Subwoofer Punch

liar
shes downstairs cookin me muffins before church

 

wow.... this is a long(but very interesting thread). I havent yet read the whole thing, so dont beat me up if I say something that was already said. Seth, the BL curve point is an interesting one, But I believe it dosent hold water. With your theory, the more BL you have, the "punchier" the woofer will be since the point that supposedly has the most "punch" is the point with the most BL..... at least thats what it looks like your saying.


Or if you are saying that subs with more parabolic curves are more" punchy" due to the lack of BL dropoff in the lower excursion-upper frequencies..... this also dosent make any sense. If you took a sub with a ruler flat BL then, it would be EXACTLY the same amount of punchy, because you still have limited excursion at higher frequencies, and you still dont have any real illinearity to speak of at that small of excursion. Actually, with that arguement, ALL drivers would be "punchy" throughout their entire pass band if you just turned down the volume(read:limit the excursion). Now I dont know about you, but I havent heard many subs that I would reguard as "punchy" at low volumes, and not "punchy" at higher volumes. Sure Ive heard many subs that just get plain sloppy at higher volumes due to extreme BL rolloff, but the sound that I relate to "punch" seems to be independant of excursion.


just my $0.02

 

So, Seth, you're saying that a sub that can effectively produce upper midbass

will have better transient response?

Sounds reasonable to me.

The way I see it, the voice coil will always hold a natural amount of Le, being there

a signal or not. So.....eh.....it sorta goes against the Le determines transient

response issue (not saying it doesn't, because it certaintly does aid in it).

The way it's been presented in my head in the past is that frequency response

IS transient response.......

Goes hand in hand with what you said.....

Think about it........






Jeff

 

If you ever come across a b10, i'll donate my 10w7 for a/b testing if you want.... I'd be interested to hear em both in the same car in optimum sealed enclosures.

 

Actually I think what makes a superwoofer is it's incredibly large linear thow within an SQL driver. The flat BL curves are only on a couple superwoofers.

Yeah, all I had available for the W7 was in the showroom. So since I knew I couldn't compare frequency response, I mainly listened for boominess and added distortion. In that respect it sounded identical to the Brahma.

From what I understand, the BL and Kms effect different things, and therefore bring forth different distortions. It just so happens that the BL distortion is a much greater product of the total distortion than the Kms distortion. It seems that Kms nonlinearities effect the frequency response more (frequency response of sub changing with excursion), while the BL nonlinearities effect more the power input (BL compression). I'm not sure why that would be more audible than the Kms.

Let's look at it this way. Kms nonlinearities effect the Qtc of the system (among other things). Let's take a look at this white paper at Adire Audio comparing the t/s parameters with excursion of the Brahma and Audiomobile Mass (a standard SGLC motor). On the bottom, they show Qtc of each sub for excursion in the manufacturer recomended enclosure of 1 cubic feet each. Both seem to have a flat curve with little change. But when you look closely, you see that the Mass's Qtc changes .8 at only 20mm of excursion (from .99 to 1.7). The Brahma has changed maybe .1. Now let's see how audible this is. How audible would it be to go from a .7 to 1.5 Qtc? Probably fairly audible. But the change would mostly be in frequency response. Sure it will sound boomier, having a Qtc that high. But I think that higher Qtc's are more because of the frequency response change (like what Seth mentions earlier, but at a lower frequency section making it sound more boomy), rather than anything else. I'm curious what it would sound like if you took a Qtc like this and EQ'd the sub back to a .707 response. Would the difference still be audible?

I remember asking Justin Weaver how much he thought we could change the box size before anyone would really notice. He said probably around 40%. That's a large change (to Qtc as well, especially if the sub needs a small box to begin with) before you could actually hear a difference. So that's why I think Kms nonlinearities add less audible distortion than BL nonlinearities.

Kippels site shows the BL distortion being much larger than Kms and Le distortion. But I don't understand why. The only thing BL nonlinearities seems to effect is SPL. So output to power input becomes worse and worse. But how does that add distortion? I suppose this would effect the frequency response as well since the sub should be getting louder to keep up with the midrange, but it doesn't. But that should be much less than how much Kms effects the frequency response. Also, how does BL nonlinearities add sonic distortion (becides effecting frequency response)? From what I have heard (Brahma compared to a/d/s/ subs, IDMAX, etc.), it seems to add some. Where does it come from?

I hope my ramblings here made at least some sense. Plus I hope I didn't pull it too far off topic.

 

Well I've come across a B10. Care to donate?

 

Well, i offered it to Seth since we both live in the same town. It would be a daily switch type thing. Sending it to you would involve shipping costs and going without bass for days, plus i wouldn't get to hear them side by side . Sooo, unless you have something to give me to run for the few weeks that i'll be without bass, i'll have to say negative on that one .

 

Yeah, I was more just kidding around.


Now that I think about it though, my head unit recently decided to die. This means that I have no way of playing my stereo, and right now my B10 is sitting on the floor of my front room. I have no extra money to replace the head unit right now. I suppose if you guys are willing to pay for shipping (with insurance), I could let you guys play with mine for a while. You MUST promise to be nice though and not break it.

One other problem though is that the guys at work decided to throw away the old box it shipped in (the B10 I have now was hand delivered by Dan himself ). So I will have to find something to be able to ship it to you guys. This may delay the possibility a little. But the offers still open.

 

Haha, i'll let Seth decide on that one, i'm a poor, unemployed college student at the moment. If that changes (which it might soon, got an interview Thursday ), then i might cover that for ya.

 

Food for thought...

The overall argument is that the reason for the punchiness exhibited by some woofers moreso than others may possibly be due to the difference in BL curves...

Just not sure about that...

Look at this...
http://www.adireaudio.com/Files/B12-10W7BL...mComparison.gif
Posted by Dan Wiggins on CarSound a few months back. This is a normalized BL comparison of the B12 vs the 10W7. (Normalized means that the peak BL has been changed to 1 for both drivers).

So really overall they look pretty darn even... W7 being flatter over part of it but falls off in the upper forward excursion range a bit premature of Brahma. They tend to fall off at the same rate though... roughly. Also the peak BL of the B12 is in the upper 14's while the 10W7 is in the lower 11's.

Still... this variance here is apparently inaudible so for the argument it can be said that they are pretty much even.

If anything on what causes this punchiness (within the case of the argument) I have to think it's got far more to do with installation specifics. Cabin and enclosure having a large effect on the response of subwoofer... the other factor with using t/s parameters as any concrete indicator of transient response is their instability once driven into substantial excursion (5mm+) and with power (VC heating factor).

 

Yeah, I kinda remember saying that... and I'll kinda stand by it.

I should clarify though...

I believe I was referring to one of two situations...

1. This is based on your average install with your average listener. I believe this is more true with the larger the enclosure... as you get into drivers that work well in tiny enclosures you would be more apt to notice a 40% increase or decrease in enclosure volume.

2. The other case where this is true is where your Qtc is already say at a relatively low point... say below .75. Make a +40% change in enclosure size and where does your Qtc go? Well, it doesn't go down much... maybe from .75 down to .70... I think if you level matched those installs most anyone would have a hard time really telling a major difference there.

BTW - that comparison above was taking a B12 in a 1.12cf enclosure (result: .75 Qtc) and upping the enclosure by 40% to 1.57cf... you result with a .70 Qtc.

Now... honestly 40% changes when they are made to enclosures that are more in the 0.8~0.9~1.0 Qtc range seem to make more noticeable differences in response.

 

Yeah, I kinda remember saying that... and I'll kinda stand by it.
[/b][/quote]
Yeah, I tried to keep it non-definite by paraphrasing you as saying "probably around" because anyone can find an instance where it isn't true (as you did).

 

Yeah, I tried to keep it non-definite by paraphrasing you as saying "probably around" because anyone can find an instance where it isn't true (as you did). [/b][/quote]
Steven,

I'm with you... just didn't want to have to explain it later so took the opportunity to do it now...

Werd.

 

Several questions must be asked when selecting any speaker element albeit woofer, mid or tweeter. What is my application? Open Baffle or Closed? How stiff is the driver of interest?
Inductance of the driver isn't a tell all parameter for the driver. Less inductance means there is either fewer turns in the voice coil or a longer path length and/ or smaller area pole or a combination of all of the above.
An axiom applies to all motors speakers included. a Motor is a Generator is a Motor. This means all motors exhibit generator action as well as all generators exibit motor action.
While some may argue that the high inductance speaker is less punch...... not necessarily true based upon inductance alone. That high inductance motor will inevitable exhibit a higher running impedance than its DCR of its winding. The motor's current will be I=(Vin - Vgen)/DCR, and its useful power will be the resistance portion of the running impedance not attributed to DCR. Speakers exhibiting low Vgen will behave pretty much the same despite thier environment as thier running impedance is dominated by DCR. Speakers with high inductances will present a lower impedance in low volume closed baffles as opposed to an open baffle application as well as may present an undesirable power factor for the amplifier causing it to run hotter than it otherwise would.
If any reader wishes to have the math worked out in terms of what a layman can measure with a digital multimeter, feel free to email me at thescottsva@hotmail.com. I'll gladly email you complete with equasions and a schematic for a test fixture.