posted
Ok, here's a thought that seems to be getting some misconceptions. How many of you feel that transient response of a speaker is affected by it's size? For example, will an 8" sub have the same transient response that a 10" or a 12' sub will have ? We're not talking Freq. response, rather the attack of the driver, how fast it will react . Which is faster, or not, and why you feel that way .
-------------------- E.C. Wuz here Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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posted
What about say- an 8W7 vs a DD 9515?? The DD is real tight, the JL is made for high excursion and low frequency response. The point being, the different construction for different purposes in subs. I get a For Real attack out of the DD 15. My 8's are really fast (8L7's), also- but by no means is my DD slow OR sloppy!!!
posted
in general, the less mass the faster it should be. so theoretically, an 8 would be expected to have better transience than an 18. but more of a deciding factor is the design, make up (cone material and treating, etc), and build tuning of the sub. i've heard 18's that snap like a whip and 10's that have as good a transience as a pillow.
Posts: 542 | From: nor cal | Registered: Aug 2004
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posted
yep, inductance from large voice coils. that and all the other things that make a sub strong, also are a hinderance. it's all a trade off for what you want to do with it.
Posts: 542 | From: nor cal | Registered: Aug 2004
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posted
Moving mass affects sensitivity, not transient response. The lighter the cone, the less power it takes to move it around. A heavy cone takes more power, but will still respond as "quickly" as the lighter cone.
Posts: 525 | From: Boston, MA | Registered: Sep 2003
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posted
i've seen it work both ways. i've seen mass added cause loss of transience, and also i've treated cones, which also adds mass, but gained depth and transience both. it's just one of those things of sometimes it does, sometimes it doesn't.
Posts: 542 | From: nor cal | Registered: Aug 2004
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posted
the motor needs to be strong enough to control the cone...if you added weight to a cone with an already weak motor it would drop the FS and sensitivity...but it probably have worse control
Posts: 3421 | From: Owosso MI, USA | Registered: Apr 2001
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posted
that's my exact thoughts on the issue. like adding 500 pounds to your car with out beefing up the engine, then comparing your 0-60 and 60-0 time differences. it's a vicious cycle. get a heavier, bigger diameter, stronger cone, then you have to beef up the voice coil to push and control it better. so now again you are adding more weight plus more inductance. that which makes it strong, can also be a hinderance. about 5 or 6 years ago, i had a pair of kevlar cone 6 1/2's. i didn't like the way they sounded, so i was going to turn them into mid bass drivers only. not for a nice snap, but more bassy. so i coated the heck out of them to add a lot of mass, to drop the fs. didn't really change the bass response of them, but brought the vocals and instruments to life. sounded so good i changed plans, i used them all the way up to 5khz. i guess it's not fair about the papaer cone subs. when i treat them, they get more bottom end, probably from the added mass lower the fs. weight % increase of cone is not a whole lot. i would say the gain of a better sounding transient response, must come from the combination of the cone being stiffend up, and the vibration dampening qualites of the compound used. so it takes away some of the harmonic distortions.
Posts: 542 | From: nor cal | Registered: Aug 2004
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posted
If you add mass to the cone of a driver with a "weak" motor, the max. cone velocity for any given input power will drop. For example, given a particular driver with a certain input current, consider what happens when the moving mass if doubled:
-the motor curent and drive frequency are unchaged, hence the force applied to the moving assembly remains unchanged
-the mass being accelerated by the motor is double, hence the acceleration is half (F=ma)
-half the acceleration = half the maximum velocity of the cone.
-half the max velocity, in combination with a doubling of the moving mass, means that the momentum of the moving assembly remains unchanged from the case where the moving part is of the original mass (momentum = mass*velocity).
You would run into problems with cone flex (by adding more mass) and distortions arising from that. As mentioned above, fs will go down, Qts will go up, and sensitivity will go down.
Does that all sound right?
Ash
-------------------- ****************************** ****************************** Posts: 1136 | From: Los Angeles, CA | Registered: Aug 2001
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posted
i think it is 1/2 mass x velocity ^2. and increase or decrease of speed has more of an effect than changes in mass. comparing apples to apples. that's why a .223 bullet is more vicious than a .45.
i don't think added mass will yield to cone flex. but a more rapid change in direction will.
to define transient response, is how fast the cone goes from point A to B and back to A again. so common sense and physics says the lighter object to do this with, the easier it will be to do it quicker. but now also, how is the transient response to the ear. a cone that is faster, might not sound like it has as much snap/impact, because of cone flex and vibrations, = distortions. after all, it comes down to what the ear hears, not what the paper says.
Posts: 542 | From: nor cal | Registered: Aug 2004
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posted
This is an interesting question...when a pressure sensor such as our ears or a mic. or the new Termlab sensor measures sound, is it measuring just pressure, or acoustic/PV power? Obviously, the two are not the same. It's feasable(sp?) that a driver in the proper environment could produce huge pressure ratios without radiating much power at all.
Has anyone out there looked into this usbject? What type of acoustic load the air inside our cars usually presents to a subwoofer? Is it mostly reactive or mostly resistive?
Ash
-------------------- ****************************** ****************************** Posts: 1136 | From: Los Angeles, CA | Registered: Aug 2001
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posted
hmm you mean if you had a driver with oodles of displacement (XMX or Parthenon?) and gave it 100 watts, would it create more cabin pressure than say a re8 with the same power? The answ...
posted
There needs to be a distinction made between the perceptual transient response and what is technically known as the transient response. Many people think that a system with a lot of midbass and not much subbass "hits harder" or is "faster," while this isn't necessarily true. The perceptual transient response of the system is not something I'm prepared to go into right here.
The actual transient response of the system, the actual movement of the cone, isn't always directly correlated with the perceptual transient response. The actual transient response of the cone is related to the steady state frequency response of the driver itself by the inverse Fourier transform (assuming linearity). There could be a case made that the driver size, cone mass, voice coil inductance, etc does affect this, but when it comes down to it, we often operate our drivers in a region where the inductive reactance is trivial, and we often use filters which alter the response of the system. In the bass range, we are operating the speaker where it is virtually minimum phase and thus can construct inverse filters and filters which change the behavior of the system to what we want it to. I guess from the point of looking at the speaker, assuming it is linear and has a moderate inductance, we could just as well call this argument a wash after applying filtering.
That is just the cone movement. In a car, the pressure can become more complicated; in the bass region, the pressure at your ears is a virtue of not only the volume acceleration of the cone, but the volume displacement of the cone in relation to the total volume of the vehicle and the modal behavior of the vehicle itself. When you take all these factors into account, I'm not really sure there is much if any case for believing that speaker size is a huge contributing factor. You might as well just get a driver that does what you want as far as volume displacement and use equalization to get the transient response you want.
Posts: 3961 | From: State College, PA | Registered: Sep 2000
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posted
so why then does my 15" sound like it's about to explode and kill everyone in my car when it plays above 70hz or so at fairly loud volumes? I'm no expert in this area but I don't think you can just use equalization to get the transient response you want. And if there is some way to do it, can someone please tell me?
posted
There are a number of possible explainations for that, but I can't say for certain if any of them are true given the brief description of the problem. It could be:
1. Nonlinearity- at that level, the sub may not be operating linearly, in which case all bets are off.
2. Modes- it could be a particularily offensive mode of the vehicle. Perhaps there is a large peak in the response because of it. Depending on the location of the sub, it may even be some time of Helmoltz resonance (trunk to cabin opening maybe)
3. Frequency response of the driver itself- if there is a large peak up there, it won't sound good either way. This could be from a small sealed enclosure or using a low-Q driver in a huge ported box tuned low.
4. Panels inside the vehicle- it may not be the sub at all- it could be a panel inside the vehicle resonating
5. Amplifier clipping- it could be that at the lower frequencies, the amp distortion isn't as offensive and you overlook it, while above 70 Hz, it is offensive.
You have to control these factors, many of them which you should be avoiding anyways, to be able to equalize. As long as the system remains minimum phase, you can construct a filter to change the transient response. You probably should be operating your system under constraints which make it virtually minimum phase, so under most cases, this can be done.
Posts: 3961 | From: State College, PA | Registered: Sep 2000
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We can see that this has no zeros and two poles in the left hand plane. It is possible to construct a filter that changes this, by simply giving it a transfer function of F(s)/X(s) where F(s) is the desired transfer function. Inverse Laplace transform this new transfer function to find the impulse response, or multiply by s^2 and some scaling factors to give the pressure response.
Posts: 3961 | From: State College, PA | Registered: Sep 2000
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