2245 in B460 enclosure

[opimax]

2 questions came up when playing w/the b460

When testing for speaker phase is it acceptable to use a 9volt battery to check which direction the speaker moves when touching + to + and - to - ?

When the 2245 moves out I use the lead thatwas touching the positive terminal of the battery as positive for the amp.

When I disconnect the battery the speaker goes back to rest. On the 2245 in its mounted position it bounces, like it is not damped enough or a car w/worn shocks and continues to bounce after a bump. not a lot, maybe 2 extra cycles. I have not noticed this on other speakers but I also don't have any other 18" speakers so i don't know if I am just being too critical.

Sounds pretty good to me, but maybe it will sound even better


Thanks

Mark

[Thom]

I'm not sure what acceptable means. I've used 9v dozens of times. Keep in mind that at least some speakers won't handle that for much more than a flash. Others will take it longer. In my experience, as long as you only touch it long enough to see which way the cone moves I've never damaged a speaker with one. Still, I use 1.5 or 3v if it's just as convenient. I'm not sure what it proves but I'll bet that if you had some way, with a relay or such, to drop a short across the speaker terminals the instant you removed the battery, it would stop real controlled. I think that would closer approximate the condition hooked to your system. You don't have a short, but you do have a signal controlling it. What you are looking at is all that mass on that loose suspension and no electrical control. It doesn't really matter if you hook that speaker terminal to the + r the - . What matters is that you are consistent and use the same rule throughout your system. In other words if you have JBL speakers where the positive terminal will pull the cone in, you can hook that to the pos of your amp if you wish but now if you get some speakers where the pos terminal will push the cane out the red will have to go to the negative on those. Phase is a relative thing.

[johnaec]

The best way to check for phase is get a CD or something that has a signal tone that's the same as the center frequency of the crossover you're using between the B460 and the rest of the system. Then send the signal through the system, and try it again with the leads to the B460 reversed. The one that results in the most bass is the correct polarity.

You can also do the battery test, but I'd suggest 1.5 volts instead - it should be enough. Then, assuming the 2245 is in the same plane as the rest of your system, you'd want the leads so that positive voltage moves the 2245 in the same direction as positive on the other speakers.

John

[soundboy]

I have two seperate 2245H systems with the BX63A crossovers. One is "in Phase" the other is reverse polarity....it depends on the rolloff and phase of the main speakers as to which way has a better blend....I always use 1.5 volt batteries...9 volts is quite a jolt! No wonder it bounces If you want info on modifying the BX63A, give me a shout...mine sound dramatically better than stock....hardly affect the high pass signal at all...anyway, good luck, Pete

[opimax]

the reason I use 9 volt it is spaced the same as banana plugs, even can do it 1 handed which at times is very convenient. i will go back to the 1.5 batteries, no need to inflict any damage. This is why I ask

The bounce on the woofer is from i would guess xmax or very close (doesn't take long to reach that point) to no signal very quickly, tap battery basically. If the 9 volt battery wasn't a bad thing I was going to ask others to try but since that is a bad idea is there another testing method which would either put my mind to rest or send me looking for a local reconer?


I do not have a x63. I use a Velodyne SMS-1 contoller. I have a Velodyne spl1200r I sometimes use to augment for movies for below 20 hz rumble that the sub filter and reflex box cut out. I would like a 63 to have for my TI collection to match the 460 but no hurry, not sure i would use on a regular basis, thanks for the offer of help, very nice of you.


thanks

Mark

[Steve Schell]

For years now I have used an old AA battery with a short wire lead soldered to the negative terminal to test speakers. It is still going strong, well enough to make a cone jump anyway.

[opimax]

I am sold on the 1.5 volts but what about the cone "bounce", any way I can test further?

Mark

[grumpy]

testing further? depends on what you have available and/or are willing to spend...
could put it back in the cab and test for frequency of minimum cone motion with
either an audio oscillator, test CD, downloadable program... + amp. Could also buy or
borrow something like the WT2 and do a pretty fair job of characterizing the driver entirely.

If I think about it when I get home, I'll touch a 9v battery to a 2245H and try to visually
compare it to your description... but I wouldn't give much weight to the result....
(even less, as mine's not in a box, tuned or otherwise). I'll have to dig up the 2245H
article here and review (an underdamped system would be expected to respond this way
to a step function).

-grumpy

[opimax]

grumpy,

Thanks, it was done in the cabinet, sounds fine but i don't have a reference to verify "fine". I realize the bounce may be nothing or it may be a symptom of a problem, it was just the first time I noticed it on any speaker. I have not had an 18 before

Mark

[WTPRO]

When you disconnect the battery the speaker is open circuit. This means there is no electrical damping. The remaining damping is mechanical. The overall resonance of the driver and box tuning then come into play. Being an 18" I would expect the resonance frequency to be pretty low, and therefor easy to see.

Best regards,
WTPro
www.woofertester.com

[opimax]

Hi,

Thanks for the answer. I didn't realize the electrical circuit supplied a resistance (now that it is pointed out makes sense , scary ).

And of course I like this answer too so I want it to be correct but if anyone else wants to post what happens when they try it it would soothe my curiosity

Mark

[subwoof]

Well a battery applied and then quickly removed is *ONE* hertz assuming it takes one second.

At that "frequency" the cabinet / speaker combination is unloaded and there is little or no mechanical dampening.

If you could make that connection 20 times in one second it would be 20Hz and the speaker would exhibit the correct dampening and not "bounce"

Also when the speaker is connected to a powered up amplifier with a large power supply it will have electrodynamic braking. Ever try to spin a tire on a lift when the transmission is engaged??

It's all physics..

sub

[GordonW]

9 volt batteries are fine for woofers (say, 8" or bigger). I wouldn't use them on smaller speakers... a 1.5v battery is better, due to the lower power handling.

But, we use 9v batteries on JBL 15" and 18" woofers all the time... as long as you don't LEAVE the connection in place for a long time (and really, it only takes one second of connection to determine polarity- anything longer than that is just wasting time and battery power!), there's no way it can cause a problem, realistically...


Regards,
Gordon.

[Thom]

I didn't stop and think that it was your sub woofer you were trying to phase. The answer about the test record was the best. Proper phase could differ depending upon placement of your sub woofer in the room. This is why all sub woofer amps have a phase switch and some good ones have a variable phase control because proper phase for your sub woofer may be somewhere in between. I'm guessing there is probably a simple circuit for variable phase but I'm not familiar with one.

[grumpy]

well... in free air, 2245H produced a step with no obvious "bounce",
(or it was much faster than I could see)
when connected to a 9v transistor battery. Although I know the voice coil
can handle the wattage dissipation, I don't think I'll be intentionally testing
the excursion limits of a driver like this again.

-grumpy