Transient response, can you tell in advance???

[buggsson 10+ year member]

Regarding transient response, you hear so many different statements and views that at least I get giddy. For example, some claim there are no such thing as fast and slow subs, others do not agree, etc. Some will have it to be an issue about mass, but then the guys at Stereo Integrity have reached the conclusion that it is inductance that is the decisive factor: http://stereointegrity.com/docs/WooferSpeed.pdf.

So I just would like to hear some current views on the subject of transient response. As far as I have been able to understand, said sub parameters that might influence transient response are:

Bl

T (Tesla, magnetic flux density)

The gap width

Le

Cms

So what I really would like to learn is if it in any way would be able to predict a drivers transient response in advance, without having to listening? If so, how do you go about to do so?

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[RAM_Designs 5,000+ posts]

To me, inductance is probably the biggest factor. I couldn't tell you anything about magnetic density or whether or not the width of the gap affects anything, but I can tell you that from past installs I've seen a direct correlation between le and transient response.

Not scientific, I know, but I hope it helps a little bit...

 

[headless 10+ year member]

subscribed for interest in this discussion

I just read that adire pdf (adire on the stereo integrity site? confused; are they the same company or something?) and the mass loaded line doesn't look any better to me than the inductance loaded line on their graphs. Different, but not better //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif I'm stupid, though. Does this mean if I ran 10 foot of, say, 18ga speaker wire to my sub that i'd noticeably effect the transient response of the speaker vs. say..10 foot of 12ga speaker wire?

 

[MikeyB 5,000+ posts]

Subscribed, I wanna learn.

Wheres Immacomputer? helotaxi?

 

[SHOemup233 10+ year member]

Subscribed, I wanna learn.
Wheres Immacomputer? helotaxi?

They haven't logged on yet I'm sure. Or audioholic. They'll come. No worries. Ha.

 

[SQBubble 10+ year member]

to me transient response depends on the enclosure for a giving sub..

 

[Immacomputer 10+ year member]

Inductance is going to be a factor in transient response as well as mechanical damping and electrical damping.

Inductance is a form of storing electrical momentum in the form of electromagnetic fields, I guess you could say. The storing and discharging of that momentum is what is going to cause the signal to lag or be delayed. You can see this effect in Adire's woofer speed paper where they compared the mass loaded and inductive loaded impulse response. The green line always crosses 0 after all the other graphs which means that it lags behind the other signals. In an enclosure system, you can have this same storing of momentum by way of ports. Ports become very inductive around their resonance and that will cause the port signal to be delayed from its electrical counterpart.

The enclosure is really going to alter the transient response the most though. Sealed/IB systems aren't very inductive by nature so they will usually offer great transient response. Ported and bandpass systems add inductive components to the over all system and that inductance will alter transient response. Keeping the group delay down will help in increasing the transient response. The group delay needed to keep the negative effects inaudible will increase as frequency gets lower. That's one reason why tuning ported enclosures low will help sound quality and transient response because the rise in group delay around tuning will be pushed lower in frequency allowing it to be worse and not have much audible effects.

You can't predict transient response just by looking at a driver's parameters but you can get an idea of how it might perform. In sealed systems, the transient response is going to heavily rely on the inductance of the driver and final Q of the system. A system Q of over say 1 (typically a small box) will start to decrease in transient response around the system resonance, which might be pretty audible if too high in frequency (common with high Q sealed systems). The lower the Q sealed system (bigger box) will have better transient response compared to the smaller sealed version. These differences are going to be kind of small though. In ported systems, you have to keep an eye on your group delay. If you're concerned about transient response in a ported systems, you should eyeball a driver with a low Q as they will usually have lower group delay and thus better transient response and keep enclosure volume on the low side. Tuning lower will also help push the group delay to a lower frequency but will usually increase it.

Does this mean if I ran 10 foot of, say, 18ga speaker wire to my sub that i'd noticeably effect the transient response of the speaker vs. say..10 foot of 12ga speaker wire?

Noticeable affect the performance? Eh, no. Will it change? Well if you rolled all those cables up into a coil, then yes, it will change the response (a coil of wire is an inductor) and add inductance. How much inductance will decide how noticeable the effects are.

 

[kush-divinity 10+ year member]

^^^this muthafukka is hellasmart.....//content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

And, you can read the forums and internet garbage for months, and still not know any more than if you just go listen at a bigger store where you can audition many woofers at once.

 

[SHOemup233 10+ year member]

^^^this muthafukka is hellasmart.....//content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif
And, you can read the forums and internet garbage for months, and still not know any more than if you just go listen at a bigger store where you can audition many woofers at once.

Most "big stores" don't have any quality stuff on site.

 

[buggsson 10+ year member]

^^^this muthafukka is hellasmart.....//content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif
And, you can read the forums and internet garbage for months, and still not know any more than if you just go listen at a bigger store where you can audition many woofers at once.

And many of the drivers I'm leaning towards, I'll have to import myself, they are not sold over here.

 

[JimJ 5,000+ posts]

And many of the drivers I'm leaning towards, I'll have to import myself, they are not sold over here.

Seas doesn't have a presence there? They're next door, relatively speaking, in Norway //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I would have thought Seas and Scanspeak (Danish) would have been available, at least.

 

[buggsson 10+ year member]

Inductance is going to be a factor in transient response as well as mechanical damping and electrical damping.
Inductance is a form of storing electrical momentum in the form of electromagnetic fields, I guess you could say. The storing and discharging of that momentum is what is going to cause the signal to lag or be delayed.

The enclosure is really going to alter the transient response the most though. Sealed/IB systems aren't very inductive by nature so they will usually offer great transient response.

You can't predict transient response just by looking at a driver's parameters but you can get an idea of how it might perform. In sealed systems, the transient response is going to heavily rely on the inductance of the driver and final Q of the system.

A system Q of over say 1 (typically a small box) will start to decrease in transient response around the system resonance, which might be pretty audible if too high in frequency (common with high Q sealed systems). The lower the Q sealed system (bigger box) will have better transient response compared to the smaller sealed version. These differences are going to be kind of small though.

Very informative and a great help on my way of understanding more about subs.

I'm going sealed.

No, I don't think that even I would have expected to be able to predict the response, but just being able to get an idea of the response if most helpful when hunting for drivers.

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!!!

 

[buggsson 10+ year member]

Seas doesn't have a presence there? They're next door, relatively speaking, in Norway //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
I would have thought Seas and Scanspeak (Danish) would have been available, at least.

Yes they are, but not on my 12" sub short list.

 

[audioholic 5,000+ posts]

There is no such thing as 'faster' or 'slower' subs. Think this is just a theory? Its not, its fact. Alterations in woofer 'speed' change the frequency its playing (a 60hz note requires the sub oscillate 60 times in one second). So if one sub was 'faster' or 'slower' than another, they would no longer even be playing the same frequency.

The guys at Stereo Integrity did not pioneer the idea that inductance relates to transient response rather than moving mass, Dan Wigging from Adire Audio did. His tech paper on the subjkect is pretty common knowledge these days. If I wasn't so lazy, Id find the link.

 

[Haunz 10+ year member]

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