I suppose that you could make a fixture to hold a depth gauge, and measure how deep the cone is relative to the frame with different orientations. But even if the cone stays close enough to centered while facing down, wouldn't gravity affect the resoponse anyway? 311 gm has to be kind of hard for the motor to lift straight up.
I would be concerned that it might sag over time with 24/7 downward force.
Lotsa downward-firing subs out there, tho....
I have had these in 2 different size boxes and so far I like the 2.2 cuft sealed boxes a little better than my 3.9 cuft sealed boxes. I am normaly a fan of vented boxes but because I wanted to keep them small this is what I found.
I now know that I have much more space then I thought so now onto the 2242's in a 10-12 cuft tuned to about 25-28 Hz.
Will post pics later.
Shane
I'm not going to comment on that since you've already built your subs, but here's what I got for numbers:Originally Posted by linear
Thanks very much for posting your numbers on sag. Based solely on that data, it seems that the Sub1500 would be OK for vertical mounting (i.e. the sag is less than 5% of Xmax). Nevertheless, since the cone is so heavy (with Mms at 300 gm), I understand that you would not recommend a downfiring application. Could you comment on this further? What upper limit should be put on Mms for a speaker to be recommended for this configuration? Does anyone know of any literature on the long-term effects of vertical mounting?
I really like the performance of the Sub1500 and I would hate to damage it, over time, due to vertical mounting. A frank opinion would be really appreciated. (I'll re-build/re-configure my subs if necessary!)
I'll get a definitive answer for you sometime next week.
Have you heard from any of your JBL contacts regarding the suitability of the Sub1500 for vertical mounting? I would love to hear what someome like Doug Button has to say on the subject.
I have been unable to find any literature or papers on vertical mounting, except for the often repeated "rule of thumb" that the sag must not exceed 5% of Xmax. (The Sub1500 meets this requirement.)
However, I did dig up some interesting details on the B&O BeoLab 5 speaker system. It uses a vertically mounted 15" driver, in a 1 cu ft (28 L) sealed box, and it is driven by an "equalized" 1000 w amplifier. The only other info that I could find out about the transducer is that its Xmax is 21 mm, and the resonance in the box is 60 Hz. This sounds a lot like the original Revel Sub15 application that the Sub1500 was designed for. In fact, I ran the Sub1500 parameters with a 1 cu ft sealed box and got a resonance of exactly 60 Hz! So, the B&O 15" driver must be very similar to the Sub1500.
Therefore, the above information begs the question - did the B&O engineers know what they were doing when they vertically mounted their driver? Can we use this design as evidence that the Sub1500 would be OK in this type of application? Perhaps, this is a loaded question to ask on a JBL forum! Can we get an opinion from the JBL engineers? Maybe B&O and JBL could "slug it out" at the next AES conference!
Regards,
Linear
"- did the B&O engineers know what they were doing when they vertically mounted their driver?"
Maybe, but it sure doesn't sound terribly good. I was impressed with it's output capability and fairly decent extension, but it just didn't have a musical sound to it... I wouldn't say it was a one note bass like Bose, but it was very lacking in detail resolution.
As for a comparison between it and the Sub1500... the Revel box was 1.5 cu ft.
Widget
The Sunfire was a "one note" wonder as well.
The sub1500 on the otherhand is more musical than most.
Only the right cab and driver can be musical! boom boom is all that people think is "great".
If they only listened to the music and not just how much "BASS" it has then maybe people would look for "Good" subs! IMO
Shane
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1
Oh look.... here's one now, and it even comes with that killer amp! I realize this is a bit steep for those of us who were lucky enough to get the Sub1500s at fire sale prices, but this is really quite the deal. I wish I had a few extra bucks lying around.
Widget
I just wonder - how much would gravity affect the +/- linearity when working against gravity to pull that heavy cone back up, compared to the gravity assist when going down? Or would they just cancel each other out, other than the sag offset?
John
Yes, today in fact.
With respect to mounting the SUB1500 face down -
In a vented system, or even a sealed system, it could easily lead to software DC rectification. That is when the software drifts outward or inward, under AC signal, as if a DC signal were present. BL, Suspension, Inductive, Asymmetries basic non-linearity's can all lead to this motion instability. It will also reduce power handling (mechanical) since the coil is moving more that it would be under normal, stable conditions. Thermal power handling could also be sacrificed since the coil will have a tendency to spend more time outside the gap, minimizing thermal transfer.
I would be worried about sag over time leading to axial coil misalignment, thus leading to or worsening the DC issue mentioned above.
Thanks very much,Giskard, for getting the expert opinion on vertically mounting the Sub1500. I've never heard of "software DC rectification", but it looks like it's something to be concerned about.
One final thought. This mechanism (SDCR!) must only be active when the speaker is being driven with signal. Otherwise, speakers would de-grade in shipping and storage. Until they are installed in a cabinet, they spent their life "Flat". On the other hand, maybe we should be storing vintage speakers on edge!
Regards,
Doug
"software DC rectification"
It's a technical term.
The designer of the SUB1500 refers to the moving assembly as software and the basket/magnetic assembly as hardware.
They do. Store them on edge otherwise their suspensions will sag. Gravity is relentless.
Most of us JBL nuts rotate our stored drivers on a regular schedule. I store most of mine vertically, but those that I can't, I flip them over regularly.
Widget
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