AR-3a: What is the importance of having an airtight seal on woofers?

[mhjmhjones]

Also, what would the effect be if your airtight seal was only 95% intact?

Thanks for the input!

 

[Porkloin]

To me, this is like the old speaker wire or grill on/off debate. Guys visualize something and cite white papers supporting that visualization, but in reality, couldn't hear a problem if faced with an actual A/B test session. Do the best you can with DRY gaskets and let your ears be your guide.

 

[GD70]

It's a must with any air suspension design speaker. The air inside the box acts like a spring. You will not get the performance the designers intended. Google air suspension speaker design for more info regarding the physics etc...

 

[Hanleyster]

Are you talking 100% air tight?

 

[mhjmhjones]

Are you talking 100% air tight?

I'm not sure how airtight mine currently are. I tried to maintain a good seal with the original waxy putty.

 

[KingBubba]

The seal should be pretty much 100%. You can use cheap and available plumbers putty to seal the drivers. Be aware, however, that the seams of the cabinet need your attention also and can be treated with the putty also. If your boxes or drivers have been leaking air, you will be astonished at the difference sealing them will make. I had a pair of ARs that had bad foams on the mids which were not clearly visible. When I noticed and refoamed the mids and checked seals, all the way around, the difference was astonishing. Sealing is important and worth every effort.

 

[Apolek]

Don't know how it translates to AR3's (same principals involved), but I know there was a significant and very noticeable improvement in bass when I sealed the surrounds on my KLH 5's (they were bone dry when I got them). Can't say for sure, but I'm willing to bet than when designers model a sealed speaker, that the software assumes a 100% seal without any leakage factor assumed.

 

[GD70]

My AR-4x's woofers dust caps are a fine mesh material that allows a small amount of air to vent by design.
All my other AR's, KLH's, ADS, are all airtight.

 

[jamie123]

with klh 23's ive applied 2 coats of sealer to the surrounds,they used to spring back when pushed in really quickly,now with the new sealer they return when pushed in slowly is this right or do i have an air leak,my way of thinking is,yes i do as if sealed properly the air inside the cabinet would push them back out again fast??

 

[GD70]

with klh 23's ive applied 2 coats of sealer to the surrounds,they used to spring back when pushed in really quickly,now with the new sealer they return when pushed in slowly is this right or do i have an air leak,my way of thinking is,yes i do as if sealed properly the air inside the cabinet would push them back out again fast??

They should return slowly. It helps control excursion.

 

[jamie123]

i thought so,but in my head the woofer taking a slow time to return doesn't make sense,if the cabinet is air tight surely the air inside would force the the woofer back out quicker? unless its drawing more air in through not being air tight??

 

[soundmotor]

If it is an acoustic suspension speaker and you push in the cone and see it slowly return to a rest position, the speaker is out of spec. The air spring has been compromised and you have something less than the desired compliance. Now, can you hear it? You would need to compare the one that leaks to one that does not on a speaker the size of the AR3a. The rate of leak may not be enough to translate into something you can actually resolve. It is usually audible (to me but not always) in very small loudspeakers (Minimus 7 sized) than large ones. Further, on a large volume speaker it may be more audible if the woofer has a floppy suspension vs. a stiff one and is therefore more dependent on a leak free cabinet. Again it would come down to a listening comparison between leaking and non-leaking versions of the same speaker.

 

[jamie123]

thanks,i thought i was on my own with that view,both speakers now return slowly since applying 2 coats of the AR guys sealer.

 

[Lesterbest]

If it is an acoustic suspension speaker and you push in the cone and see it slowly return to a rest position, the speaker is out of spec. The air spring has been compromised and you have something less than the desired compliance. Now, can you hear it? You would need to compare the one that leaks to one that does not on a speaker the size of the AR3a. The rate of leak may not be enough to translate into something you can actually resolve. It is usually audible (to me but not always) in very small loudspeakers (Minimus 7 sized) than large ones. On a large volume speaker it may be more audible if the woofer has a floppy suspension vs. a stiff one and is therefore more dependent on the air spring aspect.

Totally disagree. Pushing a driver in will always result in a slow return. That's why it's called acoustic suspension. I repaired spkrs for an Authorized AR repair station. Mortite is what we used to seal the drivers to the cabinet. Do you have all original AR drivers?

 

[Apolek]

If a speaker cabinet were 100% airtight which is unlikely, it would take a serious effort to displace the woofer (depending on the ft³ involved) and it would pop back immediately due to the positive air pressure behind it. I think making reasonable efforts without going bonkers to seal a cabinet are all that's required. No reason to break out machine tools, o-rings, vacuum grease, and pressure transducers. Although, that does sound like a fun experiment.

 

[soundmotor]

Totally disagree. Pushing a driver in will always result in a slow return. That's why it's called acoustic suspension. I repaired spkrs for an Authorized AR repair station. Mortite is what we used to seal the drivers to the cabinet. Do you have all original AR drivers?

Yeah, I went back and reread my basics. You get leaks via the cone or surround itself. However, a large enough leak will definitely translate into a driver that overloads or distorts if the cabinet is meant to be "sealed" does it not?

 

[N8Nagel]

with klh 23's ive applied 2 coats of sealer to the surrounds,they used to spring back when pushed in really quickly,now with the new sealer they return when pushed in slowly is this right or do i have an air leak,my way of thinking is,yes i do as if sealed properly the air inside the cabinet would push them back out again fast??

Same experience with the same speaker, yes, cone snapping back just as fast as it does in free air = bad, oozing back = about as good as you can hope for. That's close enough to 100% sealed that at audio frequencies it will act as if it were perfectly sealed, which is how they were designed.

My understanding is there's very little difference in the design principles of the AR3/3a/3ax and the KLH Twenty-Three.

 

[N8Nagel]

If a speaker cabinet were 100% airtight which is unlikely, it would take a serious effort to displace the woofer (depending on the ft³ involved) and it would pop back immediately due to the positive air pressure behind it. I think making reasonable efforts without going bonkers to seal a cabinet are all that's required. No reason to break out machine tools, o-rings, vacuum grease, and pressure transducers. Although, that does sound like a fun experiment.

This is true, but "close enough" and how they operate in the real world is a slow return. If you slowly push the woofer in over a period of a second or two, you will displace air out of the box through minute openings that wouldn't have enough time to move even at say 20 Hz. Likewise that air will slowly re-enter the box when you let go, if it takes a second or two to return to the rest position at 20-40x the frequency it'll work as intended.

 

[Jonny Ramone]

The PDF AR3A page mentions an "acoustic" seal ; not 100% air tight. It shouldn't bounce back immediately, but 1 to 2 seconds, something like that.

 

[Lesterbest]

Also if you go into the cabinet, don't add additional stuffing. What's there is fine. Too al dente is no good.