an unusual NSD installation

[212Mavguy]

Here's a whaddiddit for beginning tube amp enthusiasts. Should be easy for somebody more clever in amp smarts to figure out very quickly.. But since I'm severely guitarded, it took a half hour for me to fix.

 

This morning I decided to try out the newly acquired screaming deal Altec 417H series II in a 2/12 cab paired up with a JBL MI-12. The JBL was one of a pair from an ebay acquisiton that had been reconed by Orange County Speakers and then let sit for a few years in a closet unused. The Altec is VOS with original cone.

 

I mounted them up and hooked the speakers up in series, making sure to follow the color codes on the speaker terminals for a proper hookup, Altec on top of the JBL, then hooked up my HRM D-clone, set impedance to 16 ohms and fired up.

 

Wow, how disappointing. bright, nasty, lack of bottom, lack of sustain. OD was gritty and harsh , usually it's smooth and sweet.. I had the cab standing vertically. Next, I flipped the cab so that the other speaker was on top. Significant improvement, but still, signs of the original problem remained.

 

What did I do wrong? These should have sounded fat warm, glorious, and sustain for days,

[DetroitBlues]

Mismatch of the ohms on the speakers?

[212Mavguy]

Nope.

[kbp810]

I believe I know the answer to this riddle

[212Mavguy]

should I offer a clue?

[t0aj15]

Sounds to me like the speakers are out of phase.

 

If I remember correctly either JBL or Altec all those years ago wired their speakers ass backwards and as such the speaker leads had to be reversed when matched with speakers of a different make.

[212Mavguy]

Bingo!

 

The clue would have been "to assume is to make an ass out of you and me."

 

Sounds to me like the speakers are out of phase.

 

If I remember correctly either JBL or Altec all those years ago wired their speakers ass backwards and as such the speaker leads had to be reversed when matched with speakers of a different make.

 

The recones had the poles reversed at the connects, colors reversed.. I was thinking that it was due to the Altec having a lot of top end and being a high powered speaker that needed to be driven hard., I was getting ready to pull it and thought for giggles to reverse the leads on one of the speakers. Put it back up and first note I knew I had found it.

 

Learning from my mistake could help someone here sometime.

[bolero]

ah, I was going to guess the same thing!!

 

first thing I do with speakers is the battery test...9v battery on the terminals, watch which way the cone moves....that will tell you how the terminals are wired. I do it out of habit, at the main input jack after I put speakers into a cab too, just to make sure I didn't futz it up

 

all the speakers should move about 1/2" in the same dir, if they are all in phase

[Steiner]

ah, I was going to guess the same thing!!

 

first thing I do with speakers is the battery test...9v battery on the terminals, watch which way the cone moves....that will tell you how the terminals are wired. I do it out of habit, at the main input jack after I put speakers into a cab too, just to make sure I didn't futz it up

 

all the speakers should move about 1/2" in the same dir, if they are all in phase

+1

 

Learned this with multiple amps running together.

[212Mavguy]

...and multiple cabs from the same amp! Interestingly, some Fender amps and Dumbles for sure hook the speakers up with polarity reversed. Hot to the neg side.