It is also what happened when I tried replacing one of the drivers in my 2x12" guitar cabinet with an EVM12L and the other with a port.
Did you see the Jim Marshall documentary on BBC the other night.
Brilliant.
Wanted to match the Fender sound and found an alternative that thousands of rock groups had wanted all along.
There was a clip of a skiffle group from 1958 and they interviewed a James Page.
Brilliant.
Wanted to match the Fender sound and found an alternative that thousands of rock groups had wanted all along.
There was a clip of a skiffle group from 1958 and they interviewed a James Page.
Ben said "a one note sound BELOW fs". If the box is too large you can get a large spike at tuning, and if tuning is lower than fs this large spike will be below fs.
What you say is true too though, a too small box will give a humped response but that humped response will almost certainly be above fs, not at tuning.
If this is unclear I can provide pics via simulation of both situations but I don't have time to do that right now.
You seem ignorant about a few hard facts. To "play" DC in a room you need to create a constant over pressure. which of the 2 system types do You think would be able to do this...
- A vented design, or
- A IB (close box) design?
Do you think Fs has anything to do with the ability to do DC?
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This is the only speaker system I know of that can play down to DC (as opposed to "almost down to DC") Eminent Technology: home
A closed box in a air tight room - DC! I have measured it in reality with a fairly sealed room - it works actually... ok lets say, all indications point to that it works.
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Those only do 115 db or so with room gain included. Since the signal chain will never allow you to go right down to dc anyway, sealed subs are a much better option if budget is any concern at all.
It does bring up the question though, how much group delay is too much group delay? EBS alignments are quite popular and they work on that principle, a larger box, tuned lower. Of course it isn't really done to excess, but I think the frequency response would probably start to look very unappealing before the group delay got excessively high.
I think you're probably in far more danger of ending up with a poor sounding vented enclosure by going too small than going too large, unless you are deliberately trying to make something very large.
Of course this might not be quite what is being discussed however, if we're talking about deliberately oversizing and down tuning an cabinet to provide a lot of output at a low frequency.
Many sound (and less so) posts here. Problem is this forum has people from different contrasting viewpoints such as audiophiles and (or should I say, "versus") commercial/pop sound people.
Problem starts with the fact that we have no good technology for subs. Rice-Kellogg drivers are as dim-witted as using an IC engine in a car. What is needed is a driver with a 10 Hz resonance (like in the AR1 of 1954)... then we are talking sensible technology.
Until we see systems that aren't leaking at the seams to go low, we have to choose which compromises to endorse.
It is feasible to create freq responses pretty low (OK... maybe not as low to dc as Baltimore). But that can only be accomplished by means disliked by the audiophile crowd (that is, by trafficking in resonances and other gross means).
Too bad freq response is so easy to measure and other criteria are so much harder to quantify.
And worse yet, I know some person is going to chirp-in now that their sim produces perfect sound.
Ben
Problem starts with the fact that we have no good technology for subs. Rice-Kellogg drivers are as dim-witted as using an IC engine in a car. What is needed is a driver with a 10 Hz resonance (like in the AR1 of 1954)... then we are talking sensible technology.
Until we see systems that aren't leaking at the seams to go low, we have to choose which compromises to endorse.
It is feasible to create freq responses pretty low (OK... maybe not as low to dc as Baltimore). But that can only be accomplished by means disliked by the audiophile crowd (that is, by trafficking in resonances and other gross means).
Too bad freq response is so easy to measure and other criteria are so much harder to quantify.
And worse yet, I know some person is going to chirp-in now that their sim produces perfect sound.
Ben
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Like every other kind of engineering, audio engineering is all about making compromises. If you want high SPL at low frequencies, you need to compromise other things.
The Thigpen rotary woofer, with its high price and lower SPL capability, is an example of the sort of compromise you end up with if you really want frequency response down to 0Hz. (Since it's a fan, it can overcome air leaks and create a static overpressure in an unsealed room, so it really does "go down to DC".)
The Thigpen rotary woofer, with its high price and lower SPL capability, is an example of the sort of compromise you end up with if you really want frequency response down to 0Hz. (Since it's a fan, it can overcome air leaks and create a static overpressure in an unsealed room, so it really does "go down to DC".)
How do you explain Diogenes graph of close mic vs. listening position? It is only possible because of room gain and it doesn't matter if he has hvac lines open to other parts of the house or even if he opens a window. I think it is common knowledge at this point in the subwoofer DIYer community that our boundaries in a room provide gain starting at around 30Hz and Diogenes' graphs are yet another perfect example of that.
The reason you are catching some heat in this thread lately is because of condescending $hit like this. I never heard you say one of these "disclaimers" before you start telling people "how it is" and to be honest, it's getting pretty old.
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A good sub is a good sub regardless of whether you call yourself an audiophile or listen to commercial/pop sound.
We don't need a 10 hz fs and there's nothing wrong with moving coil drivers, especially for subs.
A resonant sub (like ported or tapped horn) with a gently rising response can have a frequency response curve very much like a sealed sub and sound very much like a sealed sub. I know you endorse leaky sealed subs so I'm not sure where the problem with resonances comes from. I can only guess that you haven't heard many well designed subs, especially of the resonant varieties.
No need to chirp in about sims, here's a measurement (in post 1 of this thread). 8x Sundown Zv4 18 in sealed enclosures - AVS Forum
Sealed subs flat to 5 hz up at the listening position with no eq or dsp up to the mic limit of 125 db, and plenty left in the tank beyond the mic limit. The lower frequency limit is the signal chain, NOT the sealed subs. A bit of eq gets things within about +/- 2 db from about 5 hz to 90 hz. And I think the ENTIRE system (subs, cabs, amps, dsp, mains and probably video, room furnishings, carpeting, computer and measurement equipment too) cost less than a single Thigpen rotary woofer.
There are dozens of examples like this, this one is very recent (late Sept. 2014) so it's easy to find the link.
BTW, the fs of these sealed subs is 26 or 27 hz (depending on which coil impedance he used), nowhere near 10 hz. The room is at least as important as fs, if not more.
Time to read up a bit on concepts newer than 1954.
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Further to this excellent point, look at the link I provided in the last post. The measurement of the close mic is dramatically different than the listening position measurement. That's room gain and it's not exactly a modest amount, it's a huge gain.
You can ask Diogenes how you can achieve single digit reproduction with a sealed system if you want to learn something. Looks like he's flat to 2Hz at LP with room gain. Once again, this stuff is pretty common knowledge for most DIY sub builders these days. 🙄
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As I've posted repeatedly, LOTS of ways sound gets boosted and decimated in rooms. But "room gain" is a myth.
I could be mistaken, but I believe I am not the first person to suggest that now and then total baloney is posted on the web, this site excepted, of course. And nobody has any idea what do about it. My suggest - obviously not possible to implement - is for people to think a moment about their qualifications and if it is just loose impressions or limited personal experience, to say, "My best guess is...." or something leading to decent evaluation of their thoughts.
Ben