T/S parameters... what are they good for?

[npdang]

What are T/S parameters and what do they mean? I get asked this all the time and I think well, it really isn't so important to know what they mean but rather what do they tell you about a speaker's performance?

The quick answer I'm going to give you is that T/S parameters don't tell you anything about how a speaker performs. If you've read the articles here on transient response and non-linear distortion, you already know that THESE are the things to look at when evaluating a speaker's performance.

So what can you learn about a speaker by looking at it's T/S parameters? Well, assuming that the manufacturer gives you accurate specs (keep in mind that all drivers will deviate somewhat from their manufacturer's specs), T/S parameters can tell you 2 things.

1. The efficiency of the driver using the following formula:

1 watt spl at 1 meter in decibels = 112+ 10 * log (9.64 * 10^-10 *fs^3 * vas /qes) ... for example 90db @ 1w/m sensitivity.

2. And the low end frequency response of the speaker at low levels of power, in a given enclosure. I recommend reading the Winisd/box modelling article here for more info on the use and limitations of T/S parameters, when designing and modelling enclosure+speaker frequency response.

[demon2091tb]

Is there anyway we could get a rough explination of Box Q effects...as well as FS and QTS effects.

As i slightly understand what box Q means, but not sure how its determined....As well as different effects of QTS of a driver, and applications of each QTS parameter, if at all possible.

Also how can we tell how strong a sub is going to be in the sub 40hz region, as i'm looking for a sub that can really put out down low, pretty flat from 60hz down to a good 20hz, as i'm wanting that low end rumble, and i just don't seem to be getting it as much as i beleive i should..

[trains are bad]

Is that a base ten log?

[thechris]

Q in general is a loss ratio. basically imaging a swingset or pendulum. it will swing back and forth for a long time and at the same rate. this corresponds to a high Q.

ok, so add some friction to the moving parts and they'll slow down. friction converts the energy to heat. this is actual use of energy and eventually the swing will stop. this is lower Q.

take a woofer now. normally it will want to move at a given frequency, and has a Qms related to how much it favors moving in that manner. Qms will show up when you look at a free-air impedance plot. if you use the electomagnet to stop the woofer you can get a signifigantly lower Q, Qts.

from this perspective you can see that a high Q means highly favoring one note, while a low Q means favoring a wide bandwidth. once you port a woofer, you actually intoduce a second Q and F resonant effect. you can use this second resonator to give a boost. the port will have a Q as well, and a low Q port will give a smaller boost, but will do so to more frequencies.


i saw one of my old posts. almost though someone else was pretending to be me...

for high SPL it is beneficial to have high Q values, as a high Q corresponds to low loss.

edit -- this is more of a generalization. i am not saying to look for high Qts speakers.

[Suneet]

So would the T/S parameters be good for modeling a HT theater speaker, specifically, one of those Polk Audio in-wall speakers, to figure out if one should build an enclosure for the midrange driver in the wall or not?

[a$$hole]

it would be easier just to cut a hole in a box top[ie- a shoe box ] and put the speaker face down on top of box to hear difference.