Is there a way to measure polyfill accurately?

machone

Take it easy man I was just kidding.

JLStice

Dredged posts are -thebest-

@Jstas Thanks John, that's way more comprehensive than what my understanding of stuffing ever was. Thanks for the writeup. I guess us IT people can fly a bit on the keys, but here it's definitely appreciated.

Back in my mobile SQ days we did all kinds of foam, dynamic mat, and fluff to change resonances of trim panels, the cabin, and dampen body cavities. A customers' SQ problem was seldom in the driven system. The 'professional' setups the SPL guys would sell and install to anyone with a money burning a hole in their pocket had the power and components needed just minus the brains. They'd listen to it and get tired of cabin rattle and come back and see Len or me to clean it up... We'd calculate the cabin as if it were a speaker enclosure itself, and they're just a nightmare usually.

On the built enclosures we often just lined the corners and any bracing on the inside with stiff poly-fill and the flat MDF areas would get a few layers of DynaMat... tbh, the Dynamat cleaned them up more than the fluff. Poly-fill in a ported or passive enclosure was just a no-no, but we'd see them come in all the time like that, and sealed under-sized boxes failed from overheated coils with melted polyfill or unglued spiders, etc. Just better to eat the space requirement and build the enclosure correctly. I would say cheaters never prosper... but they do, just not for long.

Viking64

Jstas wrote: »

machone wrote: »

How can you type that much!!!!

This is completely uncalled for and why I don't post much anymore. I go through all this effort to help some people out because I can. Then I get mocked and dumped on because I took some time out of a lunch break to provide an answer with complete thoughts formed with proper grammar, spelling and punctuation. All because it's beyond your comprehension that someone can form a complete answer and explain complex concepts with a keyboard.

I don't believe anyone was mocking you or dumping on you. I was the first to respond with an image, as if the dog was saying: "Holy crap! That is a lot of information about polyfill." It was in no way intended to discredit you or ridicule you.

I understand how much effort you put into your 2 posts and I can see how it may seem like it wasn't appreciated. The fact remains that we now have a permanent document detailing specifics of an often overlooked aspect of speaker dynamics that can be accessed and utilized for years to come.

I am currently in the process of modding a pair of 2.3TL's. I had everything, save for the crossovers, removed from the cabinets. One "roll" of the original polyfill in each cabinet had fallen down to about midway of the diameter of the passive radiator. After sealing them with Power Grab and adding BlackHole5, I put them back together and the sonic improvements were substantial.

At that time, the best advice I found on here, after installing the BlackHole5, was: "reinstall the polyfill" and "keep it out of the area of the PR". Your knowledge would have been invaluable to me then and is is sure to be for many others in the future. Your efforts are a perfect example of why this forum is great.

lightman1

Viking64 wrote: »

Jstas wrote: »

machone wrote: »

How can you type that much!!!!

This is completely uncalled for and why I don't post much anymore. I go through all this effort to help some people out because I can. Then I get mocked and dumped on because I took some time out of a lunch break to provide an answer with complete thoughts formed with proper grammar, spelling and punctuation. All because it's beyond your comprehension that someone can form a complete answer and explain complex concepts with a keyboard.

I don't believe anyone was mocking you or dumping on you. I was the first to respond with an image, as if the dog was saying: "Holy crap! That is a lot of information about polyfill." It was in no way intended to discredit you or ridicule you.

I understand how much effort you put into your 2 posts and I can see how it may seem like it wasn't appreciated. The fact remains that we now have a permanent document detailing specifics of an often overlooked aspect of speaker dynamics that can be accessed and utilized for years to come.

I am currently in the process of modding a pair of 2.3TL's. I had everything, save for the crossovers, removed from the cabinets. One "roll" of the original polyfill in each cabinet had fallen down to about midway of the diameter of the passive radiator. After sealing them with Power Grab and adding BlackHole5, I put them back together and the sonic improvements were substantial.

At that time, the best advice I found on here, after installing the BlackHole5, was: "reinstall the polyfill" and "keep it out of the area of the PR". Your knowledge would have been invaluable to me then and is is sure to be for many others in the future. Your efforts are a perfect example of why this forum is great.

Buttkisser.....

Viking64

lightman1 wrote: »

Buttkisser.....

Toolfan66

I wish I had the skills to type like that, I for one appreciate the work and time you took to post that info. It would have taken me half the day with my typing skills..

ken brydson

Reported... Buh bye now...

xschop

Read first reply, stopped for coffee break, then read 2nd. Very concise points, thank you. I love my Power-ported SDA's.

stainless0steel2

What happens if you add Black hole 5 behind the drivers in let's say a set of SDA 2B's. Do you still need some of the polyfill behind those drivers?

Tony M

@Jstas's very detailed explanation of whether or not to add or reduce or leave it be on speaker polyfill should be put at the top of the list in the Category of speaker tweaks and mods. Permanently.

Very , very informative ! I've seen my fair share of speaker box / tower interiors that I can say the fill in them has been so varied that I believe, like John states, each has been unique without a doubt.

Reading the explanations in John's post was like taking an advanced class on "Dampening a speaker enclosure" but taught in a way as to explain the theories and facts to my elementary level of knowledge on the subject.

Thanks John !

F1nut

stainless0steel2 wrote: »

What happens if you add Black hole 5 behind the drivers in let's say a set of SDA 2B's. Do you still need some of the polyfill behind those drivers?

You need all of the original polyfill.

Jstas

The polyfill in SDAs is not there for driver dampening. It's there for port tuning.

SDAs have passive radiators which is essentially a speaker port.

Ports work because they have a column of air in them that gets moved when the driver vibrates. That moving air in the port creates complimentary sound waves that enhance the performance of your speaker. Just like how you can feel and hear the THWHUMP of air when you shut a car door or when you shake a trashbag to open it up. The same thing happens with a port.

Port tuning is essential because you need to be able to get the maximum flow rates without hitting the cavitation point in that port to move the air and take advantage of the air spring it creates. If you move it too fast you will either compress the air in the port and enclosure too much and possibly cause physical distortion in some or all of the drivers. Alternatively, you will blow all the air out of the port and create a vacuum in the enclosure which can also cause physical distortion, attenuated performance of the driver and even cause overheating issues in the motor structure.

Port tuning means that you have an appropriate amount of air in the port and enclosure, it's weighted properly to compliment the drivers because of the port size and it's moving at the highest rate possible before cavitation or other performance killing phenomenon happen.

A passive radiator does the same thing as a port but instead of a column of air, you have a rigid, polymer disc (which is actually a cylinder) that takes the place of the air. It does the same thing which is why they have to be weighted properly so they don't move too fast or too far and make farty distortion noises.

So like a ported enclosure uses polyfill to make a box and port perform well by changing the velocity of the air being moved by the backwave off the rear of the driver, polyfill in an SDA evens out the velocity of the backwave pressure inside the enclosure. That makes the air pressure work evenly on the rear surface of the passive radiator so you get nice, tight bass response without having to have a giant driver or getting the flappy, **** noise from distortion rippling across the surface of the passive radiator.

The benefit there is that you can have a crazy, complicated load to drive in a fancy crossover network like what is needed to drive the SDA tech and you can reduce or at least make the load more reasonable by having small, efficient, easy to drive drivers. That way you get your SDA wizardry but you have a huge tower speaker that performs on the high end like a 2-way bookshelf but digs deep like 15 inch sub and can do it on 200 watts per channel for the entire array, not just the sub.

pkquat

@Jstas Excellent posts. TY. I keep forgetting to mention that in my drive by's of late.

verb

Thanks @jstas and @f1nut I think I found my answer for my 1C upgrade path. BH5 just behind the MW's and re-install the original polyfill. Correct?

http://forum.polkaudio.com/discussion/179960/another-1c-upgrade-path#latest

pitdogg2

verb wrote: »

Thanks @jstas and @f1nut I think I found my answer for my 1C upgrade path. BH5 just behind the MW's and re-install the original polyfill. Correct?

http://forum.polkaudio.com/discussion/179960/another-1c-upgrade-path#latest

Yes it is good stuff.

FestYboy

Reading @jstas 's post finally explained why I'd witness sub drivers wobble when viewed in slow-mo. I always wondered what was causing such nonlinear motion. Now I can use this to help remedy some mods I had in mind for the 505s.

wolfie62

I knew there was a reason I don't use fiberglass or polyfill! I use a damping material to kill cabinet coloration, but not fiber stuffing.

Viking64

wolfie62 wrote: »

I knew there was a reason I don't use fiberglass or polyfill! I use a damping material to kill cabinet coloration, but not fiber stuffing.

Fiberglass insulation makes for a relatively poor sound control product.

Clipdat

That must be why they use it in car mufflers.

Viking64 wrote: »

Fiberglass insulation makes for a relatively poor sound control product.

Viking64

Clipdat wrote: »

That must be why they use it in car mufflers.

Fiberglass and fiberglass INSULATION. Big difference.

Jstas

So I was going to write a big long post about passive radiators and how they work (they're ports) and I knew I remembered posting about this before.

I did.

It's in this thread.

Jstas

Also, more discussion here: https://forum.polkaudio.com/discussion/comment/312379#Comment_312379

VR3

Hard to imagine this was... 16 years ago

hytekrednek

i've read fiberglass insulation is better, and also polyfill is best. Which is actually better for the task? and why?
I replaced the fill in some old sda crs speakers with fiberglass insulation, along with a few other upgrades. Result was good, but wondering if the other upgrades are held back a bit now by the fiberglass.

xschop

The Dacron won't suffocate the enclosures like fiberglass.

Gardenstater

I just happened to be reading this earlier today. Maybe it would be useful to read: https://stason.org/TULARC/entertainment/audio/general/12-24-What-is-the-best-stuff-to-fill-a-speaker-cabinet-wit.html

Jacktogeokami

I am responding to this thread with a brand new account that I just made, because I have been looking for an answer to this question for years.
I don't have the time, money, or equipment to make the table.
What is the weight to volume and density of pily fill?
If I get the 20# box of polyfill that ships in a box that I'd 24"×20"×18" that is 5 ft³, they say to let it expand for 24 hours before using it.

The shipped density of the poly fill is 4# per cubic foot, what is the expanded density?
What is the softness of the pillow going to be if you stuff it right from the box with no time to expand except in the pillow?


Thank you for reading this far if you did, I know this was originally a thread about using polyfill to stuff a speaker and how that is a worse idea that fiberglass insulation because of the reflective nature of polyester, but the answer was not given her for the density in general terms.

Tl;Dr did we ever figure out what the density of polyfill is?

F1nut

Oki doki

Gardenstater

Jacktogeokami wrote: »

I am responding to this thread with a brand new account that I just made, because I have been looking for an answer to this question for years.
I don't have the time, money, or equipment to make the table.
What is the weight to volume and density of pily fill?
If I get the 20# box of polyfill that ships in a box that I'd 24"×20"×18" that is 5 ft³, they say to let it expand for 24 hours before using it.

The shipped density of the poly fill is 4# per cubic foot, what is the expanded density?
What is the softness of the pillow going to be if you stuff it right from the box with no time to expand except in the pillow?


Thank you for reading this far if you did, I know this was originally a thread about using polyfill to stuff a speaker and how that is a worse idea that fiberglass insulation because of the reflective nature of polyester, but the answer was not given her for the density in general terms.

Tl;Dr did we ever figure out what the density of polyfill is?

Seems like you're asking the wrong question. What is the target density that you wish to achieve in your enclosure? Once you know that, since you know the internal volume, you just determine how much polyfill you need by weight. If you don't have a digital scale I suggest you get one and they are cheap. If you have to compress it a bit by rolling it up first, do so. If you have to fluff it up, do that.

I don't know what to tell you regarding target density. Ultimately should probably be trial and error. This gives a general rule of thumb for max. values but I don't know if it is correct personally.

http://www.soundsolutionsaudio.com/forum/topic/7168-a-technical-understanding-of-polyfill/

1. If the enclosure is less than 2.5 - 3.0 cubic feet in size, you should use no more than one and a half pound of polyfill per cubic foot available in your enclosure.

2. If the enclosure is greater than 2.5 - 3.0 cubic feet in size, you should use no more than one pound of polyfill per cubic foot available in your enclosure.

Specific examples of polyfill's effects on various enclosure sizes (with varying amounts of polyfill in each size) can be found in The Loudspeaker Cookbook by Vance Dickason or in an article written by Tom Nousaine for the March/April 1995 edition of "Car Stereo Review".