How sealed is sealed?

[fb]

How can I tell if my sealed boxes are sealed well enough? There doesn't seem to be any shortage of bass, but I've not tried anything too arduous.

Is it possible to tell from these impedance graphs?

 

[Glowbug]

As long as your cuts were straight, joints are tight, used adequate glue/sealant...I wouldn't worry too much about it

 

[Zen Mod]

take 3V battery

apply voltage to speaker ; disconnect ;

if speaker is really sealed , then cone will travel back much slowly comparing to same speaker in BR box or out of box ;

you can try to listen around baskets of all drivers in box - every air leak is pretty easy to hear

be careful , don't push your ear in cone

 

[Eva]

Are both plots from two copies of the same speaker? One reveals a resonance around 160Hz that is probably adding colouration...

 

[badman]

and the other has lots of small ripples.... I think it's box stuffing time!

 

[Dr_EM]

Is sealant required around the inside joins if the panels have been bonded with glue all along? If so, what is suitable to use?

 

[richie00boy]

No you don't need sealent if your glue joints are sound. I just run my finger along the excess anyway to act as a sealer.

 

[planet10]

Are both plots from two copies of the same speaker? One reveals a resonance around 160Hz that is probably adding colouration...

You beat me too it... likely a panel that is not well enuff braced.

dave

 

[markus76]

I don't worry too much about sealing any more. Even drilled a whole (1/16") in the back of my speakers to allow for static air pressure equalization because I had the feeling the box was too airtight.

Best, Markus

 

[Iain McNeill]

If you want to tell from the impedance curve, you have to compare it to the impedance curve for the same driver in free air, away from reflective surfaces. When you put the driver in the enclosure, the impedance peak will shift up and the Q will rise in accordance with the T-S relationships with Vas and Vb. If you're not getting all the frequency & Q rise, then there must be a leak.

Joseph d'Appolito's "Testing Loudspeakers" explains all.

 

[gedlee]

I don't worry too much about sealing any more. Even drilled a whole (1/16") in the back of my speakers to allow for static air pressure equalization because I had the feeling the box was too airtight.

Best, Markus

Markus
Agreed Sealing is highly overrated and I don;t even think that its a good idea.

 

[catapult]

I can't find the pic now but someone did heroic sealing on a sub -- caulk and teflon tape on the driver's screws, etc. After playing a while, the driver heated up the air inside the box and the driver was bulging something like an inch off center. Not good.

 

[gedlee]

I can't find the pic now but someone did heroic sealing on a sub -- caulk and teflon tape on the driver's screws, etc. After playing a while, the driver heated up the air inside the box and the driver was bulging something like an inch off center. Not good.

Of course the up-side is you can use it to predict the weather.

 

[chris661]

You'd have to use something with a poly or aly cone - I've read that paper cones are porous enough for air to gradually leak through, accounting for atmospheric changes.

Hmmmm... 8" barometer anyone?

 

[fb]

Thanks everyone - I won't worry about it then The boxes are currently unstuffed, so hopefully the wobbles and resonances will be sorted out after I do that.

 

[fb]

Here's the corresponding nearfield measurements. Unsmoothed.

 

[markus76]

What do we see? How far from the membrane did you place the mike? Was the mike exactly placed the same in each measurements? Was anything else changed between measurements? A picture would help.

Best, Markus

 

[gedlee]

If thats just a leak difference then its not a small leak. Looks more like damping versus non-damped.

 

[fb]

I should have explained myself more clearly - those are 2 different systems. I only got to doing the audio measurements a couple of days ago.

Red measurement is 15" mid in ~90L sealed - this corresponds to the impedance measurement with the big wiggle at ~170hz.

The other set of measurements is 18" sub in ~60L sealed.


Both systems unstuffed, undamped, minimally braced. I'm going to add stuffing when I've got the cabs painted.