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Post subject: Speaker ohm ?
Posted: Sat Aug 10, 2013 7:14 am
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Hey guys, please forgive my ignorance, I have a Vibrolux Reverb and a Pro Rev, 73 & 74, im wanting to change speakers, whats the ohmage for each replacement speaker? 8? or 16?


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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 9:09 am
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Eight ohms in both cases.

Arjay

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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 1:27 pm
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Retroverbial wrote:
Eight ohms in both cases.

Arjay


FWIW, this Pro Reverb schematic shows two 16 ohm speakers in parallel for an 8 ohm load:

http://ampwares.com/schematics/proreverb_ab668.pdf

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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 2:33 pm
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Strange!

Amp Schematic Heaven shows that same drawing for the AB668 as well.

However, all the other permutations of the Pro Reverb amp show the pair of speakers as 8's, with the traditional parallel wiring.

The AB668's series wiring apparently didn't last long -- a little over a year, when the AA1069 circuit reverted back to 8-ohm drivers in parallel. The Pro Reverb's OT never changed from the 022848 iron, which may account for why the AB668 amps were perceived as having less available volume than the previous or subsequent revisions.

Weird (learn something new every day).

:shock:

Arjay

Edit: Just checked with an acquaintance in OKC who owns an original AB668 Pro Reverb -- the speakers are 16Ω Utah's (Fender P/N 081810), wired in series (just as the schematic indicates).

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Last edited by Retroverbial on Sat Aug 10, 2013 6:13 pm, edited 1 time in total.

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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 2:39 pm
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Retroverbial wrote:
Weird (learn something new every day).

:shock:

Arjay


And forget two things. :lol: :lol: :lol: :lol:

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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 3:09 pm
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From your lips to God's ear!

:mrgreen:

Arjay

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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 4:02 pm
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I wonder if the AB668 schematic is in error. The output tranny for all the BF and SF Pro Reverbs is the 125A6A (022848). All my info shows this OPT has a 4-ohm secondary. I remember several schemos posted on the Net, where the final impedance on the tranny was changed (hand-written over the original).

Wouldn't be the first time. :lol:


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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 4:07 pm
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Thanx guys , I knew I could count on yall....I am from Texas: I had a brain freeze and couldnt think, are both amps looking for a 4 ohm load or 8?


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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 4:44 pm
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I'd go 4-ohm total load on the secondaries. Note the two VLR schemos and the "editing."

:D

http://www.webphix.com/schematic%20heav ... _schem.pdf

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Speaker ohm ?
Posted: Sat Aug 10, 2013 6:16 pm
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BMW2002Ti wrote:
I'd go 4-ohm total load on the secondaries. Note the two VLR schemos and the "editing."

:D

http://www.webphix.com/schematic%20heav ... _schem.pdf

http://www.webphix.com/schematic%20heav ... _schem.pdf


+1

And I'd ignore that apparent anomaly in the AB668 schematic and wire those speakers (if 8Ω) in parallel.

Arjay

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Post subject: Re: Speaker ohm ?
Posted: Sun Aug 11, 2013 6:28 am
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Thanks to all


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Post subject: Re: Speaker ohm ?
Posted: Sun Aug 11, 2013 8:58 am
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Be sure to phase the speakers correctly when wiring them up regardless of which method is used.

Arjay

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Post subject: Re: Speaker ohm ?
Posted: Mon Aug 12, 2013 6:28 am
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Please educate me, phasing?


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Post subject: Re: Speaker ohm ?
Posted: Mon Aug 12, 2013 7:19 am
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hogrydr,

Phasing a set of speakers is making sure that all speakers are moving in the same direction when in use. Thus, reinforcing or adding to the overall tone (esp bass). If you have a speaker out of phase with the other(s), it will cancel out the effect of the other --- most noticeably the bass.

You need to be weary of the (+) and (-) or color codes on the speaker, itself. It is no guaranteed indication of the true phase of different makes & even different vintages of the same speaker type and manufacturer.

You can either try flipping the wiring to each speaker and note the effect on the bass. Or use the 9-volt battery test (see video on link).

Good luck with that! :D


http://speakerphase.com/


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Post subject: Re: Speaker ohm ?
Posted: Mon Aug 12, 2013 8:52 am
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BMW2002Ti wrote:
Phasing a set of speakers is making sure that all speakers are moving in the same direction when in use. Thus, reinforcing or adding to the overall tone (esp bass). If you have a speaker out of phase with the other(s), it will cancel out the effect of the other --- most noticeably the bass.

You need to be weary of the (+) and (-) or color codes on the speaker, itself. It is no guaranteed indication of the true phase of different makes & even different vintages of the same speaker type and manufacturer.

You can either try flipping the wiring to each speaker and note the effect on the bass. Or use the 9-volt battery test (see video on link).

Good luck with that! :D


http://speakerphase.com/


+1

Speakers produce sound by the vibration of the cone. A speaker's cone movement is known as "excursion" and this movement begins with either a forward or rearward excursion. In the case of a multiple-speaker array it is preferred that each of them have identical excursion directions simultaneously. Thus, in a parallel wiring configuration the incoming signal should be connected to each speaker's "+" terminal and the returning ground should be linked to each speaker's "-" terminal. In a series arrangement (where the speakers are "daisy-chained" together), the input signal should be routed to the first speaker's "+" terminal then the output (ie: the "-" terminal) is tied to the next speaker's "+" terminal. Subsequent speakers are wired in the same fashion, with the final speaker's "-" terminal being connected to the amp's return (ie: ground) wire.

Terminals are usually marked with a "+" and a "-" or color-coded as red and black. Older speakers such as vintage Jensens and the like may use a red stick-on dot only on the positive ("+") terminal.

Arjay

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