Long-term Downfiring Sub Questions

[soho54]

I messed my Sag calculations up.

I ordered two RS 15" HF drivers to be down firing in separate tube enclosures. I had used the long formula and got a Sag of 4.4%. Yesterday, I found a post by Darrenk in which he said he would not recommend them for a horizontal application, and that got me thinking. I then re-ran the calcs and came up with 5.47%. :M Unibox says .95, which no ones uses.

I spent most of the evening trying to find more info about the sag formula and long-term durability of drivers in this position. I found nothing. The only thing repeated over and over again is that you are good under 5% and that flipping the driver around every once and awhile might help.

Does anyone here have real world experience with drivers over the 5% limit? I'm I just out of luck?

[ThomasW]

The weight of the cone assembly stretchs the suspension, so reversing it doesn't help all that much.

I wouldn't get real concerned with the 5.47% unless you need to keep the subs for a really long time. If that's the case return the drivers and buy drivers that model lower.

[soho54]

I guess the time thing is my real problem. My upgrade cycle is around 5 years, so I might be pushing it. Would a 45 deg angle be better? Wonder if I can talk my wife out of the columns and into a giant 300lb box. :B

[Amphiprion]

I've always wondered where the 5% number came from. The first time I heard it, it was from Wiggins, but don't know if the recommendation predates him.

Personally, I saw a blown car audio woofer taken out of an install where it had been mounted vertically. It belonged to a friend of mine who cut out the cone/VC/spider assembly and the spider had noticeably deformed, permanently. It must have been off center by at least 5mm if not more. Now that's just one woofer, but it's been enough to keep me from downfiring since.

[dlneubec]

I did a pair of 45º down firing subs (see link). My logic, perhaps flawed, was that the weight of the cone material, etc. had an effect in either a horizontal or vertical arrangement. It seemed to me that the weight of the cone pulled against the suspension just as much in either orientation and that the suspension could sag over time either way. So, I figured 45º would be the ideal compromise between the two. 8O

I see that the HO 15" comes in at 4.7%, the IB 15" at 4.0% and the DVC15% at 3.9%. You could always send the HF's back to PE for just the cost of shipping, since they have a 45 day free return policy, and exchange for one of these others.

12"- 45º down firing sub: Image not available

[Scott Simonian]

Wtf?

People are saying these subs cant/shouldn't be downfiring?

Every sub thread anywhere nowadays everyone says, "Yeah just downfire unless you want to look at the driver."

Did I miss something?

[ThomasW]

Wtf?

People are saying these subs cant/shouldn't be downfiring?

Every sub thread anywhere nowadays everyone says, "Yeah just downfire unless you want to look at the driver."

Did I miss something?

It's specific to the driver. Drivers like the RL-p15" have a very stiff suspension so they can be mounted in any orientation. The RS15"s aren't a good candidate for down firing applications

[Scott Simonian]

Oh, really? I guess I better rethink how I'd have liked those to be positioned.

Thank you, Sir Thomas of the Infinitely Baffled.

:0)

[soho54]

I think I am just going to rig something up to hold the drivers at the zero position when not in use. Something foot activated, would be nice. I have to run around and throw 500 switches to start everything up anyway. What's two more things to remember? :B

[ThomasW]

I think I am just going to rig something up to hold the drivers at the zero position when not in use.

Won't solve the problem. Even with a battery holding the cone in the 'up' position the weight of the assembly is still pulling on sections of the suspension.

[soho54]

I was thinking of a more physical approach. Something to physically hold the weight of the down firing cone and coil in its home position when not in use. A piece that rises up from the base to meet and hold the cone. The trick will be to come up with something that won’t rattle like crazy in the down position, and will still look OK. I had already crossed the battery bit off my list. That would be way easier but as you pointed out won't take the stress off the driver.