Hey guys - yes a newbie around these parts.....

Currently have a 97 Advance, picked it up 2 weeks ago, and audio install started 36hours after having the car :P

Now, for those who know their subs - I know what Qes is, what Qms and Qts is.....

However, what defines a good Qes, Qms, and Qts?

Say without looking too much at the other theile/small parameters - a Qes of 0.392 as opposed to a Qes of 0.4xxx - are higher numbers 'better' or 'worse'*

*I know it depends on the application you put the sub to, however as a general thing.

In know a lower vas indicates better suspension of the sub - now just need to have the Qes and Qms/Qts explained a bit more.

Any help appreciated :-D

Ers.

http://www.diysubwoofers.org/definitions.htm

Fs = Resonant Frequency

Qes = Electrical Q of the driver at Fs. Qes is a measure of the driver's tendency to resonate at Fs, based on its electrical characteristics, e.g. magnet strength, magnetic circuit characteristics, etc.). The driver's overall resonance characteristics are usually dominated by Qes.

Qms = Mechanical Q of the driver at Fs. Qms is a measure of the driver's tendency to resonate at Fs, based on its mechanical characteristics, e.g. surround compliance, the compliance of the spider, weight of the cone, etc.

Qts = Total Q of the driver at Fs. Qts is a measure of the driver's tendency to resonate at Fs, based on its overall characteristics. Qts can be calculated using the equation:

Qts= Qms*Qes/(Qms+Qes))



meh i'll let tim explain it :P otherwise google is your friend :)

All the q Thielle small paramaters relate to control/suspension

Qts = total Q (i wont get technical but its calculated using Qes and Qms)
Qes = electrical control (magnet / voice coil)
Qms = mechanical control (surround/spider)

Qts is probably the most valuable for us
(note generalisations here as you need to take into account everything)
0.4 or below = suited for vented enclosure
0.4 to 0.7 = suited for sealed enclosure
0.7 or above = suited for free-air or infinite baffle IB applications

hmmm in that case then I would be better off using a ported box with my Response 12"... it has a Qts or 0.392... yeah?
Qms: 3.238
Qes: 0.446
Qts: 0.392

Hey guys cheers for the replies :-)

Yeah I've been to diysubwoofers etc and I know the technical definitions, and how to calculate each one from other parameters (getting into sub box building slightly lol )

Tim - you posted:

"Qes = electrical control (magnet / voice coil)
Qms = mechanical control (surround/spider)"

So my question I guess is - would a higher Qes value represent better control of the magnet/voice coil?

Same with Qms..

?

Poita - from what i've learnt - when you have a Qts value of just under 0.4 or just over, the sub may well be suited to both sealed and ported enclosures.....

I've got a little program that will also tell me what type of enclosure a box is suited for :-P

How about you audition them and forget about all the specs ;)

How about you audition them and forget about all the specs ;)

X2!!! lol Don't be scared to use your own judgement, its you that will have to listen to the end product...not a bass box program :P

cough cough..


Qts = total Q (i wont get technical but its calculated using Qes and Qms)

Qts= (Qms-Qes)/(Qms+Qes) .... Not that complicated is it?

You find me somewhere that has decent subs in boxes to audition and I will :(
People have maybe a couple Alpines in a box or somewhere like JB has 100 cheap subs all booming away fighting the home audio section.

Well... To answer what the Theile small parameters mean a bit more--->

The Qms is a electrical representation of a driver's physical stiffness (or load). The value is a unitless measurement, used to provide a theoretical parameter for other formulae. The representation of this number is a conglomeration of the:

(displacement of air it makes) - (at it's resonant frequency) - (the weight of the moving parts in kilograms) DIVIDED BY (the suspension stiffness).

Qms will tell you how hard its gonna be for the cone to respond to sudden changes mechanically, so I guess one could argue that this would suggest a measurement of transient response.. an indicator of "SQ".
This is what ppl refer to as "dampening". The more the cone is being "dampened" the more power that is lost trying to move the cone, however.. it can also be argued that this would indicate a better controlled driver.
The lower the number, the more losses in the "dampening". Typically, driver's with a high Qms have a more predominant peak in thier impedance throughout the frequency response range...

The Qes is a representation of a driver's electrical resistance to change. As the voice coil passes through the magnetic field, an electromagnetic back current (or "back EMF") is created that initially opposes the amplifier's input. This decreases the current passing through the coil, limiting cone movement and raising the impedance, mostly at the resonant frequency. So this parameter would tell you the electrical "dampening" with reference to electrical inputs.

So... we get the Qms, which is the physical dampening parameters (represented as an electrical load), and the Qes, which is the electrical "dampening", and squash them into each other to give the Qts.

$#it... your right Tim.... now I'm confused too :redface: :neutral:

*cough* (http://en.wikipedia.org/wiki/Thiele/Small)

Guys thanks :-)

I have a bit better understanding than before - I guess its hard to give a black and white answer when there's only a grey answer :rant: lol :cry: :cool:

As for a bass box program - hahaha thats what I use currently, though, would like to upgrade to another slightly more sophisticated program. It does what I need it to....for now.

As for testing out subs - that would be perfect, however, given that I dont have a limitless budget, a bass box program atleast gives a good indication of how a driver will perform in a given box.

And they are reasonably accurate for what they are too!! Main things I've noticed over the years is that it really is hard to tell how a given sub setup is going to sound like in a system install just by going with theoretical parameters due to the characteristics of the car itself, and the manufacturing tolerances in subs, which, for example can be up to 15% different in cheaper subs, mainly because of the materials to start with... After time, the subs parameters will slowly differ even more from the initial T/S parameters also....

Added to that, some manufacturers don't display all of the parameters, and you kinda have to fudge it yourself, which can affect the overall accuracy of a given theoretical output.

But, I guess ya gotz to start somewhere aye!!

Strange last post didnt ah, post.

Ben James - what program do you use?

Yeah one thing i've found is a lot of manufacturers dont like displaying T/S parameters, or will only display a 'few' which doesnt help much.

Currently im using bass box pro.....not a bad program, helped me put together a ported box for the fusion 12" I have - it doesnt produce a massive I guess, 'volume' of bass, however, the bass it produces is clear and sharp. Box even got rated about a friends Treo sub thats worth 3 times as much lol

I'll try and keep it simple, but there are many factors which all effect each other.

As we are talking about subs il limit my comments to subs. If we were talking tweeters/midranges/midbasses it will be a different story. (all have TS specs)

These comments are relating to good sound (SQ, not SPL - for SPL it's a different kettle of fish). For SQ if it can't handle the power but still has the sound you want you can just buy more subs and more power. And there you have the sound you want and lots of it.

(this is the only reason anyone should buy multiple subs IMO unless you want bling factor)

For subs and SQ we want high excursion and low fs as the job of the sub should always be to get low (don't confuse this with getting loud) When I say get low I mean hit the low frequencies i.e below 25 hz.

To the OP Qes and Qms are both ratios:
Qes is the ratio between total energy stored in the system vs energy lost by electrical control
Qms is the ratio between total energy stored in the system vs energy lost by mechanical control

looking for lower Qes and a higher Qms will mean that woofer is controlled more by the fluid electrical control of the magnet and voice coil rather than the spider and suspension which can get a bit messier due to the intricacies of poor workmanship and build quality. But a higher Qes will be less sensitive, with deeper bass. What will sound good changes depending on other specs and build quality, there is no hard and fast rule. So neither is better per se. Although I would lean towards a lower Qes and higher Qms if possible, that or ignore these altogether :)

TS specs are tough to work with, but all you need to know from these usually is box design, which can just use Qts.

Best bet is use your ears, audition, audition, audition. With drivers, you get what you pay for. A cheap sub will always sound cheap, more of them will be cheap and loud.

btw:
Sorry I should have elaborated on the sealed / vented guide:

All subs can perform well in sealed boxes, any driver with a Qts over 0.4-0.45 will not sound good ported.

Also look at the efficiency bandwidth product EBP as a good guide for box design;
EBP (Efficiency -Bandwidth Product) = Fs / Qes

If EBP < 55 than driver is not good ported
If EBP > 55 then you can use a ported box

Peace

Tim

Strange last post didnt ah, post.

Ben James - what program do you use?

Yeah one thing i've found is a lot of manufacturers dont like displaying T/S parameters, or will only display a 'few' which doesnt help much.

Currently im using bass box pro.....not a bad program, helped me put together a ported box for the fusion 12" I have - it doesnt produce a massive I guess, 'volume' of bass, however, the bass it produces is clear and sharp. Box even got rated about a friends Treo sub thats worth 3 times as much lol

Yeah.. I use bass box pro too! lol I think that's about all you need, and then you just go from there...

The box programs will only give you the response curve of the box and does not factor in the in cars response a lot of the time...

Poita I understand you are remote ( NT?? ).. maybe you should get a cheap flight to Sydney and spend the day going to places like Fhrx, lifestyle, Doran??

Otherwise it is aways good to see what the gear is that people us and win. Unfortunatey you may not like the sound of it, but it is a good guide. :D

Tim - awesome post :-D

Cheers guys.....

Mr Charisma - the box programs (higher end) actually can factor in a cars response, bass box pro allows you to factor in how much of a 12db rise happens, and below which frequency (it would help to actually measure this instead of guessing though).

Since we are here - Vas.

From memory, Vas will tell you how stiff the suspension is aswell?

As in, a higher Vas number indicates a less stiff suspension (of the cone/rubber) than a lower Vas number - is this true?