An experiment in box materials

[DLHgn]

There is more then just how much a piece flexes that goes into it.

I would love to use nothing but Baltic, but the reality is not everyone is willing to pay that additional price tag for the material

True that. Baltic birch is heavier than I prefer for car audio too.

I'm not sure what I want to use for my next build. I would like to use BB but I don't think I'm confident enough in my wood working skills to ensure I don't mess up a cut and waste wood considering that stuff is fairly expensive.

I would see if you can get Arauco plywood or a decent "birch" style plywood. Baltic birch really is overkill for most car audio applications. The only time I use baltic birch is when its going to be stained.

I was thinking about using it for my next HTC build. I was also thinking about staining it too

[Wasteland_Audio]

Lol i just did the math on weight per square foot for my wall. 840lbs...

[Triticum Agricolam]

TL:DR

My point is when you have a higher spring constant you increase your resonance frequency and when you have a lower mass you also raise the frequency.

Therefore my reason for preferring MDF is because it has a low spring constant and a high mass, making the resonance lower than the other choices.

This is one of the reasons I prefer plywood over MDF for subwoofer enclosures. With proper bracing its easier to push the panel resonances up and out of the passband of the subwoofer.

[Krakin]

TL:DR

My point is when you have a higher spring constant you increase your resonance frequency and when you have a lower mass you also raise the frequency.

Therefore my reason for preferring MDF is because it has a low spring constant and a high mass, making the resonance lower than the other choices.

This is one of the reasons I prefer plywood over MDF for subwoofer enclosures. With proper bracing its easier to push the panel resonances up and out of the passband of the subwoofer.

Even if the resonance is outside of the passband the enclosure will still resonate at the frequency whenever energy is applied.

[Triticum Agricolam]

Even if the resonance is outside of the passband the enclosure will still resonate at the frequency whenever energy is applied.

But aren't higher frequency resonances less energetic?

This is on the edge of my understanding, so I probably can't explain it well. My view on managing cabinet resonances mostly comes from what I've seen many cabinet designers for home audio enclosures do. They use stiff materials and brace it well to push resonances up and decrease their amplitude.

[WalledSonic]

Triticum, I am srsly looking forward to your bracing post! I'm starting my ~ 3.5' x 4' x 2' box/wall on Friday and its going in a small car where weight is my enemy. I hope to optimize my bracing strategy with some of your info. Your box builds are badass!

[Krakin]

That's just going the extreme in the opposite direction, I haven't ever really cared enough to think much on this to know which way is better.

But without calculating anything I would think you would have to do some insane bracing to get the resonance either out of the spectrum or low enough amplitude to counteract the much higher sensitivity human hearing is at a higher frequency.

[WalledSonic]

Theres no way this question can be solved with a mass-spring system alone. Damping has a major effect, especially in organic material such as wood.

If you have a low-frequency resonant enclosure that didnt damp, it would compound the pressure waves perfectly and we'd have problems if the resonance of the box was in the playing range of the woofer. You may get cancellation, amplification, or phasing issues. In Krakin's case, he's talking about MDF, which we know has a higher damping coefficient, and therefore, he may be able to get away with having a box resonance in his woofer's sound range since the damping is so high.

If you have a high-frequency resonant enclosure that didnt damp at all, you wouldnt be worrying about the reflecting waves as much since the resonance of the enclosure would be out of the range of the woofer. This is triticum's case. Although, you may end up with the box 'ringing' if there was no damping. It just depends on the frequency.

I think you're both right... kinda. In every mass there is stiffness AND damping. You've both found ways to make your medium work for you. At least, thats the way I see it. Each box is a complex mass-spring-damper system, even without the subwoofer in the equation, and I think each case has to be evaluated as it is. The fact that very few of us (if any) do any FEA modeling for the box resonance, that fact is what makes this hobby a bit of an art.

[WalledSonic]

Tangent... What if a box was made of heavy gauge steel and was designed to resonate with the subwoofer at a particular frequency... I bet you could get an amplified response out of the sub-box combo. Maybe this is the future of burp SPL? keanuwhoa.jpg

[Triticum Agricolam]

Tangent... What if a box was made of heavy gauge steel and was designed to resonate with the subwoofer at a particular frequency... I bet you could get an amplified response out of the sub-box combo. Maybe this is the future of burp SPL? keanuwhoa.jpg

I know there are some folks within the hi-fi audio circles that purposefully design their full range enclosures so that the panels resonate. They think it gives the speaker system a more lively sound. Of course there are other folks in hi-fi audio who think the first group of people are idiots, so who knows?

If someone built an enclosure with panels that purposefully resonated I would worry if they would resonate in phase or not and that they wouldn't take more energy out of the system than they radiated.