Woofer QTS explained

In this video I am explaining the importance of getting good bass from your woofer, by knowing your QTS from Thiele-Small parameters.

With numerous years of serving high-end audio clients under my belt, I am excited to offer a speaker repair and upgrade service that's sure to meet your needs. I apply the intricate process demonstrated in my videos, ensuring that your speakers are handled by an expert. For advice or packaging inquiries, please don't hesitate to contact me. If you're within the Las Vegas area, drop-off or potential pick-up can be arranged.

Kind regards
Kent Larsen

[jasonledyard]

To be honest, this is probably the most informative youtube that I've seen on audio

[johannjohann]

What alot of people don't get that there is a "trial and error" period when it comes to creating speakers. That there really are not "words" to properly explain a speaker's characteristics. That it is a marriage of art and science. And that's just the way it is. Plus, I haven't even gotten into manufacturers not offering the numbers on their speaker drivers, let alone honest and accurate numbers.

[JaMarvelousjmar]

Thank you for your time. Even though there are others breaking down the spec's, not all make it easy to understand. This is the type of content that gives the consumer a better view on the products in question and how to properly use them. Keep up the good work.

[kedricktitima]

Pure clear nice soft simple English explanation keep it up i want more videos

[Trideap]

Excellent explanation...havent seen any other video explaining Qts this simple

[Rene_Christensen]

Underdamped means Q larger than 0.5; overdamped is when Q is smaller than 0.5.

[jimgardiner]

I like the way you describe the parameters in layman terms. I agree that a higher number for mechanical damping (less damping) is good when combined with higher electrical damping (lower number) for better attack and decay. Results in a more detailed bass.

[BreezyFamily]

Did you ever do a follow up video on calculating box dimensions based on woofer QTS? Or know of any good sources? I'm trying to design a bookshelf monitor :)

[johnfisher]

Thanks! I was hoping you would talk about how those Q values impact ported vs sealed choises. I assume a high QTS would be best in a sealed box so it's less "boomy"? Likewise, a low QTS would be suited for a ported box to extend its boom? Really appreciate your content. This is good stuff!

[alexstevensen]

From what I've gathered there are three frequency areas a woofer can operate in. The +12db per octave lower area where position (force) is constant. If you were to apply a battery say 1.5 volt to the speaker then it pops forward say 2mm and that's it. That's what I mean by position = constant. It doesn't matter if we're at 2hz 5hz or 10hz..

Then there is the 6db per octave mid area around Fs where speed (voltage) is constant. And force (or current) tends to go to zero because the two forces cancel out.

Then there is the flat 0db area where acceleration is constant. (and force is constant again).

When the drivers qts is lowered that means it has a relatively lower electrical resistance that means that the area where the driver is 'in control', or the mid +6db/oct area, is widened. Here the voltage the driver generates more or less equals the voltage that's applied, that means 'speed is constant' so to speak.

In the other two areas the lower 12db and the upper 0db one, the current is limited by the resistor so you're in a kind of force = constant regime. If there was no resistance some kind of superconducting speaker it would be in 6db per octave mode all the way. I hope that made any sense. At q 0.7 there is hardly any 6db slope area and it goes directly from 12db slope to 0db flatness.

[Nihilst]

Thanx! Now I know things better. Long ago I used to have french mid sized 2, 5 way speakers with very little damping, bass reflex opening to the front. They were fairly expensive but the stands had no good wife acceptance factor. The stands were just physically useful, not for the eye. Their bass was so dry, that I assume, Qts, Qes were very low. The manufacturers even made the chassis in house. Same company also made smaller and larger enclosures using the same drivers. I think in a bigger enclosure the chassis sounded better, but I could not effort them. Sound slightly improved by using a PP layout with EL34.

[davidzoller]

So "1.2 is a very high and 1.2 is a very low Qts" - I had to listen this 2 times. Instead of Qes, Qms and Qts declaring high or low, it probably would be less confusing declaring them hard vs soft or strong control vs weak control. or fast vs slow, just anything but high vs low.

0, 707-alignment is the Qtc with f3=fc in a closed box and sure, to calculate it, the Qrs is involved, but it's definitely not the Qts of the stpeaker-driver.

Looking at the other comments, I seem the only one unhappy with this mess. Well, i'm getting more and more used to it.

[Acoustic-Lab]

In midrange maybe we need driver that have higher Qts like 1.5 or more.. if we see on tube amplifier, they have low damping factor and that's why they sound more musical on midrange.. the best way to use high qts driver by using open baffle design?? What do you think?

[DannerPlace]

Yes, I got something out of it. Thank you.

[CrashPCcz]

Lol, youtube. Someone finally doing great job knowing the shiz, and that one gets instantly disqualified. Haha good job. Don't get discouraged.

[robcoastalga]

Those are horn hybrid woofers? been considering some lii audio full range. Prob try the 6.5" full range first.

[MustangBoy]

How does QTS relate to infinite baffle application. Some say higher QTS is good for infinite baffle. But when researching a perfect subwoofer, I see some free-air subwoofer with low QTS. It made me confused. Can you clarify this?

[tomthumb]

A low qts on a PA driver can be fatiguing after a while. Above 0.3 it will start to start to sound a bit more natural and warmer

[gino]

good morning ! Thank you sincerely for the really useful and well done explanation. I understand that a low qts is also a measure of the intrinsic quality of a driver, and i see that drivers with low qts have a very high cost. I've seen some JBL woofers with low Qts .... they have crazy sized magnets ! Scanspeak makes woofers with Qts of 0.2 ... and they have become a classic. Moreover I also believe truly in instrumental tests. A driver who has an impulse response like a tuning fork (i.e. with little damping) does not do anything good I think. I have a personal experience with a Dynaudio woofer with Qts = 1. it was slow to start and slow to stop ... even using powerful solid-state amps the bass was confused ... not convincing at all. Unable to transfer the sense of rythm for instance. I think it depended on the magnet being too small compared to the moving mass of the cone. It needed a much more powerful magnet. And actually the better version had a bigger magnet and much better bass response. I think the bass Qts is so important that lately I'm very interested in field coil drivers, a concept that can provide very low Qts ... but they must sound spectacular.  Thanks again for the interesting and precious explanation. P.S. has i said that i believe strongly in measurements ? if only i could afford a well equipped lab ...

[Scandinavian_Pride]

Is there any way to look at the specs (in a speakers retail description) that I could look for when searching for a decent sub for infinite baffle? I'll see if I can find the specs on a Honda Accord trunk space...