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Our Guitar dept sent over this Blackstar HTV-412A 4-12” Marshall-looking cabinet, sloped top like the top cabinet in the rig. The back panel’s screws were all released but present. Pried it off, to find the speakers inside flapping about, only one mounted with 2 screws, two with one screw, one not mounted. T-nuts all over the cabinet, some trapped between grill cloth and baffle as well as captured by the spkr magnets, as well as the screws that were present. I pulled it all apart, setting the wiring and the connector panel aside, un-mounted the speakers and set them aside, to deal with the cabinet’s T-Nuts. Only a few of the 16 were still pressed into the wood.
All the T-nuts were present, and I used a small machinist vise to press in those that escaped the baffle, cutting into fresh wood. Only 12 of the 16 M5 x 25mm PH machine screws were present….all but two of the ext lock washers were gone. Added the missing screws & washers. After checking the four speakers, individually connected to my B & K 1023 Oscillator (directly drives spkrs) and found all are ok, I looked at the wiring and oriented the speakers accordingly on the baffles and mounted them.
I hadn’t looked at the speaker connector plate yet. Looking at it now, I see it offers two Stereo 8 ohm jacks, a Mono 16 ohm jack and Mono 4 ohm jack, all done with Cliff-style switching jacks. 4 wires connect to the jack PCB, two per spkr. I assumed these had to be 4 ohms speakers. Wrong. DCR on them is 5.6 ohms, indicating 8 ohm speakers.
With just the top two speakers connected, I got the impedance connections as called out by the plate. Normally, if it were 4 ohm spkrs, each pair you put in series, then let the jacks do the switching to yield a pair of 8 ohm loads, a 4 ohm or a 16 ohm mono load. I don’t see any way to do that with 8 ohm speakers. That yields 4 ohms, 4 ohms, 8 ohms and 2 ohms. Or Stereo 16 ohms, 32 ohms mono and 8 ohms mono. It’s always the simple stuff that messes with my head. Am I missing something here (besides expecting 4 ohm speakers x 4) ?
I checked the only other Blackstar cabinet here across the street, and it measured correctly.
All the T-nuts were present, and I used a small machinist vise to press in those that escaped the baffle, cutting into fresh wood. Only 12 of the 16 M5 x 25mm PH machine screws were present….all but two of the ext lock washers were gone. Added the missing screws & washers. After checking the four speakers, individually connected to my B & K 1023 Oscillator (directly drives spkrs) and found all are ok, I looked at the wiring and oriented the speakers accordingly on the baffles and mounted them.
I hadn’t looked at the speaker connector plate yet. Looking at it now, I see it offers two Stereo 8 ohm jacks, a Mono 16 ohm jack and Mono 4 ohm jack, all done with Cliff-style switching jacks. 4 wires connect to the jack PCB, two per spkr. I assumed these had to be 4 ohms speakers. Wrong. DCR on them is 5.6 ohms, indicating 8 ohm speakers.
With just the top two speakers connected, I got the impedance connections as called out by the plate. Normally, if it were 4 ohm spkrs, each pair you put in series, then let the jacks do the switching to yield a pair of 8 ohm loads, a 4 ohm or a 16 ohm mono load. I don’t see any way to do that with 8 ohm speakers. That yields 4 ohms, 4 ohms, 8 ohms and 2 ohms. Or Stereo 16 ohms, 32 ohms mono and 8 ohms mono. It’s always the simple stuff that messes with my head. Am I missing something here (besides expecting 4 ohm speakers x 4) ?
I checked the only other Blackstar cabinet here across the street, and it measured correctly.
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