vintageHIWATTconvention.com

Often in old pictures and videos of The Who, Pink Floyd etc. you see they stack their Hiwatt heads directly on top of eachother. Sometimes they're built into a specially made tight fitting rack case. Does this not block the air flow through the amps? It would seem the upper opening in the head case gets blocked, or at least almost. It does look very cool, and since I now have two of these amps and not enough space I though I'd give it a try. But I'm affraid it could damage the (lower of the two) amps..

pet0r wrote:...it could damage the (lower of the two) amps..

Good evening, pet0r...

So what makes you think that they weren't damaged..?
Two things come to mind... Firstly, the lower heads would not always be turned on (similarly, all the cabs were not always connected...)... Secondly, I reckon that the budget for the Floyd or Who was slightly more than my domestic budget allocated to this stuff. If it did blow up, it was replaced by a spare and fixed later, or simply replaced with new stuff. I wouldn't do to my guitars what Townsend did to his, either...
I would warn against 'stacking', unless you can mount a spacer between. Looks cool, perhaps, but I'd rather rely on the fog machine for the smoke, not my amps. If you're having space problems, you're not playing big enough stadiums...
Hope this helps...

As D said, it will not be a perfect situation. However, if you put a couple pieces of wood between the heads to space them a bit better, it will alleviate it somewhat. I'd use something like 2x2 (4x4 cm) at minimum, front to back, just inside the existing feet. Fortunately, theres long top and bottom vents on the back, and these naturally encourage airflow over the power tubes. Note also that some other tube amps (Fender is one example) have no top vent at all.

--mark

You're correct to question (convection) cooling when stacking heads. The modern "live in" road cases concern me for that very reason.

Look at old Who pics and you'll see wood blocking between Pete's heads, as mark mentioned. I'm sure that was a lesson learned the hard way .

And, as Dad3353 said, at least one of those was a spare head, ready to be jumped and fired up should another one fail.

I'm assuming this arrangement was preferable to having heads come crashing down from "normal" vibrations or when cabs were being abused (as in Pete's case).

Dave