Acoustic Suspension: Not the same as sealed box

Vintage Asylum

Classic gear from yesteryear; vintage audio standing the test of time.

Have you guys noticed that the current set of DIY woofers usually list an F3 sealed and an F3 vented, generally 25-30 Hz different with the sealed F3 being the higher number. Yet vintage acoustic suspention designs are widely known for producing extended deep bass relative to the vented designs of the day.

What's going on here? Well just because a woofer lists a sealed F3 doesnt somehow magically make it an acoustis suspension woofer. If you go back to the Villchur patent, an acoustic suspension system used a special woofer with a very floppy surround which stiffened in the perfectly sealed box. Nearly all vintage acoustic suspension woofers (with perhaps the notable exception of the epi design, which was routinely used in both vented and closed box enclosures in the 70s and somehow managed to produce very deep bass in both) would be totally unsuitable for a vented box design.

The other rather interesting puzzle is the Utah 12 inch cloth surround woofer, advertized as an acoustic suspension woofer in a 10 x 23 x about 9" sealed box. I can vouch for the fact that sealed these woofers produce very deep bass, (in most respects comparable to Advent deep bass) in my mind much better than a modern 12 inch DIY woofer would produce, sealed. But Utah also marketed a similar system that was ported and only slightly larger, about 11 x 25" box. The two puzzles I've long pondered are 1. exactly what are the differences were between the cloth suspension woofer Utah used in the acoustic suspension ve the vented enclosure? and 2. how the laws of physics for the required size of a sealed versus vented box would lead to an optimal vented box only marginally bigger than for the sealed box. I've looked at a number of photos of the woofer used in the vented box, and it appears to be almost identical to the one I have in the unvented box.

There are other odd Utah questions too to puzzle over--for example, how they cooked up this idea to use a giant 8-inch sealed back mid-range speaker (understandable perhaps with a 12 inch woofer crossed over low, but they cross over high in the mid 2 KHz range and then the big mid is permitted to play for only 1 octave up quite high --wild and crazy stuff from the perspective of basics of 3-way speaker design.

The crossover in the Utahs is really minimal which suggests to me that if you build your own drivers its not that difficult to match them so well that electrical crossover components are all but unneeded. Whatever these skills were, they seem to have been lost to history.

David

This post is made possible by the generous support of people like you and our sponsors:

Sonic Craft

Topic - Acoustic Suspension: Not the same as sealed box - DavidLD 05:17:28 12/01/07 (7)

RE: Acoustic Suspension: Not the same as sealed box - peanutbutternut 12:21:01 01/05/08 (0)

RE: Acoustic Suspension: Not the same as sealed box - Bold Eagle 16:13:22 12/02/07 (0)

RE: Acoustic Suspension: Not the same as sealed box - Pete B. (Unregistered) 15:00:20 12/02/07 (2)

RE: Acoustic Suspension: Not the same as sealed box - Bold Eagle 16:22:54 12/02/07 (1)

RE: Acoustic Suspension: Not the same as sealed box - Pete B. (Unregistered) 20:55:05 12/02/07 (0)

RE: Acoustic Suspension: Not the same as sealed box - Old nuff 2 no better 07:18:59 12/01/07 (1)

RE: Acoustic Suspension: Not the same as sealed box - Chef Henry 10:50:29 12/01/07 (0)

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.