Driver Qts Question Regarding SQ

[mike1234]

I've been receiving conflicting information regarding driver Qts and how much this affects system performance. Some say that Q makes absolutely no difference what-so-ever if the system is EQed flat. Others disagree.

Let me just ask this... Given two raw drivers, one with a 30 pound cone and a 1 ounce magnet (extremely high Q) and another with a 1 ounce cone and a 30 pound magnet (much lower Q), which one is likely to sound better? Remember, we're EQ-ing the FR flat... or trying to anyway.

Granted... This is an extreme case and is purely hypothetical.

[billfitzmaurice]

> Some say that Q
> makes absolutely no difference what-so-ever
> if the system is EQed flat.

That advice, and purveyors of it, should be ignored. That being said, extremely low Q drivers choke off bass response. While it's possible to EQ it out if the driver has adequate xmax it takes a lot of power to do so. High Q drivers have a better extension, but with low sensitivity, and they require very large cabs. Either extreme should usually be avoided.

But the driver Q's are just two factors in an equation that contains at least seventeen factors, so as is usually the case with broad generalizations this one is too simplistic.

[mike1234]

I can EQ FR and add amplification as needed. I hate flabby and/or muddy bass every bit as much as I despise gritty/harsh highs or inarticualte midrange. I can compromise in some areas, i.e. buying used equipment, but I really don't need to completely compromise SQ. I fully believe one can have it all if one understands how to choose/compromise properly.

I simplify my inquiries intentionally. Otherwise I receive relies with diffuse disorganized information... or at least this is my perception. This is probably due to my lack of communication skills an inability to filter through details as well as my lack of knowledge on the subject. This process just works better for me and my ADD brain :-)

> That advice, and purveyors of it, should be
> ignored. That being said, extremely low Q
> drivers choke off bass response. While it's
> possible to EQ it out if the driver has
> adequate xmax it takes a lot of power to do
> so. High Q drivers have a better extension,
> but with low sensitivity, and they require
> very large cabs. Either extreme should
> usually be avoided.

> But the driver Q's are just two factors in
> an equation that contains at least seventeen
> factors, so as is usually the case with
> broad generalizations this one is too
> simplistic.

[billfitzmaurice]

For every ten guys who swear that a 1 cu ft sealed sub using a ten inch driver with a Qts of .15 driven by two thousand watts is the only way to go you'll find nine who say that four fifteens with a Qts of .8 in an IB is better, and then there will be six guys who say a dozen fifteens with a Qts of 1.2 in open baffle beats them both. And then I'll tell you that two eights with a Qts of .38 horn loaded is better than all the above.
Sound quality is subjective. Only you can say what you like the best.

[mike1234]

So I'm back to square one. I need to experiment and trust my own ears... no one else's. Sigh... I guess my opinion of what "tight", or "articulate", or "correct timbre" means is completely subjective (useless rhetoric).

> For every ten guys who swear that a 1 cu ft
> sealed sub using a ten inch driver with a
> Qts of .15 driven by two thousand watts is
> the only way to go you'll find nine who say
> that four fifteens with a Qts of .8 in an IB
> is better, and then there will be six guys
> who say a dozen fifteens with a Qts of 1.2
> in open baffle beats them both. And then
> I'll tell you that two eights with a Qts of
> .38 horn loaded is better than all the
> above.
> Sound quality is subjective. Only you can
> say what you like the best.

[Andy_G]

a local guy, also call Bill, has 16 (iirc) x 15" subs operating infinite baffle !!

serious bass for exposive movies !!!

[chrisn]

> For every ten guys who swear that a 1 cu ft
> sealed sub using a ten inch driver with a
> Qts of .15 driven by two thousand watts is
> the only way to go you'll find nine who say
> that four fifteens with a Qts of .8 in an IB
> is better, and then there will be six guys
> who say a dozen fifteens with a Qts of 1.2
> in open baffle beats them both. And then
> I'll tell you that two eights with a Qts of
> .38 horn loaded is better than all the
> above.
> Sound quality is subjective. Only you can
> say what you like the best.

Wouldn't the driver with tons of EQ have a lot more distortion than the driver with unassisted low end?

[Pete Schumacher ®]

> Wouldn't the driver with tons of EQ have a
> lot more distortion than the driver with
> unassisted low end?

Not necessarily.

It all depends on the motor/cone design. It does seem foolish to try and EQ more bass from a low Q driver, when a higher Q will simplify things so much.

Mike just can't make up his mind. Me thinks he frets too much.

Pull the trigger dood. Find out for yourself that a higher Qts driver, like the RSS390HF, is an excellent sounding sub.

[mike1234]

I'm just going to buy several drivers and give them a try. I'll be testing drivers with Qts ranging from .30 to .70 (at least) and EQ-ing them to match FR. My only concern is for SQ (textural detail and dynamics). This is for an IB system, BTW.

> Not necessarily.

> It all depends on the motor/cone design. It
> does seem foolish to try and EQ more bass
> from a low Q driver, when a higher Q will
> simplify things so much.

> Mike just can't make up his mind. Me thinks
> he frets too much.

> Pull the trigger dood. Find out for yourself
> that a higher Qts driver, like the RSS390HF,
> is an excellent sounding sub.

[mike1234]

This is a cut/paste from... <A HREF="http://subwoofers.cc/HomeAud/Informa...sub_manual.htm">http://subwoofers.cc/HomeAud/Informa...sub_manual.htm</A>

This information leads me to believe that the AE IB15 is an excellent choice (maybe the best choice) due to the Q vs. resonance of the driver.

Any arguements for/against?

"System Q: Total system Q, (Qts), is kept appropriately low by the careful design integration of driver mechanical and electrical Q parameters, crossover resistive losses, aperiodic loading and the correct amount and type of internal stuffing. A common misconception is that certain Qs are more "correct". But specifying system Q without regard to total system transfer function is misleading. For instance, a Qts of 1.0 with a system resonance, (Fs), of 70Hz will sound very "boomy" and poorly controlled. On the other hand, a Qts of 1.0 with an Fs at 30Hz will sound not sound "boomy", but rather quite powerful. Audiophiles often refer to electrostatics and full range ribbon transducers as "fast", when in fact most of these devices have an undamped Qts of between 1 and 3 at their fundamental resonance! Because of the dipole radiation pattern and losses, this high Q can still be subjectively acceptable if properly accounted for in the design. The Sub 1 has a Qts of <1 at an Fs of 28Hz. Combined with a non-resonant total system design the result is a very tight, lightning "fast" bass response without overhang."

[mike1234]

...I guess I'll be testing drivers of high refute with Qts ranging from .25 to .71 as follows.

AE IB15 (Qts= .71)
RSS390HF (Qts= .42)
"suggestions?" (Qts= ~.25)

[billfitzmaurice]

> Wouldn't the driver with tons of EQ have a
> lot more distortion than the driver with
> unassisted low end?

Yes, although the EQ is not the reason why. Distortion is directly proportional to excursion. The least efficient alignment needs the highest excursion for a given SPL, and therefore has the highest distortion. One reason for my preference for folded horn subs is that not only do they require the least excursion for a given SPL, their folds are low-pass filters, which filter out whatever ddistortion is created.

[mike1234]

[mike1234]

Won't all drivers of the same size moving the same distance produce the same SPL? Why would a low Q driver moving the same distance as a high Q driver be more distorted if EQ has nothing to do with it?

> Yes, although the EQ is not the reason why.
> Distortion is directly proportional to
> excursion. The least efficient alignment
> needs the highest excursion for a given SPL,
> and therefore has the highest distortion.
> One reason for my preference for folded horn
> subs is that not only do they require the
> least excursion for a given SPL, their folds
> are low-pass filters, which filter out
> whatever ddistortion is created.

[billfitzmaurice]

Don't confuse driver Q with system Q, it's not the same thing.

Equally important is that the system Q in and of itself tells you almost nothing. I pay no attention to it, as system response defines what you hear, not system Q.

[mike1234]

I'm concerned soley about SQ, not FR. That is... accurate transient response and timbre or tightness. I can EQ FR flat.

> Don't confuse driver Q with system Q, it's
> not the same thing.

> Equally important is that the system Q in
> and of itself tells you almost nothing. I
> pay no attention to it, as system response
> defines what you hear, not system Q.

[billfitzmaurice]

> Won't all drivers of the same size moving
> the same distance produce the same SPL?

No. Not even close. You need to learn how to model speakers.

[billfitzmaurice]

> I'm concerned soley about SQ, not FR. That
> is... accurate transient response and timbre
> or tightness. I can EQ FR flat.

What you're describing are midbass and midrange attributes, not those of the sub-bass (20 to 80 Hz) range.

[mike1234]

[same area] x [same distance] does not = same volume???

> No. Not even close. You need to learn how to
> model speakers.

[mike1234]

...but I have to disagree on this one. Even amplifiers can have an impact on SQ of low bass. I know this because I can hear it. I may not know much but this I do know.

> What you're describing are midbass and
> midrange attributes, not those of the
> sub-bass (20 to 80 Hz) range.