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15" Jensens [message #8394]

Mon, 12 March 2007 01:01

C4ster
Messages: 686
Registered: June 2001
Location: Mukwonago, WI (Milwaukee...

Senior Member

Hi guys, I am replacing 4 Jensen C15L speakers in my red siren Ross cabinets. The cones look like they have limited "in" travel because of the at rest position. I would think these speakers are due for a recone. Your thoughts.
Conrad

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Re: 15" Jensens [message #8399 is a reply to message #8394]

Mon, 12 March 2007 07:03

stevem
Messages: 4756
Registered: June 2004
Location: NY

Senior Member

The only time a cone will travel in (toward the magnet) is if they are wired with the wrong polarity. A cone will always travel out from the at rest position and as the inner spider and the cone surround ages the cone may go back to the at rest position all the way.
A speakers voice coil can bottom out and be damaged if wired wrong and driven with enough wattage.

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Re: 15" Jensens [message #8401 is a reply to message #8399]

Mon, 12 March 2007 08:22

C4ster
Messages: 686
Registered: June 2001
Location: Mukwonago, WI (Milwaukee...

Senior Member

I have to respectfully disagree. Your output from the amp at idle should be 0 volts. It is absolutely imperative that the amp be biased to achieve that goal. The output applied to the speaker will not cause any movement at 0 volts. That being said, the output goes from positive to negative with every alternation and the speaker cone MUST move both in and out and the excursion MUST be equal in both directions. I agree, too much movement in can cause the VC to bottom but the speaker must be able to move in both directions smoothly and equally. I have never heard that a speaker only moves out. When a battery positive is applied to the positive terminal, the speaker should move out, and if the battery is reversed th cone moves in. JBL's are opposite but it's all north-south magenetic physics. The polarity is only important when phasing multiple speakers of the same frequency range, ie subs, lows, mids, highs, with lows being most important. Speakers in the same cabinet must be phased or the movements will cancel.
Conrad

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Re: 15" Jensens [message #8425 is a reply to message #8394]

Tue, 13 March 2007 06:53

stevem
Messages: 4756
Registered: June 2004
Location: NY

Senior Member

I can`t belive I did not catch that, I wanted to say" on the negitive part of the sine wave the cone travels in"
And for some reason I have seen alot of CTS and eminence 15s That are old and worn where the cone is now sitting at a slightly outword resting postion compared to when new.
Sorry folks, thats what I get for tyin to think too much at 6:30 in the mornin after loosin a hours sleep!

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Re: 15" Jensens [message #8426 is a reply to message #8394]

Tue, 13 March 2007 06:58

stevem
Messages: 4756
Registered: June 2004
Location: NY

Senior Member

Another important thing to check in reguards to phase is when using 2 different amps, 2 weeks ago was the second time in 6 months that I saw a band whos guitarist used two amps with a stereo modeling pedal, one of which was out of phase with the other.It was not too teribly bad with his amps on oposite sides of the stage, but during a break we put both amps side by side and the problem was right in your face.

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