Foam lining in speakers = good
oohhbehave
Posts: 9
I've been searching around on the internet about what tweaks I can do to make my speakers better. One of the easyist thing to do is to line your speakers with some kind of sound absorbing material to reduce "sounds waves" generated by the back of the cone from bouncing back at the cone and coloring the sound of the speakers. It sounded logitcal enough, so I attempted to try it out. I ordered some 1" thick Acoustic Barrier foam from parts-express.com to try and line my Polk T90e speakers (Monitor 60).
I only lined one speaker so I can compare it directly with one speaker that wasn't lined. Although the difference is subtle, it's still pretty noticeable. The foam lining eliminated the echo in some female vocales and instruments. When the sound gets busy with 4 or 5 different instruments, the none foam speaker would miss a few instruments from time to time. Not so with the foamed speaker. Every instrument was present at all times.
Now, I just got some Acoustic stuffing as well. Anybody know how much I should use? Is there a rule of thumb? What changes in the sound am I looking for when using Polyester acoustic stuffing?
Thanks!:D
I only lined one speaker so I can compare it directly with one speaker that wasn't lined. Although the difference is subtle, it's still pretty noticeable. The foam lining eliminated the echo in some female vocales and instruments. When the sound gets busy with 4 or 5 different instruments, the none foam speaker would miss a few instruments from time to time. Not so with the foamed speaker. Every instrument was present at all times.
Now, I just got some Acoustic stuffing as well. Anybody know how much I should use? Is there a rule of thumb? What changes in the sound am I looking for when using Polyester acoustic stuffing?
Thanks!:D
Post edited by oohhbehave on
Comments
-
Too much stuffing will make the speaker sound dull and kill bass response. Use just a little behind the midrange/woofers.
And did you mean Sonic Barrier? I use that in all my speakers."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Yes, Sonic Barrier is the correct name of the foam. Thanks for the correction!
If too much Polyester stuffing makes the speaker sound dull, how does too little affect the sound? -
Face,
I have a set of SDA SRS 1.2TL's, that only have the factory "polyfill"?? Should I leave them alone, or would one of these products help??
Pio Elete Pro 520
Panamax 5400-EX
Sunfire TGP 5
Micro Seiki DD-40 - Lyra-Dorian and Denon DL-160
PS Audio GCPH phono pre
Sunfire CG 200 X 5
Sunfire CG Sig 405 X 5
OPPO BDP-83 SE
SDA SRS 1.2TL Sonicaps and Mills
Ctr CS1000p
Sur - FX1000 x 4
SUB - SVS PB2-Plus
Workkout room:
Sony Bravia XBR- 32-Inch 1080p
Onkyo TX-DS898
GFA 555
Yamaha DVD-S1800BL/SACD
Ft - SDA 1C
Not being used:
RTi 38's -4
RT55i's - 2
RT25i's -2, using other 2 in shop
LSI 15's
CSi40
PSW 404 -
You already found that out.oohhbehave wrote: »Yes, Sonic Barrier is the correct name of the foam. Thanks for the correction!
If too much Polyester stuffing makes the speaker sound dull, how does too little affect the sound?
Sonic Barrier on the back wall behind the drivers may help imaging and midrange. Just make sure to keep the polyfill away from the passive radiator.Face,
I have a set of SDA SRS 1.2TL's, that only have the factory "polyfill"?? Should I leave them alone, or would one of these products help??"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
When I foamed and lightly stuffed my Monitor 5 Jrs, there was a clear improvement in tightness of the sound, as well as cleanness. And I just used cheap craft store foam.
-
Keep polyfil away from any driver, not just PRs. Especially with a vented pole piece. Unless it's a full shielded driver. If those polyester strands get inside the motor structure of the driver they can really muck things up and cause driver failure.
Honestly, a home speaker is usually designed to a fairly optimum enclosure size. Acoustic foam can help but the benefits are usually minimal. I wouldn't bother with polyfil at all. Polyfil doesn't slow down the backwaves as much as it slows down the air movement. Well, I guess that's a little contradictory.
Polyfil is used in enclosures where the optimum cabinet size could not be achieved due to one constraint or another. It is used to slow down the air movement inside the enclosure so that the enclosure behaves like it is larger than it is. It doesn't have very good baffling properties like foam does. Over-stuffing the polyfil can be used effectively to dampen resonances in a cabinet or a large driver like a subwoofer. It can also keep a subwoofer from "popping". The "popping" being that resonant echo that you can sometimes get in enclosures when the driver is playing a musical or other programming peak. It isn't as pronounced in a sealed enclosure but a vented or PR enclosure can amplify the sound through port noise or PR distortion.
For a mid-range driver or bass driver, polyfil can tame resonances near the upper crossover points which can lead to overly bright midrange. Keep in mind that it doesn't cut this stuff out entirely but reduces it enough to make it a non-issue in playback. However, polyfil is a band aid. It doesn't fix an underlying problem, it just covers it up. That problem being poor crossover design, poor build material selections, poor driver design, poor enclosure design or any combination of any/all of those.
Polyfil does not stop the backwave. It merely slows things down enough so that the backwave hits the cone at a different time so it doesn't cancel things out.
Acoustic foam will not necessarily cancel the backwave as much as it diffuses it so it's not a direct reflection. It is a useful tool in creating a sonically dead enclosure. It is not necessarily used to make up for short comings in an enclosure but rather use as dampening to make an otherwise smooth and reflective surface not smooth or reflective anymore. Good enclosure materials like MDF, void-less plywood or even solid wood, when finished, can have a very smooth and even surface which can cause many reflections. Securing even just a small square of foam the same size as the rear of the driver and directly behind it can make a noticeable difference as you have found.
I would forgo the polyfil. It's not going to benefit you a whole bunch. Especially in a rather tight enclosure like a T90e.
A better option would be to do some work on removing right angles inside the enclosure. Acoustic foam cut and shaped then secured in place to eliminate a corner or even a sharp edge can help you solve such a problem. The issue with the corners and edges is that the airflow and backwaves can cause eddys and corner loading which changes the pressure inside the enclosure, makes it uneven and can cause distortion in the drivers. Elimination of these edges in one way or another can make a very audible difference. A good example is subwoofer boxes for SPL competition. Making a square box gets lots of airspace but the corners provide spots for the air to get jammed up and build pressure. When I build a slot loaded box for an SPL competition, I use fiberglass to round corners inside the box and acoustic foam to cut reflections. A particularly skeptical person I know believed that a gigantic box was the way to go. Math told me that the box could be 30% smaller than he believed if you took airflow management in to concern. I tested a box I built. It reached 142.4 dB without my interior finishing. I took the box home, did my finishing and returned and with just the airflow management the same box hit 143.8 dB. Still not believing me, we each built a box our own ways with the same drivers. My box was considerably smaller and installed in the same car, I picked up 3.6 dB over his box. His theory that bigger is better has merit but there is a point where efficiency becomes the top concern. Doing the little tweaks like sound deadening, polyfil and rounding corners and even flaring ports improves efficiency. If my box was built to the same size as his was and used all of the little efficiency tricks I used in the small box, he probably would have had 3-5 dB on my box.
Everything you do will change the properties of that enclosure. Have fun messing around! That's how I learned about stuff. Just think thinks through before you do something permanent to an expensive pair of speakers. I know I hate messing something I paid hard-earned money for but something I built myself, the whole reason I built it was to experiment.Expert Moron Extraordinaire
You're just jealous 'cause the voices don't talk to you! -
Can I just tightly pack some filling in the corners to "round" out the corners?
Face- can you explain how polyester filling can increase imaging and midrange? -
Imaging and midrange quality can increase since you're lessening or eliminating reflections off the back wall and sound passing back through the speaker cone."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
-
Why should the poly-fill be kept away from the PR's? My RTA11TL's only had poly-fill above and behind each mid-woofer. However, my Monitor 5A's are stuffed with it even around the PR. They were like this from the factory. Is this wrong?
When I put Sonic Barrier in my RTA11TL's, I only used it on the sides and behind the mid-woofers. None was placed near the PR's. Is it wrong to put Sonic Barrier behind the PR's?
Thanks for educating us
StanStan
Main 2ch:
Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.
HT:
Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60
Other stuff:
Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601 -
This is all excellent information! On a related note, from what I understand polyfill works best in a sealed cabinet as it slows down the backwave and make the cabinet seem bigger. But for ported designs, you are not supposed to use dampening material that reduces the internal air volume of the enclosure. Does fiberglass reduce the internal air volume of ported cabinets? I'm specifically referring to the pink, fluffy Owens Corning fiberglass roll that Home Depot sells for home insulation.
-
Since the passive radiator is acting as a port, it's well documented that you don't want to block your port with fill. As for your M5A's, is it possible that the fill fell down?Why should the poly-fill be kept away from the PR's? My RTA11TL's only had poly-fill above and behind each mid-woofer. However, my Monitor 5A's are stuffed with it even around the PR. They were like this from the factory. Is this wrong?
I don't see a problem in that.When I put Sonic Barrier in my RTA11TL's, I only used it on the sides and behind the mid-woofers. None was placed near the PR's. Is it wrong to put Sonic Barrier behind the PR's?"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
I tried both polyfill and foam , the foam I used was the eggshell crate type , on all polyfill type or fiberglass I just add a few inches to the sides stapled on loosley .
I tried loose fill cabinets but the low bass seamed to get worst , I think a proper size box with a port wont need any fill because that would change the port .
But sealed you have more room for error and adding to the walls will deaden the sound . -
Thanks Face, that sounds reasonable. As for my M5A's, they are STUFFED from top to bottom with Daycron so this looks to be intentional or a mistake. I picked them up used about a year ago but I strongly believe that I was the first to crack them open. Therefore, I don't think anyone modified them. Unlike others, I have not been too impressed with the bass response. I may start experimenting with lesser amounts of Daycron, removing it from around the PR.
I did find a photo of an M5B that had the Daycron only down as far as the XO and there was none behind the PR. I am curious about anyone else with Monitor 5A's, how is the Daycron (poly-fill) arranged?Stan
Main 2ch:
Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.
HT:
Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60
Other stuff:
Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601 -
Very little. To see how much air it displaces, step on it.Does fiberglass reduce the internal air volume of ported cabinets? I'm specifically referring to the pink, fluffy Owens Corning fiberglass roll that Home Depot sells for home insulation."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Face,
Have you done any interior acoustic modifications on SDA cabinets?Proud and loyal citizen of the Digital Domain and Solid State Country! -
Sorry, I haven't...Mr. Starfighter.
Only on my Tannoy's and custom speakers/cabinets."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
So the foam and polyfill pretty much do the same things. I tried stuffing one speaker with polyfill to compare and I couldn't tell the difference. Weird huh?
What should i do next to better these speakers? Maybe replace the woofers with higher end woofers? -
The foam will work at lower frequencies, and IMO is more effective overall.
Leave the drivers alone, if anything, you could upgrade the crossover. Replace the factory caps with caps of higher quality such as Dayton, Sonic Caps, Claritycaps, etc..."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
How would updgrading the Caps(capacitors?) affect the speakers? I don't want to just upgrade things without reason.
I'm pretty new to the speaker game, but I'm really trying learn. I should be getting my Speaker Design cookbook soon.
Thanks for all of your answers FACE
-
They can make a difference. How much depends on the speakers themselves, associated gear, etc... In your case, an upgrade to the HF(tweeter) cap should be noticeable, possibly mid and LF also. I would check out Dayton caps, Sonic Caps, and Claritycaps. The best cap should go on the tweeter."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
-
Another option that I was toying around with is to use 1" thick Mineral Wool. Even though it has the same dampening characteristics as fluffy fiberglass, due to its rigid form is it safe to assume that it would take up internal air volume and that I'd need to make the cabinet bigger to compensate for the lost volume?Very little. To see how much air it displaces, step on it. -
If you use it behind the drivers, it's not going to take up that much displacement. Also check out Rockwool.
Just curious, why wouldn't you want to use something like PartsExpress's Sonic Barrier?"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Yes it's going to be Roxul 6.0 pcf mineral wool. It has the same dampening characteristics as Owens Corning 703/705 but at a significantly lower price. The cabinet that I'll be working with a good size (48" x 18" x 8") so even with Sonic Barrier the price adds up quickly.
I've been looking at various dampening materials and at the same dampening values, here's the hierarchy from highest to lowest price:
Blackhole 5
No Rez
Sonic Barrier
Owens Corning 703/705 batt
Roxul Mineral Wool batt
R-series pink fluffy Owens Corning fiberglass insulation from Home Depot
I've narrowed down my choice to the pink fluffy stuff and Roxul mineral wool. The Roxul stuff is easier to work with because of its rigid form but does cost a bit more money.
Now I'm trying to find out which of these two will take up very little internal air volume so as not to worry about adding additional depth to the cabinet to compensate for the lost volume. It's already pretty deep as it is (18"). The deeper the cabinet the closer it'll get to the rear wall. -
Don't forget, the top three also help dampen your cabinet walls."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
-
AS far as Polyfill (or eq) 'reducing' the internal volume, it actually makes your cabinet 'act' as a larger box thru slowing down the sound waves.
How well braced are those 48" panels? Definitely some reverberation going on there, could use some supports and some dampening as well. -
What about using Dynamat?
Media Room 7.1
Sharp lc37d64u | Sanus vmsab-03 | Sonax ZX8680 | Yamaha htr-6290b | Emotiva xpa1 x 2 & xpa5 | RTiA 9 & 7 | CSiA 6 | FXiA 6 | Sanus NF30B-03 | Velodyne dls-3750r | Dual 505-3 m97xe | Monster avs2000/hts5100
HTPC
Intel e5300 | Asus p5q DLX | LG ch08 BD | OCZ 4g reaper2 | WD 1TB | Sapphire 4890 VaporX 1g | Asus Xonar HDAV 1.3 | OCZ modXtreme 700w | Antec Fusion remote MAX
A fool and his money are easily parted
I don't drink Koolaid
Need some cable's? Just ask
-
From my understanding, polyfill is used primarily in sealed cabinets for exactly that purpose, but ported cabinets should just be lined with dampening material and no polyfill. Please correct me if I'm wrong.AS far as Polyfill (or eq) 'reducing' the internal volume, it actually makes your cabinet 'act' as a larger box thru slowing down the sound waves.
How well braced are those 48" panels? Definitely some reverberation going on there, could use some supports and some dampening as well.
The cabinet has 1.5" thick front baffle and top. 3/4" thick on the rest. It also has 4 braces spaced out about 7.5" apart. Note that I haven't built it yet but it looks pretty solid on paper. -
well from my limited experience and understanding, slowing sound waves is the same whether ported or sealed & passively radiated. Theoretically, if you have the cabinet size perfect, you would not need fill. But IDK what/ or if the 'perfect' size can be attained.
I do know that it has added deeper response in the PR' speakers I have played with and I have heard. Maybe someone else has played more with ported speakers.. -
That may deaden the cabinet walls, but I wouldn't use it anywhere except on stamped baskets, etc...sTiLlLeArNiNg wrote: »What about using Dynamat?
There are plenty of OEM's who use polyfill in ported speakers, check out Polk's LSi and RTi series.From my understanding, polyfill is used primarily in sealed cabinets for exactly that purpose, but ported cabinets should just be lined with dampening material and no polyfill. Please correct me if I'm wrong.
The cabinet has 1.5" thick front baffle and top. 3/4" thick on the rest. It also has 4 braces spaced out about 7.5" apart. Note that I haven't built it yet but it looks pretty solid on paper.
Again, the fill is not always for cabinet volume.well from my limited experience and understanding, slowing sound waves is the same whether ported or sealed & passively radiated. Theoretically, if you have the cabinet size perfect, you would not need fill. But IDK what/ or if the 'perfect' size can be attained.
I do know that it has added deeper response in the PR' speakers I have played with and I have heard. Maybe someone else has played more with ported speakers..
Here is some reading: http://www.troelsgravesen.dk/tips.htm and http://www.troelsgravesen.dk/cabinet-damping.htm"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
AS far as Polyfill (or eq) 'reducing' the internal volume, it actually makes your cabinet 'act' as a larger box thru slowing down the sound waves.
How well braced are those 48" panels? Definitely some reverberation going on there, could use some supports and some dampening as well.
Close. You get the illusions of a bigegr box due to heat. Compress a gas, it heats up and pushes back even harder than iof it didn't heat up. Rarify a gas, and the opposite happens.
Fiberglass absorbs the temperature differences and makes the box go from adiabatic to isothermic.
Slowing down sound waves would apply to stuffing a port and finding the new resonant frequency.
BTW, Roxul mineral wool(aka safe'n'sound) is great stuff. I chose it for my sound absorbing panels because it's more effective than OC703 and 706 in the midrange. The OC wins at absorbing bass(not by much either). As fantastic as it is, it's no more rigid than plain fiberglass and handles the same. OC is stiffer.
