Inflate the bladder just enough to slip the skate under the middle and then lower the speaker onto it. That means selecting the size, shape and the top surface of the skate you are going to use, to make sure that you can get the speaker on and off in a stable fashion. This works well on speakers the size and shape of the Stenheim A5 or the Wilson Sasha and has the benefit of leaving the spikes in situ and their adjustment intact.
Getting serious…
For really large and heavy speakers, there really is no substitute for heavy-duty casters. Fitting and removing them (nearly always) means replacing the spikes and can be time consuming, but once on wheels, you can take a speaker almost anywhere. Just make sure you check the height and width of any doorways and figure out how to traverse any steps or thresholds.
If your speaker has a standard thread size – like M8 or M10 for instance – you should have no trouble finding stock casters that will fit directly. Just make sure that the threaded posts are not too long or they won’t go in all the way and will likely bend as soon as the caster meets any kind of obstruction. I have sets of both M8 and M10, both with softly shod 70mm wheels that roll easily irrespective of the weight being carried. They have axle locks to render the speaker immobile, although the lever/friction locks you also see are just as effective. But the really important thing is that they are rated for 280kg per set of four, making them useable with any speaker I’m prepared to tackle on my own. Just don’t be tempted to skimp on the quality of the casters you purchase: Casters that collapse under the weight of your speakers are not just useless, they are potentially dangerous! Always buy casters that are load rated and don’t just assume that because they supported your last set of speakers they’ll with the new (inevitably bigger) ones…
Where things get complicated is with the increasing number of speakers that use much larger threads for their feet/spikes. Sonically it’s a smart move, offering greater stability, the option to run fine threads for more precise adjustment and a much greater contact area between footer/spike and speaker. In my specific scenario, the speaker I need to move is the Peak Consult Dragon Legacy – all of 225kg, with six feet each running on an M16/1 thread. You just try finding casters with an M16 thread and I can pretty much guarantee that the thread pitch is going to be 2mm, not one. Fortunately, as is increasingly the case, the Peak speakers use outriggers to offer greater stability. That means that the footers are located in through holes with top-caps to lock them off. Each outrigger is 15mm deep. The posts on my M10 casters have 30mm threads, so the solution here is fairly straightforward. The internal diameter of the through holes is 15mm, so I sourced some nylon spacers, 15mm in diameter and with a 10.4mm central bore. As luck would have it, I actually found them ready cut to 15mm height, but I could just as easily have (and have in the past) bought tubing with the correct dimensions and cut it to size. The spacer offers a nice, snug fit in the speaker outrigger and a play free fit to the casters’ threaded posts. Both the size and the material are important. You don’t want the spacer to wobble or shift in the threaded hole or against the caster. Too tight and you can’t get it onto the post of the caster or through the outrigger. The nylon is resilient enough to support the lateral force on the caster’s post, soft enough not to damage the internal thread on the outrigger. The Peaks have Teflon washers that sit under their top-caps and I left these in place (with the metal washer on top) to help protect the top surface of the outriggers – and to ensure secure clamping of the caster in the through hole, despite the use of a spacer. If the spacer is too long the caster might tilt under side loading, either marking the outrigger or in a worst-case scenario, allowing the speaker to tip.
Safety First!
Using the jack, it’s easy to replace the footers with the casters, but the order in which you do it matters. You are going to have to raise the outriggers (and thus the whole speaker) enough to present the threaded post on the caster in a near perpendicular attitude to its mounting hole.One trick here is to insert the caster’s threaded post from below, adding the spacer from above once the post is in place. The Narrow post will slip into place at a more acute angle than if the spacer is in place to start with – meaning you don’t need to lift the speaker quite so high. Depending on the size of the wheel and the height of the post, you could end up raising one face of the speaker significantly – resulting in a serious tilt. Which side you raise depends on the aspect ratio of the speaker’s footprint (how wide it is as opposed to how deep) and it’s weight distribution. Most (but not all) box speakers have most of their drivers on one side, which leads to an off-set centre of gravity. This is a particular issue if, like the Stenheim U2 or the Peak Consult Dragon Legacy, there are large drivers (with massive motor assemblies) located at the top of the enclosure. Tilting the speaker moves that mass a long way. Tilt it enough and there’s a real risk that the centre of gravity escapes the speaker’s footprint!
