Stuffing materials and methods are also investigated. I suggest you to read these, they should be available online for free:
G.L.Augspurger - Transmission lines updated, Parts 1,2,3
These days, more popular form for diy is mass-loaded TL with only partial damping. Performance of these is more similar to vented box, with similar benefits as above.
For reference, look for more recent article M.J.King - "Classic Transmission Line Enclosure Alignments", where he took bass-reflex alignment tables as starting point.
But, driver itself is criticaly damped at Q=0,5 and its possible, with larger TL volume, to extend the bass by 1/2 of an octave.
So, benefits are superior cone control, and lower F3. Also more uniform impedance.
Stuffing materials and methods are also investigated. I suggest you to read these, they should be available online for free:
G.L.Augspurger - Transmission lines updated, Parts 1,2,3
These days, more popular form for diy is mass-loaded TL with only partial damping. Performance of these is more similar to vented box, with similar benefits as above.
For reference, look for more recent article M.J.King - "Classic Transmission Line Enclosure Alignments", where he took bass-reflex alignment tables as starting point.
What about a sealed VS a vented but with a flat enough phase towards the lows, say below 100 hz ?
Whih one willl have the less boxy sound, then ?
Also, some involve the material of the cabinet as of course the construction (as talked : length of resonance modes), DC value of the coil, notch of the second resonance and so on...) I am myself lost now... not saying talking of sealed I do find bass band pass not bad at all either !
Whih one willl have the less boxy sound, then ?
Also, some involve the material of the cabinet as of course the construction (as talked : length of resonance modes), DC value of the coil, notch of the second resonance and so on...) I am myself lost now... not saying talking of sealed I do find bass band pass not bad at all either !
I'm curious, how can you listen about the cone control, what are you supposed to be listening? Extra bass extension should be readily audible unless there happens to be room mode null. If the boxes one is comparing are considerably different in shape and size there could be significant difference on the mid range performance, I think also audible. Not sure how to listen for cone control though?
Guys, I haven't even finished building my other speakers yet (12" sealed + 3" wg), and I'm already tempted to try out a TL.
Compared to my sealed boxes, my ported boxes always seemed like failures. Deeper bass extension for sure but I could never find a sweet spot between over-stuffed, dull and distorted, and resonant overhang. So I want to be a bit careful before committing to a lot of woodwork.
I used to play trumpet and euphonium, and I noticed that the 'rounder' the instrument, the more mellow the tone at the end of the horn. Trumpets have these very long and straight sections that are folded with tight curves. Same sort of thing with trombones, and they're both very bright.
Fluegel horns are a bit more mellow than trumpets, and pretty much the only difference is they do is use bigger radii and reduce the length of the straight sections.
Euphoniums are rounder and more mellow again. French horns are basically a spiral. Translating that to speakers, to me that suggests that the kinks in the pipe could have a big impact on the high frequencies of the back wave.
Compared to my sealed boxes, my ported boxes always seemed like failures. Deeper bass extension for sure but I could never find a sweet spot between over-stuffed, dull and distorted, and resonant overhang. So I want to be a bit careful before committing to a lot of woodwork.
I used to play trumpet and euphonium, and I noticed that the 'rounder' the instrument, the more mellow the tone at the end of the horn. Trumpets have these very long and straight sections that are folded with tight curves. Same sort of thing with trombones, and they're both very bright.
Fluegel horns are a bit more mellow than trumpets, and pretty much the only difference is they do is use bigger radii and reduce the length of the straight sections.
Euphoniums are rounder and more mellow again. French horns are basically a spiral. Translating that to speakers, to me that suggests that the kinks in the pipe could have a big impact on the high frequencies of the back wave.
The old click test is our friend here:
Attachments
But with way more degrees of freedom to juggle when designing a TL.
Modern quarter-wave modelers have dramatically opened up the possible design space for loudspeakers, providing fairly accurate virtual simulations so that you don’t have to build & try.
dave
It can easily be surpassed. Take the same concept and properly model it. El-Pipo gets moving because BIG. But for the woofers used it likely needs to be much bigger. Blowing up 1 of the original woofers and moving to one probably actually worked better.
And don’t forget Nelson’s room. It makes a significant difference. I have similar.
dave
BTW: i have a mini El-Pipo project (PVC pipes cut to length, drivers, active XO) for anyone can come pick up.
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I imagined the above mentioned mini El-pipos with fins (and i had Emac caps for a fancy nose cone/dustcover but they dissapapeared in the purge).
dave
A must read, but his software is very limited. MJK (NLA) is likely best, HornResp is the current standard, there are a couple others. All still need better data on teh effects of damping. My goto tool for quarter-wave (TLs) is Dr Scott (Scottmoose). He has all those tools and some of his own, and, most importantly, vast experience.
http://p10hifi.net/TLS/downloads/AugspurgerAES107rev2.pdf
dave