# Fast Bass, Slow Bass - Myth vs. Fact



## Oliver

SoundStage! Max dB - Fast Bass, Slow Bass - Myth vs. Fact (06/1999)

Oh , that's how it works 

what's a trough ?

peak-to-average ratios for these stimuli: 
SOURCE MATERIAL CREST FACTOR
ROCK MUSIC 10 dB
HORNS (legato notes) 10 dB
REEDS (legato notes) 12 dB
STRINGS (bowed) 15 dB
SPEECH 20 dB
PIANO 30 dB
POP MUSIC 40 dB
STRINGS (plucked) 40 dB
DRUMS 40 dB
ORCHESTRAL MUSIC 50 dB
INDIVIDUAL PERCUSSION INSTRUMENTS 60 dB
GENERAL HIGH-FIDELITY REPRODUCTION 60 dB


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## ncv6coupe

good read here a$$hole, key points that i saw were. 

"But large dynamic drivers (woofers) operating at the top of their range and medium-sized dynamic drivers operating at the bottom of their range can often diverge significantly in their phase response. Bass linearity is greatly involved also; you may see a flat frequency-response curve, but the speaker can still sound like it has lumpy bass response because of less-than-ideal phase (or other) relationships between the midrange driver and woofer. Get the midrange or woofer a little ahead of or behind the other driver, and comb filtering starts. Your absolute best shot(at integrating mids and subs) is using an active crossover with infinitely variable phase/frequency, polarity, time domain and amplitude adjustments. *You can hear even small errors show up as speed problems in the bass or midbass. These are the kinds of "character" that will remain with the speaker no matter where it is used. The fact is, bass detail comes from the midrange driver* If you hear a system (hopefully not yours) that sounds "fast" or "slow" in the bass, enough that you have noticed anyway, that system has a problem." 

To sum that up is why many people with powerful subs(including myself) have issues with high spl playback when that sub really gets cranking and their mids and struggling to keep up.


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## M-Dub

I like it slow, then fast


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## Electrodynamic

You might want to also check out this paper: http://www.stereointegrity.com/Files/WooferSpeed.pdf


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## titansfan

Electrodynamic said:


> You might want to also check out this paper: http://www.stereointegrity.com/Files/WooferSpeed.pdf


Nice paper!!! Thanks for sharing.


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## MarkZ

ncv6coupe said:


> good read here a$$hole, key points that i saw were.
> 
> "But large dynamic drivers (woofers) operating at the top of their range and medium-sized dynamic drivers operating at the bottom of their range can often diverge significantly in their phase response. Bass linearity is greatly involved also; you may see a flat frequency-response curve, but the speaker can still sound like it has lumpy bass response because of less-than-ideal phase (or other) relationships between the midrange driver and woofer. Get the midrange or woofer a little ahead of or behind the other driver, and comb filtering starts. Your absolute best shot(at integrating mids and subs) is using an active crossover with infinitely variable phase/frequency, polarity, time domain and amplitude adjustments. *You can hear even small errors show up as speed problems in the bass or midbass. These are the kinds of "character" that will remain with the speaker no matter where it is used. The fact is, bass detail comes from the midrange driver* If you hear a system (hopefully not yours) that sounds "fast" or "slow" in the bass, enough that you have noticed anyway, that system has a problem."
> 
> To sum that up is why many people with powerful subs(including myself) have issues with high spl playback when that sub really gets cranking and their mids and struggling to keep up.


I really like this explanation. I clicked on this thread half expecting people to be talking about speakers moving too slow and other such nonsense. Yes, the entire situation (well...almost) can be encapsluated by the frequency response of the system -- frequency response being amplitude response _and_ phase response. If your speaker's amplitude response can extend high enough, then it won't be "too slow". After you put it in a box, however, funny things can happen. And then when you put that box in another box (eg. the trunk), even funnier things can happen. And when you mate multiple drivers, even funnier things can happen (explained above).

Car audio is a game of cascading filters.

Which brings up another point -- reflections and echos can be detrimental not just through cancellation but also through psychoacoustic smearing. To use an extreme example, reverb can be thought of almost as anti-transient behavior. If that makes sense.


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## ncv6coupe

how about we factor in most cars have a high bass lets say somewhere between 60-100 hz suckout. ugh im trying to wrap my head around fixing this in my car by using a ported midbass at 71 hz.


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## sqshoestring

All those issues have to be minimized in auto use with xovers at ~50-100Hz.

Agreed midbass is a huge part of it in a car, huge-r with big subs. My car is a joke at the moment with the 20 Fs 15s at 50Hz and my worthless mids trying to pull 80 at best. No time and still not entirely sure what direction I will go with to solve that problem. 10s and 4s in the doors sound like a real mf of an install, the doors are not that big and its going to be stealth. Still like that idea though. Shallow 10s are pretty flat 50-200Hz in the tests I saw.


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## 60ndown

i havent and wont read 30+ page threads, but i thought the ms-8 fixed everything?

ive read a couple times recently that even if a vehicle sounds good at medium volumes, 

when played loud, everything changes ?

and if all subs play at the same speed, why does anyone ever talk about transient response and inductance?


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## MarkZ

60ndown said:


> i havent and wont read 30+ page threads, but i thought the ms-8 fixed everything?
> 
> ive read a couple times recently that even if a vehicle sounds good at medium volumes,
> 
> when played loud, everything changes ?
> 
> and if all subs play at the same speed, why does anyone ever talk about transient response and inductance?


Honestly, I don't know why people talk about transient response and inductance of subs.


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## 60ndown

meh, if the quality of our bass was determined by tuning only, we'd all be running $12 funky pups,

all *good* amps sound the same, not moofas.


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## Oliver

> The fact is, *bass detail comes from the midrange driver *If you hear a system (hopefully not yours) that sounds "fast" or "slow" in the bass, enough that you have noticed anyway, that system has a problem."
> 
> To sum that up is why many people with powerful subs(including myself) have issues with high spl playback when that sub really gets cranking and their mids are struggling to keep up.
> 
> Andy Wehmayer
> 
> Lycan is right. Qtc does define transient response for a woofer in a sealed box in an anechoic environment (minimum phase system). For a woofer in a sealed box in a car, it still defines the transient response of the speaker and enclosure, but it no longer defines the response of the entire system, because it's no longer minimum phase. _In a car there are many radiators (vibrating panels) and many reflections._
> 
> The driver Qts and system Qtc (and all Thiele and Small parameters) only define the behavior of the system at and slightly above rolloff. They have nothing to do with midband response shape. *Snappy, punchy midbass depends on flat response between 1k and 4k.* If you don't believe me, listen to your favorite midbass track on a pair of headphones through a 100Hz low pass filter. Then try 200 Hz. There's no snap or punch down there.


_It is a very complex problem making a system that sounds good, If all the little things come together , then you will have an exceptional sound _


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## mattyjman

thanks for posting this... if we had a sticky system, this should belong there


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## gitmobass

I wonder how I'm gonna break this to the local DD dealer... He believes that because the cone on the 9512 is so light nothing sounds faster and the 9512 is therefore the peak of SQ.


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## thehatedguy

Yeah but that premise has already been proven wrong. Wiggins did bad math.



Electrodynamic said:


> You might want to also check out this paper: http://www.stereointegrity.com/Files/WooferSpeed.pdf


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## ncv6coupe

"BL is time invariant, assuming small excursions (assume an ideal motor with a flat BL curve; I know, most drivers don't have that, but assume that it does, like our XBL2 enabled motors)." 

I read that adire paper back in like 2003. 7 years later overhang coil woofer technology is right about lined up with xbl^2 motors so that selling point was the shin dig back then. Hence why we should build big ported boxes with "regular woofers" tuned low and worry about getting our mids to play to 120dbs around the x-over point. (flame suit on, lol)


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## thehatedguy

Jeff/werewolf/lycan has shown the math a few times that shoots the Adire paper's claims down.


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## Electrodynamic

thehatedguy said:


> Jeff/werewolf/lycan has shown the math a few times that shoots the Adire paper's claims down.


If you have the link I'd like to read up on it.


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## MarkZ

60ndown said:


> meh, if the quality of our bass was determined by tuning only, we'd all be running $12 funky pups,
> 
> all *good* amps sound the same, not moofas.


Maybe we all soon will. I test the cheapo chip amp from parts express this week. See how it does with 12v input. If the output doesn't tank, I see no reason not to use something like that. Do you?


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## 60ndown

ncv6coupe said:


> "BL is time invariant, assuming small excursions (assume an ideal motor with a flat BL curve; I know, most drivers don't have that, but assume that it does, like our XBL2 enabled motors)."
> 
> I read that adire paper back in like 2003. 7 years later overhang coil woofer technology is right about lined up with xbl^2 motors so that selling point was the shin dig back then. Hence why we should build big ported boxes with "regular woofers" tuned low and worry about getting our mids to play to 120dbs around the x-over point. (flame suit on, lol)


dude, in 2003 you were leik 18, prolly out at hooters eating pizza not reading technical papers on moofas. 


:laugh:


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## 60ndown

MarkZ said:


> Maybe we all soon will. I test the cheapo chip amp from parts express this week. See how it does with 12v input. If the output doesn't tank, I see no reason not to use something like that. Do you?


ive owned 2 of the original sonic impacts for a few years, one powers my home made motorcycle battery fostex driver'd boombox 


great amp.

im guessing we need 100 clean rms per side on our midbass tho, and the SI can only do about 10 i believe?

Class-T amp review


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## MarkZ

No, i'm referring to the Sure amps. 100x4, 100x2 configurations. Less than $50 per.


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## 60ndown

MarkZ said:


> No, i'm referring to the Sure amps. 100x4, 100x2 configurations. Less than $50 per.


news to me, i look forward to your report......

might this mean i dont need to drop $1500 on exotics?







all good amps sound the same


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## lycan

guyz, do a search ... we've talked about transient response & "speed" a bunch of times.

The problem with that Adire paper is that it erroneously equates the _rise time_ of the transient response with the _complete time-domain transient response_. Coil inductance ONLY impacts rise time, in much the same way that a low-pass crossover impacts rise time. Don't low-pass your drivers, or you'll slow them down! 

The fact is, the COMPLETE time-domain transient response is DOMINATED by overshoot & ringing ... which are controlled by the driver's (plus enclosure) _high-pass_ T/S parameters, and NOT the _low-pass_ dynamics (including inductance and low-pass crossover filters).

Bottom line : if the driver's coil resistance divided by coil inductance (divided by 2pi) is _at least_ two times higher than the intended low-pass crossover, you can feel free to absolutely ignore coil inductance (at least, the linear term). It won't slow your driver down anymore than the crossover.

And if you don't understand why the crossover slowing-down the driver's rise time is a GOOD thing, you've got a lot to learn about crossovers ...


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## thehatedguy

<- was searching, but I think the math was lost in the deleted Klippel thread.

http://www.diymobileaudio.com/forum...r-buck-aka-loudspeaker-hell-4.html#post957717


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## lycan

Every year or so, that Wiggins paper is brought out of the closet ... even though its analysis & conclusions are questionable at best. It simply focuses too much attention on the WRONG thing : namely, transient response rise time (influenced by inductance, possibly, but also influenced by low-pass crossover), rather than transient response overshoot & ringing (impacted by mass, compliance and all the other T/S stuff).

Woofers are SUPPOSED to have slow rise times  They are NOT, however, "destined" to have sloppy overshoot & ringing 

Here's a couple threads that can be pulled out next year when the Wiggins paper is uncovered again :

http://www.diymobileaudio.com/forum/diyma-tutorials/30-transient-response-stored-energy.html

http://www.diymobileaudio.com/forum/diyma-tutorials/9579-loudspeaker-inductance.html

Please ... someone save this current thread, along with the two threads just referenced, so that next year when the Wiggins paper shows up, a simple response can be posted. And i won't have to type this all over again ...


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## loddie

Lycan,

Thanks for the links

Off-topic: PM sent regarding your tutorial on "clocks"


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## ncv6coupe

60ndown said:


> dude, in 2003 you were leik 18, prolly out at hooters eating pizza not reading technical papers on moofas.
> 
> 
> :laugh:


no no my friend, when i was 17 i was doing 7.1 surround sound with L-R difference signal with mixer boards and the whole nine yards in my bedroom with 60 cu subwoofers with 10's 12's 15's all mixed in hanging around the pro audio reggae band guys in the islands playing with "grass":laugh: I had no idea to the science behind it but i sure knew how to make things sound good. if only i could find a computer with a floppy drive as i had a (sony mavica) lol i have some pictures of this somewhere but since i came here to the US and started reading up on this forum in particular everything is starting to click as to why what i was doing sounded so damned good. Time to get it in the accord which is harder than i thought, but hey I'll get it sometime before the year is done. hopefully and pull in the MECA lanes next season.


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## Electrodynamic

Qtc and Qts do affect LOW end response, but they have precious little to do with anything ~2X above F3. How fast a system can transition IS a factor of inductance.

Have you actually measured a speaker in several different Qtc enclosures and determined which has the highest bandwidth (which, if you believe the concepts you're using, you understand that bandwidth IS transient response via the Fourier Transform – of which Andy Wehmeyer agrees, as well as many others).

In fact, where you (lycan) responded and linked to the 2005 thread, even werewolf confirms what Dan wrote - transient response and bandwidth are inextricably linked. 

And in the second one, werewolf kind of gets it in that the output a few octaves above F3 is where you hear the bass "snap"; it's in the 100-200 Hz range, not the 30-40 Hz range. By the time your subwoofer is operating in the "snap/punch" region, the impact of the tuning and the mass is gone - it's purely up to the transducer then.

ncv6coupe, I'm intrigued to see how you think that "overhang coil woofer technology is right about lined up with xbl^2 motors." I haven't seen a single gap overhung motor come close to the linearity that XBL^2 is capable of. Let alone the degree of linearity and Xmax per mounting depth.


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## lycan

Electrodynamic said:


> Qtc and Qts do affect LOW end response, but they have precious little to do with anything ~2X above F3. How fast a system can transition IS a factor of inductance.
> 
> Have you actually measured a speaker in several different Qtc enclosures and determined which has the highest bandwidth (which, if you believe the concepts you're using, you understand that bandwidth IS transient response via the Fourier Transform – of which Andy Wehmeyer agrees, as well as many others).
> 
> In fact, where you (lycan) responded and linked to the 2005 thread, even werewolf confirms what Dan wrote - transient response and bandwidth are inextricably linked.
> 
> And in the second one, werewolf kind of gets it in that the output a few octaves above F3 is where you hear the bass "snap"; it's in the 100-200 Hz range, not the 30-40 Hz range. By the time your subwoofer is operating in the "snap/punch" region, the impact of the tuning and the mass is gone - it's purely up to the transducer then.
> 
> ncv6coupe, I'm intrigued to see how you think that "overhang coil woofer technology is right about lined up with xbl^2 motors." I haven't seen a single gap overhung motor come close to the linearity that XBL^2 is capable of. Let alone the degree of linearity and Xmax per mounting depth.


first of all, lycan = werewolf.

Second, inductance CAN limit the high frequency performance of a driver ... no question about it. BUT BUT BUT ... it does so, in EXACTLY the same way that a low-pass crossover does. Limiting the bandwidth of a driver by putting a crossover on it, has the EXACT same impact : it slows down the rise time. In this sense, drivers are "slowed down" by a low-pass crossover. Should we : not low-pass drivers, OR just make sure the inductive low-pass frequency is at least two times higher than the intended crossover frequency?

*The transient response of a driver IS : the COMPLETE time-domain response of the driver to a transient input. The transient input may be an impulse function, a step function, or a variety of other functions. IF we choose an impulse function, the ENTIRE frequency response of the driver (not just it's "bandwidth") is the Fourier Transform of the transient response. This is only true if the excitation is an impulse.*

There are MANY components to a driver's transient response ... NOT just the rise time. Just like there are MANY components to a driver's frequency response ... NOT just the bandwidth. Often, we hear "sloppy" bass with excessive overshoot & ringing, and we call the driver "slow". The overshoot & ringing has NOTHING to do with inductance, but EVERYTHING to do with mass, compliance, enclosure, etc. which ALL contribute to the driver's HIGH-PASS behavior, and NOT the low-pass behavior.

In short : drivers in enclosures are BANDPASS elements. They have low-pass dynamics, and they have high-pass dynamics. Their transient response (properly defined) is dominated by their high-pass dynamics (overshoot & ringing from T/S parameters), not their low-pass dynamics.

EDIT : by "bandpass", i do not mean a "bandpass enclosure for a subwoofer". I mean a classic, bandpass frequency response : high-pass dynamics at lower frequencies, and low-pass dynamics at higher frequencies. The transient response of any such system is dominated, in time, by the high-pass dynamics (at lower frequencies). For the drivers in question, it's these high-pass dynamics (at lower frequencies) that contribute to overshoot & ringing (via Qtc & Fc). The low-pass dynamics (at higher frequencies) limit the risetime in the transient response. The limiting factor to risetime MAY be inductance, or it MAY be the INTENDED low-pass crossover.


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## Thoraudio

numbers aside, from a practical stand point, almost all 'slow' bass problems I have seen are the result of the 'mid' bass units. 

Bass is easy in a car, thanks to cabin gain. High frequencies are easy, thanks to the inherent high sensitivity of tweeters + relative ease of placement. 

Midbass and midrange are very difficult to implement correctly, and in actuality, that's where most problems with 'slow' bass and 'harsh' highs exist.


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## lycan

Quick quiz  I've got two drivers-in-enclosures :

*Driver A :*

Coil resistance : 8 ohms
Coil inductance : 2 mH
Fc : 40 Hz
Qtc : 0.70

*Driver B :*

Coil resistance : 4 ohms
Coil inductance : 2 mH
Fc : 40 Hz
Qtc : 1.40

Two questions :

1. If I put NO low-pass crossover on these drivers, how does the transient response compare?

2. If I put a second-order low-pass crossover on each driver at 100Hz, how does the transient response compare?

For your excitation function, you may use a step or impulse (they are intimately related). And remember : transient response has _many_ elements ... including risetime, overshoot & ringing.


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## ncv6coupe

Electrodynamic said:


> ncv6coupe, I'm intrigued to see how you think that "overhang coil woofer technology is right about lined up with xbl^2 motors." I haven't seen a single gap overhung motor come *close to the linearity that XBL^2 is capable of*. Let alone the degree of linearity and Xmax *per mounting depth*.


Lets be careful with where this may end up, Your not 100% serious with that comment though right?  lets not introduce any "variables", big loud woofers are gonna be well, BIG if not used in multiples then you ease size requirements. I'm not talking about shiny mirror polished subs here, the criteria is far and few with my comment about overhanged coil woofers and i think you should know i wasn't trying to step on xbl^2 motors toes when i said that, I HATE subwoofers playing bass thats why i like large boxes crossed low. you will probably say that in a car theres only soo much room why lug around all that weight takes the fact of its a car out of context, i have no need for my trunk, this car is a DD for the time being but its the "Weekend Warrior" whenever i finish my install. heres a snapshot of good ol' linearity *not the best *but lets just say getting close.

and you know how to interpret this data sorry if i posted a bigger picture then i would blow the subs "cover" a simple overhang 27mm high xmax driver here. 
Bl 11.8587 K 4.9596
Bl x coef A -0.00115 K x coef A -0.0012
BL x^2 coef B -0.00045 K x^2 coef B 0.0007


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## thehatedguy

Nick also licenses XBL2 from Dan so he might be a bit biased as to what it can and can't do.

I would submit that an Acoustic Elegance woofer with the full copper sleeve on the pole would be pretty nice in terms of inductance variations...and could be even better with the Faraday rings like you also use.


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## ncv6coupe

I guess thats why they call you the hated guy, i know things but i dont kno things.!.! nuff said, ok one more thing, this is my most outlandish comment i may ever say, xbl2 motors mean more in mids than subs. i do not have a ee degree but i have good ears which arent bass (linear anyway) pun intended


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## thehatedguy

Well way back when Dan Wiggins said the benefits of XBL2 would be seen more in mids and highs over subs...just that nearly 10 years later there isn't many mids using the technology and no commercially available highs.


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## 60ndown

i switched out an alpine 15" type R today for a jl 12w6v2, 

same settings, same box 

(apparently the 12w6 works well in about 4 cubes @ 30)

i changed nothing else

the jl IS much faster.


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## Oliver

60ndown said:


> the jl IS much faster.


It's the *peninsula power factor* !


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## ncv6coupe

lycan said:


> Quick quiz  I've got two drivers-in-enclosures :
> 
> *Driver A :*
> 
> Coil resistance : 8 ohms
> Coil inductance : 2 mH
> Fc : 40 Hz
> Qtc : 0.70
> 
> *Driver B :*
> 
> Coil resistance : 4 ohms
> Coil inductance : 2 mH
> Fc : 40 Hz
> Qtc : 1.40
> 
> Two questions :
> 
> 1. If I put NO low-pass crossover on these drivers, how does the transient response compare?
> 
> 2. If I put a second-order low-pass crossover on each driver at 100Hz, how does the transient response compare?
> 
> For your excitation function, you may use a step or impulse (they are intimately related). And remember : transient response has _many_ elements ... including risetime, overshoot & ringing.


well the tables are gonna be reversed in a sense,

1. _*driver A and b*_ have equal attack/rise time(equal fight) but driver A has faster *decay* so a bass pluck is just that nothing "extra", Driver A is going to *appear* niceR and tighteR or faster well up into the midrange because the driver is better damped so amplitude response should be fairly smooth. remember NO CROSSOVER APPLIED

2. You better cross driver B lower at 70 hertz or you will have a poorly detailed SLOW bass presentation because the damn sub is playing "chords" shall we say ring ring ring, it has even slowER rise time than mr.quick/driver A and still has very poor decay since its q is soo high so the woofer is still flopping up and down while your (real midbasses and midranges) are speeding along 2 ms forward in the song. you have ripples in the frequency response/amplitude response(comb filtering) and these get very audible as frequency gets about a octave up(200hz-up) with that shallow 12db filter which affects the entire region of frequency the sub is playing none the less. The sub amplitude will still be too high so it dominates and you guessed it, bass, tom and snare drum mud. but maybe you like that sound though


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## ncv6coupe

a$$hole said:


> It's the *peninsula power factor* !


that old uggly ripply BL curve(gross exaggeration) i posted earlier speaks millions about overhang coiled woofers these days but the rules still apply just keep it 60-70hz and down on the x-over with that HUGE ported box and enjoy subwoofer bliss. also high pass, 17mm xmax isn't quite the norm for big boy bottom feeders at high power.


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## lycan

ncv6coupe said:


> well the tables are gonna be reversed in a sense,
> 
> 1. _*driver A and b*_ have equal attack/rise time(equal fight) but driver A has faster *decay* so a bass pluck is just that nothing "extra", Driver A is going to *appear* niceR and tighteR or faster well up into the midrange because the driver is better damped so amplitude response should be fairly smooth. remember NO CROSSOVER APPLIED
> 
> 2. You better cross driver B lower at 70 hertz or you will have a poorly detailed SLOW bass presentation because the damn sub is playing "chords" shall we say ring ring ring, it has even slowER rise time than mr.quick/driver A and still has very poor decay since its q is soo high so the woofer is still flopping up and down while your (real midbasses and midranges) are speeding along 2 ms forward in the song. you have ripples in the frequency response/amplitude response(comb filtering) and these get very audible as frequency gets about a octave up(200hz-up) with that shallow 12db filter which affects the entire region of frequency the sub is playing none the less. The sub amplitude will still be too high so it dominates and you guessed it, bass, tom and snare drum mud. but maybe you like that sound though


you've got some good points and ideas  but not an accurate answer 

I'll tell ya guyz, until this quiz can be answered with reasonably accuracy, the transient response of drivers can _never_ be understood ... much less discussed and debated.

More clues :

The driver inductance (at least, the linear term) forms a first-order, low-pass filter ... NOTHING MORE. It's IDENTICAL to some "baggage" carried around by the driver, in the form of an "inherent" first-order low-pass crossover. The frequency of the first order low-pass is : Re/(2pi*Le). Where (in frequency) is this "inherent" low-pass of each driver? Are they the same? I do agree ... in the absence of an _applied_ crossover, these "baggage" or "inherent" crossovers will slow down the "attack" or "rise time". What's the rise-time of a first-order low-pass filter?

Next, we apply the intended, second-order low-pass. What happens when this new, intended low-pass is "cascaded" with the "inherent" or "baggage" first-order inside the driver? What has changed? *Haven't we "slowed-down" the drivers even worse with this newly applied crossover?* 

Finally, how is overshoot & riniging impacted by all this LOW-PASS talk? What will DOMINATE the complete time-domain transient response ... the low-pass dynamics, or the high-pass dynamics?

*Perhaps most importantly : Is a woofer perceived as "slow" and "sloppy" ... rather than "fast and tight" ... because of rise time dynamics at a few hundred hertz, or because of high-pass dynamics, especially overshoot and ringing, at forty hertz ??????????????*

Please give this stuff some more thought. It's pretty fundamental to driver transient response. Without a firm grasp on these points, we're all wandering in the dark ... relying on rumors and gurus.


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## 60ndown

a question,

semantics aside, generally speaking, and on topic,



are sealed boxes generally slower then big ported boxes?

im currently playing with 2 boxes,

4 cubes @ 28

1.25 sealed.

and a jl 12w6v2 and 1500 wrms

yes maybe the sealed box is more linear (before eq), and the ported box is louder and lower, 

but im wondering if the fact that there is much less 

*restriction of the cone / Q / under/over damped?* 

in the big ported box, that cone can respond a lil faster? 

or am i hearing things ??

generally speaking


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## tornaido_3927

lycan said:


> The limiting factor to risetime MAY be inductance, or it MAY be the INTENDED low-pass crossover.


Sorry for what I think might be an elementary question.. 

From what I've read on that 'wooferspeed' paper with the rise time being slowed due to the inductance of the driver (because the inductor stores energy), will the rise time be affected by a low pass digital crossover as opposed to using an actual inductor?


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## lycan

tornaido_3927 said:


> Sorry for what I think might be an elementary question..
> 
> From what I've read on that 'wooferspeed' paper with the rise time being slowed due to the inductance of the driver (because the inductor stores energy), will the rise time be affected by a low pass digital crossover as opposed to using an actual inductor?


YES.

The inductance stores energy. The inductance slows down the rise time. When we put a low-pass crossover on the driver, we are doing the _exact same thing_. In fact, we make the situation even worse ... the low-pass crossover is probably LOWER in frequency than the first-order, low-pass baggage of the driver's inductance.

*The crossover we put on the driver SLOWS IT DOWN EVEN MORE.*

What's up with that ??????????? 

Yeah ... it's just one problem i have with that referenced paper 

Bottom line : The driver's inductance is IDENTICAL to a first-order, passive low-pass crossover filter. It's "impact" on transient response is exactly the same as a low-pass crossover. If it's at least two times higher in frequency than the low-pass crossover you're going to put on your driver anyway, feel free to ignore it. The inductance ain't slowing anything down more than you are _supposed to do_ with the intended, applied electrical crossover.

Woofer still sounds "slow" and "sloppy", instead of "fast" and "tight"? Look at the parameters that DOMINATE the transient response : overshoot & ringing, from Qtc & Fc. Inductance has nothing to do with these dominating effects. Inductance ain't the problem, if it's low-pass is higher in freq than the crossover.


----------



## pionkej

lycan said:


> Quick quiz  I've got two drivers-in-enclosures :
> 
> *Driver A :*
> 
> Coil resistance : 8 ohms
> Coil inductance : 2 mH =.002H
> Fc : 40 Hz
> Qtc : 0.70
> 
> *Driver B :*
> 
> Coil resistance : 4 ohms
> Coil inductance : 2 mH =.002H
> Fc : 40 Hz
> Qtc : 1.40
> 
> Two questions :
> 
> 1. If I put NO low-pass crossover on these drivers, how does the transient response compare?
> 
> Driver A:
> f=8/(2*3.14*.002)
> f=636hz
> 
> Driver B:
> f=4/(2*3.14*.002)
> f=318hz
> 
> The *rise time *portion of transient response will be better with driver B I believe with NO low-pass crossover because it has a lower inductance driven "low-pass crossover"
> 
> The *decay* time of driver A is going to be better since they both have an FC of 40hz but driver A has an QTC of .7 leaving it close to the "ideal" alignment of .707 that is the compromise between extension and optimum transient response (.5). Driver B has a QTC of 1.4 which means it is severly under-damped at 40hz which allows for more overshoot and ringing.
> 
> 2. If I put a second-order low-pass crossover on each driver at 100Hz, how does the transient response compare?
> 
> If you put a crossover on both drivers at 100hz, driver A becomes the clear winner. Since both 318hz (driver B) and 636hz (driver A) are higher than 200hz (one octave above 100hz) neither driver is affected because, "The inductance ain't slowing anything down more than you are supposed to do with the intended, applied electrical crossover." That means that driver A now has better transient response in *decay* and equal transient response in *rise* as driver B making it the winner.
> 
> For your excitation function, you may use a step or impulse (they are intimately related). And remember : transient response has _many_ elements ... including risetime, overshoot & ringing.



I read the threads you linked and I think I have this worked out, please "guide" me along if I'm wrong...even if it involves more calculations.

I also hope I am right because it would explain alot about an issue I'm currently experiening. My midbass is not matching well with the rest of my system. After looking at it, my subs have a QTC of .485 and my midrange has a QTC of .592 while my midbass sits at .914.  If I am correct and I'm experiencing lots of overshoot and ringing in this range which is making things sound "muddy", it happened because I used a driver suited for IB applications (believing people when they call doors IB) and not realizing my door is actually much more a "leaky box" in reality which dramatically changes the parameters of a speaker I need to use.


----------



## WRX/Z28

60ndown said:


> i switched out an alpine 15" type R today for a jl 12w6v2,
> 
> same settings, same box
> 
> (apparently the 12w6 works well in about 4 cubes @ 30)
> 
> i changed nothing else
> 
> the jl IS much faster.


So if the alpine was playing 60 cycles/second (60hz), how many does the JL play with the same tone? Can you time it for us?


----------



## 60ndown

WRX/Z28 said:


> So if the alpine was playing 60 cycles/second (60hz), how many does the JL play with the same tone? Can you time it for us?




if its a complicated bass line (60hz-33-36-26-60-53 repeatedly), the R was struggling to make the changes accurately (sounded muddy and off, worse at higher volumes) whereas the w6 does it much better.

but if all you want to do is listen to 60hz sine waves i can sell you my R


----------



## WRX/Z28

60ndown said:


> if its a complicated bass line (60hz-33-36-26-60-53 repeatedly), the R was struggling to make the changes accurately (sounded muddy and off, worse at higher volumes) whereas the w6 does it much better.
> 
> but if all you want to do is listen to 60hz sine waves i can sell you my R


So 60 exactly and then 33 exactly then 36 exactly? Did the slower Alpine end up at say 59, then 32, then 35? or are you saying the sub couldn't play the next note? 

Figure out where your cabin gain peak is, and apply some cut there (~6db). You'll probably be pleasantly surprised with the results...


----------



## ncv6coupe

Lycan, i posted a reply last nite but i guess it never came through, i purposely didnt mention voice coil weight and magnet strength because i didnt want to get too ahead of myself. the low pass behavior dominates the transient response, how about giving the woofer a big stiff high energy storing low resonant frequency cone coupled with a magnet that cant control it up high when its time to "stop" i compare this to when i build a speaker box, u make the box stiff u get a higher resonance, but u need the box to be heavy or your sub bass sounds gurgled. i know that the voice coil cause a 90 degree phase shift almost always in the "midbass". add in another 180 degree phase shift with the 12db low pass and u have a 18 db crossover, 270 degree phase shift per octave, this sounds like crap at 500 hz with high inductance woofers and matching midbass with that radical swing is TOUGH. ill post some more a little lateri know i missed some stuff but i cant scroll up and down on my phone too well


----------



## lycan

ncv6coupe said:


> the low pass behavior dominates the transient response, ...


no, it doesn't.

That's the essence of what's wrong with the Wiggins paper.

The low pass behavior dominates just the RISE TIME of the transient response, which is but a SMALL PART of the complete transient response. And even for this SMALL FRACTION of the complete transient response, the inductance may not even matter ... if the intended crossover electronically applied to the driver is LOWER in frequency than Re/(2pi*Le).

Now, as far as the VAST MAJORITY of the transient response, this majority is dictated by the high-pass behavior of the driver ... classic T/S stuff ... that contribute to overshoot and ringing. Inductance has no impact on this vast majority of the complete transient response.


----------



## lycan

Guys, this topic is clearly endlessly confusing.

My recommendation : read the classic Thiele/Small papers! Understand what is meant by transient response. Understand why Small can have an elaborate, meaningful discussion of transient response ... without even mentioning driver inductance.

Understand how the classic T/S parameters control Qtc, which determines overshoot and ringing. Understand that drivers in enclosures exhibit a high-pass response ... and these high-pass dynamics translate into overshoot and ringing in the complete time domain transient response.

THEN ... and only then ... does it make sense to consider the smaller impact of driver inductance, or low-pass crossover (whichever is lower in frequency).

Otherwise, we're all lost in quagmire of terms that nobody quite understands ... and we're left to believe in myths & rumors about why our subs sound "slow" and "sloppy".


----------



## pionkej

lycan said:


> Guys, this topic is clearly endlessly confusing.
> 
> My recommendation : read the classic Thiele/Small papers! Understand what is meant by transient response. Understand why Small can have an elaborate, meaningful discussion of transient response ... without even mentioning driver inductance.
> 
> Understand how the classic T/S parameters control Qtc, which determines overshoot and ringing. Understand that drivers in enclosures exhibit a high-pass response ... and these high-pass dynamics translate into overshoot and ringing in the complete time domain transient response.
> 
> THEN ... and only then ... does it make sense to consider the smaller impact of driver inductance, or low-pass crossover (whichever is lower in frequency).
> 
> Otherwise, we're all lost in quagmire of terms that nobody quite understands ... and we're left to believe in myths & rumors about why our subs sound "slow" and "sloppy".


Lycan, did you see my post on the last page? Was it anywhere close to being right? If not, I would still like to know as I am happy to do more research to learn this. I felt like I was on to something playing with Unibox yesterday BEFORE this thread was posted, but I didn't know the "why". I'm dying to find out now.


----------



## lycan

pionkej said:


> I read the threads you linked and I think I have this worked out, please "guide" me along if I'm wrong...even if it involves more calculations.
> 
> I also hope I am right because it would explain alot about an issue I'm currently experiening. My midbass is not matching well with the rest of my system. After looking at it, my subs have a QTC of .485 and my midrange has a QTC of .592 while my midbass sits at .914.  If I am correct and I'm experiencing lots of overshoot and ringing in this range which is making things sound "muddy", it happened because I used a driver suited for IB applications (believing people when they call doors IB) and not realizing my door is actually much more a "leaky box" in reality which dramatically changes the parameters of a speaker I need to use.


Your answers to the quiz are quite good!

Driver A has a higher "inherent" low-pass due to driver inductance, which means it will inherently have a faster rise time. That benefit will be completely neutralized, however, when we low-pass BOTH drivers at 100Hz (well below EITHER "baggage" crossover).

Driver B remains "slow" and "sloppy", in all cases, due to the worse overshoot & ringing from high Qtc. And this remains true, before & after any impact of driver inductance is completely eliminated.

*Allow me to repeat :* Driver B remains slow & sloppy ... due to classic underdamped transient behavior ... even AFTER the effect of driver inductance is completely nullified (by the applied crossover at 100Hz).

I'm not saying driver inductance doesn't matter. I'm just saying it's a far cry from _dominating_ the driver's complete transient response! Heck ... it might not even _contribute_ to the transient response, once the driver is crossed-over with an electronic low-pass crossover.


----------



## ncv6coupe

i will try to read those theile small papers later as im trying hard to get my ahhhaaa moment of fully understanding it in words AND SOUND. Im off track somewhere. I
think im stuck right at the fence of realizing that high pass=decay. correct me if im wrong if we were to flip a high pass the other way then what is that, thats why i believed earlier that low pass was the correct term, not from going by what is in the wiggins paper


----------



## lycan

This response will be geeky ... but it's undeniably true, nonetheless.

A driver in a sealed box (including IB) has a 2nd-order high-pass response. Those "two orders" come from two energy storage elements : mass & compliance. When you include driver inductance, OR put a low-pass filter on the driver, you've added a low-pass response as well ... so that the whole system now has a band-pass response. This low-pass element also corresponds to an energy storage element ... the inductance in the coil, or energy storage in the low-pass crossover.

To an electrical engineer, all of these energy storage elements contribute to "poles" in the system transfer function. There's two poles at low frequencies ... from mass & compliance ... that dictate the high-pass response. And there's (at least) one pole at higher frequencies ... from inductance, or crossover ... that dictate the low-pass response.

Which poles DOMINATE the transient response of the system? Why, the lower frequency poles, of course 

So ... if you're trying to examine transient behavior by examining the energy storage in the inductance, while ignoring energy storage in mass & compliance ... you're barking up the wrong tree.


----------



## pionkej

lycan said:


> Your answers to the quiz are quite good!
> 
> Driver A has a higher "inherent" low-pass due to driver inductance, which means it will inherently have a faster rise time. That benefit will be completely neutralized, however, when we low-pass BOTH drivers at 100Hz (well below EITHER "baggage" crossover).
> 
> Driver B remains "slow" and "sloppy", in all cases, due to the worse overshoot & ringing from high Qtc. And this remains true, before & after any impact of driver inductance is completely eliminated.
> 
> *Allow me to repeat :* Driver B remains slow & sloppy ... due to classic underdamped transient behavior ... even AFTER the effect of driver inductance is completely nullified (by the applied crossover at 100Hz).
> 
> I'm not saying driver inductance doesn't matter. I'm just saying it's a far cry from _dominating_ the driver's complete transient response! Heck ... it might not even _contribute_ to the transient response, once the driver is crossed-over with an electronic low-pass crossover.



Great! I'm glad that there is a "why" behind what I was experiencing. It also makes sense why I can cut out the midbass and run the subs up to 150hz to meet the 5.25" and get better coherance right now (though the stage pulls back a bit at times). 

I'm curious, it seems .707 is what many consider the "optimum" alignment because of the compromise between extension and response. Since we have healthy amounts of cabin gain at low frequencies in a car, would it be better to target a driver that models in the .5-.6 range? Also, what about drivers that fall around .2-.3? I would assume they would tend to have lots of "snap" from being over-damped but lack a lot of low end extension even if the driver displacement is present.

Two things to note about all of this...

1.) People REALLY need to pay attention to the enclosure's they use. Like I said in my first post, I bought my midbass off modeling them IB (since that is what I thought my door was from people's comments) and after these issues I measured it closely (around 2.25cubes), added that the "box" was "leaky", and modeled it. My Qtc went from .707 to .915! Hello muddy sounding midbass.

2.) This should bring to light why it can be dangerous asking people how speakers sound. My door may be larger, smaller, sealed better, sealed worse, than your door and while a driver may sound great or bad for me, it could be the exact opposite in someone else's ride.


----------



## lycan

pionkej said:


> Great! I'm glad that there is a "why" behind what I was experiencing. It also makes sense why I can cut out the midbass and run the subs up to 150hz to meet the 5.25" and get better coherance right now (though the stage pulls back a bit at times).
> 
> I'm curious, it seems .707 is what many consider the "optimum" alignment because of the compromise between extension and response. Since we have healthy amounts of cabin gain at low frequencies in a car, would it be better to target a driver that models in the .5-.6 range? Also, what about drivers that fall around .2-.3? I would assume they would tend to have lots of "snap" from being over-damped but lack a lot of low end extension even if the driver displacement is present.
> 
> Two things to note about all of this...
> 
> 1.) People REALLY need to pay attention to the enclosure's they use. Like I said in my first post, I bought my midbass off modeling them IB (since that is what I thought my door was from people's comments) and after these issues I measured it closely (around 2.25cubes), added that the "box" was "leaky", and modeled it. My Qtc went from .707 to .915! Hello muddy sounding midbass.
> 
> 2.) This should bring to light why it can be dangerous asking people how speakers sound. My door may be larger, smaller, sealed better, sealed worse, than your door and while a driver may sound great or bad for me, it could be the exact opposite in someone else's ride.


Good points to note 

My advice is quite similar : make sure you understand your enclosure and it's impact on driver's transient response ... this is CLASSIC Thiele/Small stuff ... before you go looking at inductance.

In geek-speak : make sure you understand your _low frequency poles_, and their impact on transient response, before you spend too much time on the _higher frequency poles_.

Don't understand poles and frequencies and all that stuff? That's what modeling programs are for  None of us have any business building boxes and discussing transient response UNTIL we model our drivers in enclosures, and analyze the TRANSIENT RESPONSE as well as the frequency response


----------



## DanWiggins

lycan said:


> Guys, this topic is clearly endlessly confusing.
> 
> My recommendation : read the classic Thiele/Small papers! Understand what is meant by transient response. Understand why Small can have an elaborate, meaningful discussion of transient response ... without even mentioning driver inductance.


Do not forget that T/S relates only to the two octaves centered about Fb; beyond that bandwidth it does not apply, per Thiele's own cautions. 

And inductance does matter, Thiele and Small made the simplification of ignoring an inductance large enough to introduce a filter within 3 octaves of Fb, which clearly does NOT hold for most current overhung subwoofers.

Then consider that F3 for most car audio subwoofer systems is around 30-40 Hz, meaning the impact of T/S modeling is basically gone by the time you're up around 80-100 Hz, where the "impact" and "speed" of bass is perceived. And where the inductive peak of many subwoofers is present.



> Understand how the classic T/S parameters control Qtc, which determines overshoot and ringing. Understand that drivers in enclosures exhibit a high-pass response ... and these high-pass dynamics translate into overshoot and ringing in the complete time domain transient response.


Understand that in order to reach that high pass filter, the signal must FIRST go through the low pass filter (and associated delay) of the driver's inductance.



> Otherwise, we're all lost in quagmire of terms that nobody quite understands ... and we're left to believe in myths & rumors about why our subs sound "slow" and "sloppy".


Consider the impact of psychoacoustics and the latent time of fusion. In the midbass range (where slow or tight bass is perceived, typically 100 to 300 Hz), events which happen within ~4-5 milliseconds are perceived as the same event. Events which happen outside that time are perceived as discrete events.

A 200 Hz inductance corner of your subwoofer means that the signal can be delayed by 5 milliseconds, right on the border of misaligning with your midbasses and other drivers. Add in the modulation of inductance with position, power and frequency and you end up with a delay that can vary from 3 to 10 milliseconds depending upon signal content, significantly impacting imaging and tonal preference.

Low inductance - even it if varies a lot with power, stroke, and frequency - moves this effect even higher in bandwidth, where the crossover can ameliorate the effect significantly.

Anyway, I believe we can fully agree that frequency response IS transient response, for a single driver. Good transient response necessarily requires wide bandwidth, there's no way around it.


----------



## DanWiggins

thehatedguy said:


> Well way back when Dan Wiggins said the benefits of XBL2 would be seen more in mids and highs over subs...just that nearly 10 years later there isn't many mids using the technology and no commercially available highs.


There are actually close to 100 commercially available midranges and highs (full range and tweeters) using XBL, many of which are purchased every day in Best Buy and other stores. You'll find XBL drivers in everything from low end laptops to car audio products to mid-fi home audio to the ultra-fi end of audio to desktop phones to PA speakers to recording monitors. Last year saw just over 2 million XBL drivers rolled out, this year should see closer to 3 million.

Most companies choose to not use the label (and add, as a condition of licensing, a non-disclosure requirement relating to who my client is) as they wish to maintain their own "mystique" about designing and building their own speakers, but it's used nevertheless.


----------



## MarkZ

DanWiggins said:


> A 200 Hz inductance corner of your subwoofer means that the signal can be delayed by 5 milliseconds, right on the border of misaligning with your midbasses and other drivers.


What signal? By 200Hz, the signal should already be attenuated by 12-48dB for most users, depending on their lowpass crossover setting.


----------



## lycan

DanWiggins said:


> Do not forget that T/S relates only to the two octaves centered about Fb; beyond that bandwidth it does not apply, per Thiele's own cautions.
> 
> And inductance does matter, Thiele and Small made the simplification of ignoring an inductance large enough to introduce a filter within 3 octaves of Fb, which clearly does NOT hold for most current overhung subwoofers.


Doesn't matter that the T/S parameters don't apply beyond piston range ... the poles (and resultant dynamics) from mass & compliance will STILL be lower in frequency, and therefore MUCH more impactive to complete transient response than inductance.


> Then consider that F3 for most car audio subwoofer systems is around 30-40 Hz, meaning the impact of T/S modeling is basically gone by the time you're up around 80-100 Hz, where the "impact" and "speed" of bass is perceived. And where the inductive peak of many subwoofers is present.
> 
> 
> 
> Understand that in order to reach that high pass filter, the signal must FIRST go through the low pass filter (and associated delay) of the driver's inductance.


Doesn't matter which filter the signal sees "first". The cascade order of linear, time invariant systems DOES NOT MATTER. The transient response would be IDENTICAL if the signal "saw" the inductance last. And yes, i'm restricting the discussion to the linear aspects of inductance ... can't hope to understand the nonlinear effects until the linear ones are well comprehended.

What DOES matter, is the time constants (and possible Q, for complex poles) associated with the poles ... not the order in which the signal passes through them. Low frequency poles will have longer time constants, and will therefore dominate the transient response (and complex pairs will also tend to ring).


> Consider the impact of psychoacoustics and the latent time of fusion. In the midbass range (where slow or tight bass is perceived, typically 100 to 300 Hz), events which happen within ~4-5 milliseconds are perceived as the same event. Events which happen outside that time are perceived as discrete events.
> 
> A 200 Hz inductance corner of your subwoofer means that the signal can be delayed by 5 milliseconds, right on the border of misaligning with your midbasses and other drivers. Add in the modulation of inductance with position, power and frequency and you end up with a delay that can vary from 3 to 10 milliseconds depending upon signal content, significantly impacting imaging and tonal preference.
> 
> Low inductance - even it if varies a lot with power, stroke, and frequency - moves this effect even higher in bandwidth, where the crossover can ameliorate the effect significantly.
> 
> Anyway, I believe we can fully agree that frequency response IS transient response, for a single driver. Good transient response necessarily requires wide bandwidth, there's no way around it.


Yes, there is a way around it.

Good transient response FIRST requires that the LOW FREQUENCY dynamics are well behaved, before we worry about the high frequency dynamics.

*Purely high-pass filters ... with infinitely wide "bandwidth" (zero inductance, if you will) ... can have LOUSY transient response, if the Qtc is too high !!!! *That's one of the major conclusions of T/S analysis, and why inductive behavior can't always be blamed for terrible transient response.

*Worry about the low-frequency poles & dynamics FIRST, then worry about the high frequency poles & dynamics ... for the simple reason that low frequency poles & dynamics will tend to dominate the transient response.* That's why T/S analysis STILL remains fundamental & relevant.


----------



## lycan

MarkZ said:


> What signal? By 200Hz, the signal should already be attenuated by 12-48dB for most users, depending on their lowpass crossover setting.


exactly.

Yet another reason why looking to inductance first, in order to understand transient response, is the wrong approach.

Not only are the inductive dynamics _higher in frequency_ than the mass & compliance dynamics (which means the inductive time constants are "shorter lived" than those resulting from the other, more significant energy storage elements in the driver), but it may very well be that the inductive low-pass is completely "swamped" or "over-ridden" by the intended low-pass we apply to our woofers.

Which potentially makes inductance about 4th on the list of importance ...

Is inductance important? Maybe ... but if Re/(2pi*Le) is at least twice the intended crossover frequency, you may CERTAINLY feel free to ignore it (at least, the linear part of inductance). The mass, compliance and crossover filter (in that order) will dominate the transient behavior.


----------



## thehatedguy

I for one would like to try some of these out. The only tweeter that I knew about was the ADI ceramic dome, and the only mids that I know can be purchased are the ones from CSS and Exodus Audio. I know you have some product in a few studio monitors, but getting those drive units isn't practical.

If anyone can point me in the direction of 2-3" fullranges that use the technology and good 1" tweeters, please do so...can be via PM if not want to make it public.



DanWiggins said:


> There are actually close to 100 commercially available midranges and highs (full range and tweeters) using XBL, many of which are purchased every day in Best Buy and other stores. You'll find XBL drivers in everything from low end laptops to car audio products to mid-fi home audio to the ultra-fi end of audio to desktop phones to PA speakers to recording monitors. Last year saw just over 2 million XBL drivers rolled out, this year should see closer to 3 million.
> 
> Most companies choose to not use the label (and add, as a condition of licensing, a non-disclosure requirement relating to who my client is) as they wish to maintain their own "mystique" about designing and building their own speakers, but it's used nevertheless.


----------



## jp88

thehatedguy said:


> I for one would like to try some of these out. The only tweeter that I knew about was the ADI ceramic dome, and the only mids that I know can be purchased are the ones from CSS and Exodus Audio. I know you have some product in a few studio monitors, but getting those drive units isn't practical.
> 
> If anyone can point me in the direction of 2-3" fullranges that use the technology and good 1" tweeters, please do so...can be via PM if not want to make it public.


heres a 3 inch fullrange with xbl
Audience A3 3" Full Range Driver | Parts-Express.com


----------



## ncv6coupe

"Built like a high-power subwoofer driver that employs a large neodymium motor structure, big voice coil, and suspension venting, the A3 is capable of 12 mm of usable excursion with less than 1 dB compression at levels up to 95 dB SPL. Despite this brute-strength functionality, the driver is ultra-responsive at 2.5 grams total moving mass". *OMG what a mini beast*


----------



## thehatedguy

I forgot about the A3. Wish I could fit it in the car...and the price was a bit better.


----------



## 60ndown

i cant read (and understand) all this technical stuff, my ADD kicks in hard by the 2nd line 



any of you techies wanna break it down real simple for me ?

id like to know.


----------



## MarkZ

60ndown said:


> i cant read (and understand) all this technical stuff, my ADD kicks in hard by the 2nd line
> 
> 
> 
> any of you techies wanna break it down real simple for me ?
> 
> id like to know.


In ADD vernacular...

1. a speaker's inductance is a low-pass filter
2. if the low-pass crossover point on your head unit is set much lower than the inductance's crossover point, then the inductance's crossover point doesn't matter.
3. a speaker's transient response is therefore not described by how fast it takes to respond to the note, but rather the ringing after the note stops.


----------



## DanWiggins

lycan said:


> That's why T/S analysis STILL remains fundamental & relevant.


All well and good, if you limit yourself to simple T/S analysis, and do like Thiele and Small did and discount/negate inductance. However, you keep forgetting Thiele and Small's caution - it's only applicable at small signals and assumes negligible inductance - both of which are not valid assumptions for the vast range of operation of mobile audio subwoofers. Today, most companies use T/S parameters as a starting point only, and really work on the nonlinear analysis techniques to design systems and speakers.

Inductance and bandwidth are integral to each other; transient response and bandwidth are integral to each other as well. You seem to only focus on that first octave or so right around the Fb of the system, yet that is NOT what is perceived as "tight" or "quick" bass for most subwoofer systems. From a perception of transient response standpoint, that first octave is essentially irrelevant. Inductance, however, WILL be an issue. Especially when you have an inductive peak around the crossover point. A 3 dB peak at 120 Hz will be readily audible, even with a 70 Hz 4th order low pass filter. and that 120 Hz peak is unfortunately quite common in today's subwoofers. Meaning inductance WILL impact the audible transient response - and interact with the low frequency end of things as well.

Inductance has a very large impact in the audible transient response of speakers as well, you can see it in Klippel measurements (particularly with distortion components which have an audible impact on the "sound" of the transient response). Furthermore, the order of the filters IS important, as the box and power delivered to the driver will feed back and affect the inductance. You cannot simplify it as you're trying to do.


----------



## DanWiggins

MarkZ said:


> What signal? By 200Hz, the signal should already be attenuated by 12-48dB for most users, depending on their lowpass crossover setting.


Signals that are 20+ dB down are still readily audible and can be detrimental to the reproduction of sound.


----------



## DanWiggins

lycan said:


> exactly.
> 
> Yet another reason why looking to inductance first, in order to understand transient response, is the wrong approach.
> 
> Not only are the inductive dynamics _higher in frequency_ than the mass & compliance dynamics (which means the inductive time constants are "shorter lived" than those resulting from the other, more significant energy storage elements in the driver), but it may very well be that the inductive low-pass is completely "swamped" or "over-ridden" by the intended low-pass we apply to our woofers.
> 
> Which potentially makes inductance about 4th on the list of importance ...
> 
> Is inductance important? Maybe ... but if Re/(2pi*Le) is at least twice the intended crossover frequency, you may CERTAINLY feel free to ignore it (at least, the linear part of inductance). The mass, compliance and crossover filter (in that order) will dominate the transient behavior.


Real world subwoofers often have inductive peaks down in the 100-150 Hz range and WILL IMPACT the sound quality.


----------



## ncv6coupe

the *good* large, stiff, heavy coned earthquake tone reproducing things that we use to add what we know as dynamics have limited range in the upper end compared to ___^2 but it doesn't mean much if you have really Really loud and flat speakers to "keep up" before the vocal range.


----------



## MarkZ

DanWiggins said:


> Signals that are 20+ dB down are still readily audible and can be detrimental to the reproduction of sound.


Their impact is minimal. Especially when another driver is playing the same signal at 0dB. You can calculate the cancellation of one wave even 180 deg out of phase, for example, with another wave playing -20dB. Which I think describes the scenario you presented. A 0dB signal minus a -20dB signal produces what... a -0.05dB signal? Inconsequential.


----------



## 60ndown

anyone want to offer a couple/few example set ups that would work well ?

subwoofer-make model+xover point+slope, mid bass (same) midrange (same) tweet same.

2 or 3 examples using well know currently available drivers would be great 

then i can go check the ts params and understand more in my own time.

*maybe* :blush:

or just post up your current substage and xover points etc and how happy you are with perfomance.?


----------



## lycan

DanWiggins said:


> All well and good, if you limit yourself to simple T/S analysis, and do like Thiele and Small did and discount/negate inductance. However, you keep forgetting Thiele and Small's caution - it's only applicable at small signals and assumes negligible inductance - both of which are not valid assumptions for the vast range of operation of mobile audio subwoofers. Today, most companies use T/S parameters as a starting point only, and really work on the nonlinear analysis techniques to design systems and speakers.


I'm not forgetting anything!

First, i've already stated ... multiple times, in fact ... that this whole discussion pertains to the LINEAR range of operation (aka small signals).

Second, i've already stipulated that the classic T/S analysis only pertains to the piston range of operation. AND IN THAT FREQUENCY RANGE, it identifies two dominant energy storage mechanisms and their impact on transient dynamics. The fact that there are OTHER higher-frequency dynamics outside the piston range does NOT negate their impact! This is the point YOU keep missing (or ignoring).


> Inductance and bandwidth are integral to each other; transient response and bandwidth are integral to each other as well. You seem to only focus on that first octave or so right around the Fb of the system, yet that is NOT what is perceived as "tight" or "quick" bass for most subwoofer systems. From a perception of transient response standpoint, that first octave is essentially irrelevant.


Absolutely FALSE.

Subwoofers are perceived to be slow & sloppy PRIMARILY becuse of transient ringing and overshoot ... both of which arise from mass & compliance (not inductance), and both of which are impossible from the first-order filter formed by coil inductance and resistance. Furthermore, as I've stated multiple times (and argued in both time & frequency domains), it's the LOW FREQUENCY POLES & DYNAMICS that will absolutely DOMINATE the transient response. That ain't inductance ... even if we IGNORE the applied crossover (as you tend to keep doing). 



> Inductance, however, WILL be an issue. Especially when you have an inductive peak around the crossover point. A 3 dB peak at 120 Hz will be readily audible, even with a 70 Hz 4th order low pass filter. and that 120 Hz peak is unfortunately quite common in today's subwoofers. Meaning inductance WILL impact the audible transient response - and interact with the low frequency end of things as well.


How does a LINEAR inductive pole, typically located well over 100 Hz, "interact with the low frequency end of things"? That's simply not possible with a linear, time invariant system.


> Inductance has a very large impact in the audible transient response of speakers as well, you can see it in Klippel measurements (particularly with distortion components which have an audible impact on the "sound" of the transient response). Furthermore, the order of the filters IS important, as the box and power delivered to the driver will feed back and affect the inductance. You cannot simplify it as you're trying to do.


The order of linear, time invariant poles is absolutely irrelevant. The fact that the signal sees the highest frequency one "first" does not elevate it's importance over the lowest frequency one !!!!

Anyway, here's a quick question. Two drivers, A & B.

*Driver A :*

Fc = 40 Hz (from classic T/S analysis)
Qtc = 2.0 (from classic T/S analysis)
Inductive low-pass (Re/2pi*Le) = 300Hz
Crossed over at 120 Hz by an active crossover

*Driver B :*

Fc = 40 Hz (from classic T/S analysis)
Qtc = 0.7 (from classic T/S analysis)
Inductive low-pass (Re/2pi*Le) = 250Hz
Crossed over at 100 Hz by an active crossover

It's obvious which system has "more bandwidth". Which system has the better transient response?


----------



## ncv6coupe

MarkZ said:


> 3. a *SUBWOOFERS* transient response is therefore not described by how fast it takes to respond to the note, but rather the ringing after the note stops.


i got your back homey


----------



## 60ndown

how bout y'all post up your current substage and xover points etc and how happy you are with perfomance.?

and vehicle so we can guess at transfer f / cabin gain.


----------



## ncv6coupe

60ndown said:


> how bout y'all post up your current substage and xover points etc and how happy you are with perfomance.?
> 
> and vehicle so we can guess at transfer f / cabin gain.


no no, your going about this all wrong, this thread will be derailed in .02 seconds, which happens to be very close to my group delay peak


----------



## 60ndown

ncv6coupe said:


> no no, your going about this all wrong, this thread will be derailed in .2 seconds, which happens to be very close to my group delay peak


derailed or clarified?

all this techno talk is for nothing if you guys who actually understand it cant bump accurately?

now, what ya runnin?


----------



## lycan

MarkZ said:


> Their impact is minimal. Especially when another driver is playing the same signal at 0dB. You can calculate the cancellation of one wave even 180 deg out of phase, for example, with another wave playing -20dB. Which I think describes the scenario you presented. A 0dB signal minus a -20dB signal produces what... a -0.05dB signal? Inconsequential.


... at the very least, i think we can agree that this effect sure ain't gonna _dominate_ the transient response  and it sure ain't the _first_ place to look if your sub sounds "slow".


----------



## Hernan

Sorry for my ingnorant opinion.
I use and love some XBL2 midbass. Very good midbass. Even good midrange on axis.

The questions is... in a typical car audio install, is the driver inductance so critical?
So many other factors going on...


----------



## tornaido_3927

lycan said:


> Anyway, here's a quick question. Two drivers, A & B.
> 
> *Driver A :*
> 
> Fc = 40 Hz (from classic T/S analysis)
> Qtc = 2.0 (from classic T/S analysis)
> Inductive low-pass (Re/2pi*Le) = 300Hz
> Crossed over at 120 Hz by an active crossover
> 
> *Driver B :*
> 
> Fc = 40 Hz (from classic T/S analysis)
> Qtc = 0.7 (from classic T/S analysis)
> Inductive low-pass (Re/2pi*Le) = 250Hz
> Crossed over at 100 Hz by an active crossover
> 
> It's obvious which system has "more bandwidth". Which system has the better transient response?


Driver B?

Did I win!? 

I've been trying to read up on transient response and also the T/S params that are affecting it and in what way, and the main point I keep coming across is just the effect of QTC in relation to it.

From what I gather, (and I'm not sure how correct my info is, as of course anyone can post on the interwebs, and the really technical explanations can be a bit over my head) that a QTC of <0.707 will yeild the best transient response.

There are obviously many other things that will affect transient respsonse but this was just the main info I kept coming across. Also, this was what I found in relation to sealed boxes, I am not sure how this may be applied to other types of enclosures.

I hope I'm understanding :blush:


----------



## lycan

tornaido_3927 said:


> Driver B?
> 
> Did I win!?
> 
> I've been trying to read up on transient response and also the T/S params that are affecting it and in what way, and the main point I keep coming across is just the effect of QTC in relation to it.
> 
> From what I gather, (and I'm not sure how correct my info is, as of course anyone can post on the interwebs, and the really technical explanations can be a bit over my head) that a QTC of <0.707 will yeild the best transient response.
> 
> There are obviously many other things that will affect transient respsonse but this was just the main info I kept coming across. Also, this was what I found in relation to sealed boxes, I am not sure how this may be applied to other types of enclosures.
> 
> I hope I'm understanding :blush:


Yes, you won 

*Driver B has the better transient response, by far ... even though Driver A has the wider bandwidth.* The high Qtc of Driver A (in the lower frequency, high-pass regime) means that the transient response of Driver A will overshoot and ring A LOT ... yielding a system that will sound slow & sloppy, instead of fast & tight. Furthermore, the "ringing frequency" will be in the vicinity of a LOW-ish 40Hz (Fc) ... that's where the frequency peak will be from that high Qtc 

What about the wider bandwidth of Driver A? The first thing to consider is this : how useful is that bandwidth in the given application? In other words, will I be crossing over to another driver before I can use that "extra bandwidth"? If the sub itself can play well out to 1kHz ... what does it matter, if i'll be crossing it over in my system at 120Hz? If I am crossing over well below it's inductive low-pass, the "extra bandwidth" and potential benefit of faster rise time is nullified, and _being compensated elsewhere_ (in the midbass driver, for example).

Then consider how much that wider bandwidth has helped you, if the sub is overshooting & ringing at a low ~40Hz ??????

Yes ... that dusty old T/S parameter, Qtc, has by far the biggest impact on transient response. Why? Because it describes the "quality factor" of the LOWEST FREQUENCY poles, established by T/S analysis _in the region where T/S analysis is perfectly valid_ ... and the lowest frequency poles are the place to start when analyzing transient response (cuz they have the longest time constants, and will therefore dominate transient response).

I'm not saying inductance doesn't matter. I'm just providing an analysis outline we can use to judge it's importance. For good transient behavior, the order-of-importance is :

1. Start with classic T/S analysis ... available in your favorite modeling program  You'll learn the Qtc and Fc of your sub-in-enclosure, and the impact to transient response.

2. Figure out where you're going to crossover your sub. Often dictated by localization concerns, and how strong your front midbass drivers are, in a vehicle.

3. THEN compare the inductive low-pass of a candidate sub to the intended crossover, to see if the inductance is low enough to no longer be of concern.

In short: when analyzing transient response, start with the LOWEST FREQUENCY dynamics (the ones with the longest, and possibly complex, time constants) ... and work your way up


----------



## pionkej

60ndown said:


> derailed or clarified?
> 
> all this techno talk is for nothing if you guys who actually understand it cant bump accurately?
> 
> now, what ya runnin?


What you are asking for won't work, but see my comment below. When you model a sub, make sure the box it is in has a Qtc between 0.5-0.707. If you hit that mark at it doesn't have the output you want: add more drivers, increase driver size, or add more power (if the driver can take it).



tornaido_3927 said:


> Driver B?
> 
> Did I win!?
> 
> I've been trying to read up on transient response and also the T/S params that are affecting it and in what way, and the main point I keep coming across is just the effect of QTC in relation to it.
> 
> From what I gather, (and I'm not sure how correct my info is, as of course anyone can post on the interwebs, and the really technical explanations can be a bit over my head) that *a QTC of <0.707 will yeild the best transient response.*
> There are obviously many other things that will affect transient respsonse but this was just the main info I kept coming across. Also, this was what I found in relation to sealed boxes, I am not sure how this may be applied to other types of enclosures.
> 
> I hope I'm understanding :blush:


From what I understand a Qtc of 0.50 will have the best transient response. 0.707 is chosen because people think it is the best _compromise_ between transient response and low end extension. Think of it this way, as Qtc goes toward 0 you gain "snap" and good transient response and as Qtc goes toward 1 you gain "boom" but more overshoot/ringin. 

Here is how I would classify things when modeling speakers:

0.1-0.5 = Critically over-damped (lots of "snap" but no extension)
0.5 = Best transient response
0.5-0.7 = "Sweet Spot"
0.707 = Good transient response + Good extension
0.707+ = Critically under-damped (lots of "extension" but at the cost of overshoot/ringing)

Keep in mind that this information can be important when modeling midbass and midrange drivers as well. You door is really a "leaky box" (unibox will model for this at the click of a button) and not IB if you are using a driver with a VAS of greater than about 20L (based on an "average" door that is 60L)...MEASURE YOUR OWN DOOR BEFORE MODELING.


----------



## 60ndown

pionkej said:


> What you are asking for won't work.


asking people to post what sub they are running will work if they do it. several people here talking all sorts of tech, if we knew what sub stage they were running we would have a good idea of how their theory translates into real world application.

but as you can see, nobody has.

im sure many believe its better to keep it a secret and let people think we know whats up, then reveal what we actually run and leave our sub stage open to criticism? 

im sure every system is a plethora of compromises.

im sure if we decided in this thread what are the best drivers in the world, and installed those drivers in 10 different vehicles, performance would vary wildly.

this is basically a 

whats the best sub thread right?

its like a guy that says he can build an 8 second 1/4 mile car, but never builds it 


c'mon fellas,


real world, what you running? (driver/s, ported/sealed) ?


----------



## MarkZ

what the hell's a sub stage?


----------



## jp88

60ndown said:


> asking people to post what sub they are running will work if they do it. several people here talking all sorts of tech, if we knew what sub stage they were running we would have a good idea of how their theory translates into real world application.


It really doesn't matter what specific sub they are running in their situation.
They are trying to teach people how to fish, metaphorically speaking.


----------



## 60ndown

MarkZ said:


> 3. a speaker's transient response is therefore not described by how fast it takes to respond to the note, but rather the ringing after the note stops.





ncv6coupe said:


> 3. a *SUBWOOFERS *transient response is therefore not described by how fast it takes to respond to the note, but rather the ringing after the note stops.
> 
> i got your back homey






MarkZ said:


> what the hell's a sub stage?



....


----------



## 60ndown

jp88 said:


> It really doesn't matter what specific sub they are running in their situation.
> They are trying to teach people how to fish, metaphorically speaking.


but can they catch fish in the real world?


----------



## Volenti

60ndown said:


> real world, what you running? (driver/s, ported/sealed) ?


My personal vehicle isn't running anything of note (mechanics car syndrome), however my current home stereo (which could be loosley described as a set of splits+sub) uses 4x 12'' subs/woofers (closer to woofers than true subs) in an offset, partially damped, tapered TL.


----------



## pionkej

60ndown said:


> asking people to post what sub they are running will work if they do it. several people here talking all sorts of tech, if we knew what sub stage they were running we would have a good idea of how their theory translates into real world application.
> 
> but as you can see, nobody has.
> 
> im sure many believe its better to keep it a secret and let people think we know whats up, then reveal what we actually run and leave our sub stage open to criticism?
> 
> im sure every system is a plethora of compromises.
> 
> im sure if we decided in this thread what are the best drivers in the world, and installed those drivers in 10 different vehicles, performance would vary wildly.
> 
> this is basically a
> 
> whats the best sub thread right?
> 
> 
> 
> c'mon fellas,
> 
> 
> real world, what you running? (driver/s, ported/sealed) ?


What you are asking for doesn't really do anything compared to what had been discussed (including the chart I posted above). There are multiple modeling programs available for free and I believe they all show what Qtc is after you enter the box parameters. Modeling things yourself based on the type of box you like will yield much better results than people saying "this is best"...and no, this isn't a "what's the best sub thread." 

I don't think it is that anyone wants to keep it a secret though, it just isn't really useful.

For me: AE-IB12 (x2), IB, 200w ea.

That setup sounds great in my car. What the information you asked for doesn't tell you is that my trunk is around 14 cu/ft (7 per sub for airspace calcs), has a Qtc of .485 (near "perfect" transient response), and will hit [email protected] per driver (111db for the pair) before cabin gain. Is that enough output? It is for me, for others, I don't know. I do know that if I take 14 cu/ft and divide by 3 (like I'm adding a third driver) and model the sub that way my Qtc goes to .524 (still in the "sweet spot") and if I could fit a 3rd AE-IB12 I would then be up to 114db before cabin gain.

Basically this thread has been about how to find the sweet spot between good transient response (which helps things sound clean) and good low end extension (which gives people the bass they want). This isn't just about subs either (it may have started that way but has thankfully become much more), it affects midbass and midrange as well.


----------



## 60ndown

pionkej said:


> What you are asking for doesn't really do anything compared to what had been discussed (including the chart I posted above). There are multiple modeling programs available for free and I believe they all show what Qtc is after you enter the box parameters. Modeling things yourself based on the type of box you like will yield much better results than people saying "this is best"...and no, this isn't a "what's the best sub thread."
> 
> I don't think it is that anyone wants to keep it a secret though, it just isn't really useful.
> 
> For me: AE-IB12 (x2), IB, 200w ea.
> 
> That setup sounds great in my car. What the information you asked for doesn't tell you is that my trunk is around 14 cu/ft (7 per sub for airspace calcs), has a Qtc of .485 (near "perfect" transient response), and will hit [email protected] per driver (111db for the pair) before cabin gain. Is that enough output? It is for me, for others, I don't know. I do know that if I take 14 cu/ft and divide by 3 (like I'm adding a third driver) and model the sub that way my Qtc goes to .524 (still in the "sweet spot") and if I could fit a 3rd AE-IB12 I would then be up to 114db before cabin gain.
> 
> Basically this thread has been about how to find the sweet spot between good transient response (which helps things sound clean) and good low end extension (which gives people the bass they want). This isn't just about subs either (it may have started that way but has thankfully become much more), it affects midbass and midrange as well.


much better, i can understand 80% of that, thanks


----------



## ncv6coupe

60 you are taking markz's view out of context, a technical "substage" sounds like the road pavement roller flattening new ashphalt. rumble city. now think about this one. like 2 weeks ago my sub sounded warm like my 4 infinity kappa 6.5." they just werent loud enough down low for me. in 2 weeks my subs are still gonna sound warm like b&c 8ndl51's and very loud low clean and super accurate regardless of high volume playback at the volume level goal im trying to achieve, 120db's if you are wondering. piece of cake right? ha i beg to differ! with a eq and ONLY A EQ i can make my sub sound like whatever i want it to. (insert low distortion required notice sign here) 
edit; its all about keeping the sound on top of the dashboard at high, i mean very high volume. thats not very easy and no 6.5 inch mid is gonna do that and i dont care what anyone says. LOL


----------



## thehatedguy

FWIW, one v2 IDQ-15 infinite baffle.


----------



## MarkZ

thehatedguy said:


> FWIW, one v2 IDQ-15 infinite baffle.


Heh, that was my last sub and configuration. When I swapped it out with the JBL w15gti recently, I didn't notice a very big difference in transient response. The only real difference I could tell between the two (at moderate volumes, at least) was that the IDQ15 had a pretty significant hump below about 40Hz. So much so that I had applied a highpass filter to it (centered at around 30Hz or so), which I no longer needed with the JBL. After changing the filter/level adjustments, I had a hard time telling the difference between the two subs.

FWIW, the Qts of the IDQ15 is 0.28, and the Qts of the JBL is 0.48.


----------



## thehatedguy

Mine is crossed anywhere between 80 and 100 hertz on a 24 dB slope depending on what kind of magic I want the MS-8 to do. I haven't gone any higher yet, but it might be good to 125 hertz right off of the cuff.


----------



## 60ndown

now we're getting somewhere.


----------



## tornaido_3927

Yay! I thought there was going to be far more to it that I had no idea about! Although there still probably is 



lycan said:


> To an electrical engineer, all of these energy storage elements contribute to "poles" in the system transfer function. There's two poles at low frequencies ... from mass & compliance ... that dictate the high-pass response. And there's (at least) one pole at higher frequencies ... from inductance, or crossover ... that dictate the low-pass response.
> 
> Which poles DOMINATE the transient response of the system? Why, the lower frequency poles, of course



In relation to mass and compliance in regards to transient response, are there certain values that should be sought after for certain applications, (eg. a midbass driver requires a mms range of xx-xx grams), or maybe a ratio of mms:cms, or are these two parameters less relevant if the Qtc of the system will give a good transient response (.5 - .7)??


----------



## lycan

tornaido_3927 said:


> Yay! I thought there was going to be far more to it that I had no idea about! Although there still probably is
> 
> 
> 
> 
> In relation to mass and compliance in regards to transient response, are there certain values that should be sought after for certain applications, (eg. a midbass driver requires a mms range of xx-xx grams), or maybe a ratio of mms:cms, or are these two parameters less relevant if the Qtc of the system will give a good transient response (.5 - .7)??


*Qtc* and *Fc* are the two primary parameters you need to know 

The work of Thiele & Small (largely based on Beranek's earlier work) was "groundbreaking" precisely _because_ it "boiled down" the mass, compliance, BL and loss terms into these two fundamental parameters : *Qtc* and *Fc*. These are, ultimately, the two "degrees of freedom" needed to _completely_ describe the transient response (and frequency response) of a linear, 2nd-order system.

Yes, coil inductance makes the system third-order. But for the reasons already discussed, it's importance is secondary (even tertiary?) compared to *Qtc* and *Fc*, when describing transient response.

I encourage everyone to experiment with different enclosure sizes, and different drivers, in your favorite modeling programs  Observe the effect of different values of *Qtc* on : frequency response, and time-domain transient response.

IT MAKES SENSE to understand the primary factors that influence transient response ... before you worry about the secondary & tertiary.

Furthermore ...

IT MAKES SENSE to understand the small signal, linear behavior of system ... before you worry about nonlinear behavior.


----------



## Oliver

specs for a midrange

TECHNICAL DATA:
Sensitivity 2.83V/1M 89dB
Free air resonance Fs 75 Hz
DC resistance 3.2 W
V.C. inductance 0.22 mH
Power 40W
Effective cone area 49 cm2
V.C. diameter 38 mm
V.C. height -
Air gap height -

Lin. & max. excursion ±3/ ±7 mm
Air gap flux density -
BL 5.3 Tm
Moving mass incl. air 6.5 g
Net weight 0.51 kg

specs for a subwoofer


Free Air Resonance (Fs): 23.5 Hz
Electrical “Q” (Qes): 0.476
Mechanical “Q” (Qms): 7.517
Total Speaker “Q” (Qts): 0.448
Equivalent Compliance (Vas): 3.68 cu. ft. / 104.3 liters
One-Way, Linear Excursion (Xmax)*: 1.25 in. / 32 mm
Reference Efficiency (no): 0.269%
Efficiency (1W/1m)**: 86.3 dB SPL
Effective Piston Area (Sd): 107.35 sq. in. / 0.0693 sq. m
DC Resistance (Re): 2.41 ohm***
Nominal Impedance (Znom): Dual 1.5 ohm
Thermal Power Handling (Pt): 1500W
Driver Displacement: 0.21 cu. ft. / 5.9 liters
_
would either one of these sound good ?_

here are the TS specs for the woofer.

Qts: .45
Qes: .48
Qms: 7.48
Fs: 23.29 Hz
Re: 2.81
Vas: 55.79 L
Mms: 257 g
Bl: 14.81 T*m
SPL: 83.50 dB
Sd: 556 cm^2
Xmax: 28.75 (Physical Linear) mm
Voice Coil: 76MM mm

http://www.diymobileaudio.com/pics/diyma12.jpg

*does this one look good to you on paper ?*


----------



## 60ndown

so 4 pages of tech talk breaks down into 

IB 15s rule


----------



## Oliver

Yup !
use a .22 for plinking and a big un to knock em down


----------



## Oliver

bump


----------



## sqshoestring

60ndown said:


> so 4 pages of tech talk breaks down into
> 
> IB 15s rule


 Bah haha. I almost wish I would have tried to fit 18s now that I have the 15s in there IB, but I could not find an 18 like I wanted at the time. These 15s die off at 25Hz unless I can figure out how to get a port to work or something crazy like that....so they can hit 20Hz. But hey, I certainly can live with what I have now. Compared to the box subs I tried, well there is no comparison. These put a  on my face every time I dial them up.


----------



## Oliver

Can you hear 15 Hz / amp you are using ?


----------



## SSSnake

I agree with the small signal analysis to date - inductance rules rise time and Qtc & Fc rule in terms of ringing and overshoot

My question is there a hard and fast rule for where small signal ends and large signal begins?

Because I think we will find in practical application there is more to this story...

inductance variation and any variation in parameters that affect the reactance of the system will likely have an effect on what we perceive as "fast/slow" bass.


----------



## tornaido_3927

I'd really like to know about the small vs. large signals as well, I've heard it mentioned by some of the more knowledgable folk here in regards to measurements.. Made me wonder what changes between the two.


----------



## lycan

"small signal" ends when distortion become significant.

The difference between large & small signal is the presence of distortion components (harmonic, intermod). Any input/output relationship you want to measure ... let's lump them together, for now, and call them "gain" ... has a value that you can analyze and measure for "small signals". Signals are "small" if we can neglect distortion components. At some point as you keep raising the signal amplitude, the "gain" changes ... and you get a different effective "gain" value than you did for small signals only. This can only happen if there's significant distortion components in the output spectrum.

Mathematically, we might describe the input/output relationship of any system by a "transfer curve" we can draw on a graph (input on x-axis, output on y-axis). For "small signals", we can probably approximate most systems (curves) as a straight line, in the vicinity of some "operating point". But as signals get larger, the "curvature" of the input/output transfer curve will start to become significant. This is the same thing as saying that distortion components will rise in the output spectrum.


----------



## SSSnake

A somewhat concrete definition (and one I hadn't heard before - or at least remembered - been a while since I read thiele small). However, this is likely different for different drivers/systems.

The last time I looked at the output of a sub (again a while back), I fed it a 20Hz tone and there was what I would term as significant distortion at MOST drive levels. I'll see if I can dig up the plot. My point is how often is a sub in the small signal region? My guess is not that often (only a guess). The output levels were not enough to drive it "beyond the pistonic range" but it still had significant distortion products. 

The distortion products did not seem to vary widely with drive level and therefore the gain was likely fairly constant which seemed to be the second part of your criteria. Not nitpicking your comments just seeking to gain a greater understanding.


----------



## SSSnake

If we measured the output levels throughout a given passband and at various input voltages it would likely give us enough detail for a rudimentary transfer function. It might be interesting to see a what levels the function becomes nonlinear.


----------



## lycan

Most analog systems (with very, very few exceptions) get MORE linear as the signal passing through them gets SMALLER.

This is equivalent to saying this : draw some random input/output curve on a piece of paper. Make sure it's rather gently varying curve, and not a perfectly straight line. Pick some "operating point" on that curve. As the signal "variation" around that operating point gets smaller, you'll notice that a straight line becomes a better approximation to that curve  In other words, for small variations or perturbations, a straight line is a good approximation to most analog systems ... including loudspeakers.

Or, we could just say that the first term in a Taylor Series tends to be the dominant one, for small signals 

So ... as the signal level exciting your subwoofer decreases, you should see the harmonic terms in the output decrease _even faster_. For example, a 6dB _decrease_ in signal should result in a ~12dB _decrease_ in the 2nd harmonic, for a net 6dB _improvement_ in signal-to-distortion ratio.


----------



## SSSnake

> Most analog systems (with very, very few exceptions) get MORE linear as the signal passing through them gets SMALLER.


Completely agree



> Or, we could just say that the first term in a Taylor Series tends to be the dominant one, for small signals


Again I completely agree (long time since I did anything with a Taylor series) as the signal level variation is decreased the apparent slope of the function will tend to zero...



> So ... as the signal level exciting your subwoofer decreases, you should see the harmonic terms in the output decrease even faster. For example, a 6dB decrease in signal should result in a ~12dB decrease in the 2nd harmonic, for a net 6dB improvement in signal-to-distortion ratio.


Again I completely agree. 

My point is at audible levels are we still in a small signal domain for sub operation or are we already crossing into areas where non linear terms dominate (or at least become a factor in ) what we hear. If so, then thiele small analysis decreases in importance and other factors (such as variability in reactance - inductance variance, variations is the suspension system) can effect what we hear.

I have admittedly not done enough research to substantiate this theory and was just putting this out there for discussion. Many of the forum members have much more experience than I and I am interested in their thoughts on this subject as picking subs and enclosures based upon an equivalent Q and Fc values don't yield identical results (at least IME).


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## sqnut

So, how is all this going to affect the sound, when your sound and ears are in the zone? The sub then is only a part of your sound. Its only there for presence......what should I look out for? 

Not trying to start anything, just opening up another perspective.


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## lycan

SSSnake said:


> Completely agree
> 
> 
> 
> Again I completely agree (long time since I did anything with a Taylor series) as the signal level variation is decreased the apparent slope of the function will tend to zero...
> 
> 
> 
> Again I completely agree.
> 
> My point is at audible levels are we still in a small signal domain for sub operation or are we already crossing into areas where non linear terms dominate (or at least become a factor in ) what we hear. If so, then thiele small analysis decreases in importance and other factors (such as variability in reactance - inductance variance, variations is the suspension system) can effect what we hear.
> 
> I have admittedly not done enough research to substantiate this theory and was just putting this out there for discussion. Many of the forum members have much more experience than I and I am interested in their thoughts on this subject as picking subs and enclosures based upon an equivalent Q and Fc values don't yield identical results (at least IME).


tell ya what ... you can help answer the question  i'll pave the path, then ask you to walk it.

1. Establish an SPL level, for frequencies below 80Hz, in a vehicle. Not a max level you need to achieve to win an SPL competition, but a comfortable listening level where _quality_ matters more than _quantity_.

2. Reduce that dB level by some reasonable estimate of cabin gain below 80Hz. For example, let's assume cabin gain increases (as frequency decreases) at 12dB per octave below 80Hz. 

3. Determine how much excursion you need from, say, a 12-inch driver to hit that cabin-gain-reduced SPL level. Note that the free-space excursion requirements needed from a driver as frequency decreases, are nicely balanced by the cabin gain described above 

4. Compare that excursion to the max excursion you can get from a modern 12-inch driver.

Now we're in a position to understand how important small-signal analysis might be for subwoofers in vehicles


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## thehatedguy

Given cabin gain and the "free" output in this area, our subs probably would never leave the small signal realm under "normal" listening?


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## lycan

thehatedguy said:


> Given cabin gain and the "free" output in this area, our subs probably would never leave the small signal realm under "normal" listening?


probably pretty close to the truth 

BUT ... we can _quantify_ this a bit  by following the post above


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## sqshoestring

thehatedguy said:


> Given cabin gain and the "free" output in this area, our subs probably would never leave the small signal realm under "normal" listening?


Have no doubt my pair of 15s IB do not appear to move in the SQ sweet spot for me. They are about flat to 30Hz and will go to 25Hz before they drop off, on tones by ear. At .25" excursion they are certainly louder than I would listen to for any length of time, in fact my 4x50rms on highs becomes limiting around that point. Just a rough generalization, and I'd also add the car does not have tons of cabin gain as various single 12s in boxes were not impressive below 40Hz even some dual 12 and 10 boxes were nothing like the IB in that range.

Of course that was the idea, cheap subs tend to do pretty well at low excursion.


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## SSSnake

The wife has me on a short leash this weekend due to a family reunion but I will "walk the path" once I get broken free. 

You may have to feed me a little on this one... I remember there is a calculation tying SPL at a given freq to excursion but I will have to dig a little bit to find it (if I remember correctly you posted the equation on this forum a while back). I may have to request the equation if I can't find it in my <ahem> library. 

As always thanks for the discussions as they have always been insightful.

While this is a great and sound theoretical approach I would love to be able to make actual in car measurements to provide supporting data. However nothing in my toolbox is going to let me get accurate excursion numbers. Hmm, I wonder if I could rig something up with a LED, photo detector, and a ruler... Probably a bridge too far with the current workload and family obligations.

Have a great weekend!


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## SSSnake

OK - I just couldn't let it go before heading home for the evening...

The search function was my friend. SPL = 102.4db + 20log(displacement in m) + 20log(Sd in m^2) + 40log(Freq) - from a previous Lycan post

Using an AE IB 12" and assuming 1 mm displacement we ended up with 93.001db. More than enough output for normal listening (this assumed no cabin gain at 80hz). If we follow the cabin gain rule and add 24 db of free gain into the equation at 20hz then we end up with the same number (except for round off error). 

But will we really see all 24 db? Even if we assume only 12db of cabin gain excursion requriements are still tiny (roughly 4mm).

OK my theory sucked... But what I can't resolve is why I seem to hear a difference between sub systems with similar Fc and Qts values. Psychoacoustic influence? The next question is why do I care about Xmax?


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## sqshoestring

I've seen the figures on it, you need a lot more xmax to get low. Or of course cone area does the same thing.

Also note your hearing is less responsive at low frequencies, add to that ambient noises (noise floor) in a car. IMHO you can need a lot of output at <35Hz to realize it for SQ listening. A pair of 15s is a lot of sub the way I see it, but at 20-30Hz it is not that much.

I have a hard time comparing sub setups, unless the car is the same. I had boxes in this car that worked well in other cars, not in this one. This car is loud at 40Hz and above but not much under that (before the IB subs install).


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## lycan

SSSnake said:


> OK - I just couldn't let it go before heading home for the evening...
> 
> The search function was my friend.  *SPL = 102.4db + 20log(displacement in m) + 20log(Sd in m^2) + 40log(Freq)* - from a previous Lycan post
> 
> Using an AE IB 12" and assuming 1 mm displacement we ended up with 93.001db. More than enough output for normal listening (this assumed no cabin gain at 80hz). If we follow the cabin gain rule and add 24 db of free gain into the equation at 20hz then we end up with the same number (except for round off error).
> 
> But will we really see all 24 db? Even if we assume only 12db of cabin gain excursion requriements are still tiny (roughly 4mm).
> 
> OK my theory sucked... But what I can't resolve is why I seem to hear a difference between sub systems with similar Fc and Qts values. Psychoacoustic influence? The next question is why do I care about Xmax?


the equation looks right.

YES ... you can do the calculation at 80Hz, and assume that cabin gain nicely compensates for free-space requirements on volume displacement, as frequencies get lower. So the excursion you need for a given SPL at 80Hz, will be about the same excursion you need for that same SPL at 40Hz and 20Hz ... in a vehicle.

Now i haven't checked your math, but one or two millimeters of excursion from a 12 or 15 inch sub for reasonable listening levels in a car? Sounds about right  Compared to 10, 12, 15 or even 20mm of pretty linear excursion available from modern subs ... i'd say we're still pretty "small signal" in a car.

Or, at least we can safely conclude that small-signal analysis is far FAR from worthless, for subs in cars at normal listening levels.

As far as hearing a difference between subs with the same Fc and Qtc values ... you have efficiency (or simple level) differences, cone flex issues (not standing wave or resonance problems in the cone, because those can't be supported at such long wavelengths) ... and possibly inductance issues at higher frequencies, depending on where the subs are crossed-over (i've argued that inductance isn't the _first_ place to look for transient problems, but nobody has suggested that it can be ignored in all cases either).


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## tornaido_3927

lycan said:


> ..and possibly inductance issues at higher frequencies, depending on where the subs are crossed-over (i've argued that inductance isn't the _first_ place to look for transient problems, but nobody has suggested that it can be ignored in all cases either).


Not sure if I've posted this before, but in regards to inductance and transience (more specifically rise time) I recall the inductance starts to affect it near where the HF rolloff actually occurs. Of which I found a page to help distinguish where that would be so you can know when to not let it be the end all of your system design.

Frequency Calculator and Crossover Design


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## sqshoestring

lycan said:


> the equation looks right.
> 
> YES ... you can do the calculation at 80Hz, and assume that cabin gain nicely compensates for free-space requirements on volume displacement, as frequencies get lower. So the excursion you need for a given SPL at 80Hz, *will be about the same excursion you need for that same SPL at 40Hz and 20Hz ... in a vehicle.*


I've never had that happen to me. Is it our hearing and/or noise floor that causes the need for more output at low frequencies...and is not included in the calculations? Does it depend on amount of cabin gain? This car actually has a little more bass with a window open.


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## sqshoestring

That may be fine for others, but I put quad 12s and now pair of 15s in my car largely to get 20-35Hz....as most other subs will play 40 and up. To me SQ is 20-20K, or what I can hear of it. I can get a 25Hz tone to play on it, but the 20Hz tone just moves the subs with no sound at least with doors open. It is very hard to get that low in a car in my experience. From 30Hz up I can over run the highs on a 4x75 alpine no problem, with two pyle 15s not even working hard. But if I want to screw around and light up some pop music, I can turn the 20-30Hz way up trying to get enough output to shake the car a lot, it gets the subs moving for sure. But the more you turn it up the less bottom you get. Part of it could be limited xmax with these cheap subs I don't know, they seem to get over 1" total at around 200rms when I was testing one on tones, they don't want to go much more than that. I need to put an RTA together some day.

Anyway below 25Hz on a sweep the sound cuts of around 23Hz sort of abruptly. From roughly 27Hz up it is fairly flat by ear.


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## subwoofery

Maybe it's as simple as you couldn't hear 20Hz, some might but you cannot? 

Kelvin


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## sqshoestring

subwoofery said:


> Maybe it's as simple as you couldn't hear 20Hz, some might but you cannot?
> 
> Kelvin


I don't think so, but not sure what the deal is. When I had the 12s in there I could get 20Hz so I don't think it is me. Sure it is more of a feeling than sound really. Can only figure the quad 12s had more surface area and could do more down there, but they required much more EQ to sound flat they really wanted to play above 40 due to the sub used and possibly because I was very close to Vas even though they had a lower qts. Had to cut 50Hz on the EQ a lot and run two LP at 50 on top of that. Now these 15s I can run near no EQ at all, and they love to make 30-35Hz, but for some reason they die at 25Hz and I'm not sure why. Wanted to try porting the trunk but there is little room in the baffle to do it. The model ported would give a flat line to 20Hz if I cut above that (if it worked), now it does roll off under 30 but my EQ is not very good at boosting down there. Have a PEQ that will but not ripped up my wiring to try it yet. That still does not explain why it will not play a 20Hz tone hardly, if that is true no EQ is going to help. The last option is it could be the amp has a built in subsonic, some of them do roll off down there and do not tell you about it. I swapped amps once and it was better but maybe this Alpine dies at <30Hz? The subsonic in the amp is turned off.


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## Oliver

sqshoestring said:


> I don't think so, *but not sure what the deal is. When I had the 12s in there I could get 20Hz *so I don't think it is me. Sure it is more of a feeling than sound really. Can only figure the quad 12s had more surface area and could do more down there, but they required much more EQ to sound flat they really wanted to play above 40 due to the sub used and possibly because I was very close to Vas even though they had a lower qts. Had to cut 50Hz on the EQ a lot and run two LP at 50 on top of that. Now these 15s I can run near no EQ at all, and they love to make 30-35Hz, but for some reason they die at 25Hz and I'm not sure why. Wanted to try porting the trunk but there is little room in the baffle to do it. The model ported would give a flat line to 20Hz if I cut above that (if it worked), now it does roll off under 30 but my EQ is not very good at boosting down there. Have a PEQ that will but not ripped up my wiring to try it yet. That still does not explain why it will not play a 20Hz tone hardly, if that is true no EQ is going to help. The last option is it could be the amp has a built in subsonic, some of them do roll off down there and do not tell you about it. I swapped amps once and it was better but maybe this Alpine dies at <30Hz? The subsonic in the amp is turned off.


*You don't have what you nee*d


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## sqshoestring

Oliver said:


> *You don't have what you nee*d


The 15s model better, they sure tune far better....but not the same amp I had a kicker on the 12s. They sound good and its not like they don't move with a 20 tone, but that does not mean the output is not rolling off. Actually I don't see how it could be the subs they don't care what signal they get. Suppose I should put another amp in there. The first one was a kenwood 900rms class D, it did the same thing but a little worse. It does happen, most people don't care about <30Hz why make an amp work there and waste power. Thankfully I have a few amps laying around, what I don't have yet is heat in my garage and I can't find my remote.

Yeah I could put AE IB15s in there and boost 20Hz. Even at 25Hz I can't really complain that much it sounds great. A second set of 15s would take up too much trunk space or I'd go for it.


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## Oliver

It's not the size of the driver that totally predicts low end.

There are many factors.

Ported box would boost the frequency you mentioned, if it were tuned at that specific range.

A bigger amp would help if ... and only if "The excursion was optimized or maximal [ 3" peak-to-peak ].

The low notes with authority syndrome demands it !


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## subwoofery

sqshoestring said:


> The 15s model better, they sure tune far better....but not the same amp I had a kicker on the 12s. They sound good and its not like they don't move with a 20 tone, but that does not mean the output is not rolling off. Actually I don't see how it could be the subs they don't care what signal they get. Suppose I should put another amp in there. The first one was a kenwood 900rms class D, it did the same thing but a little worse. It does happen, most people don't care about <30Hz why make an amp work there and waste power. Thankfully I have a few amps laying around, what I don't have yet is heat in my garage and I can't find my remote.
> 
> Yeah I could put AE IB15s in there and boost 20Hz. Even at 25Hz I can't really complain that much it sounds great. A second set of 15s would take up too much trunk space or I'd go for it.


Out of curiosity, what was the FS of the 12s and what's the FS of the Pyle 15s? They might just unload near 20Hz-25Hz. What you need is not a second set of 15s but a pair of 15s better suited for your application (a lower FS 15) 

Kelvin


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## sqshoestring

The 12s were infinity 1252w, Fs 24 and qts .48, xmax 12.5mm. The 15s are Pyle Fs 20 and qts .7, iirc that is what AEs are. Far as xmax I don't know, I was able to get over 1" with 170rms amp on one testing unmounted with sine tones. However I am not talking about xmax limited sound, I hardly ever play them that loud as I can not hear the highs. If I drop a bass CD in and just crank them the back seat moves and it has a lot of bass, but I'm not into that, the closest I get is top 40 pop/dance a lot of it has great bass tracks. The idea was not to have big xmax, not to have the distortion issues and compression, etc. And they do that, I have to be flat out screwing off to get big xmax from them. I have larger amps for the highs, but this 4x50 is enough say 80% of the time. I have a 880PRS with the 16 band EQ running it. I have a 1Kw I can run on the subs, but was planning on trying a 350rms next it would save room if it were enough spark for them. I had 420rms on the quad infinitys from the kicker 700.5 and same deal I hardly ever used it all. They were too heavy the back of the car actually sat lower. I could clip it on bass music and the subs didn't even care...at ~100rms each. But the 12s were rated in the manual at 150rms when IB not the normal box 300rms. How do IB subs unload? I want to try porting the trunk because the model looks so nice, but there is no room for the size port I should use....if it even worked.


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## Oliver

sqshoestring said:


> How do IB subs unload? I want to try porting the trunk because the model looks so nice, but there is no room for the size port I should use....if it even worked.


Unloading is most commonly associated with a ported enclosure, as the sub becomes uncontrolled by the box it is subject to the restraints of the suspension system { strong, stiff suspensions being preferred }.

In your instance , the sub may be limited in it's range of movement , P-P , a street bike can be ridden on a trail but the shocks are not excursing far enough to handle jumps.

Your subs might be motor limited , just not enough oomph to hit the low notes with authority.

Distortion can be affected by many things , ideally - you want a large motor with a shorting ring and perhaps an under hung design = big $$$$$


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## omega48er

M-Dub said:


> I like it slow, then fast


THATS WHAT SHE SAID!!!


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## sqshoestring

Oliver said:


> Unloading is most commonly associated with a ported enclosure, as the sub becomes uncontrolled by the box it is subject to the restraints of the suspension system { strong, stiff suspensions being preferred }.
> 
> In your instance , the sub may be limited in it's range of movement , P-P , a street bike can be ridden on a trail but the shocks are not excursing far enough to handle jumps.
> 
> Your subs might be motor limited , just not enough oomph to hit the low notes with authority.
> 
> Distortion can be affected by many things , ideally - you want a large motor with a shorting ring and perhaps an under hung design = big $$$$$


I always assumed an IB sub was unloaded similar to ported under tuning.

You could well be correct in that they are reaching their limits, you only get so much sub for <$50 lol. The idea was to use a pair and together the output might be enough. However at higher output (than I would need for SQ listening) they will show more xmax, but if the VC is out of the field low frequency reproduction will be affected. They will put out 30-35Hz significantly over the levels I need for daily use, that is why I question if they are at their limits at 20Hz at lower output levels....but the increase in xmax needed is on a curve. I can't seem to find a chart. Motor strength could also be an issue, but one would think if that were the case the lowest frequencies would diminish as input power increased right? It does some but seems to be common to any sub I've ever run. I went with this pair of 15s because it was overkill and would avoid these issues....for typical SQ listening levels; loud enough to beat road noise which I would not describe as that loud compared to what I see out there.

Still, if a trunk _did_ act as a ported enclosure, regardless of the low frequency abilities of the sub one would still get more output at tuning frequency as the model suggests...right? Porting can add significant low end to a $15 woofer in a home speaker. My model does show it falling off under 30Hz just like it does, and a peak at 30 with porting that is large enough to give a flat line to 20Hz if the peak were flattened. There in lies my interest in a 'trunk port'...lol.


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## boarder124

The ported trunk thing is the reason why i wonder why some people try so hard to seal off the subs from the trunk. If you are able to get almost all of the IB surface sealed off, except for some small holes and tiny gaps, wouldn't they combined act like a port and give you a boost in the sub sonic's? I also went from a sealed setup, to a fully sealed IB setup, and back to the sealed setup with the same PG xenon 12" subs and found that i was more happy with the sealed setup in the end and it seemed like i had the same if not more lowend with the sealed subs and the spl was much better above 60hz


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## subwoofery

boarder124 said:


> The ported trunk thing is the reason why i wonder why some people try so hard to seal off the subs from the trunk. If you are able to get almost all of the IB surface sealed off, except for some small holes and tiny gaps, wouldn't they combined act like a port and give you a boost in the sub sonic's? I also went from a sealed setup, to a fully sealed IB setup, and back to the sealed setup with the same PG xenon 12" subs and found that i was more happy with the sealed setup in the end and it seemed like i had the same if not more lowend with the sealed subs and the spl was much better above 60hz


IB alignment you need displacement. Your power handling goes down IB, therefore you need to make up for that with bigger or more drivers. Some people are OK with 1 small sub but not often  

Another thing, I don't have the specs for the Xenon but it might not be suited for IB (low Xmax). 

Kelvin


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## sqshoestring

Possibly, but you know your holes are never going to tune where you want them too. The typical issue is they allow the sound to cancel by not tuning. That said I never had an issue or could tell the difference between sealed and almost sealed. Little holes will not pass enough air to matter.

The experience with your subs depends on their specs, and how you like your bass. A low Qts and/or high Fs sub tends to not work that well IB. They can if you EQ them they can take a lot of power/have big xmax. Simply put a low Fs and high (0.7) qts is best for IB long as your trunk is well over Vas. That gives a flat response. In a box unless its huge they will lose low bass badly. Most subs now are lower qts made for boxes, this sub will have less low bass IB, but in a box it will have better bass just not the very lowest bass. I ran some low Fs but low qts 12s and they pounded at 50Hz, they would get down low with EQ. I had to cut the 50+Hz hard to get them sounding nice for my tastes. In a smallish box they put out 40 and higher quite well, a sound I hated personally but some may like it.


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## Brian Steele

sqshoestring said:


> I ran some low Fs but low qts 12s and they pounded at 50Hz, they would get down low with EQ. I had to cut the 50+Hz hard to get them sounding nice for my tastes. In a smallish box they put out 40 and higher quite well, a sound I hated personally but some may like it.


Are these the same Infinity 1252s that you subsequently used IB?


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