# Absorbing Midrange Backwave



## 6262ms3 (Feb 27, 2008)

I've done some searching but couldn't quite find what I'm looking for. For those using small enclosures for their midranges (ie: pods in a-pillars or kick panels), what stuffing material do you prefer to attenuate backwave reflections? From what I've read on various forums, polyfill is not effective at absorbing midrange frequencies. Also wondering, did you notice any subjective improvement in the midrange after reducing these internal reflections? Or is it kind of moot in a car environment?


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## seafish (Aug 1, 2012)

Any open cell material (fiberous or synthetic) will work to reduce backwaves in a speaker enclosure, but is the actual THICKNESS of the material that is important to dampen backwaves. It must be at least 1/4 the wavelegnth being reproduced if it is going to have ANY affect on the back wave. ALso, if it is going to be exposed to moisture, like in the door, it must be waterproof.

Some ideas are open cell foam, melamine foam, poly fill, rockwool, etc. The key is the "open cell" structure of the material.

All that being said, what will work even better to improve SQ in a vehicle is to reduce surface reflections by covering hard reflective surfaces like the dash and or console divider (obviously NOT the winshield…lol) with thin layers of sound adsorbing materials.


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## oabeieo (Feb 22, 2015)

I have 7" midrange in fiberglass a pillars and have a fb of 250hz. The Q is at around .75 so it has a lot of ring throughout the pass band of the driver. The ringing also had its harmonic effects that definitely plays against the cone of the speaker and caused considerable coloration 

I started by drilling a 2" hole in the "pod" which really helped a lot under 200hz and narrowed the Q of the box. 

Finding fb will be a huge benefit on how to approach a good dampener. 

The thickness of the dampening material really should be somewhere around .25 wavelength, obviously that's not feasible . I ended doing a thick CLD tile from focal. It's a dampener on bottom with a hard foam attached to it. That helped a lot but still had ringing down low at fb. I tryed diffrent carpets and foams, thick house carpet with dynamat melted to the bottom worked very very dam good, in fact that worked the best in my experiments, however I could not kill it all the way. I decided to just cross over the mid a oactave above fb and that realized that was the best I was going to get. At that point sealing the back of the midrange with duck tape layers and layers around the basket of the driver making a sealed back speaker worked the best, but it lost depth. Trade offs. I un duck taped the speaker wanting to try to get back down into the 400s(hz) and filled the entire pod with foam on top of my carpet/dynamat Home made CLD. That worked pretty good but it still rang in the 250s. At that point I realized it wasn't going to happen for me and the only way was to make my "port" bigger. So I did and made it 4" and have it on the back side of pod firing into glass behind the pod. That worked the best and have the pod stuffed TIGHTLY with foam to created a AP situation as best I could. 

TLDR, you can't get rid of ringing , can make upper harmonics a ton better but that's it


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## oabeieo (Feb 22, 2015)

Edit: do not use modeling clay. That **** melts ! And WILL drip down all over your speaker in the heat. It turns into melted crayons FAST! I destroyed a favorite set of morel drivers that way.


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## seafish (Aug 1, 2012)

oabeieo said:


> Edit: do not use modeling clay. That **** melts ! And WILL drip down all over your speaker in the heat. It turns into melted crayons FAST! I destroyed a favorite set of morel drivers that way.


How would modeling clay work to reduce backwaves??


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## oabeieo (Feb 22, 2015)

seafish said:


> How would modeling clay work to reduce backwaves??


Well it dampens the walls of the enclosure, and lowers its resonant frequency. 

Makes it so back waves don't vibrate the walls as much. It works good just melts lol


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## T3mpest (Dec 25, 2005)

If it's not going to get wet, I highly suggest plain old fiberglass batting. It's ridiculously effective at absorbing sound and dirt cheap the local hardware store.


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## tonynca (Dec 4, 2009)

Does anyone have a solution that works? I'm running speaker pods for my 3" mid-range and I'm getting some horrendous resonance at 1-3khz. It's so bad that it makes my ears ring at high volume. Any help is appreciated.


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## SkizeR (Apr 19, 2011)

seafish said:


> It must be at least 1/4 the wavelegnth being reproduced if it is going to have ANY affect on the back wave.


This is not exactly true. unfortunately, absorption isnt nearly as easy or predictable as blocking (like with mlv). each material will have different absorption coefficients regardless of how thick or thin in is relative to the wavelength. Also, with a decent absorbing material, 1/4 wavelength is where it starts becoming efficient at absorption, but it starts much before that.


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## SkizeR (Apr 19, 2011)

tonynca said:


> Does anyone have a solution that works? I'm running speaker pods for my 3" mid-range and I'm getting some horrendous resonance at 1-3khz. It's so bad that it makes my ears ring at high volume. Any help is appreciated.


is it resonance of the panel, driver, or the airspace in the enclosure that is resonating?


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## mattkim1337 (Jan 31, 2018)

How did you determine that it's the backwave that you're hearing? Could it possibly be comb filtering or reflections throughout your listening environment? Have you measured your frequency response to identify problem areas (peaks)? If yes, then try lining the enclosure with some CLD tiles or adhere a thin layer of closed cell foam to it, or make the pod more rigid.


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## seafish (Aug 1, 2012)

SkizeR said:


> This is not exactly true. unfortunately, absorption isnt nearly as easy or predictable as blocking (like with mlv). each material will have different absorption coefficients regardless of how thick or thin in is relative to the wavelength. Also, with a decent absorbing material, 1/4 wavelength is where it starts becoming efficient at absorption, but it starts much before that.


Ok thanks for clarifying...nonetheless, IMO, it is a good rule of thumb and a decent place to start.


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## SkizeR (Apr 19, 2011)

seafish said:


> Ok thanks for clarifying...nonetheless, IMO, it is a good rule of thumb and a decent place to start.


I'll see if I can find the page in a book that goes into some detail about it. It's at the shop though

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## tonynca (Dec 4, 2009)

SkizeR said:


> is it resonance of the panel, driver, or the airspace in the enclosure that is resonating?




I got the pods from the German dude. It's metal inside. I don't remember the focal 3w2be resonating this hard when I tested them with towels in the corner of my windshield. I've been trying really hard to tune these but they're just unbearable on songs with a lot of 1-3khz. I played them solo at 500-4000hz today and yup it's them that's squealing.

I know a bit about timing by now and I was definitely not hearing this type of ringing with them out of the pods. 

I'm pretty sure it's back waves resonating hard in the pods. 


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## tonynca (Dec 4, 2009)

mattkim1337 said:


> How did you determine that it's the backwave that you're hearing? Could it possibly be comb filtering or reflections throughout your listening environment? Have you measured your frequency response to identify problem areas (peaks)? If yes, then try lining the enclosure with some CLD tiles or adhere a thin layer of closed cell foam to it, or make the pod more rigid.




My 6.5" in a two way has comb filtering I know what that sounds like. This is straight up ringing. It sounds worst than if I were just to do a 2 way.

No wonder why I kept turning down 1-4khz when I'm tuning even though my curve was Andys curve it still sounded so harsh. 


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## SkizeR (Apr 19, 2011)

tonynca said:


> I got the pods from the German dude. It's metal inside. I don't remember the focal 3w2be resonating this hard when I tested them with towels in the corner of my windshield. I've been trying really hard to tune these but they're just unbearable on songs with a lot of 1-3khz. I played them solo at 500-4000hz today and yup it's them that's squealing.
> 
> I know a bit about timing by now and I was definitely not hearing this type of ringing with them out of the pods.
> 
> ...



oh well duh.. those enclosures are _way_ too small for those mids. Those mids want at least 2 liters, aka, pretty much IB. Although the VAS does make it less sensitive to enclosure size, it still is too small. I don't understand why people use those pods for midranges. That resonance is most likely a massive peak in the response right before a brick wall of a roll off of the low end. could be that, or it could just be the enclosure itself is resonating. Or could be the back wave interacting with the cone (which comes back to 1) to small of an enclosure, and 2) the enclosure is a sphere..)


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## tonynca (Dec 4, 2009)

SkizeR said:


> oh well duh.. those enclosures are _way_ too small for those mids. Those mids want at least 2 liters, aka, pretty much IB. Although the VAS does make it less sensitive to enclosure size, it still is too small. I don't understand why people use those pods for midranges. That resonance is most likely a massive peak in the response right before a brick wall of a roll off of the low end.




I'm gonna try stuffing them with some open cell material. Not sure what yet. 

If that doesn't work. I'll drill out a big ass hole and epoxy them to the pillars. Thanks. 


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## SkizeR (Apr 19, 2011)

tonynca said:


> I'm gonna try stuffing them with some open cell material. Not sure what yet.
> 
> If that doesn't work. I'll drill out a big ass hole and epoxy them to the pillars. Thanks.
> 
> ...


Try cotton or fiberglass insulation. Open cell foams "fibers" are to large for what you want to do here. 

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## tonynca (Dec 4, 2009)

Thanks I will try some synthetic cotton balls 


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## SkizeR (Apr 19, 2011)

tonynca said:


> Thanks I will try some synthetic cotton balls
> 
> 
> Sent from my iPhone using Tapatalk


https://www.amazon.com/Organic-Raw-...ds=raw+cotton&qid=1556072471&s=gateway&sr=8-2


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## tonynca (Dec 4, 2009)

SkizeR said:


> https://www.amazon.com/Organic-Raw-...ds=raw+cotton&qid=1556072471&s=gateway&sr=8-2




Not sure if I want specks of cotton seeds in the voice coil lol. I think I'll stick with cotton balls. 


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## SkizeR (Apr 19, 2011)

tonynca said:


> Not sure if I want specks of cotton seeds in the voice coil lol. I think I'll stick with cotton balls.
> 
> 
> Sent from my iPhone using Tapatalk


I have loads if it at the shop. I dont think its seeds. More like little specs of, well, idk but it's all so intertwined that they arent going anywhere. Especially with now little air gets moved from a midrange 

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## Patrick Bateman (Sep 11, 2006)

I don't understand this thread.

Sound is generated when a loudspeaker moves air.

If your box is sealed, how is the *backwave* of the loudspeaker going to generate sound *outside* of your enclosure?

IE, you might want to put fiberglass insulation in a loudspeaker enclosure to lower the peak of the QTC resonance, but if you're trying to "absorb the backwave", what is the point exactly?


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## Patrick Bateman (Sep 11, 2006)

SkizeR said:


> oh well duh.. those enclosures are _way_ too small for those mids. Those mids want at least 2 liters, aka, pretty much IB.


There's no such thing as "an enclosure that's too small."

Plenty of prosound midranges use enclosures with a volume of air that's literally just big enough to cover the basket.

Works great. Raises the efficiency and the power handling at the cost of extension:


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## SkizeR (Apr 19, 2011)

Patrick Bateman said:


> There's no such thing as "an enclosure that's too small."
> 
> 
> 
> ...


If hes talking about something resonating and the q is well above 1, yeah, I think I'm in every right to say the enclosure is too small 

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## Patrick Bateman (Sep 11, 2006)

tonynca said:


> I got the pods from the German dude. It's metal inside. I don't remember the focal 3w2be resonating this hard when I tested them with towels in the corner of my windshield.












When you place an unbaffled loudsepaker into the corners of your dash, there's a null that's formed. The null is shaped like a donut, and it wraps around your loudspeaker.

The reason that it sounds nice is because that null keeps the loudspeaker from radiating into the corner. 

Basically the sound can't radiate backwards because the dipole radiation forms a null.

Dipoles sound nice. They're tricky, but they can sound very natural.




tonynca said:


> I've been trying really hard to tune these but they're just unbearable on songs with a lot of 1-3khz. I played them solo at 500-4000hz today and yup it's them that's squealing.


When you put a loudspeaker in a sealed enclsoure and stick it in a corner, a significant fraction of the sound wraps around the enclosure and radiates BACKWARDS. When it does this, it reflects off the corner, then gets mixed into the initial wave.

Because the reflected energy is delayed, it creates a series of notches in the response. 

You can measure this with REW.



tonynca said:


> I know a bit about timing by now and I was definitely not hearing this type of ringing with them out of the pods.
> 
> I'm pretty sure it's back waves resonating hard in the pods.


Loudspeakers generate sound by moving molecules of air. When you put a loudspeaker in a sealed enclosure, the backwave can't generate sound because it can't move air. (it's sealed.)

Hence, this isn't "back waves resonating hard in the pods" it's "your midrange pods are reflecting off the corner of your dash."










That's why it's vital to minimize baffle diffraction as much as you possible can.


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## OCD66 (Apr 2, 2017)

Patrick Bateman said:


> I don't understand this thread.
> 
> Sound is generated when a loudspeaker moves air.
> 
> If your box is sealed, how is the *backwave* of the loudspeaker going to generate sound *outside* of your enclosure?


Sound is generated equally on both sides of the cone. The rear output bounces off of the enclosure and transfers back through the cone. With a delay.


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## tonynca (Dec 4, 2009)

Patrick Bateman said:


> When you place an unbaffled loudsepaker into the corners of your dash, there's a null that's formed. The null is shaped like a donut, and it wraps around your loudspeaker.
> 
> The reason that it sounds nice is because that null keeps the loudspeaker from radiating into the corner.
> 
> ...


I stuffed the pods with cotton balls lining the back of the pods. 70% of the resonance is now gone but now I'm left with a speaker that doesn't seem to play sound clearly at high volume. I'm guessing that it's fighting the sealed enclosure and not breathing properly.

I had the speaker playing tried to wrap a towel around the pods and the speaker to extend the air volume a bit more and it seemed to help a bit. 

I'm not sure if it's air the pods needs or maybe it's the reflections off the windshield. I'll try stuffing some towels in the back corner to see if it helps.

Please don't judge me but here's a song (Madonna - Hung up) with a lot of 1-4khz that I'm using to test the speakers. I would solo the Focal to play by itself and listen and I found that they are super ringy around 2-4khz. When I play them solo I set the crossover to 300-4000hz 24db LW slope, 12db slopes dont change in terms of them ringing around 2-4khz.

I used my Dynaudio BM5A MK3 studio monitors as a reference in my room so I know what to listen for. I would also put a Fabfilter Pro-Q3 and solo around 2.5khz and they do not sound harsh at all. So smooth these speakers. I wish my car sounds 70% of this.

I'm attaching a pic of the pods mounting location and how they are stuffed.


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## tonynca (Dec 4, 2009)

Tried this tonight...









minimal difference. Yes there's less reflections but I don't think reflections are the issue.

I started listening to the focal by itself again and removed like 10db of 2.5khz and it's starting to sound way better. 

Please note that I'm also listening to the speaker without any EQ to make sure it's not my tune or something. 

Doing an AB compare with and without EQ is night and day. There is just so much resonance without EQ. 


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## dumdum (Feb 27, 2007)

from experience the focals need to breath, they don't like being in small enclosures as said, you wouldn't get a twelve inch sub and put in a 0.05 cubic ft box? set them free into the pillar as you describe!


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## tonynca (Dec 4, 2009)

dumdum said:


> from experience the focals need to breath, they don't like being in small enclosures as said, you wouldn't get a twelve inch sub and put in a 0.05 cubic ft box? set them free into the pillar as you describe!




Yeah...

I'm gonna try and build a 3L sealed box and put them in there to test first before I go through all the trouble of building pillars.

A sealed box is easier to make 


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## dumdum (Feb 27, 2007)

at 20 degrees c the wavelength of 2.5khz is approx. 13.78cm, which id guess is about to the back of your pod and forward again

to whoever said a sealed pod cant generate noise from the back wave... it does it by basically reflecting in the pod and then the cone acts like a mic diaphragm and resonates, you then hear the waves from the front of the cone playing the rear wave, phase is all over the shop!

that's why I am not a fan of small enclosures like this generally

the drivers that were mention which are closed back are baffled or very shallow and the airspace forms part of the suspension also so the driver/cone/suspension are tailored to play efficiently as a trade off to bandwidth I find


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## tonynca (Dec 4, 2009)

dumdum said:


> at 20 degrees c the wavelength of 2.5khz is approx. 13.78cm, which id guess is about to the back of your pod and forward again
> 
> 
> 
> ...




Pod is about 7cm deep
Just measured


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## DavidRam (Nov 2, 2014)

tonynca said:


> Pod is about 7cm deep
> Just measured
> 
> 
> Sent from my iPhone using Tapatalk



My home speakers... 4" Focals in a very small enclosure that perform VERY well. 
https://www.crutchfield.com/S-PU3KN...iLUU7CfZ4S1TmmsnfoLkpkn0TSX87FLxoC550QAvD_BwE

I hope you can make those pods work, they look amazing!


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## Patrick Bateman (Sep 11, 2006)

OCD66 said:


> Sound is generated equally on both sides of the cone. The rear output bounces off of the enclosure and transfers back through the cone. With a delay.


Sound is generated by the movement of air molecules.

In order for that reflected backwave to generate sound *it must move air*and it cannot move air because the enclosure is sealed.










B&W used to go to herculean extremes to attenuate the backwave, but stopped, because there's just bigger fish to fry.

My 'hunch' is that people think that addressing the back wave of a loudspeaker should be done, because they imagine that a lot of sound can penetrate the cone of a loudspeaker. For instance, if your neighbor is playing loud music, you can hear it through your wall.

The thing is, *you hear your neighbor's music because it's moving your wall.* The efficiency of a radiator is based on the SIZE of the radiator, and due to that, a very small amount of motion on a wall generates a lot of sound. Same reason that an 18" woofer is more efficient than a 9" woofer (which is also counterintuitive) and why knocking on a door makes a lot of noise.

Quieting down the *enclosure* walls makes a great deal of sense because the walls of the enclosure are exposed to the room, and their surface area is large.

Worrying about the backwave in an enclosure is (mostly) silly. I guess it might be worthwhile if you had your system completely dialed in and you were just looking for things to tinker with.


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## Patrick Bateman (Sep 11, 2006)

dumdum said:


> at 20 degrees c the wavelength of 2.5khz is approx. 13.78cm, which id guess is about to the back of your pod and forward again
> 
> to whoever said a sealed pod cant generate noise from the back wave... it does it by basically reflecting in the pod and then the cone acts like a mic diaphragm and resonates, you then hear the waves from the front of the cone playing the rear wave, phase is all over the shop!
> 
> ...


When people say _"I don't like the sound of small enclosures"_ they're generally saying _"I don't like the sound of the peak that occurs in small enclosures."_

Basically there IS a peak when the enclosure is too small. But you can EQ it away with a simple 2nd order highpass filter.

When you do that, you wind up with a speaker with power handling that can be as much as 2-4x higher. You get a crazy gain in headroom and dynamics.

It helps if you're using drivers with low QES, and most car audio drivers don't have a low QES. Prosound drivers work very nicely in very very small enclosures. The French speaker companies make a lot of drivers that are pretty close to prosound, companies like Focal, Triangle and Audax.

More info: Satellites and Subwoofers


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## Patrick Bateman (Sep 11, 2006)

tonynca said:


> minimal difference. Yes there's less reflections but I don't think reflections are the issue.
> 
> I started listening to the focal by itself again and removed like 10db of 2.5khz and it's starting to sound way better.
> 
> Please note that I'm also listening to the speaker without any EQ to make sure it's not my tune or something.


Post your measurements and we'll get you sorted out. Do the measurements in AND out of the enclosure please.


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## seafish (Aug 1, 2012)

Patrick Bateman said:


> Sound is generated by the movement of air molecules.
> 
> In order for that reflected backwave to generate sound *it must move air*and it cannot move air because the enclosure is sealed.




PB, this is just wrong...of course the air can move, though only until it hits the back of the enclosure and is then reflected back in to backside of the speaker cone where the process happens all over again thus lightly interfering with the cone's movement. 

What don't you understand about that??


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## tonynca (Dec 4, 2009)

Patrick Bateman said:


> Post your measurements and we'll get you sorted out. Do the measurements in AND out of the enclosure please.


So you want me to measure 1m from the speaker in free air and in its enclosure?


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## Patrick Bateman (Sep 11, 2006)

seafish said:


> PB, this is just wrong...of course the air can move, though only until it hits the back of the enclosure and is then reflected back in to backside of the speaker cone where the process happens all over again thus lightly interfering with the cone's movement.
> 
> What don't you understand about that??


Ugh I feel a ban coming on, but here goes:

*Sound is produced by the motion of air.*
The backwave of a loudspeaker cannot move air if the enclosure is sealed.

I think you guys are visualizing the loudspeaker cone producing a wave, that wave being reflected by the back on the enclosure, then radiating out of the cone.

That *could* happen if the enclosure was sufficiently large, and if the loudspeaker cone was lossy. IE, if the reflected wave had the ability to move the cone.

*For the most part* neither of those conditions are true. That's why I qualified my last post, and mentioned that it might be something to address if you're system was already optimized to the nth degree.










Here's an example of a sealed loudspeaker in a box that's 100% empty, and stuffed with polyfill.

Below 150hz, you might hear a VERY subtle difference. The limit of human hearing perception is something like 3dB, and it's frequency dependent. My money bets you can't tell the difference between these two boxes.

NOTE: a reflection *outside of the box* can create dips as severe as ONE HUNDRED DECIBELS and as big as SIX decibels. That's why I find it odd that people in this thread are obsessing about reflections IN the enclosure. It's what's outside the box that counts.

So when OP says "my speakers sound like ass in the corners" imma gonna jump to the conclusion that the problem is a reflection in the car, not a reflection inside his freakin' enclosure. Call me crazy.

In the measurement posted above, note that there IS a peak and a dip at 170hz. 170hz is 80 inches long. The sub box holds an an 18. I'm going to predict that the peak and the dip are occurring due to a standing wave inside of the box. Standing waves happen at quarter waves, IE, if the interior of this sub box is 20 inches long, that's why there's a peak and a dip at 170hz.

This is also why car cabins have a dip at 60hz.

If OP's enclosures are 6" deep, then you would expect a peak and a dip somewhere around 563hz. Considering that he's complaining about a dip in the upper treble, I still hold firm to my statement:

the problem is the cabin, not the enclosure.

Data courtesy of data-bass : https://www.data-bass.com/data?page=content&id=79#!prettyPhoto


P.S. the other factor here, is that the amplifier is controlling the motion of the loudspeaker cone. A loudspeaker that isn't powered could very well transmit sound from the other side. For instance, if you have a loudspeaker in the door of your car, one reason that you might put it in an enclosure is that the loudspeaker will radiate sound when it is not powered. IE, road noise can radiate through your loudspeaker cone. This is less of a problem when you're playing music, because again, then the amplifier is in control of cone motion.

This is one of those things you find out the hard way when you measure loudspeakers, that the mere presence of an unpowered loudspeaker in proximity of the one you're measuring can screw up your measurements. Because the unpowered speaker will behave like a passive radiator. The trick is to plug it into an amp. If you ever listen to a set of speakers in a room full of other speakers, the other speakers should be powered for this reason.


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## Patrick Bateman (Sep 11, 2006)

tonynca said:


> So you want me to measure 1m from the speaker in free air and in its enclosure?


1) turn off your EQ

2) measure your focals in their enclosures

3) measure your focals with no enclosure, on that towel

Measure one channel at a time plz


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## SkizeR (Apr 19, 2011)

i cant picture that being very productive tbh, especially after my installer has been ****ing around with drivers wrapped in towels for the past 4 months and tuning them with him


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## tonynca (Dec 4, 2009)

I got some good data to work with here.

I measured with and without towel in free-air, pods aimed directly at mic at about 3" away, and one in my seating position with the mic pointed up into the roof.

Free-air with towel response is awesome... These really are super flat and linear in response in free-air. It looks like the pods chokes them up pretty good and cause a 5db dip in the 400-1500hz area. I guess in the pods they still work decently well but I'm losing 5db of output. I think I'm going to really look into getting these pillars made. I still don't know where to point them for best response in the driver seat yet. I have not posted my left and right response but the right side takes a pretty fat dip at 600hz where they are pointed now. I will do some further testing to see if pointing them up at the roof helps.


My cross over is LW 24db/slope @ 300-6000hz during this testing.


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## Hillbilly SQ (Jan 26, 2007)

I'm not taking sides here. One thing this thread NEEDS is hard objective measurements to see who's right and who's blowing smoke. So far PB showed measurements of an 18" sub in a sealed box with and without polyfil. In a blind test I agree it would be mostly impossible to tell the difference between stuffed and unstuffed. 

Here's what I'm proposing someone on here do. It would take some good test equipment to make the measurements valid enough to be posted here as hard evidence of what helps, what hurts, and what's just a waste of time and resources. I don't have good enough test equipment to really make this test truly objective and would be accused of skewing the results if someone didn't agree with the findings.

Someone with the time and tools to do it correctly should take a TINY enclosure like a pvc endcap and test a random midrange/wideband driver in it with it sealed, sealed with polyfil, sealed with ocf, a hole drilled in the back, a hole in the back stuffed with polyfil, and a hole in the back stuffed with ocf. 

I use 2" pvc endcaps in the dash locations of my Ram. I know for a fact that drilling a small hole in the back (1/4" does fine) and stuffing with polyfil or ocf helps a ton with low end extension. With these pods sealed up with ocf in them my gb25's rang like crazy in a certain vocal range if crossed below 800hz. This is why I crossed them at 900hz for a while. After opening up the back of the "enclosures" I can cross down to 300hz (could go lower if I wanted to) with no ill effects. I'm sure with the big booty gb25's in there those pvc endcaps netted nowhere close to what they needed sealed. I originally thought I had enough of an AP vent with the hole the wire went through but the speakers wanted more breathing room. To be fair my findings are completely subjective and have no objective data to back up my claims. My ears sure know what they're hearing though.


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## ToNasty (Jan 23, 2013)

tonynca said:


> Tried this tonight...
> 
> 
> 
> ...


Would you happen to know what would happen if the enclosure is to big for the mid? I dont think ill have that issue. But im doing a 40mm mid in my pillars and want to be prepared for this


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## SkizeR (Apr 19, 2011)

Hillbilly SQ said:


> I'm not taking sides here. One thing this thread NEEDS is hard objective measurements to see who's right and who's blowing smoke. So far PB showed measurements of an 18" sub in a sealed box with and without polyfil. In a blind test I agree it would be mostly impossible to tell the difference between stuffed and unstuffed.


That already exists here.. GlassWolf's Pages


TLDR, and bolded at the bottom of the page: "I also found that stuffing gets less effective as box size increases. The morale: The bigger your box is, the harder it is to fool your woofer."

so PB posting it up with an 18 falls right in line with that. try it with the mid at hand and itll be a different story


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## Caspase-9 (Feb 23, 2015)

tonynca said:


> I got some good data to work with here.
> 
> I measured with and without towel in free-air, pods aimed directly at mic at about 3" away, and one in my seating position with the mic pointed up into the roof.
> 
> ...


What did you end up doing here? I’ve got a set of 3” midranges from the Focal ES165KX3 set, installed in the very same pods, and mounted just like yours in the A pillars of my vette. My amps are not yet installed, so I have not tested anything, but if this installation did not work well I may need to do a rethink. One other question, is can we really say the pods are “sealed”? Doesn’t the mounting hardware create a vent (albeit small) to the inside of the pillars? I’m a newbie so I’m just trying to learn. Thanks.


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## tonynca (Dec 4, 2009)

I ended up making some custom a-pillar pods. 

Even the Focal 3w2be sounded better in the custom pods than the little metal pods. It sounded less like a Bluetooth speaker and more spacious. The only word I could describe the metal pod was that it sounded compressed. 

The metal pods you have are not technically sealed but I would say they might as well be categorize as so because there is barely any air leaving that tiny mount. 

If I were you get some custom pillars made to mount the speakers by a local shop or send them to installers on here. It’ll cost you but at least you get the most out of your system. 

The only issue I have with my current setup is there is a bit of resonance somewhere in 2-4khz area during some songs.


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