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Subwoofer experiments can be enlightening!
- Thread starter AdamG
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Blumlein 88
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I think of that as more of an exclosure than an enclosure. But I'll keep it under wraps.
...and transmission line and open baffle...
I have at least 3 (sealed, ported and passive radiator). Most of them I built, but both purchased speakers are vented. There are valid considerations for almost every type I own. You may get some better choice with subwoofers, but vented speakers otherwise pretty much basically dominate the market. You can have a preference, but if you get eliminate vented designs, your choices are much more limited. Of the major speakers discussed on this forum, almost all are vented (KEF, JBL, Revel, Genelec).
Debate all you like, but vented speakers are hard to avoid.
I have at least 3 (sealed, ported and passive radiator). Most of them I built, but both purchased speakers are vented. There are valid considerations for almost every type I own. You may get some better choice with subwoofers, but vented speakers otherwise pretty much basically dominate the market. You can have a preference, but if you get eliminate vented designs, your choices are much more limited. Of the major speakers discussed on this forum, almost all are vented (KEF, JBL, Revel, Genelec).
Debate all you like, but vented speakers are hard to avoid.
...and transmission line and open baffle...
I have at least 3 (sealed, ported and passive radiator). Most of them I built, but both purchased speakers are vented. There are valid considerations for almost every type I own. You may get some better choice with subwoofers, but vented speakers otherwise pretty much basically dominate the market. You can have a preference, but if you get eliminate vented designs, your choices are much more limited. Of the major speakers discussed on this forum, almost all are vented (KEF, JBL, Revel, Genelec).
Debate all you like, but vented speakers are hard to avoid.
There is nothing wrong with sealing ports honestly, i mean it sucks to have an oversized speaker but what can you do?
I prefer sealed and make up for the lost efficiency with overkill surface areaDebate all you like, but vented speakers are hard to avoid.
Other than the fact that you are left with neither sealed nor properly vented and kinda don't get the main advantages of either. Audioholocs has good article on that matter if I remember.
You can’t blame manufacturers for opting it. A port is an efficient way to lower f3 frequency and distortion at f3.Debate all you like, but vented speakers are hard to avoid.
REALLY? I thought engineers were all just slaves to the marketing yahoos and those yahoos only wanted ported speakers!
Let's turn the volume knob to the maximum and listen to https://www.digido.com/portfolio-item/we-have-lift-off-now-in-surround/
20 hertz into a 31 hertz tuned sub can be fun and even enlightening, but practically it doesn't make sense.
20 hertz into a 31 hertz tuned sub can be fun and even enlightening, but practically it doesn't make sense.
a google search was not successful, was it an article specifically about this?
So far I'm not really seeing anything of worth being stated in that screenshot other than 'Don't do it'.
So I'm not really buying it to be honest.
Maybe I can try to explain?
A port is a Helmholtz resonator. On an electrodynamic speaker system, it is tuned to a frequency where the driver's piston displacement is no longer increasing due to reaching its excursion limit (Xmax). At the tune frequency almost all the sound pressure waves generated are by the resonator and the driver cone's excursion drops to zero. Naturally as we are in analogue environment, this happens gradually before and after reaching the tune frequency. Below the tune frequency the cone starts to move again. However, as the cone excursion value increases with the cube of the frequency, the cone moves dramatically more than it was above the tune frequency. That is why you must use a HP filter below the tune frequency, otherwise you may damage the cone or at best produce to much distortion.
In a sealed speaker you have no resonance to generate sound pressure waves. All sound is generated by the driver cone's movement.
If you stuff the port you are reducing the Q of the resonance. You are not converting the enclosure to a sealed one. With a stuffed port the resonance curve will get shallower and wider. In some instances you may want that. For instance to reach lower frequencies and or swapping flat response target with lower frequency extension.
In short, such a design is not an aberration as the article above says. It is simply a design and like all designs it has to be designed correctly and the compromises made fits the spec.
That's a very interesting statement, my experience has been that excursion returns to reasonable levels when I seal the port. I don't know how that aligns with this new information.
I should measure if my ports are still outputting anything with the way I have them sealed.
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Whenever I am in a position to offer an authoritative response I open my trusted reference book, a signed copy of Richard Small's 1972 Ph.D. thesis. Chapter 4 explains vented designs. The chart below shows what happens when you alter the Q, i.e. stuff the port. The efficiency, i.e. the resonance level is reduced.
See, with sealed you just put the drivers into a cab and stuff works, no potential issues with almost anything and low group delay, for domestic use the simplicity is hard to pass on and if you are going the multisub route lack of output shouldn't be a thing.
It just it seems at a certain point the resonance is completely gone because the excursion is back to sealed levels under the tuning frequency.
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