sealed vs. vented

[spam91dog]

Always wished to have a pair of Altecs. Finally purchased some Santiago 878a's mostly because sold nearby. These are sealed. Are vented more preferred? Should I think about venting these?

[MikeInNH]

There are advantages to both. But I always found a properly tuned vented cabinet to be better. The main reason to vent over sealed is efficiency. A sealed speaker requires more power to produce the same sound level as a vented speaker. The advantage to sealed speaker cabinet is usually extended (lower) frequency response. But with a properly tuned vented cabinet the difference is almost nothing.

[GM]

Greets!

Assuming they still have 411 woofers, the cab is acoustically too small to realize any useful gain from venting without sacrificing some LF extension and sound quality (SQ).

GM

[Tom Brennan]

LeRoy--leave them alone. The drivers, 411s, used are designed for sealed use and probably will work poorly if vented. One doesn't simply vent a woofer intended for sealed use; one must start with a woofer intended for vented use.

[Tom Brennan]

Mike---For a given sized box a vented can go lower than a sealed.

Vented systems are more efficient not because they're vented per se but because they allow the use of more sensitive woofers---big motors and light cones don't do so well in sealed boxes but can work well in vented ones.

It may start with the driver chosen, then working backwards the driver must be used properly.

On the other hand one may start with a certain type of cabinet and f3 and start figuring, then one must find the right driver.

[MikeInNH]

Mike---For a given sized box a vented can go lower than a sealed.

<font size="2" face="Verdana, Helvetica, sans-serif">But MOST manufacturers don't build them right. A good vented MAY go lower, but at a certain frequency it drops off real fast. A sealed unit will roll off a lot more gradually.

Vented systems are more efficient not because they're vented per se but because they allow the use of more sensitive woofers---big motors and light cones don't do so well in sealed boxes but can work well in vented ones.

<font size="2" face="Verdana, Helvetica, sans-serif">That's interesting Tom because that's NOT what I've observed. I've built sealed cabinets and vented cabinets using the same woofer and the vented speaker is noticably more efficient.

[Tom Brennan]

"I've built sealed cabinets and vented cabinets using the same woofer and the vented speaker is noticably more efficient."


Yeah, well audiophiles "notice" many things, so did the girls at Salem.

Let's get this straight, are you claiming that a woofer in a vented box has a lower F3, thus being more efficient merely at the bottom of the band? Or are you claiming that a vented box makes a woofer more efficient overall, you know, like all the way from F3 to low pass?

[MikeInNH]

Or are you claiming that a vented box makes a woofer more efficient overal

<font size="2" face="Verdana, Helvetica, sans-serif">Yes this is what I've observed. I used a Altec 10" woofer (from a Model 7). I was experimenting with building a sub. I build two subs, one that was vented and based on the same dimensions as the Model-7 it came out of. The other was a sealed cab based on Thiel parameters. Both sounded GREAT, but the sealed cab was noticably less efficient then the vented. Atec did a GREAT job in designing the origional Model 7 cab. It's base was tight and sounded great. The sealed cab was also great, but just not as efficient. Sorry I didn't have the instruments to measure exactly how much.

[GM]

Greets!

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 app. Also, as cab Vb shrinks, the vent gets to be long enough to have audible pipe modes that comb filter with the system's mids/HF since they aren't blocked by the XO. They can be damped of course, but not without rolling off the extra vent efficiency, making the extra $$/effort mostly moot. This is the case with the 878 IMO.

WRT the 411 being a poor candidate for vented alignments, I've done a few that might change your mind , but they aren't particularly small.

As always though, YMMV.

GM

[RonSSS]

About the 411......
The very first ones had an inverted cloth surround with the black goo applied.

Later models used a more normal foam rubber type surround.

The two will not have the same T/S parameters.

I had mine re-coned at GPA, and the T/S parameters after reconing more closely matched a 416-8B. So I used them in 8 ft^3 vented boxes with excellent results. These are now my subwoofers.

BTW I measured the T/S parameters of them before re-coning and they matched spec quite well. Too bad the cones had sunk badly. Otherwise I would have left them alone.

Ron