Almost every so called "back loaded horn" found on the Internet is really acting as a quarter wave resonator at low frequencies and not as a horn. Most "back loaded horns" do not behave as a horn until your reach a few hundred Hz.
By my definition, a horn is not simply an expanding geometry. A horn's mouth size determines what frequency it efficiently couples to the air in the room producing a smooth increase in SPL output over a wide frequency band, not a narrow peak in SPL output. A horn is highly damped by the mouth and therefore does not exhibit peaking SPL associated with quarter wave resonances or require any fiber stuffing. This is easily seen in the electrical impedance plot of an unstuffed enclosure, if there are multiple peaks then you have standing waves and your expanding geometry is behaving as a quarter wave resonator and not like a horn. An expanding geometry with a port or restriction at the end is not by any stretch of the imagination a horn.
There is nothing wrong with these types of "back loaded horn" designs or the expanding geometry with a restriction at the end designs (mass loaded). But where the designer can miss the boat is by trying to apply horn theory and sizing equations to the quarter wave resonator geometry at low frequencies. If the designer recognizes the physics of the air motion and designs the enclosure as a quarter wave resonator for the low frequencies transitioning to a horn at the higher frequencies then the correct geometry trade-offs can be made and the design will perform better.
Martin
Ok thank you. Densely written, but good. Two things I still don't get is
1. Why would you you choose either design. What does a TQWT with BR do better than a plain horn or visa versa?
2. How can a ported speaker work as a horn at higher frequencies through such a small port? It doesn't seem like a very good coupling to the air to slowly let the pressure wave expand, and then wham! a wall with a small tunnel through?
1. Why would you you choose either design. What does a TQWT with BR do better than a plain horn or visa versa?
2. How can a ported speaker work as a horn at higher frequencies through such a small port? It doesn't seem like a very good coupling to the air to slowly let the pressure wave expand, and then wham! a wall with a small tunnel through?
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I am definitely dense. 🙂
1. A real back loaded horn that behaves as a horn at frequencies of 40 - 50 Hz would need to have a huge mouth for sound not to be reflected back into the horn generating standing waves. Even including room boundaries the mouth would still need to be very big. So a TL or TQWT with some form of restriction (mass loading) acting as a quarter wave resonator is smaller and can generate bass at 40 - 50 Hz.
2. It can't by my definition of a horn.
Martin
Sure had me fooled, but then I assume English isn't your first or maybe even second, language.
Because they can. 😉 Horns, even small ones where most of its gain BW is due to 1/4 WL action provide more gain and somewhat better damping than any of the vented (ML) variants, but they will be larger and if not well coupled to the room to acoustically increase the horn, i.e. corner or at least wall-floor and/or wall-ceiling loaded, then it won't have as smooth a response nor as wide a ~flat in-room response.
In short then, it's not about either having any problems per se, it's about size for most folks and/or design, build complexity. Ditto TL Vs BR, though not as much so since MJK's software became widely available.
GM
Yeah I like to do that.
Surely it wasn't that bad. Did you take offence at something you thought I implied?
If you are only concerned about footprint a horn needn't take up more space.
Of course there is the imposing psychooptical effect of a large tower. But that' just a matter of getting used to it.
I don't know about complexity. I'd say a Metronome is quite a bit more complex to make than a BIB, with all the angled cuts. Even a microtower is complex if you want the internal bracing various cut-outs.
Yeah I like to do that.
Surely it wasn't that bad. Did you take offence at something you thought I implied?
more likely your general tone and questioning the anecdotal experience and technical expertise of some very competent participants to this discussion who continue to contribute to the DIY community could be considered less than conciliatory at best, if not malevolent
huh? unless you're aware of an effective method of folding/compressing space (wouldn't that be nice), horns by their very nature will need more of it for uncompromised wide bandwidth than a simple pipe, MLTL or BR monkey coffin
see Nelson Pass' Kleinhorn
That sounds like semantics to me- I wouldn't confuse attention to details of fabrication/ assembly of build with complexity of functional design parameters - with elaborate use of multiple/ composite materials, artisan grade joinery or finishing even a 1 cu ft sealed box could become a complex (i.e. time consuming) project
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Oh Please! If that really is the case, I think it's time to get over yourselves. B-)
While I respect the expertise of people in here I, A. Have no way of knowing who's just a poser and who really knows a lot. I don't use the forum enough for that. B. Even among experts there is sadly still religious notions and poorly concealed conjecture.
Well verticality and use of corners is the two but very good ones I can think of.
Ok horns might be a bit more complex, to a lot more complex depending. But they also sound a bit better to a lot better. So yeah, it's a trade-off.
My thinking is just that the jump in complexity, from when you are doing a building project anyway is negligible.
Personally from my experience with BR in any form, I would only consider doing it if space was at an absolute premium. BR can sound good if done exactly right, but I'd always wonder how much better a horn would have sounded with a box a little bigger.
yes, we all need to question our own motives, but not all present have the same "self" (ego) to surmount
and as many of us will recall from well over a decade of discussions on various forums, it's all too easy to innocently misinterpret or willfully ignore either technical facts or a poster's specific point of view or expression of goal / compromise
several folks here have been involved in conversations with purveyors of "BLH" designs that started out innocently enough, but devolved into acrimony, so this was starting to sound familiar...
regarding the "folding of space" - mea culpa for the sarcastic remark - but I think there would still be some limitations of net physical volume to which a BLH horn intended for "full" bandwidth could be manipulated with the goal of reduced "footprint" without severe compromises
This is certainly the reason that I've personally avoided larger rear loaded horn designs such as the KleinHorn, and the much smaller but still substantially dimensioned and complex builds such as Jensen Imperial, Steve Deckert's interesting corner horn, Big Fun, etc., etc.
While certainly a simple build, the only 2 BIBs that I've heard were not without their issues, not the least of which for many folks is availability of the essential corners in the right place.
So in the spirit of getting over ourselves, if the underlying crux of your questioning is "why would a DIY builder choose any given speaker design type?", I think the answer is whether or not they understand how/why it works, and they accept any inherent compromises - because it works for the particular application.
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