Subwoofer Punch

Here is a tech summary of a woofers quickness (I quickly summarized it below, with as long as this post is, I want to make this less painful for you guys, but I do suggest you read it) and how it is determined. This is essencially transient responce (TR), or the quickness/reaction time of the speaker. In it we see the TR of the woofer is most directly affected by inductance. The lower the inductance the more adept the woofer is at handleing transients. Now, if we look at the low inductance of the Brahma 12 (.9 MHz) which is a very laid back, or smooth woofer with the higher inductance, like the W7 and IDMax (I wish I could find those specs, I read them somewhere, maybe Steven can shoot them out, but neither Jl or ID has them listed) and they are punchy woofers we will see what I am getting at. Basically, the punchy woofers tend to be stronger in the upper subwoofer frequencies or what I call midbass frequencies. Of course, having one of the meanest midbass sets in my car allows me a very low crossover (that one was for you trifle ), so I let them handle the punch.

My personal feelings are that the BL curves more radically affect the punch of the woofer, then Le. This theory eliminates the thought of quickness and accuracy being more the show of a punchy woofer. In my observations, I find a parabolic Bl curve has a tendancy to be more punchy. I will elaborate why I feel this is the case, if you don't mind reading...

In a quick model of any sealed woofer and with a particular focus on the excursion of the driver (use ISD fellas, for a goof Model up a 10W7 sealed [I'm picking on you Chris, but for a reason... simply because we know the punch of the 10W7 and I will post a DUMax of the driver too] and go with the reccomended enclosure for simplicity). You will find greater excursion down low, whereas in the upper sub-midbass range, you will find reduced excursion. Bear this in mind as we look at the DUMax of the 10W7. I don't want to sound like I am picking on the W7. I feel the 10 and 13W7s are both tremendous drivers, and the LCSG topography is really not represented in this dumax. The combo of the flat BL (very atypical of the LCSG design) and KMS are impressive in such a standard topography in anyones book I think. Cool...

Now, with the BL indicator of motor strength throughout the linear excursion (for those of you that don't know, the BL curve is a display of the motors strength (NA) across it's excursion (MM)) we can address the idea at hand. Notice how as the woofer's excursion stays low, the strength of the motor is greater in a parabolic BL situation, but as excursion climbs, the strength begins to fall off. Now, with the all the strength motor of the woofer is used at higher frequencies (lower excursion), and a loss of strength due to overall excursion at lower frequencies (as evidenced by the comparison of the BL in the DUMax report Vs Excursion at freqency graph on your modeling program), where do you think we will hear attenuation?


The upper sub frequencies of course... Right where the "punchy" effect of the driver is felt!!!

so the motor is pushing it's ass off completely through the stroke of the higher frequencies, but it kind of weakens as it is required to push further in the lower frequencies. Think of a thick rubber band, and how it becomes more work the more you stretch... the way your fingers tire, like the motor as it looses strength

Now take a flat BL driver (and KMS is important here too as the suspension will affect the movement of the cone) that maintains more strength across a broad excursion. The linear output creates a more laid back output, as there is no attenuation up high, or obviously down low. What I feel this leads to is a more accurate reproduction of subbass, without coloration. The punch may be beneficial to you if you cross high, but if you cross low, you are allowing the midbass drivers to pull the soundstage forward, and you are only asking the sub to do what it is supposed to do... recreate sub frequencies.

Any thoughts or opinions on this?

 

I will summarise the tech paper on woofer quickness for you. Essencially it lays to rest the old thought that the weight of the cone is the primary reason for quickness or slop in a driver. That is untrue. Generally the moving mass is use to controll or manipulate the FS (resonant frequency) of the driver. But, with that being said, it remains constant. It does not change, it always weighs the same... What does change is the current travel through the coil, which changes direction of the cone. The lower the inductance, the easier it is for the current to change direction, or react... whichever it is to accomplish....

 

Oh I agree... I meant to illustrate that the SGLC is not typically flat by saying...

Sorry if I left that hanging some, I was trying to clear it up as briefly as I could (in my 5000 word summary :lmfao: ). Anyhoo, I was not aware of any radial drilling for flux dispersion. Makes sense to me though.

I thought the Le was 4MHz, but I was concerned about putting such a high # Le down and being incorrect. Thanks Steven, I thought you were involved in the conversation.

But Steven, you keep refering to LE distortion... Are you just refering to reduced transient responce, or actual distortion? I was not intending to discuss distortion as audible distortion here, just the "punchyness" (is that a word? <_< ) of the woofer. I would love to go on with distortions, specifically the BL distortions that get ignored by people who... well, I'll leave that alone for now . I guess what I am trying to illustrate was simply the attenuation of the upper sub frequencies causing a punchy sound evident in many woofers.

While I agree this may lend to some low frequency distortion, the W7 will throw that idea in the shitcan. The 10W7 is a punchy woofer, yet it displays no audible distortion when extended... Of course, I am aware of the distortion rate being well over 10% down this low before we can hear it, but I have to feel it may be something in that tremendous suspension of the driver that lends to it's distortion-free sound .

Now, I will look at those questions first Luv posed, and those you posed as well...

 

OK, good input there Luv, but I think now you are bringing processing into the equasion, rather then the subwoofer itself... I will elaborate in a minute, but first we will discuss your chosen crosover settings, and why that low of a cross is not too particularly common in CA.

I agree wholeheartedly with your chosen crossover setting(as it is exactly the same as mine). We have subwoofers to reproduce subwoofer frequencies, not midbass frequencies. Plus, a lower cross tends to pull the soundstage forward in the vehicle, as well as eliminate seperation caused by the directional frequencies (I'd say ~70Hz and above). But, we need to remember a couple things regaurding the crossover points.

First, the typical person who puts a sub in their car is looking for exagerated output. Typically, a big sound with the kickdrums, or the rap-bass as moving... Kickdrums are not low frequency information, rather they may dwell down low, but really are apparent in the upper sub, lower mid frequencies. Same with rap-bass really. They try to keep it's levels at a higher sub frequency as well, to keep it closer to the typical resonant frequency of most vehicles (yes, they do it for a reason too ). So to attenuate the kickbass/rap bass feeling, the woofer is crossed higher. So essencially, you are correct with your assertation of the crossover frequency as a determining value of the punch, but you are forgetting the electronics ahead of the subwoofer itself... Let's discuss the crossover, or the heart of this matter in a second, but I also want to touch on another reason many cross so high.

Second, most people do not have a midbass driver capable of keeping up or extending low enough to cross their subs that low. Those of us with high end sets are afforded the luxury of a low crossover setting, but most people out there do not have these high dollar comps. So, the installer understands the crossover relationship between front stage and subwoofer, and he doesn't want to loose any information, so he crosses the sub and front stage similarly. He cranks the HPF as low as he can untill the fronts display audible stresses, and sets the subwoofer frequency accordingly. Viola'! Now we have a high crossover setting.

No, let's discuss the crossover. A crossover is not a dead cutoff. When you set your crossover to 65Hz, it does not mean that all information is cut off at 65Hz. This frequency is the base value for the beginning of the elimination of certain frequencies. How fast does this information get cut off? That is where a bit of knowledge of your crossover comes into play...

12, 18, and 24 Db crossovers or slopes are the most common. Lets discuss what these figures mean. The listed # is how many decibles the information is reduced per octave... I have a hard time explaining it, so I will try to quote someone and use a graph for it...

Graph Legend:
--------------------------------------------------------------------------------
Cyan = 6dB/octave
Red = 12dB/octave
Green = 18dB/octave
Violet = 24dB/octave

In reading his explination, I am not sure it is simplified, but the graph should clear thigs up some. So, even if you are crossed at 65Hz, if you have a referance output of say, 120 Db on a 12Db crossover set at 65Hz, you still have an output of 108Db at 130Hz!!! There is your subwoofer punch

Make sense?

 

Steven, interesting information there, regaurding the sine wave, compared to music. True, and I never considered it. I am interested in hearing Chris's 10W7 again. I want to do a bit of listening to the effects of the punch when the woofer is in the midst of performing low octave duties. I have a couple songs in mind to accomplish this (thank God for Tool in these situations). Anyways, hopefully Dan can lend some insight as to how this works...

 

OK luv, I will try to field this for you... I know sometimes I go a bit overboard and have issues explaining things like Chris (Geo) does... but I try .

As far as crossover points, sure they totally affect the punchyness of the sub. I mean, if you cross down at 60Hz, you will remove some of the information above that, where if you cross at 80 you are allowing more information then you were with the filtered setting at 60Hz, so no doubt you will be able to manipulate the upper sub, lower mid frequencies... Therefore affecting the punch of the sub.

I don't know if I would call those that choose a setting of 80-90Hz as being novices though. Cort (flawlesskid) does know about playing with crossovers. Yet he chooses to cross higher than I choose, and his midbass drivers are plenty capable. This is a good example of my "first" scenario in crossover point selection... The exaggerated user. Cort likes a punchy sound, so he chooses to add the extra umph of the sub to help with the midbass chores. This doesn't make him a novice, it is simply his personal preferance. Also, I think it does very well in his system.

Available power will definately affect the system. If you increase the available power, you will increase the charachteristics of the speaker in question similarly. Now, I will use a tweeter for an example (as I'm sure you have heard the diffeance up there)... Think of a tweeter that you find bright... Now, turn the volume of the HU lower and the harshness you typically hear becomes less, however it still exists. Now, turn up the HU volume. Ahh!!! the tweeter becomes more harsh. But remember, the sonic charachter is always there... it is always harsh. So similarly, I feel the punchy woofer will always display the punchy charachter, but with more power it should become more evident.

Will BL or KMS curves be indicative of this? Sure. Just figure as the power is increased the amplitude will increase as well.

Will the Re or Le be affected? DC resistance will never change (we don't add coil windings as the subwoofer moves, that is constant). But LE can be affected in certain design configurations. I think Steven covered this pretty well here...

Enclosure design can greatly affect this, but it can also add unwanted coloration to the sound. Smaller sealed enclosures will add a mid frequency boost, but at a risk of sounding boomy. A punchy sub with the QTS indicative of a ported application will still sound punchy in a ported box though. I think you are a bit mistaken in that respect, but it also will struggle with the low notes in a sealed enclosure. We can manipulate woofers through enclosure design without a doubt. But I feel to a certain degree the sonic charachter will remain the same.

 

Yep. I knew what you were saying, but I did feel the need to point out that sometimes people who know what they are doing will cross a bit higher.

I've always known you to be respectful, and never meant to insinuate you weren't

 

I want to discuss something you mentioned here in a bit, but first I want to elaborate some on my enclosure manipulation. I was a bit buzzed last night, and I left a few stones unturned.

When you look at a DUMax report, and the TS params, you recieve a basic outline of what the woofer will sound like. It's sonic charachter as I like to call it. Now, there are definately ways to manipulate the drivers overall sound through enclosure (size/type), electronic means (both crossovers and EQs), and placement (this includes direction, as it greatly affects the sound). However, these "archaic" (I like the choice of words ) methods will never eliminate the sonic charachter, but they can shift how it is presented to you.

If you take a woofer with a bit of punch, and throw it in a critically dampened enclosure, you are going to affect the punch, but I feel it is simply because you are manipulating, or attenuating, the low end of the driver. Now, I am not modeling a driver here as we speak, but you may want to do it to understand what I am getting at. Model up a typical sealed driver in a .7 alignment, then increase the size about 160% to achieve a .5 or critically dampened enclosure. Look at how the low end and upper end is affected. Typically the enclosure characteristics indicate a flattening of the low end, and a reduction of the upper sub/lower mid frequencies. Now, in an anechoic situation this is great, but in car where cabin gains are very real, this becomes very apparent. The low end is considerably enhanced, but the punch is still there. Why then do I say it is affected? Quite simply we are attenuating the low sub frequencies through manipulation and affecting the "punchy" sound through an evening of the playing field (bringing the low end up), not through manipulating the punch itself. So you see, the sonic charachter remains the same.

Likewise, we can manipulate the upper sub frequencies through shrinking the enclosure size somewhat. You will never be able to bring a Shiva to the punchy level of an IDQ. While you can take the smooth rolling bass of the Shiva and manipulate it some through making the enclosure smaller, we will make the driver sound very boomy before we ever attenuate the midbass region enough to achieve that level (trust me, I manipulated the hell out of those drivers... I had them in 15 or 20 differant boxes, just experimenting).

Now, I feel that this aforementioned bit of info will help with you question posed above. Consider the fact that we are able to manipulate the drivers somewhat to generate what we are looking for. However, the basic signature is always still there. What do the TS and DUMax really tell us? How the woofer sounds. Do they tell us everything about how they will sound? Yes, we cannot shift the sonic charachter of the driver in question. But, we can, through archaic methods (I love that) somewhat alter how the sound is delivered to us...

I think Kurt put it better than anyone else I can think of here:

While I think "ignorant" could have been more politely stated as "less knowledgeable" I think the point is clear... Everything I need to know is listed in the #s.

But, is how much I can manipulate it in there? Well, if that is the question at hand, and you need to manipulate it that much, chances are real good that the driver in question doesn't belong in your application

 

It has nothing to do with the A. It is a general observation... Read it and comment.