The big difference was the 4x12 lead and bass cabinets for the IV heads. Those cabinets have two speaker jacks, each pair of 12 inch speakers are wired to each of the two jacks. and each jack was a 4 ohm load to the IV bass or lead heads. The IV bass and lead heads had two of the 130 power amps in the head and required two speaker cords to connect both amps to the cabinets. The lead IV and bass IV cabinets were also offered with Electo Voice SRO speakers as a option. Hope this helps clarify that series of amps and cabinets.
Don

There are only two companys that I have ever known to make production 4-15" cabs and that was Sunn and Acoustic.

Very interesting amp! I see it is a export model from the photo on the back that shows the speaker outputs and voltage requirements. You have what we call the Big K model.

My advise was based on the model previous to yours was labeled the same lVB and had two two channels, a 7 band graphic EQ, and two 130 watt rms power amps housed in the chassis and you had to use two speaker cables to the 4x12 speaker cabinet so each pair of speakers were driven by each internal amp. (think of it as a stereo amp that runs as a mono amp.)

Your model has two 1/4" speaker outs and what we would call XLR jacks. I am looking at my literature on your amp, and it states 300 watts RMS into 4 ohms. From your photo's it appears to be one power amp. The catalog shows your amp is sitting on a 2x15 cabinet. My literature does not show your cabinet. If your speakers are 16 ohms and wired in series, you would have a 4 ohm cabinet and there would be no need to add a second cabinet.

I left selling Kustoms in late 1979 and your cabinet may have came out after I left the music store.
The blank metal plate on the front panel was a cover plate that you could buy two options and plug into the amp. A 5 band rotary EQ and a patch panel to insert effects and choose what channel you wanted the effects to run to.

As far as any amp. If the amps states 200 watts into a 4 ohm load, if you have a 8 ohm load, the amp will not produce the stated 200 watts.

pleat

Wow, that's one massive power amp! I did a quick review of the photos, and here's my 2 cents.

The XLR jacks were added after it left the factory, definitely not original.

The photo shows that the current speakers are wired in series. You need to check the impedance of each of the individual speakers and see how you can wire the cabinet to take full advantage of the power of the head.

And Pleat erred in his last post, if all four 16 ohm speakers are wired in parallel they will equal 4 ohms, not series.

I've had both of my K-IV Bass and Lead heads opened and there is not two 5065 boards in them. There is a single massive board. This is the later 400 watt version with the voicing control. I found this out the hard way while playing Bass one day. I had just paid a couple bills getting this cab rated at 300 watt reconed and it played four songs and quit. Smoke rolling out of the ports told me the whole story. I went to the web site to find there were two versions of that amp and the first ones were 270 watt and the later versions with voicing control were 300 or 400 watts. These later IV's are very serious amps and wont have mercy on under rated speakers. Steve C

If those 15's are the black widow in your Peavy Cab theres no worry about blowing them, it should be good for at least 4 or 5 hundred watts. Most standard 15's are good for 100 to 150 watts with a 2 1/2 to 4" copper voice coil unless its got an aluminum voice coil I would say the lower of the two. I don't know what IV model you have and what kind of speakers your using so I couldn't say if your safe or not. Its just some issues to consider that I learnd the hard (expensive)way when dealing with the IV model with voicing control. They are truly a beast, I've run four 4X12 cabs with mine at one time. These babys are the bomb for outdoor gigs, but a little, wait! no! way over kill for indoors unless its like the TEXAS STATIUM !! "Just say'n" Steve C

PS: I have run it with two 8 ohm K215B cabs indoors with some success, but even at low volumes when my bass guitarist was really getting into those strings the headroom it has would step on everyone elses toes.

Your absolutly right "A whole lot warmer". Its good to have the headroom like that when you need it, thats my thinking. Its a bad thing to grab a good lead and just tear it up right and later hear "Man that was awesome but we couldn't hardly hear you out here. Like I said I have both voicing control models, the bass and the lead and both are awesome beasts. I used two 412 cabs on my lead head one time for an outdoors gig and my ears had a ring for a couple days afterwards,"now you dont get that kind of thing from just any amp". Your 2 black widows will be at minimum 300 watt rms each, thats 600 for the pair and thats good for 1000 watt peaks easy. At 300 or 400 watts rms you'll never come close to hurting those Black Widows. Your safe there. Steve C

PS: That low B on a five string bass will massage your feet right there on stage with that thing!!!!