| Bill Fitzpatrick |
| Of all the stuffing material available, which has the greatest potential for providing an increase in the apparent box volume? |
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| BassAwdyO |
| The theory behind the apparent increase in box volume is the idea that the sound waves must travel around the fibers of the stuffing creating a longer path to the other side of the enclosure. Assuming that is correct, I would think that something with ALOT of fibers would be best. |
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| simon5 |
| That or you can pack it tighter. |
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| Ron E |
| quote: | Originally posted by BassAwdyO
The theory behind the apparent increase in box volume is the idea that the sound waves must travel around the fibers of the stuffing creating a longer path to the other side of the enclosure. Assuming that is correct... |
It isn't correct.
A fiber the size of a hair doesn't present a barrier to a wavelength the size of a room. The standard line goes that the fibers absorb and release heat and change the compression and expansion to isothermal rather than adiabatic - causing a reduction in the speed of sound and thus making the box appear bigger. Having said that, I do not believe that toeing the party line reveals the truth.. The true mechanism is more complicated - and may be a viscous effect rather than the thermodynamic effect that is most frequently cited.
I believe that fiberglass is probably the best, and certainly the most cost effective. |
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| BassAwdyO |
| Either way, I havent found any reason to believe stuffing actually attributes to better sound quality in the bass region. |
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| Collo |
I read somewhere that fibreglass is no good to use because the fibres are too brittle, causing them to disintegrate and become lodged inside the motor assembly of your drivers. I just stick with the normal stuff you get from Jaycar
Collo |
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| tiroth |
| quote: | Originally posted by BassAwdyO
Either way, I havent found any reason to believe stuffing actually attributes to better sound quality in the bass region. |
You should come listen to my latest speaker. Unstuffed, it sounds atrocious, so much so that I considered going back to the drawing board. Stuffed, it is nice and tight. There was a major difference in measured total Q.
It may be true that stuffing will not contribute significantly to a design that already is perfect (although I still think it would help damp the backwave on drivers with light cones), but it is completely false that stuffing has no effect when used in boxes that are "too small."
I too am interested in Bill's question; I've always suspected that fiberglass would be a superior material in everything other than safety, but I've never seen any real tests on performance of different materials. |
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| serengetiplains |
| Has anyone tried duck or goose down? It deadens sound like no other substance I know. |
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| Bill Fitzpatrick |
I tried a whole live goose once but the system sounded honky.
My original question was only for information purposes. The enclosure is a 5000 cu.in. woofer box that would effectively go to 6000 if stuffed. That amounts to a minor Q change and a difference of 1 db at 30Hz according to WinISD.
Fiberglass doesn't cut it for mid-range boxes where everything from the back of the cone should go into a black hole.
I remember speakers from the 70's where most mfgs. would just toss in a few big hunks of fiberglass and call it a day. |
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| BassAwdyO |
| I'm just saying that I personally havent experienced any difference with stuffing and not. I'm not saying that it 100% doesnt and cant do anything. Did Q raise or lower? What kind of stuffing did you use? |
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| tiroth |
| quote: | Originally posted by Bill Fitzpatrick
Fiberglass doesn't cut it for mid-range boxes where everything from the back of the cone should go into a black hole. |
The ideal material for stuffing probably isn't the ideal material for damping. I generally use bitumin impregnated felt on all walls except the baffle, with egg-crate (open cell) foam on the back wall and fiberglass stuffing. The egg-crate foam does not increase the box size (in fact, I believe the reverse is true) but it sure does damp/break up the back wave.
| quote: | | Did Q raise or lower? What kind of stuffing did you use? |
It lowered, of course. Fiberglass, packed to a progressively higher density farther from the driver. |
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| BassAwdyO |
| I figured Q would be lower because otherwise the stuffing wouldnt make the apparent box bigger, but smaller. But you used the ugly word tight to describe the stuffed bass, and only god knows why, but some people call high Q tight and some call low Q tight. |
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| Bill Fitzpatrick |
This business of bass having an attribute called "tight" is ridiculous.
To settle the issue to one's satisfaction all that is necessary is to listen to the woofers with an active 100Hz 4th order low pass filter in the the line before the power amp. Low Q, high Q, whatever Q, there is nothing going on that could be remotely described as tight.
In fact, there is so little going on that you might wonder why you need a woofer at all. |
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| richie00boy |
| Just out of interest, what kind of music do you listen to mostly, and what kind of music would you have used for the test you describe? |
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| Bill Fitzpatrick |
It wasn't a test, just a general observation based on decades of experience. I turned off my satellite amp just now to verify. Billy Idol was playing.
In 1974 when I had a audio store I put together a woofer-satellite system, bi-amped. I had the employees listen to it so I could get thier opinion. After the music was playing for some minutes there was a general agreement that it sounded good. My partner then walked over and turned the woofer amplifier on!
Like I say, there isn't that much information below 100Hz. What little exists is nice to have though. |
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| tiroth |
To me, tight means "not boomy/honking." Within reason, I don't think extension has much to do with this, i.e. it is a function of Q and group delay.
I do think that some novices use the word as a general superlative with no particular meaning. I agree that such a meaning is of zero value in any quantitative discussion, if that is what you are saying Bill. |
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| BassAwdyO |
| Bill, what kind of EQ are you using to render your music bassless? Because a statement like, there isnt much information below 100hz is obsurd. The bass guitar for instance can go down to 32hz or so on a 5 string I believe. The grand piano starts somewhere around 26 or 28hz and goes up. The pipe organ can go down to infrasonic frequencys. Electronic bass can be any frequency, but most rap rock and pop music have beats between 30-70hz. |
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| Bill Fitzpatrick |
The real problem is that there is, as far as I know, no agreed upon definition of "tight" as regards to speakers.
You mention "honking" which to me describes a characteristic of the mid-range.
Then you mention "boomy." Bass by itself IS boomy, sounding like rolling thunder from afar.
In itself, group delay for the bass doesn't mean much. If you were playing bass only and had a group delay of a week it probably wouldn't sound much different than a group delay of 0.
So, if we're voting on the definition of tight, I cast mine for the ability to follow the leading edge of a percussive waveform. That requires that the rest of the spectrum be present. |
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| tiroth |
When I saw your 100Hz remark earlier, I thought that I agreed with the test but not the conclusion.
Yes, bass by itself IS boomy. But in a full range design, boominess is usually because the bass (or a few frequencies therein) have unnatural prominence, destroying the spectral balance. |
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| Bill Fitzpatrick |
BassAwdyO:
A stout defender of bass, I see by your moniker.
I don't equalize my system to be bassless. I love bass. All I'm saying is that in comparison to the rest of the spectrum, there is little activity in the sub 100Hz arena. I didn't say that sub 100Hz information had no value. I do say, now that I'm pressed, that if speakers got paid in relationship to the work they perform, subs would have a poverty level income.
And please don't talk about acoustic instrument fundamental frequencies as if there were no harmonics involved. |
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| Bill Fitzpatrick |
| quote: | Originally posted by tiroth
But in a full range design, boominess is usually because the bass (or a few frequencies therein) have unnatural prominence, destroying the spectral balance. |
You'll find me in complete agreement. |
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| BassAwdyO |
| Work? I think my sub does more work than any of my other speakers. None of them can shake the room and make pictures rattle, ceiling lights flail, curtians blur, windows flex. It takes alot of displacement to play sub 20hz and the sub can do the work. I believe sound should be mixed on recordings down to at least 10hz and good systems should go that low. Group delay should be as small as possible for the best transient response, but low group delay in the audible bass range is most crucial. |
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| Bill Fitzpatrick |
| That's not the kind of work I meant. |
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| simon5 |
| I want subs to be flat to 8.2 Hz, to play the lowest organ note to date. |
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