Transient response, can you tell in advance???

[audioholic 5,000+ posts]

cone velocity is directly related to amplitude.. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

That's only a half-answer. The full answer would be that cone velocity is directly related to amplitude, and frequency. Frequency being the more dominant factor.

 

[Haunz 10+ year member]

If we are playing the same CD I'm quite sure amplitude is the deciding factor on RMS cone speed...

 

[audioholic 5,000+ posts]

If we are playing the same CD I'm quite sure amplitude is the deciding factor on RMS cone speed...

Your attempt to stack the deck to negate one factor in the equation does not change the fact that frequency is most definitely the dominant factor in cone velocity. If you had stipulated originally that you were ignoring frequency, I would have agreed with you. But you didn't, which made your one-liner an incomplete answer. *shrug*

 

[Rashaddd 5,000+ posts]

Doesn't power compression and nonlinear BL come into play? Or will that be marked by changes in inductance as well?

I have only a very basic understanding of the subject

 

[innsanes 10+ year member]

idmax period!

 

[Haunz 10+ year member]

Your attempt to stack the deck to negate one factor in the equation does not change the fact that frequency is most definitely the dominant factor in cone velocity. If you had stipulated originally that you were ignoring frequency, I would have agreed with you. But you didn't, which made your one-liner an incomplete answer. *shrug*

Dude, cone velocity is directly related to amplitude.. and I don't see why frequency should be considered because it is going to be what it is..

If you want to consider how velocity may change with frequency thats fine and dandy.. but typically if you double frequency (and cycles per second) you are going to halve the cone's excursion for the same overall velocity.. so I'm really not sure what you are trying to get at.. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[bose301s 5,000+ posts]

Just want to point out why the Adire stuff is on SI's site. Nick thought it was really good info and since Adire went out of business and their site was going to be taken down, he got permission to post them on his site.

 

[buggsson 10+ year member]

Just want to point out why the Adire stuff is on SI's site. Nick thought it was really good info and since Adire went out of business and their site was going to be taken down, he got permission to post them on his site.

Well, then it must have been the Adire paper I read then.

When I related to fast and slow subs, I didn't doubt there would be differences in cone speed, I was trying to relate to that sometimes you hear a sub being referred to as being fast or slow, where I would guess slow would mean muddy or unclear in the bass reproduction?

I'll try to get these two questions answered again, it would be most helpful:

What is the final Q, I have not learnt to master the car audio terms as yet, would it be the Qtc value? And while about terms, the mechanical and electrical damping respectively, what are those? What are they called, I guess they have letter abbreviations as well, and for transient response, are they supposed to be high or low?

A question about Qms, as I am going sealed, I am supposed to have a loose suspension, and I have always believed that it was supposed to be a high Qms value to be a loose suspension, now I just saw in other forum that a high Qms is supposed to mean a stiff suspension, which is it? And then I saw this "A High Qms means low damping in the suspension relative to the mass." I'm confused right now!!!

 

[audioholic 5,000+ posts]

If you want to consider how velocity may change with frequency thats fine and dandy.. but typically if you double frequency (and cycles per second) you are going to halve the cone's excursion for the same overall velocity.. so I'm really not sure what you are trying to get at.. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

Its almost like you are intentionally misunderstanding. Now you want to add output into the discussion? I dont care if cone excursion necessary for equal output varies with frequency, I never argued that point. My point was, and it still is, that cone velocity is related to frequency. You can say "well we are listening to the same CD anyway" or try to factor output levels into it now, but it does't matter. You cannot, and still not have, argued my point... that cone velocity is related to frequency.

Dude, cone velocity is directly related to amplitude.. and I don't see why frequency should be considered because it is going to be what it is..

Frequency is not a constant, it is a variable.

 

[bladebarrier 10+ year member]

The overall transient ability of a woofer is based on many factors, but the capability of having the enclosure be large and allowing the driver itself to be the major control factor is a large part of it.

Transients have to do primarily with the cone material, the dampening of the enclosure, and electrical/mechanics of the driver.

Car audio tends to be intrinsically poor for transients. The main reasons are that woofer materials for car audio are designed to withstand the elements and be more rugged, than what could be used in a home environment, and that car audio speakers tend to be designed for smaller enclosures.

Essentially you want as light of a cone as possible, while retaining stiffness. In car audio you also factor in moisture and temperature to a large degree. A car audio driver will often have a massively thicker cone when compared to a home speaker.

Paper is still one of the best speaker materials due to it's weight, but a thin paper woofer in a car would be absurd because it would be destroyed by the environment very quickly.

 

[thch 10+ year member]

so what is the question? it almost seems that all of the analysis thus far only goes so far as to prove inductance and mass are not limiting factors.

look at the OP's PDF link. the timescale is on the order of 5ms, with visually identifiable events within a fraction of a millisecond. pretty much all of that is stuff that is well above 200hz. the main parts are closer to 2khz it would seem.

This calls into question the validity of the testing -- after all, for car audio someone will be using most likely a 4th order (-24dB/oct) lowpass below 2000hz and even below 200hz. when this is added to the response the "transient" response would likely look almost like a flat line. in the 5ms timescale the filter would largely reject the impulse, except for the lower frequency components, which would not appear "transient" on the 5ms timescale.

further, the zoomed in picture shows a delay difference of what seems to be 1 sample, or 21us. this would be similar to having the woofers located a massive 1/4 to 1/2" further away from you then the rest of the speakers. its likely your time correction features won't even be able to correct for such a small difference.

really, it seems odd to work on this without some form of time-frequency analysis. something that isn't time only, or frequency only. for example, looking at the plot you can somewhat see what looks like part of a ~2khz peak at the beginning. but the fourier transform shows that 2khz isn't a dominant part of the signal.

I often wonder how much things like EQ's and just levels in general come into play. severe clipping seems horrible for transients. any note that starts and then decays that is followed by a second note will no longer decay significantly before the next note starts. that means the notes blend together.

likewise, I would think anything that is significantly resonant would be a good canidate for issues. resonance is of course a seperate phenomenon from simple inductance, and its probably best to avoid calling all delays "inductive", or attributing all delays to "inductive effects".

I also wonder about anything that generates distortion as well. after all, if the woofer continues to generate distortion at midrange frequencies after the real mids have decayed away, you'll end up hearing the sound from the woofers. This might elongate what you preceive as the attack of the note.

pretty much the above is all hypothesis, based loosly on things i've tried, as well as a technical background and engineering mindset. Now here's a fun part, a chance to play along at home. Find a song you consider "transient heavy", at least in the bassline. at more reasonable volumes, try adjusting the level of the woofer down a little and see how that affects the sound. likewise, try adjusting the crossover up a little, or better yet -- if you have a HU crossover try using a variety of filter slopes as well. keep in mind that prolonged exposure to loud music will skew your hearing a bit, making long tuning sessions less useful.

 

[Immacomputer 10+ year member]

What is the final Q, I have not learnt to master the car audio terms as yet, would it be the Qtc value? And while about terms, the mechanical and electrical damping respectively, what are those? What are they called, I guess they have letter abbreviations as well, and for transient response, are they supposed to be high or low?
A question about Qms, as I am going sealed, I am supposed to have a loose suspension, and I have always believed that it was supposed to be a high Qms value to be a loose suspension, now I just saw in other forum that a high Qms is supposed to mean a stiff suspension, which is it? And then I saw this "A High Qms means low damping in the suspension relative to the mass." I'm confused right now!!!

The final Q is the same thing as the Qtc for a sealed box system. The Q relates to the damping of the system in terms of 1/(2*damping ratio). So the higher the damping, the lower the Q. Damping is the ability to absorb energy from a system and expel it in another form to reduce the amplitude of oscillations. So if you put a mass on a rope and let it swing in air, the system would not be very damped and the mass would swing back and forth for a while. That represents a low damped or high Q system. If you tried to swing the same mass in water, the mass would probably not swing back and forth and instead would slowly come to a stop at the bottom of the swing with very little over shoot. This would represent a more damped system or a lower Q system. Then putting the mass in mud would cause the mass to barely move. All it's velocity would be lost to the mud which means the mud heavily damped the system or has a very low Q.

A high Qms means softer suspension or low losses from the mechanical system. Electrical damping is Qes and mechanical damping is Qms.

 

[Papermaker85 5,000+ posts]

i keep seeing inductance this inductance that... its not only inductance, its only one part of the equation...

reactance is what your looking for. its call inductive reactance in woofers becasue the inductance is above 0mh.. this is dependant on inductance, frequency, B(density of the permant magnetic field) current(amperage) throught the coil partical to L(increased current means increased magnetic density in the coil) as well as back EMF. mass also has alot to do with it as well as the dampning of the cabin and box...

now if you want to keep the best transiant response you want low lowest amount of mass;

back EMF(comes from b/l and type guage of conductor the inductor is made up of)

inductance

B/L

and the ideal amount of dampning for your application(ported, sealed, larger rooms, large boxes etc...

and also a very narrow bandwidth as efficiency is several affected by bandwidth...

not to mention cone material is also improtant to transoant response... metal cones paer cone CF cones all have different dampning resonances and stifnesses.. when your pushing any transducer hard these factors are important as well...

now speaking on that why most high outut woofers sound bad? high MMS high inductance very very stiff suspensions(requiring larger boxes with higher tunings to aid efficiency which raise group delay, higher inertia etc..

but there are many high output woofers that can sound excellent BECAUSE they can be equiped with softer suspensions have good efficiency(rasied vas) and usualy are very well built(super strong cones that have very little breakup and the proper dampning) and in some cases offer lower inductance and mass(any good one that is like the 9515/99z... in this case they just suffer from non linear suspensions that are very stiff.. you cna get soft spiders but there still not as linear as i would like to calll a SQ woofer... anyways i hope this helps a bit... its much more complicated then listed here but thats for another day...

 

[Immacomputer 10+ year member]

Cone material, mass, efficiency, and bandwidth are not going to affect transient response directly, especially not in the bass frequency range.

i keep seeing inductance this inductance that... its not only inductance, its only one part of the equation... reactance is what your looking for.

Umm... inductance IS reactance. It's the storing of current in the form of an electromagnetic field. When a speaker is playing a frequency near a resonance point and then it stops playing it to play another one, the stored current in the EMF will discharge and the burn off of current will change the response time and will cause a delay in the signal.

Reactance is either capacitive or inductive. Capacitive reactance will cause the current to lead the voltage while inductive reactance will cause the current to lag the voltage. Hmm... sounds like it should be inductance we're looking at, whether it be electrical or acoustical. And that acoustical inductance is what is really going to affect transients.

 

[Haunz 10+ year member]

I dont care if cone excursion necessary for equal output varies with frequency, I never argued that point. My point was, and it still is, that cone velocity is related to frequency.

Dude, we are seriously OT here.. but really what exactly are you trying to argue ???

If we send 1000 watts of power to a woofer at 50hz and then send 1000 watts to the same woofer at 100Hz then the woofer will cycle back and forth at 2x the rate; but the amplitude (xmax) will be cut in 1/2 for the same average velocity...

So how can you possibly say that cone velocity is dependant on frequency ???

Clearly, at any given frequency cone velocity is dependant on amplitude and the amount of voltage we are sending the sub.. And if you vary the frequency then the amplitude will change, but cone velocity will not.. In otherwords, cone velocity depends on the amount of power we send the driver; and has little to do with frequency..