sealed vs. vented

GM · November 1st, 2006, 07:22 PM

Originally posted by RonSS:
About the 411......

Later models used a more normal foam rubber type surround.

I had mine re-coned at GPA, and the T/S parameters after reconing more closely matched a 416-8B.

Bummer. forums

**Jim Butler** · November 2nd, 2006, 02:46 AM

Really, GP's 411 recone resembles a 416-8B!? Anyone else with a similar issue with 411 recones? I'm plannig on having GP do several 411's and really want the orginal low freq capability of this woofer.

**MikeInNH** · November 2nd, 2006, 01:50 PM

Sounds like you're not comparing 'apples to oranges' since the cabs have different Vbs, ergo the larger vented cab will have more box efficiency potential; so to clarify my earlier response, there's a point in cab Vb where there's only some gain in the narrow BW around/at Fb with vented Vs sealed, which can sound very 'one note' on music, etc., that excites the cab, so in this case, sealed is normally preferred in a HIFI

Let me get what you're saying...I built a Sealed speaker to it's OPTIMAL size cabinet. Then I built a Vented speaker to it's OPTIMAL size cabinet...and I found the vented to be more efficient. So what...you're suppose to built a sealed unit to NON -OPTIMAL size so it's as efficient as the Vented speaker. There's engineering and then there's real-world/practical engineering. I prefer the later.

**Old Guy** · November 2nd, 2006, 02:01 PM

I've always understood the efficiency as being for the venting. You sreinverting the phase of the rear wave so there should be a net gain in radiated energy.

The sealed box does roll off more gradually in the very deep bass.

So I would think the efficiency argument depends on what frequency you are talking about. Overall output honors though go to the vented box.

**bfish** · November 2nd, 2006, 04:53 PM

Don't worry, Jim.

I've recently reconed both 411s and 416s with GPA parts, hubcaps and paper plates like they should be. Even weighed the 411s to compare, the old ones were 1/2 gram heavier (dirt and moisture). I'd call both an amazing match even before considering the 30 year production span. When they're in boxes, I'll test them, but I'm not worried in the least. Nor do I have any complaints about the 515s, 421s, etc.

I'd expect different T-H between cloth-roll 411s and foam, but then Altec changed that, not GPA. I'm no foam-lover, but consider it best here, the cloth-rolls just won't hold up. I'll bet most any still in use with cloth have wornout spiders and rubbing coils. In a mag-down position, a good spider (411) will still maintain a flat profile even if the surround's gone. They just can't do it forever.

**bfish** · November 2nd, 2006, 05:56 PM

Here's a useful resource on the subject;

http://www.diysubwoofers.org/

**Jim Butler** · November 3rd, 2006, 02:19 AM

Bfish,

Thanks for the info on the 411 recones. I have a couple in 620 cabs and they play great (and low). If they were more like 416-8B's I think it would be noticeable.

GM · November 3rd, 2006, 08:20 PM

Originally posted by MIkeInNH:
<blockquote>quote:<hr /> Sounds like you're not comparing 'apples to oranges'........

Let me get what you're saying...I built a Sealed speaker to it's OPTIMAL size cabinet. Then I built a Vented speaker to it's OPTIMAL size cabinet...and I found the vented to be more efficient. So what...you're suppose to built a sealed unit to NON -OPTIMAL size so it's as efficient as the Vented speaker. There's engineering and then there's real-world/practical engineering. I prefer the later.<hr /></blockquote>Greets!

Hmm, that should read: "not comparing apples to apples.........".

Hmm, 'optimal' is application dependent and there's situations where a large sealed alignment would be better than if vented due to its slower roll off slope with its greater efficiency down low WRT a vented alignment, but I understand and agree with your point that a T/S max flat vented alignment will have much more LF gain BW than a sealed one, though as I noted, the cab size required is much larger. It's not relevant to LeRoy's question though since his volume (Vb) is fixed and optimized for a sealed alignment, which as you've already proven to yourself is too small for either an optimal or even acceptable vented alignment.

I do too, and I figured I'd posted enough on the subject to make it clear, but apparently not.

GM

**MikeInNH** · November 6th, 2006, 02:32 PM

since his volume (Vb) is fixed and optimized for a sealed alignment, which as you've already proven to yourself is too small for either an optimal or even acceptable vented alignment.

Why would ANYONE build a sealed cabinet that is NOT optimal for a sealed cabinet. That doesn't make sense. What you're saying is you want to build a sealed cabinet to get the maximum efficiency out of it...but you don't care about sound quality?? What kind of engineering is that.