Speakers sound better without fill

[LZTYBRN]

So I built some Overnight Sensations MTMs, and about a month ago, I tried filling them with polyfill, but no matter how I filled it, the speakers only sounded worse than being empty. I tried it every different way I could, from extremely dense filling to very light and everything in between. I also moved the filling around the enclosure. I was waiting for them to sound "huge," but basically it only sounded quieter, and more noticeably lost bass output.

Anyway, I'm going to finally be painting them this week, and I figured it would be a good time to try to fill them one more time. I'm looking for advice on placement of the polyfil and possibly an estimate of how much would be good (like what fraction of a one pound bag?)

[killa]

odd. I have always had the exact opposite experience.

[critofur]

Regular "pillow stuffing" poly-fill is usually not the optimum choice...

Most important however: whatever fill you do use, do NOT block the port tube inside the cabinet, if you don't want to reduce your bass.

[LZTYBRN]

odd. I have always had the exact opposite experience.

I figured that was the case. That's why I'm so confused lol.

Regular "pillow stuffing" poly-fill is usually not the optimum choice...

Most important however: whatever fill you do use, do NOT block the port tube inside the cabinet, if you don't want to reduce your bass.

I used the acousta stuf they sell on PE, if that's what you're talking about. What do you recommend? I also ordered some of the 1.5" egg crate foam, but it was so thick, there was like no room left in the enclosure, so I didn't use it.

And I didn't block the ports, except for on my last few attempts at getting it right.

[ROTECH]

Perhaps we all have different ears and preferances?

[jimangie1973]

In my experience, Acousta Stuf works great. I think ordinary pillow stuffing accomplishes the same thing though. I've had the best result by tightly jamming the fill into areas of the ported enclosure which are separated by braces. I usually VERY tightly fill the area behind the tweeter which kills the vertical standing wave. If you have a vertical brace, you can stuff behind it. I then use 1" sonic barrier around the woofer and port in ported enclosures. This has very little effect on the port output. Bass sounds great. It does completely remove boxy sound caused by internal standing waves and reflections.

Jim

[fastbike1]

FWIW, Paul's recommendation was a "few light handfulls of polyfill behind the woofers."

I fluffed a "handfull" and glued it to the central brace. I did not otherwise line or stuff these enclosures, as per design.

[generic]

I thought products like sonic barrier were better for directly behind the driver. I thought poly fill helped simulate a larger box.

Is this not correct?

[cjd]

I thought products like sonic barrier were better for directly behind the driver. I thought poly fill helped simulate a larger box.

Is this not correct?

Depends in part what the goal is - though in most cases, part of that goal is to manage reflections (particularly those that might bounce back out through the cone, but by no means exclusively)

Both materials will change things, just differently. The wall-applied materials often help manage panel resonance as well.

Usually the designer will specify what they designed with, and that's what you should use.

C

[fbov]

So I built some Overnight Sensations MTMs, and about a month ago, I tried filling them with polyfill, but no matter how I filled it, the speakers only sounded worse than being empty....

...And I didn't block the ports, except for on my last few attempts at getting it right.

When building a ported enclosure, you generally want to:
- line the walls with absorbant to reduce reflections of higher frequencies and prevent any acoustic resonances. 1" is enough, and 2" may not be better.
- leave the volume between speaker and port as open as possible
- add fill only if needed, as in the ends of a tall tower, and always obey your ears.

You say you didn't block the ports? But they sound better when empty... the ports disagree with you, that's why they sound better empty. System performance is the ultimate arbiter of what did and didn't happen. What you did affected the bass enough for you to hear it, so learn from what your ears tell you. It may ahve been a very subtle effect...

And then there's the system performance target - how are they supposed to sound? You expect them to sound "huge" but in the bass range, a small speaker can only be "huge" if it's boomy, 1-note bass. Flat, accurate response won't sound big in the bass, but the speaker may, none the less, fill the room very well. Remember, these are 100mm class drivers. They won't compete with larger drivers in bass extension or SPL.

Have fun,
Frank

PS Fill is the light, airy fiberous stuff. Absorber is usually a foam or fiberglass product that's much denser, and intended for surface treatment.

[jsr]

I have a pair of OS TMs I built recently that I lined the sides with an open cell foam I had laying around and no other fill. I used it just for resonance control. AS mentioned, they don't sound like my Nichikuros with a 6.5" driver and a much larger cab, or a small tower, but when turned up, they fill the room nicely with a fairly balanced sound. For some music I listen to, I still run them with a sub, but for others, they sound full enough alone. I know there are big expectations in the bass department with these small dishes because all the reviews say "wheres the hidden sub". I had a similar thing with the Speedsters I built. The Speedsters have much more bass than the OS and can, on certain material, sound like theres a small sub (or like a larger speaker), but neither met my bass expectations from just reading the reviews of super hero bass power. I think different people just have different experiences which change their expectations for performance and thus subjective descriptions are prone to such variances in accuracy.

[jeff_free69]

I thought poly fill helped simulate a larger box.

Is this not correct?

I think thats only for sealed boxes;
for vented, its to control the mids coming thru the ports, but I guess actually reduces the net internal volume very slightly.

[LZTYBRN]

Thanks for the advice everyone. I'm thinking only thing I can do is more experimentation.

You say you didn't block the ports? But they sound better when empty... the ports disagree with you, that's why they sound better empty. System performance is the ultimate arbiter of what did and didn't happen. What you did affected the bass enough for you to hear it, so learn from what your ears tell you. It may ahve been a very subtle effect...

I'm not sure what you mean. Are you saying just do what sounds best, or that I did something wrong? What do you mean by the ports disagree with me?

And then there's the system performance target - how are they supposed to sound? You expect them to sound "huge" but in the bass range, a small speaker can only be "huge" if it's boomy, 1-note bass. Flat, accurate response won't sound big in the bass, but the speaker may, none the less, fill the room very well. Remember, these are 100mm class drivers. They won't compete with larger drivers in bass extension or SPL.

The only reason I said I was trying to get them to sound huge, is because that's what Paul Carmody wrote on his website. He said that it suddenly sounded huge when he got the right amount. And I'm NOT, and never was, expecting amazing bass from these. But it's just curious to me that the stuffing has negative effects on bass, and sound overall (to my ears at least).

[whatatrip]

So I built some Overnight Sensations MTMs, and about a month ago, I tried filling them with polyfill, but no matter how I filled it, the speakers only sounded worse than being empty.

I have a pair of OS and they sound great without any filling. I will play around with some filling when I get around to putting a finish on the boxes but until then my wife has been listening to them on her computer. They sound great just the way they are. They will not play real loud, thump your chest or rattle the china but they certainly play loud enough to fill an 18 x 24 room with quality sound. I am using the little Datyon DTA-1 15 watt per channel amp.

Attached is the ARTA measured frequency response of the pair together, no gating, just pure raw sound measurments.

[billfitzmaurice]

So I built some Overnight Sensations MTMs, and about a month ago, I tried filling them with polyfill, but no matter how I filled it, the speakers only sounded worse than being empty.

Ported cabs are not filled. They should be lined, with an inch to two inches of polyester batting or foam, how much depending on the size of the box. Smaller boxes don't support internal reflections to as low a frequency as larger boxes, so the lining need not be as thick.

I thought poly fill helped simulate a larger box.

It lowers Q, which is similar in effect but not the same thing. Stuffing also lowers Q in a VB, which upsets the tuning and can result in a loss of bass.

for vented, its to control the mids coming thru the ports,

That, and to reduce reflections back to the cone, which will cause peaks and dips depending on their degree of phase when they arrive.

[blank264]

I originally stuffed my OS mtms according to the directions but that was too much. I reduced it to an uncompressed handful like others have mentioned already and they sound much better. Over stuffing seemed to reduce the spl a lot.

[fbov]

...I'm not sure what you mean. Are you saying just do what sounds best, or that I did something wrong? What do you mean by the ports disagree with me?...

I mean that physical systems work by fixed laws. If you do something that comes out differently from what you expect, the issue is in your understanding of the system.

In this case, you don't think you've messed with the driver-box-port resonance link, but the port output is lower and you get less bass. Whatever you did had affects you didn't anticipate, so revisit the situation and try to learn what it's teaching you.

DIY is experience-based learning! And stick with what sounds best...

Have fun,
Frank

[LZTYBRN]

I mean that physical systems work by fixed laws. If you do something that comes out differently from what you expect, the issue is in your understanding of the system.

In this case, you don't think you've messed with the driver-box-port resonance link, but the port output is lower and you get less bass. Whatever you did had affects you didn't anticipate, so revisit the situation and try to learn what it's teaching you.

DIY is experience-based learning! And stick with what sounds best...

Have fun,
Frank

That makes sense. But to be honest, I don't really understand the stuffing at all.

Do you think I should try using the foam lining, even though it only leaves about 2 inches of space? Or should I order some thinner foam?

[bkeane1259]

I don't like PE's acoustistuf at all....Sorry PE.

Try open cell foam (maybe 2" thick) glued to the rear wall only. Do not line every wall...there's no need and you will reduce bass output by heavily lining every wall, anyway.

It can be memory foam type or mattress topper (egg crate) type -- whatever you already have or can obtain at minimal cost. Walmart and Target sell egg-crate toppers for cheap. There's no need to splurge on this and it will make a favorable difference, by reducing midrange leakage and reflective waves while maintaining your bass output.

When/if you try this, don't focus on the bass -- try to listen to midrange clarity. There's more going on inside the cabinet than bass and because the box is ported, lining "does" make a difference and should not be eliminated completely.

[LZTYBRN]

I don't like PE's acoustistuf at all....Sorry PE.

Try open cell foam (maybe 2" thick) glued to the rear wall only. Do not line every wall...there's no need and you will reduce bass output by heavily lining every wall, anyway.

It can be memory foam type or mattress topper (egg crate) type -- whatever you already have or can obtain at minimal cost. Walmart and Target sell egg-crate toppers for cheap. There's no need to splurge on this and it will make a favorable difference, by reducing midrange leakage and reflective waves while maintaining your bass output.

When/if you try this, don't focus on the bass -- try to listen to midrange clarity. There's more going on inside the cabinet than bass and because the box is ported, lining "does" make a difference and should not be eliminated completely.

Thanks. I already have 1.5" eggcrate, so I'll definitely try that.

So what do you guys listen to when testing your speakers?