Wich material has to be used to properly fill a closed cab???

[Avezzano]

explaining better: I am building a cab (details for later on, when I will finish it!)

which material has to be stuffed inside and how much (which percentage of the total volume)? I always thought about standard 3/4 cm foils of syntethic "sponge" (usual stuffing stuff used for shipping) glued on the internal walls, you know? But someone said me that for a closed cab there is a completely different approach/theory for what concerns stuffing inside: first it has to be stuffed COMPLETELY (??Is that true??), then a soft material has to be used some like real sponge or... or... ???

Thanks to anybody will help me

[billfitzmaurice]

A sealed cab may be completely filled with polyester batts or pillow stuffing if the cab Q is higher than roughly 0.9, to reduce Q and in so doing tame boomy response. I know that's very technical, but there's no non-technical way of explaining it, nor is there a way of knowing how much filling to use if you can't either measure the cabinet Q or know the driver specs to calculate it. The Q of the Ampeg SVT, for instance, is about 0.85, so there would be little, if anything, to be gained by filling it. It should still be lined with an inch or so of damping.
If you don't know what the Q is of your proposed cab you should reconsider building your own until you've learned more about how cabs are designed and built.

[Mousekillaz]

I have built hundreds of bass cabs. The filler serves a couple of different functions. First off the best fill to use is fiberglass, but it has its down sides. Spun Dacron is a popular alternative, but doesn't have the same thermal properties. If you use a glass mat ensure your driver(s) have good screens on the voice coil vent. I prefer the formaldehyde free glass-mat products. The amount used is somewhat subjective, If your cabinet is built to the drivers spec size, usually a minimum amount of material is used to achieve the desired result. If the box size is under the recommended Vb, adding more fill can slightly offset a too small enclosure. The principle behind this "trick" is surface tension. The air inside the box will adhere to the fibers of the filler, which in essence fools the driver into behaving as if it were in a larger enclosure. You might notice a slightly smoother extended low bass response. The second effect at work is converting mechanical energy into heat and then absorbing and dispersing that energy. The air rushing about inside the box will heat up. Add to that, the electrical energy used to move the voice coil and things can get rather warm inside the cabinet. The thermal properties of glass mat over a polyfill are substantially better, but it will make you itch like crazy, hence polyfills popularity.
Another point is, when using a Helmholtz resonator (a port) The volume of air inside the box, behaves as if it were in a sealed cabinet,up until the volume of air inside the port is excited, at the tuned frequency. So the air volume inside the box does not get exchanged with the cooler external air, like many would believe. It is a tuned port not an air vent.
Acoustic suspension enclosures are typically far less efficient. Add to that their relatively flat frequency response characteristics and they just generally aren't the best design for the purpose of live bass amplification. I could definitely see using a sealed cab in a studio situation, in fact upon reflection they might be inherently better.
My Advice, find a speaker building software program FIRST. before you start wasting wood. Then experiment with the amount of fill, starting with the least amount and adding some more until you can hear no difference ora negative result is achieved
And have some fun with your project.
One other thought; MDF is a great product for building cabs, provided they don't get moved much, otherwise use a high grade ply.

[billfitzmaurice]

Originally Posted by Mousekillaz

If the box size is under the recommended Vb, adding more fill can slightly offset a too small enclosure. The principle behind this "trick" is surface tension. The air inside the box will adhere to the fibers of the filler, which in essence fools the driver into behaving as if it were in a larger enclosure. .

That was a popular theory until fairly recently, but it's been proven incorrect. This shows the result on measured response of the same driver in a sealed cab, unlined and stuffed, and the measured impedance and Q.



In the low end the stuffed cab's midbass hump is reduced, which to some extent emulates a larger box. But a larger box would have a lower F3 as well.

[Avezzano]

Thanks, guys! What I am doing is this: I had (in the garage) a brand new 100 w 4 ohm 10" (25 cm) RCF woofer just lying there wrapped in the plastic since some 20 years or so. I don't even remember when and where I bought it. I thought: it's about time I do something with that, in specific, specially now that I have the Little Mark II; so just to have a small cab to be left as "resident" in the living room for home practice at low volume.

To avoid possible damages anyway and to have possibly a more "performing" cab (!), I said to myself: let's add another speaker in series, so I built this cab (external dimensions cm 48x30x30 inches 19x13x13) that has two separate and completely independent closed cabinets for each speaker: 1/3 of the internal volume reserved for a 6" 100 w 4 ohm woofer (still to be provided) and 2/3 of the internal volume for the RCF 10" woofer. I used 1,5 cm ply (0,6 inches) for all the cabinet and 2 cm (0,8 inches) for both the front panel and the internal dividing wall between the two volumes.

I think (hope!) it should work, since opening my Polytone Minibrute I, I see that there is even... no stuffing inside at all... let's see how things go...

Uh: to further protect the cab from the Marbass power I also add a 5 amperes fuse, btw...

(A very rough drawing is sketched here below... you get the idea...)

[T-Bird]

Hi.

What program/formula You used to end up with those dimensions?

Regards
Sam

[Avezzano]

nothing: I am just doing a trial and error attempt but I don't think it will be that bad, since a couple of "reflections":

1) Marco De Virgiliis developed the Microbass 601 micro-combo and then improved the concept with the 801; those are super tiny cabs that work very well in any case for practice. Ok: you won't shoot "Pink Floyd at Pompei" using them, but...

2) my 100 w 10" Polytone works just fine and has the same dimensions of the chamber reserved for the woofer only (no stuffing whatsoever inside, btw!)

3) this 10" RCF woofer was mounted for a very brief period on another "empirical" little amp I built some 20 years ago and I remember it working fine without resonances whatsoever anyway. It was a combo with a closed cab: slightly larger/deep than the cone max dimension, something more than a shoes box; then after the test I said to myself "ok, I will now dismount everything and build another even larger cab" and so it stayed in the garage for 20 years... now that I am providing the speaker with a bit more volume, so it "should" go ok...

4) lots of hope in the good luck that goes with every bass player...

[billfitzmaurice]

Originally Posted by Avezzano

nothing: I am just doing a trial and error attempt

That usually ends up with a lot of trial and even more error. To repeat, you should reconsider building your own until you've learned more about how cabs are designed and built. This is a good place to start, but certainly not end, the process:
The Speaker Building Bible - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com

[Avezzano]

thanks, Bill! I am afraid that now it is too late for me. Cab is done and after all I already had the 10" woofer and only had to buy the wood and work the cab out. Only real expense is the additional 6" woofer. V.

[billfitzmaurice]

Originally Posted by Avezzano

thanks, Bill! I am afraid that now it is too late for me. Cab is done and after all I already had the 10" woofer and only had to buy the wood and work the cab out. Only real expense is the additional 6" woofer. V.

You do not want a 6" woofer. You want a 6" midrange. The size of the sub-enclosure for it would be no more than 5 liters, and a crossover must be employed.

[exmaxima1]

Originally Posted by Avezzano

which material has to be stuffed inside and how much (which percentage of the total volume)?

As Bill noted, the usual filling is some fibrous material like pillow filling or fluffed fiberglas. The rule of thumb was approx .5-1.0 lb of filling per Ft3 of cabinet volume.

In 1971, my science fair project was called "Adiabatic to Isothermal Conversion" which demonstrated the increase in apparent volume of a speaker box when you added the filling. I forgot most of what I did back then (college killed alot of brain cells), but here is a more recent analysis I found:

Stuffing and Idiabatic/Isothermal Question

Good Luck!

[billfitzmaurice]

Originally Posted by exmaxima1

In 1971, my science fair project was called "Adiabatic to Isothermal Conversion" which demonstrated the increase in apparent volume of a speaker box when you added the filling.

In 1971, and for that matter 2001, the heat conversion theory was accepted as Gospel. It's now realized that heat doesn't create the lower Q of a stuffed cab, but is a by-product of the process that lowers Q. The referenced document never mentions Q, and in that seems oblivious to the fact that any alteration of the box response must be accompanied by a change in Q.

[Avezzano]

>Good luck!

Thanks!!!

You do not want a 6" woofer. You want a 6" midrange. The size of the sub-enclosure for it would be no more than 5 liters, and a crossover must be employed.

no way, man (sorry): I want a two woofers (small) cab and I think that (my very very very humble and "rough", evidently uneducated opinion!) it could definitely be done even with a small volume. That is not so small if you look at the dimensions above sketched anyway: 12 litres the top part (the bottom one is around 24 litres). I just remained with my jaws dropped when I heard the Markbass 601 then the 801 and so I conclude that it can definitely work fine!!!! Go with your mind at ten years ago: would you have bet a few dollars/euro, then, on a excellent quality 4x6 cab for a pub-gig?

Crossing my fingers hard...

[Avezzano]

Found the 6" woofer!!! Corrected: found a much better product than the Ciare: this is now a real woofer, neodymium, 120 w 4 ohm 95 dB spl !!!



FaitalPRO - Professional Loudspeakers Made in Italy

[billfitzmaurice]

For the best results never mix different drivers within the same passband. As for that Ciare, without a crossover you'll blow that to Kingdom Come long before you'll reach the capability of any decent ten.

my very very very humble and "rough", evidently uneducated opinion!

Look at my public profile.

[Avezzano]

don't know, Bill: it is stated it actually IS a full range (had an email exchange with a Ciare representative and he said that this is an excellent small woofer or mid, depending on how you use it); 80w / 4 ohm and I will put it in series, so with moderate to medium volume it should work! (Corrected, see my above post!!)

Note that I will also put a 3 amps fuse as a further safe precaution.

In the meantime:

[SBsoundguy]

Originally Posted by billfitzmaurice

That usually ends up with a lot of trial and even more error. To repeat, you should reconsider building your own until you've learned more about how cabs are designed and built. This is a good place to start, but certainly not end, the process:
The Speaker Building Bible - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com

Threadstarter, despite what some of the links say don't use MDF. The rest of the info is great.

[Avezzano]

Despite what some of the links say don't use MDF. The rest of the info is great.

Thank you!! As you can see from pics I used multi-laminate and it is as solid as a rock. I just want to build me a home or pub cabinet despite my... deep ignorance!!!

[Avezzano]

For the best results never mix different drivers within the same passband.

so, following this line of thought, coupling a 4x10 cab on top of a 1x15 should be even more wrong, but this one seems to be one of the most common rigs for bigger acts!

Bill, obviously I understand I have ZERO knowledge only if I look at your professional skills!!! But I prefer to look at this cab as a mini stack with a 1x6 on top of a 1x10!

[dmusic148]

Originally Posted by Avezzano

so, following this line of thought, coupling a 4x10 cab on top of a 1x15 should be even more wrong, but this one seems to be one of the most common rigs for bigger acts!

And yet, in spite of that, its still wrong.