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Post subject: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Oct 31, 2012 6:54 pm
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I read on FenderGuru.com about disconnecting 2 of the 4 speakers in the Super Reverb to drive the amp harder at lower volumes, for better tone at lower volumes. It looks the 4 speakers are wired in series, so I assume just having just the first two in series would be the trick? Disconnecting the last two.

Just making sure this is ok to do. I've read warnings about running your amp w/out any speakers connected and warnings about matching the impedance and damaging speakers and amps. So I just wanted to get some opinions on here that it's safe and all that.

Thanks in advance.

Schematic is here: http://www.webphix.com/schematic%20heaven/www.schematicheaven.com/fenderamps/cbs_70w_mstrvol_pullsw_super-pro-bmstr_rev.pdf


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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Oct 31, 2012 7:02 pm
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The original Super Reverb's four 8-ohm speakers are wired in parallel for a total load of 2 ohms.

HTH

Arjay

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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Oct 31, 2012 8:13 pm
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Right, thanks for the correction. 4 in parallel, I intend to run it wired 2 in parallel. Just disconnecting the last two. Sound legit?


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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Oct 31, 2012 8:54 pm
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I tried it out. Sounded great! I used two of these speakers instead of the originals.

http://www.parts-express.com/pe/showdet ... er=290-476

Eminence Legend 8 Ohms each, so I'm running 4 Ohms of impedance with the speakers.

There's still a little but of low end rumbling. Playing a heavy Em chord with reverb, you can hear it rumble around a little. I'm not sure if something in the cabinet is vibrating (speaker attachment or the grill vibrating on the cabinet or something) or if it's due to some electronic issue and that rumbling is coming from the amp. Anyway it sounds a lot better with these two speakers instead of the original 4 Fender speakers.


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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Oct 31, 2012 11:11 pm
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What are those "original speakers"......got any pics?

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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Thu Nov 01, 2012 12:49 pm
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The originals are 'Fender Musical Instrument Special Design Speaker'. I bought the amp in '85 and gigged with it 3x week for about a decade. I've been rebuilding it and I think these old speakers are done. I'll save them in case my heirs want to sell the amp someday :lol:

They sounded ok until you played some bass strings, SRV style, and would get a terrible farting/rumbling sound. I think they are just worn out.

Image

Image

Image

Image

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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Thu Nov 01, 2012 1:08 pm
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Rola's from the 44th week of '75. They never were anything to write home about.

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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Sun Nov 04, 2012 8:01 pm
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How much did it reduce the volume? How was the tone changed as compared with all 4 speakers?


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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Sun Nov 04, 2012 9:33 pm
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I don't know if the loudness is 50% lower or 30% lower but I can run it with both volumes around 4 to 5 in the living room without my ears ringing after :)

Tone is pretty darn good. Not SRV but as close as I've gotten to date. I'll post a sample if I get motivated to record one.


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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Jan 08, 2014 11:22 am
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russpatterson wrote:
I read on FenderGuru.com about disconnecting 2 of the 4 speakers in the Super Reverb to drive the amp harder at lower volumes, for better tone at lower volumes. It looks the 4 speakers are wired in series, so I assume just having just the first two in series would be the trick? Disconnecting the last two.

Just making sure this is ok to do. I've read warnings about running your amp w/out any speakers connected and warnings about matching the impedance and damaging speakers and amps. So I just wanted to get some opinions on here that it's safe and all that.


Yeah, I was thinking about doing this as well, but there are indeed varying opinions out there, many that do warn about speaker or transformer damage. I have a 67 SR that I sure don't want to risk damaging. More opinions about the safety of this mod would be greatly appreciated.


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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Jan 08, 2014 3:01 pm
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shelshaf wrote:
I have a 67 SR that I sure don't want to risk damaging. More opinions about the safety of this mod would be greatly appreciated.


Safety would be assured by merely buying a smaller, lower-powered amp.

I wouldn't hazard an original '67 Super Reverb under any circumstances.

Arjay

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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Jan 08, 2014 4:16 pm
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You would be changing the impedance and increasing what the OT would be seeing when taking speakers out of series. The OT has Pri,4000 and 2ohm sec.

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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Jan 08, 2014 6:53 pm
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Boy, I'd be hesitant to changed the setup to a 2 X 10 inch, 4-ohm setup. Not on a permanent basis. You lose so much of the Super Reverb tone. Maybe one of these would be nice on the "wish list?" :D


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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Jan 08, 2014 7:01 pm
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BMW2002Ti wrote:
Boy, I'd be hesitant to changed the setup to a 2 X 10 inch, 4-ohm setup. Not on a permanent basis. You lose so much of the Super Reverb tone. Maybe one of these would be nice on the "wish list?" :D


Image


+1

Or a Vibrolux Reverb (the silverfaces are still reasonably-priced).

Arjay

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Post subject: Re: Speaker disconnect mod for 70's Super Reverb
Posted: Wed Jan 08, 2014 7:15 pm
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Won't sound right anyway because you would be effecting the whole output stage changing the load.

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