Greets!
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>Thanks for taking some time to answer my questions. I appreciate the effort.
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You're welcome! If you only knew.
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>So they can indeed be used in a TL. That's great to know because I wasn't sure if anyone had ever attempted a TL with these oldie-but-goodies.
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This, and the Eclipse Swan 305, were very popular drivers around here in the 'good 'ol days' since they gave incredible bang/buck, so they've been put in everything from sealed to PA scoop bins.
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quote:
No, and in some cases a good trade-off between size/performance is to tune it to as high as ~(SQRT(2)*Fs), or ~29-30 Hz with this driver. This driver's Fs is low enough to use the higher tuning since room gain will boost it down low and the higher tuning will increase its midbass efficiency, a win-win alignment.
>This is extremely interesting. Hmm, speaking of midbass, I currently have too much midbass from an Obcon enclosure with two Sony tens (vintage 1992) in it (driver specs available upon request) that has a Qtc of around 1 or so with aproximately 1.269 ft³ volume. According to an internet sealed encloser calculator, my drivers want a 1.9 ft³ enclosure. I added a pillow and that helped quite a bit. It has a few dips in frequency response as observed with sine wave sweeps, but it falls flat on its face below 35Hz. The typical bass boost from 70 to about 120 is still there, as is common in most consumer bass products, so I'd like to avoid a repeat if possible on the TL.
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The driver's Le, Qts and amount of line stuffing will determine gain, so we're talking apples n' oranges.
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>Incidentally, my bro has a KLH floor sub for home theater and its published frequency response is 40-180Hz. It has a single front firing 10" and a rear firing port. It has very similar performance to the Obcon box. Surprisingly so (it can get louder and has a smoother curve, but falls flat right around 35Hz as well). Heh, that KLH is supposed to be a subwoofer? Dubious.
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'Sub' = infrasonic = reproduces the <20 Hz BW. 'LF' (AKA 'low bass') = 20-40 Hz, 'mid bass' = 40-80 Hz, 'upper bass' = 80-160 Hz.
Unfortunately, with the advent of HT and cinema sound marketing types calling the DD LFE system's <120 Hz BW a 'sub' channel, the average consumer considers whatever they hook up to the LFE channel a 'sub' regardless of what its BW is. All they know is that to go really low is ~inversely proportional to price, just like when buying a car, 'speed costs, how fast can you afford to go?"
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>I supose it's ok for non critical listening, as I suspect most consumer bass products are, but it is a bit too slow, muddy, and port noise can be heard etc. This is the sort of thing I want to avoid and why I chose to start learning about transmission lines. I want the effortless, clean bass everyone is always talking about. I prefer SQ over SPL and will do whatever it takes, within my limited budget, to get it.
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Well, TLs will please then. FWIW, most folks opt for either large sealed, IB, or EBS vented alignments for high SQ music or HT.
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>What is the ML in ML-TL? Mass loaded? Does mass refer to the stuffing density? Or just that it has stuffing in it as opposed to an empty one?
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Correct. No, it refers to mass loading a TL with a vent, AKA vented tower or column design. Properly done, stuffing is minimal since you want all the pipe action you can get.
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>Ah, I think I understand. So the driver is damped to the point where it will start to behave as if it were in a larger encloser, even though it isn't? That's sort of what I had imagined happening instead of actually slowing the speed of sound down. That's a relief.
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Correct.
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>Heh, wouldn't slowing down the speed of sound lower octaves and generally make things sound too slow? Kinda like the opposite of trying to speak in a less dense atmosphere like talking after breathing in helium from a balloon?
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No, we are amplitude oriented animals so it's the relative amplitude differences we key on, not the 'speed' per se.
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>I think I see what you're saying. As far as I can tell, my driver's only Q that is too high is the QES at 0.44/0.42.
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?? Ideally, you want a flat in-room resp0nse with a critically damped (0.5 Qt) audio system, ergo the room gain curve would have to be a mirror image the system's 6 dB/octave roll off slope. Only in your dreams!
Second best is a 0.7 Qt system (12 dB/octave roll off) that matches a perfectly sealed room's ideal 12 dB/octave gain curve. In some rooms you can get 'close enough'.
Since a properly stuffed TL typically has a ~IB response over most of its roll off BW before ultimately increasing at 24 dB/octave, it stands to reason that either a driver in a 0.7 Qtc sealed alignment or a 0.7 Qts driver in a TL are the 'no brainer' choices.
Many folks prefer to use low Qts drivers in TLs though because they sound 'fast', which really just means it doesn't have much bass. Different strokes..........
That said, there's no such thing as too much speaker damping if you think about it, so using a low Qts driver to get the damping and some form of series resistance to raise its effective Qts to get a more tonally balanced response is the 'Hot Ticket'. To get reasonable efficiency down low though normally requires multiple drivers.
So from this it's obvious that the 40-1350 has anything but too high a Qes/Qts for good performance.
All of this assumes an ideal room with the speakers well away from any boundaries though, or pretty much the opposite of what most have for an audio and/or HT room, so 'subs' generally need to be overdamped to compensate for the added gain of a wall/floor or corner position so a 0.32-0.42 Qts driver usually blends the best overall in-room. This puts the 40-1350 ~spot on for most apps, being flexible enough for a wide selection of sealed or vented alignments.
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>I'm supposed to aim for QES of 0.3 to 0.4, right? In this case, wouldn't a tube of 14" diameter be better than 12"? If QES is electrical and QMS is mechanical, then QTS is the total, right? Anyway, the QTS of 0.38 is on the high side, but probably not enough to turn me away from using tubes instead of wood.
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See above.
The required tube diameter is a function of net Vb required divided by its length.
Correct.
Qts has absolutely no bearing on whether to use a tube or some other construction/shape.
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>Heh, at this point, I'm so confused I don't even know what I want anymore. 12" diameter, 14" diameter, one driver, two drivers...
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I assumed as much, and why I suggested you avail yourself of my experience.
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>I think I'd like to keep stereo bass which would require two TLs with one driver each. I have some material that has stereo bass, so this is important to me. Then again, SQ and accurate low frequencies are also important to me. Can I have both?
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Sure, it just means more $$/work for you.
I find this hard to believe since historically it's been a music/HT industry standard to mix all output to mono below ~120-150 Hz depending on whoever is responsible for the 'mix'.
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>What is IB? If I was going to tackle woodworking, non-void plywood sounds good. I bet it'd be safer (less dusty) than working with MDF. I'd honestly like to avoid woodworking if I could, and the sonotube idea would allow it. Hence my stubborness to abandon it.
>More to come.
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Infinite baffle, i.e. a baffle acoustically large enough that the driver's rear output will never be heard/felt. Mostly it's used to describe a sealed cab's Vb that's at least 4-10x the driver's Vas.
Yes, plywood is much safer overall to work with.
I hear ya, and have used more than my share of cardboard, concrete and terra cotta tubes, but they are much more hassle than wood once you move away from the 'sub' BW.
'Lucky' us!
GM
