# More Bass / Less Space



## Patrick Bateman (Sep 11, 2006)

This one has come up a few times before, so I thought I'd post a quick thread on how to get more bass in less space.

First off, there isn't anything particularly magical about a loudspeaker. It's a cone attached to a voice coil that's moving air around. Sure, at high frequencies we start to see issues with beaming and directivity, but at low frequencies, it's basically an air pump.

There's a big demand for small speakers, and box sizes have been getting smaller and smaller for decades. But Hoffman's Iron Law (google it) dictates that efficiency is going to suffer as the box size gets smaller.

This creates a conundrum - as the market dictates smaller and smaller subs, you need more and more power to reach the same SPL.

One easy solution is to simply use the whole damn trunk. There is literally enough air in the trunk to mount ten or twenty woofers, if it's well sealed.

But that creates a new problem - where do you fit all these woofers?

Traditionally, we wall off the trunk like this:








Another solution, which I haven't seen a lot, is to use an ARRAY of subwoofers.







If you've ever gone to a concert, you've seen one of these.

The problem in our cars is that it won't fit. But remember, woofers are just an air pump at these frequencies. So start thinking of creative ways to mount them. 






The guys at Subaru have come up with some interesting packages 















Here's a pic of a subwoofer array inspired by audio reviewer Tom Nousaine. Tom has reviewed hundreds of subs, so the fact that he uses this for his own home gives you an idea of how well it works...















The Tymphany LAT basically takes the same idea, but crunches it down to the smallest package possible. The cool thing about the LAT is that it's push-pull. When you invert half the woofers, and invert their polarity, you reduce 2nd order harmonic distortion. It's a cheap and easy way to make a subwoofer sound cleaner.

I can think of a few arguments *against* the idea, so let's run them down one-by-one:


_"A real "sound quality" sub is a small sealed box"_
At low frequencies, a woofer is little more than an air pump. SPL is determined by how much air you can move. To move a lot of air, a small sub has to move a lot further. Distortion rises with excursion. Therefore, everything else being equal, the sub with more cone area will generally sound cleaner. This mounting arrangement is simply a way to cram more cones into less space.

_"It's too much work"_
This is a valid argument. It takes a bit of fabrication, but if you like it clean and you like it loud, it's worth a look. I think it's particularly well-suited to leased cars, since you can cram a couple of eights into the space where a 6x9 would fit. Heck, you could even put a pair of sevens *inside* a car door with a bit of creativity. Slot loading is also a way to squeeze more bass out of a small woofer (see below.) Remember, there's no magic here; we're just moving air molecules from Point A to Point B.

_"Is it *safe* to mount two subs so close together?"_
This is another valid argument. "Slot loading" *will* change the sub's response. Ironically, it usually makes them work even better! Here's why: in the lab, woofers are measured in a giant IEC baffle. They're "pushing" against a huge volume of air (the entire room, in fact.) When you reduce the volume of air in front of the cone, it changes their parameters. Theoretically, we would expect the free air resonance to go *down*, and the mechanical Q to go *up*. Theory is great and all, but what happens in the real world?

Here's a measurement of an eight inch woofer in a baffle:
* f(s)= 38.36 Hz
* R(e)= 5.99 Ohms
* Q(ms)= 4.752
* Q(es)= 0.517
* Q(ts)= 0.466
* L(e)= 0.91 mH

Here's the _exact same woofer_, but slot loaded. (In these measurements, the slot is 1/2" deep.
* f(s)= 36.34 Hz
* R(e)= 5.98 Ohms
* Q(ms)= 5.016
* Q(es)= 0.623
* Q(ts)= 0.554
* L(e)= 0.95 mH

As expected, FS went down, while QMS and QTS went up. I'm not entirely sure why LE went up by 4%.

The sub above is a CSS Trio8. If you have a 12 cubic foot trunk and are using four subs, slot loading the subs drops the F3 from 58hz to 46hz. Not too shabby - _that's almost half an octave more extension._ Nothing fancy was done to the woofer; I just placed a slab of wood half an inch from the face of the woofer.


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## Patrick Bateman (Sep 11, 2006)

In another thread, someone asked why you'd invert one woofer. Here's an explanation, swiped from the marketing propaganda of a subwoofer:

_"The SUB 212’s unique “push-pull” configuration is designed not only to increase output, but also to reduce distortion. A push-pull subwoofer uses two drivers: one mounted facing forward, the second mounted backward with the magnet facing out. Utilizing two drivers doubles the maximum output, while the push pull configuration reduces even harmonic distortion. Typically, in a more conventional design, at high output levels, second harmonic distortion dominates the distortion spectrum of most subwoofer drivers and is caused by asymmetric operation of the suspension and magnetic structure. In simple terms; the output of the driver is slightly different when the cone is moving away from the magnet, as compared to when it is moving toward its magnet.


Push-pull operation reduces this even harmonic distortion in a clever application of physics. As mentioned before, push-pull uses two drivers, one reversed from the other. The bottom driver has its magnet facing out of the box and is driven electrically out–of–phase from the front driver, which keeps both drivers acoustically in phase. However, when the front driver’s cone is moving away from its magnet, the bottom driver’s (reversed) cone is moving towards its magnet. This puts the even harmonic distortion components of the bottom driver out-of-phase with the front driver. When you combined the outputs of both drivers, the even harmonic distortion of both drivers cancels, reducing the overall distortion of the subwoofer."_

While a lot of this sounds like marketing, I've measured push-pull, and it reduces 2nd harmonic by as much as 10dB. That's *very* audible.

It should also work at higher frequencies too, but the limiting factor will be how close you can get them together. Closer is better.


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## Thaid and Bound (May 15, 2010)

Patrick Bateman said:


> I've measured push-pull, and it reduces 2nd harmonic by as much as 10dB. That's *very* audible.


Having messed around with "clamshell" isobaric configs for years, and loving the linearity the direct, phase + time coherent motor coupling can achieve I understand the basic principles being discussed, however I'm struggling to picture how a baffle/slot with an inverted woofer+phase could get anywhere close to the linearity improvements if clamshell-isobaric, given that dynamics of the woofer-woofer relationship - which is basically just the the ass of one woofer fighting against the face of another, right?

Maybe it doesn't compare to isobaric's linearity? Still cool if it's better


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## lycan (Dec 20, 2009)

Patrick Bateman said:


> In another thread, someone asked why you'd invert one woofer. Here's an explanation, swiped from the marketing propaganda of a subwoofer:
> 
> _"The SUB 212’s unique “push-pull” configuration is designed not only to increase output, but also to reduce distortion. A push-pull subwoofer uses two drivers: one mounted facing forward, the second mounted backward with the magnet facing out. Utilizing two drivers doubles the maximum output, while the push pull configuration reduces even harmonic distortion. Typically, in a more conventional design, at high output levels, second harmonic distortion dominates the distortion spectrum of most subwoofer drivers and is caused by asymmetric operation of the suspension and magnetic structure. In simple terms; the output of the driver is slightly different when the cone is moving away from the magnet, as compared to when it is moving toward its magnet.
> 
> ...


who wants to see the math? I can feel the love ...

let's say each woofer can be described thusly :

*OUTPUT = gain*INPUT + alpha*(INPUT)^2*

There's the linear term, *gain*, and the term that generates 2nd harmonic distortion, *alpha*. We want *alpha* to be pretty small, so the sub behaves _linearly_. I told you guys these power series are pretty darn handy ...

Now we are going to use TWO of these subs. Let's NOT invert one first :

*COMBINED OUTPUT = gain*INPUT1 + alpha*(INPUT1)^2 + gain*INPUT2 + alpha*(INPUT2)^2*

If we connect the inputs together, *INPUT = INPUT1 = INPUT2*

*COMBINED OUTPUT = 2*gain*INPUT + 2*alpha*(INPUT)^2*

OK, nothing particularly interesting there ... we've got twice the output. So let's INVERT the second sub, and see what happens :

*COMBINED OUTPUT = gain*INPUT1 + alpha*(INPUT1)^2 - gain*INPUT2 - alpha*(INPUT2)^2*

And we'll connect the inputs together again, so that *INPUT = INPUT1 = INPUT2*

*COMBINED OUTPUT = 0*

OOPS !!!! :blush: when we invert one of the subs, we better invert it's input signal too, so that : *INPUT = INPUT1 = -INPUT2*

*COMBINED OUTPUT = gain*INPUT + alpha*(INPUT)^2 - gain*(-INPUT) - alpha*(-INPUT)^2*

or

*COMBINED OUTPUT = 2*gain*INPUT*

voila !!!!! we've eliminated the term that generates the second harmonic 

For those following along, you can see if this same trick works for _cubic_ terms in the power series, which is the term that generates 3rd harmonic distortion ... or not? That's your homework 

And if you think this same "trick" works for other "systems" as well ... like certain circuit elements that tend to be "large" in 2nd harmonic (*cough* mosfets *cough* vacuum tubes) ... well, that's where you'd be right


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## Thaid and Bound (May 15, 2010)

lycan said:


> who wants to see the math? I can feel the love ...
> *COMBINED OUTPUT = gain*INPUT + alpha*(INPUT)^2 - gain*(-INPUT) - gain*(-INPUT)^2*


COMBINED OUTPUT = gain*INPUT + alpha*(INPUT)^2 - gain*(-INPUT) - alpha*(-INPUT)^2


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## lycan (Dec 20, 2009)

Thaid and Bound said:


> COMBINED OUTPUT = gain*INPUT + alpha*(INPUT)^2 - gain*(-INPUT) - alpha*(-INPUT)^2


fixed !!! 

thank you for reading, and following along!


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## dcm220 (May 22, 2009)

lycan said:


> who wants to see the math? I can feel the love ...
> 
> let's say each woofer can be described thusly :
> 
> ...


That's cool. 

Homework answer: It will not work for the 3rd (or any other odd numbered) harmonic. Aren't the odd numbered harmonics the ones that are more offensive to your ears?


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## lycan (Dec 20, 2009)

dcm220 said:


> That's cool.
> 
> Homework answer: It will not work for the 3rd (or any other odd numbered) harmonic. Aren't the odd numbered harmonics the ones that are more offensive to your ears?


Correct answer  Negative polarities, raised to odd orders, remain negative. So the odd-order terms behave just like the first-order gain term ... any simple, inversion-based cancellation of the odd harmonics, will also cancel the fundamental 

And yes ... generally speaking, odd-order harmonics are more offensive than even. So the "inversion technique" is not a panacea ... but it's pretty interesting and useful nonetheless.


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## lycan (Dec 20, 2009)

oh ....

why is the "square term" in the power series expansion responsible for generating the *second harmonic distortion* component?

The answer is another quiz, this time a simple trig identity  Let the "*INPUT*" in the power series expansion (above) be a sinewave at frequency *f* :

[sin(*2pi*f*t*)]^2 = [sin(*wt*)]^2 = [sin*x*]^2 = ?


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## Patrick Bateman (Sep 11, 2006)

dcm220 said:


> That's cool.
> 
> Homework answer: It will not work for the 3rd (or any other odd numbered) harmonic. Aren't the odd numbered harmonics the ones that are more offensive to your ears?


By that logic, we should all be listening to $28 subwoofers instead of $347 subwoofers.
















For instance, the top graph is a $28 Dayton 8" woofer. The bottom graph is a $347 Scan Speak woofer. Below 100hz, you can see why the Scan Speak costs more than 10x as much - it's low frequency distortion is about 15dB lower.

But in my measurements, simply inverting and flipping the polarity of a woofer can reduce 2nd harmonic by 10dB.

So do the math - it gets you "in the ballpark" of the Scan Speak.

I think this "trick" is particularly effective when you combine it with modestly priced woofers which *already* have distortion reducing mechanisms. (The $28 woofer above uses a conventional motor.) For instance, a $15 Dayton Neo Sym woofer isn't going to perform as well as a Scan Speak woofer. But if you use an array of them to reduce excursion, then use this trick to reduce 2nd harmonic distortion, you might just exceed the Scan Speak's performance... _for $60._


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## bullet (Jul 8, 2008)

My head just exploded!


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## Thaid and Bound (May 15, 2010)

bullet said:


> My head just exploded!


Seeing as you're still posting I posit a reasonable amount of your brain stem must have survived the incident. Perhaps we should call you Mike? :laugh:


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## RMF419 (Feb 13, 2008)

The technical writing was well beyond my knowlege on this subject. How well would the Tymphany LAT work in the 6x9 location in a car. You could probablly get two per side.


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## Patrick Bateman (Sep 11, 2006)

RMF419 said:


> The technical writing was well beyond my knowlege on this subject. How well would the Tymphany LAT work in the 6x9 location in a car. You could probablly get two per side.


Here's the short version 









So you just leased a new Audi, you want some bass, but you can't cut a hole in the car? Don't sweat it. At low frequencies, woofers are little more than an air pump. Don't fret if you can't mount a twelve on the rear deck. _All that matters is moving air, and directing it into the cabin._
An array of small woofers can move as much air as one large woofer. For instance, four 6" drivers can move as much air as a twelve. (yes, this ignores xmax.)
A side benefit of using multiple small woofers instead of one big woofer is that you can reduce 2nd harmonic distortion by as much as ten db by inverting one woofer, and flipping it's polarity.
Don't be afraid to mount them very VERY close together; while it changes their parameters, it typically *increases* the amount of bass. Which is a good thing 
Tymphany knows this, and that's why the LAT looks the way it does. But you don't have to buy a LAT. You can make your own. Two woofers can be better than one, and if you're adventurous, try eight!


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## Patrick Bateman (Sep 11, 2006)

Another option, to get bass up front, would be to DIY a Tymphany LAT clone.









Picture something like this, mounted horizontally, under the dash.









I can fit eight of these horizontally under the dash of my Accord, if the cone is mounted *just* clear of the magnet.









Eight of the Dayton ND90s can move more air than this eight inch woofer

A side benefit is that you can "taper" the response to control the beamwidth and increase high frequency extension. Neat


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## lycan (Dec 20, 2009)

if you have a separate time delay, attenuation, and filtering on each driver ... you have tremendous flexibility to "steer" the main lobe 

"phased array radar" does something _very_ similar, for "beam steering"


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## chad (Jun 30, 2005)

That array is likely being used for pattern control where the inverted cabs are being fed a different signal to reduce the amount of energy behind the array line..... but it sure is a strange looking design for the intended purpose, they are often times MUCH more organized.


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## chad (Jun 30, 2005)

lycan said:


> if you have a separate time delay, attenuation, and filtering on each driver ... you have tremendous flexibility to "steer" the main lobe
> 
> "phased array radar" does something _very_ similar, for "beam steering"


pow, exactly


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## chad (Jun 30, 2005)

I am using this:

http://www.eaw.com/Info/EAW/Technical_Papers/DSA STEERING VS TILTING.pdf

In this room, you can see them on either side of the proscenium 2 deep.










They work unbelievably well, the coverage is incredible.


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## RMF419 (Feb 13, 2008)

Patrick Bateman said:


> Here's the short version
> 
> 
> 
> ...


Thanks for lay version...


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## khmerpimpin (Apr 19, 2010)

this would be a great diy with some decent drivers, can someone show me how to make the frame of the enclosure? id like to try this with 2 12's, or maybe 4 8's (I can fit this under my dash!)


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## wiseman454 (Nov 30, 2009)

Patrick, I have been searching for days now and cannot find the post about mounting a baffle directly in front of a sub cones. This lowered the fs by 3hz and and a few other things.
I thought you said this "mass loaded" the subs but "mass loading" searches get me a bunch of talk about clay, lead and sand!
I have a have a question, a few actually. I have a situation where I believe I can get a .35-.5 sealed box under my front fenders in my truck...to the sides of the cab. Its lifted and I have tons of room. I wanted to fire the midbass driver into a baffle and "slot" its output into the cab through a 5"x3"x6" triangle cutout in the sides of my cab VERY VERY far forward and VERY wide. 

If the baffle is not flat against the sub will this cause issues? 
Will firing the sub into a very small chamber of sorts with a large hole cut into it cause trouble? The large holes are the triangle cutouts I spoke of that are far and wide in my cab.
I just don't know of frequencies in the 50 -800 Hz range will like being "directed" in this manner... as in lots of early reflections. Maybe it will be ok at 60hz to 350hz? 
I am very sorry if this is in the wrong place I really did try to find my answer before I stepped on your thread. 
Thank you
Will Schlentz.


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## Topper (May 31, 2007)

this sounds very interesting and is something i'd like to try but am still confused on how its properly executed. Does anyone have pix on how they did it in their own car? and could you put like a write-up on how you wired them.

(this is all assuming your using the entire trunk as the enclosure right?)

(also is this the same as isobaric?)


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## wiseman454 (Nov 30, 2009)

HOLY BEJEEZUZ it's this thread!!!!!! I missed it. That right there is some funny stuff!


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## Blake Rateliff (Jul 12, 2008)

If I was to build a midbass array like this (LAT clone), what determines the maximum frequency it can play properly? I assume slot size and spacing as well as woofer spacing and total length come into play. Is there a set of rules I can apply to designs like this?


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## wiseman454 (Nov 30, 2009)

Not the same as isobaric there is no pairing of the drivers and halving of the total vas.
I believe that the woofer itself will tictate the majority of the tuning not the "ports and length" the ports are not really ports just the slots the subs are playing into. The extra db and lower fs comes from the close proximity to each other.


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## Blake Rateliff (Jul 12, 2008)

I do realize they will not act as ports. I figured that multiple woofers in this configuration would act as an array though and wondered whether woofer spacing, slot size, and array length would limit the max frequency that could be played while having the array act as one speaker in a midbass application (< ~250-500hz). Are the frequencies there still low enough not to worry about it?


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## Blake Rateliff (Jul 12, 2008)

Ok I've calculated the length of a 500hz wave to be about 27". Would it be correct to assume that spacing and array size are not of any concern at that frequency provided the total dimensions are all smaller than 27" ?


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## wiseman454 (Nov 30, 2009)

I wish I knew that one my good man. I am wanting to know the answer to a similar question with a different set-up. Looks like me bulding it is the only way to tell witch sucks because its gonna be a ton of work.


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## Topper (May 31, 2007)

I'd like to try this in my ride to take advantage of the reduction in the 2nd order harmonic distortion but i got some questions (this all assumes the use of just 2 subs):

- Will this work even with regular sealed box designs?

- If so, please see drawing below:










- Is there an ideal slot size? Is there a limit to how small a slot you can go before it starts causing problems?

- I'm assuming the slot is only open on one side and closed the other 3 sides right? 

- The drawing shows the subs in their own separate sealed enclosures - this is fine right? and its also fine if they were in one common area?

- Would it be of any benefit if the slot was angled (so that the subs aren't playing into each other but rather at an angle facing the opening of the slot)?



Also just out of curiosity, would i benefit at all from a reduction in distortion of i did away with the slot altogether and just used a regular design sealed box for 2 subwoofers with one sub mounted inverted like drawing below?


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## Oliver (Jun 25, 2007)

Topper,

At 60 hZ or 80 hZ ... or probably 100 hZ and down to say 20 hertz it is not unusual to have 10% distortion go completely unnoticed.

If your amplifier is putting out twice as much rms as your subwoofer calls for and your gain is barely turned up, if you don't have a problem with powering 2 subwoofers and only getting the output that 1 [ one ] subwoofer will make . . . then this is for you !!

Most would not spend the money for a Focal subwoofer , let alone two of them and then two class AB amplifiers making twice the power at 4 ohms as one class D amplifier costs for less even and odd order harmonics.

"TO EACH, Their OWN"

You might want to look up Isobaric box !


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## Topper (May 31, 2007)

a$$hole said:


> Topper,
> 
> You might want to look up Isobaric box !


already did but am looking to hopefully take as much of the benefits of that design while removing the major disadvantages . Not sure if its possible but this topic gives me hope


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## Volenti (Feb 17, 2010)

Topper said:


> I'd like to try this in my ride to take advantage of the reduction in the 2nd order harmonic distortion but i got some questions (this all assumes the use of just 2 subs):
> 
> - Will this work even with regular sealed box designs? *Yes*
> 
> ...


answers in *bold*


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## Patrick Bateman (Sep 11, 2006)

Topper said:


> this sounds very interesting and is something i'd like to try but am still confused on how its properly executed. Does anyone have pix on how they did it in their own car? and could you put like a write-up on how you wired them.
> 
> (this is all assuming your using the entire trunk as the enclosure right?)
> 
> (also is this the same as isobaric?)











Here's a pic of my new midranges. This is a full-on horn, so it's a lot more elaborate than a simple sealed box. But you can see the inverted mounting in the far right corner there.
















A previous iteration of the same device. Same concept here, one driver is flipped, and they're as close together as humanly possible. I actually went overboard here, and the woofer cone started rubbing against the plywood. Don't do that 








Quad twelves in a Danley SH-412


































Above are some pics of the Danley home theater subs. Guess where I get my ideas from ​
This _isn't_ isobaric. In an isobaric design we're basically turning two drivers into *one* driver with twice the motor strength _but the same cone area.[/b] A slot loaded design is no different than the conventional designs we know and love, the only difference is this:


The foot print is smaller. There's no reason a woofer has to face forward, or upwards. It can face any ol' direction you want, and there's nothing stopping you from pressing two woofers *very* close together.
You might as well invert one of them. It lowers 2nd harmonic, and it's easier to push two woofers together if one is inverted. (IE, the magnet of one nearly touches the basket of the other.)
This *does* raise QTS and lower FS. But that's a good thing in the car isn't it? It allows you to use smaller woofers than you normally would, and that allows us to further reduce the box size.

If you go really crazy with this, it will reduce your power handling. But you really have to take it to an extreme for that to happen. For instance, if you tried to cram all the output of a 12" woofer through a 3" hole.

Also, all the pictures above are horns. But this same trick works for anything. You can do it with a sealed box, and infinite baffle, a vented box, even a bandpass. (All speaker enclosures follow the same set of rules; while a vented box, a TL and a horn may look different, they're all points on the same continuum.)

_


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## wiseman454 (Nov 30, 2009)

What about a midbass running from 80hz to 1000hz playing through a hole? will said hole have a cRazy effect of the output or will this hole act as the origin of the all the frequencies?


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## Patrick Bateman (Sep 11, 2006)

wiseman454 said:


> I wish I knew that one my good man. I am wanting to know the answer to a similar question with a different set-up. Looks like me bulding it is the only way to tell witch sucks because its gonna be a ton of work.




Despite it's name, you can use hornresp to model just about anything. Sealed, vented, bandpass, front loaded, horn, etc... You just gotta remember that all these things are points on the same continuum. To model a sealed box in hornresp, just model a horn with an insanely short length. Like an eighth of an inch 

So let's crunch the numbers!









Fs=30.95 hz
Qms=12.2863
Qes=0.2365
Qts=0.2320
Vas=23.88 l
SPL=86.59 1w/1m
Re=3.4
Le=2.42
BL=13.15
Xmax=16mm P-P​
This is an MCM 55-2421. Four of these will set you back a whopping $126. It's a pretty awesome sub for the car, because it works in a really REALLY tiny box, and it's rolloff is a nice match for a car's cabin gain.















Here's the predicted frequency response of the MCM in a REALLY tiny box. As in "about four inches deep." It's so small, the biggest challenge is shoehorning the woofer in there. I modeled it with 250 watts into 4ohms, which gets only 90db at 40hz. But factor in cabin gain, and a single woofer will deliver something like 105-110db in the car. (If you're wondering why the response is rolled off, that's because Hornresp includes the effect of inductance, and the MCM has a lot of it.)







Here's my crummy illustration of the sealed box and the slot loaded box. For the slot loaded box, I've included the effect of the divider between the trunk of the car and the cabin of the car, by including a three foot by two foot baffle.






Here's hornresp's simulation of the slot loaded sub. See that U-Shape, with the sound exiting the slot?






Here's the predicted response. Basically, below 200hz the response is exactly the same. Above 200hz, there's a hyooge peak, due to the cavity. So you need to filter out the high frequencies. But that's standard operating procedure with a subwoofer, right?






If you want to play with the numbers, here they are. The software is free. (google it!)
The slot is ten inches deep. The mouth of the slot is just 1.5" wide. I hope the illustration above gives you an idea of what it looks like.


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## Patrick Bateman (Sep 11, 2006)

wiseman454 said:


> What about a midbass running from 80hz to 1000hz playing through a hole? will said hole have a cRazy effect of the output or will this hole act as the origin of the all the frequencies?



When you take a woofer, clamp it to a board, then drill a hole through the board, you just added a "coupling chamber."

The coupling chamber will roll off the highs. You can predict it's effect by calculating the volume of the air between the cone and the board, along with the size of the hole.

Generally this isn't a real hot idea, unless you're *trying* to roll off the highs.

You can simulate this with hornresp of course.

OTOH, if you're trying to intentionally roll off the highs, and you have the gear to measure the response, then *yes* this is effective. For instance, if you have a car with doors deep enough to fit an eight, but the stock locations will only allow a 5" driver, you could use this technique to cram a big midbass into the doors. Just keep in mind that it *will* roll off the highs.


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## Brian Steele (Jun 1, 2007)

Patrick Bateman said:


> Despite it's name, you can use hornresp to model just about anything. Sealed, vented, bandpass, front loaded, horn, etc...




I believe that HornResp does not include losses in its modelling. The end result of this is, among other things, (1) frequency response peaks will not be as high (and dips as low) as indicated in the model (2) overall output may not be as high as indicated in the model.


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## Topper (May 31, 2007)

Patrick Bateman said:


> Despite it's name, you can use hornresp to model just about anything. Sealed, vented, bandpass, front loaded, horn, etc... You just gotta remember that all these things are points on the same continuum. To model a sealed box in hornresp, just model a horn with an insanely short length. Like an eighth of an inch
> 
> So let's crunch the numbers!
> 
> ...


Hey Patrick help me understand the illustrations posted - Based on this, what was the advantage firing into the slot brought over the regular ordinary sealed box?


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## Patrick Bateman (Sep 11, 2006)

Topper said:


> Hey Patrick help me understand the illustrations posted - Based on this, what was the advantage firing into the slot brought over the regular ordinary sealed box?


It's a way to cram a square peg into a round hole. For instance, if you're leasing a car with 6.5" holes in the rear deck. Instead of looking for a 6.5" sub, go ahead and get a 12" sub, then slot load it into the 6.5" opening.

It's also attractive for infinite baffle. For instance, mounting a pair of tens behind the seats in a sedan is a fairly standard configuration. But slot loading gives you the freedom to mount FOUR fifteens, if you package them cleverly.


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## sqshoestring (Jun 19, 2007)

Patrick Bateman said:


> It's also attractive for infinite baffle. For instance, mounting a pair of tens behind the seats in a sedan is a fairly standard configuration. But slot loading gives you the freedom to mount FOUR fifteens, if you package them cleverly.


Right, I looked into this but hate to give up trunk room especially when a pair of 15s will give me all the output I want. But, you could stand them up in a slot manifold on each side next to the wheel well, slotted into the seat. I also thought about a double ended slot where the front sub fired at the baffle with the second sub behind it, and the slot between opened into the (seat) baffle on both sides. That was still around a foot deep with 15s. I did think it might work well with cheap quad shallow 12s, since you can get them for $50 or so, if you didn't need huge output it could be impressive and not take up much room. Though I don't know what kind of distortion you get from those likely more if you push them. It would also cancel driver vibration if that matters.

I have lost count of how many times I mounted IB subs in front of a hole half the size, and it worked perfectly, better than a poorly designed manifold. The lower Fs and greater capacity of the larger sub is a far, far better deal.


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## fish (Jun 30, 2007)

sqshoestring said:


> Right, I looked into this but hate to give up trunk room especially when a pair of 15s will give me all the output I want. But, you could stand them up in a slot manifold on each side next to the wheel well, slotted into the seat. I also thought about a double ended slot where the front sub fired at the baffle with the second sub behind it, and the slot between opened into the (seat) baffle on both sides. That was still around a foot deep with 15s. I did think it might work well with cheap quad shallow 12s, since you can get them for $50 or so, if you didn't need huge output it could be impressive and not take up much room. Though I don't know what kind of distortion you get from those likely more if you push them. It would also cancel driver vibration if that matters.
> 
> I have lost count of how many times I mounted IB subs in front of a hole half the size, and it worked perfectly, better than a poorly designed manifold. The lower Fs and greater capacity of the larger sub is a far, far better deal.


Sorry, but could someone please sketch up what this would look like IB? I'm


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## Volenti (Feb 17, 2010)

fish said:


> Sorry, but could someone please sketch up what this would look like IB? I'm


Think he's talking about something like this:









but I could be wrong.


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## Patrick Bateman (Sep 11, 2006)

Volenti said:


> Think he's talking about something like this:
> 
> 
> 
> ...


Yep! You could also use the same mounting scheme for any box type. Sealed, vented, horns, etc...


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## sqshoestring (Jun 19, 2007)

Or this way but would be more complex to build:








I came up with this as a solution to the seat cushion being close to the baffle, this would offer more area exposed to the seat foam as well as two vent exits. Just guessing it could lessen nodes some as multiple subs would.

Dipole sub IB: Dipole Woofer

On the other hand for my install with two 15s, I can't find a good reason to not mount them flat since there is room to do so. I could invert one, but this being a daily driver I doubt it would make a difference a human could hear in there. Flat would be easier, and I would not need a grill to protect the face of the sub in the trunk or have to offset the baffle to fit inverted.

I looked at the LAT I have, certainly it is just cones stacked up on poles each running inverted to the next. Very compact. I would run them IB if the cost were better they look ideal for it. Came so close to buying the little ones for midbasses.


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