Good Evening everyone. I am building a few boxes and I read on one of the building blue prints. It said Don't use egg shape foam for the inside of a box for sound absorbing for the back sound waves. Why not? I have never had trouble with this egg shape foam before? I was told to use cotton or wool felt instead? Why not Acousta suff poly fill? So on to the next question? Binding post made of 100% copper sounds better then brass? I keep reading this? Does it really make a night and day improvement? I just wanted to get every ones thoughts on these clams? Thanks for your help. Jeff
Regarding Egg shape foam.
I have used it on PA speakers, but I newer actually measured response in an anechoic chamber. And Yes speaker manufacturers usually use poly fill or fiber glass, so it must be better. Older speakers used wool.
I'm sure if You google around You'll find someone who did measurements.
Yes, they are more expensive so should sound better.
Brass is only 28% as conductive as copper, so You will loose some power.
I have used it on PA speakers, but I newer actually measured response in an anechoic chamber. And Yes speaker manufacturers usually use poly fill or fiber glass, so it must be better. Older speakers used wool.
I'm sure if You google around You'll find someone who did measurements.
Yes, they are more expensive so should sound better.
Brass is only 28% as conductive as copper, so You will loose some power.
Egg box, closed cell, acoustic foam is is used to alter the high frequency response of cabinets and transmission line speakers. It does not work well for low frequencies as the amount of damping / energy absorption which the foam can support is relatively small.
For absorbing the back sound waves, an absorbent of a heavier structure, such as a mixed cotton and wool felt, is preferable because it will work better at lower frequencies.
The power loss in a brass binding post will be insignificant, taking other resistive losses into account.
For absorbing the back sound waves, an absorbent of a heavier structure, such as a mixed cotton and wool felt, is preferable because it will work better at lower frequencies.
The power loss in a brass binding post will be insignificant, taking other resistive losses into account.
Now am starting to get the picture. I know another engineer that uses only pink acoustic stuff and side ports for his speaker boxes. I will start using Acousta suff not egg foam stuff. As of binding post I will look around. Thanks. Jeff
The majority of open-cell egg-crate acoustic foam has relatively poor acoustic damping characteristics. It's widely used because it's convenient, not because it's particularly great. If you want qualitative defaults, OC-703 acoustic fibreglass board or its equivalent rockwool, SAE (or their equivalents) rated felts, with F10 being reasonably similar to OC-703 are about as good as it gets for resonable money. Acoustastuff, jute carpet underlay and certain grades of Ultratouch recycled denim are not far behind. Treated wool is OK, but don't use untreated: moths love it, and that is no joke.
Copper binding posts are nice inasmuch as their resistance is low compared to some, but copper being copper, they're soft, so mechanical integrity isn't great, and you'll have to treat them carefully. If they're not plated, they're also as noted above a recipe for oxidation.
Copper binding posts are nice inasmuch as their resistance is low compared to some, but copper being copper, they're soft, so mechanical integrity isn't great, and you'll have to treat them carefully. If they're not plated, they're also as noted above a recipe for oxidation.
Thanks ScottMoose, Sorry for the late reply. I guess I never thought that the type of absorption product makes a difference on how it makes the box sound? I learned something new today. Still learning as I go on. I did use the egg acoustic foam for a ported box with a 6 1/2 inch driver and a back enclosed seas fabric tweeter. I will look at the type of felt and wool material I need to use for my builds. Thanks for giving me the number of the felt and wool that should work for me with my full range drivers I am using. So what kind of binding post would you use Scottmoose? I know there are a lot of hyped products out there that you can get lost in? Also could I use quite batt 30 soundproofing insulation or no? Thanks Jeff
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What is used inside a box for damping depends on the box. Some are interchangeable.
Foam does not work that well, it is used commercially because of consistency during manufacture,
Acoustastuff is used as volume fill, suitable for sealed boxes, TLs that require volume fill for the low pass function.
Natural materials typically damp better than synthetic, hence the suggestions of cotton or wool felt for lining reflex boxes.
I have found the big fat solid copper binding posts to not so good and a PITA to use. I believe little metal is better than big fat, probably the best from ETI or WBT next gen. It turns out that the really cheap posts sound better than pricier ones because they use less metal. Look for plastic nuts, not metal. From experience the binding posts you need to beable to easily remove them so as to change wire when you have to. I also like the plugs to not stick out (ie less easily broken off), this points to a cup with the posts in it, i prefer as small a hole in th ebox as possible.
The ones i have too many of are cheap, plastic nuts, 2” cut-out and sound quite decent for little money.
dave
While the 1st math bit has been largely discredited tha actual graphes of damping material absorbtion ranges at the end are useful:
Bradbury's Fiber Equations
dave
Bradbury's Fiber Equations
dave
Its diy. The user may want to try different wire. Or swaps drivers and needs to replace the wire because it is no longer long enuff. Lots of reasons Scott.
Perhaps you should think about it before asking silly questions (you are good at that).
dave
Perhaps you should think about it before asking silly questions (you are good at that).
dave
Thanks again Dave. Yes being able to easily remove binding post great idea. Yes the next gen WBT or the ETI binding post can get pricey. I like the idea of plastic nuts over metal just little things that helps out. Thanks Dave again. Jeff
Thanks Dave again the information is very much appreciated. Jeff
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I use polyfill (or the visaton equivalent, wich is easier to find here) or Rockwool Sono (wich is almost an equivalent of OC703) for my speakers. a few layers (1cm thick) of old jeans is good for lining reflex boxes, but not for sealed (and i gues neighter for TL's). long hair sheepwool is also good for sealed boxes, but it's organic so prone to mold and inscect.
And for binding post, most that are sold now in diy stores are good, i mostly use dayton gold plated binding posts as they are not too expensive, very wel build and easy availeble here.
And for binding post, most that are sold now in diy stores are good, i mostly use dayton gold plated binding posts as they are not too expensive, very wel build and easy availeble here.