Hi guys. I have a little project on the go with my HRDV 410 but which applies to most amplifiers if anyone is interested. One of the things which limits good sound at low levels is multiple speaker setups like mine. I use a Fryette PS-100 with my amp and the overall sound is absolutely superb at even moderate volumes, the tone remains the same as when I am at high levels while gigging. However, when I take it right down as during home late night practice, tone suffers as we all know.

One major reason is that, as level reduces the speakers eventually do not get driven outside of their linear excursion zone and add their own version of limiting which they are designed to work in. That's one of the differences between a hifi speaker and a guitar speaker. The hifi speaker must stay within the linear excursion zone which is wide by design, while the guitar speaker is meant for use outside of it so it is narrower by design. (For any fellow technoheads, that's also why Thiele Small parameters do not hold for guitar speakers.) If we reduce the speaker count then, for the same output power, more of the signal power will be handled by each speaker therefore driving each one further and keeping its tonal contribution. Reduce your speaker count and you drive each speakers harder thus allowing them to pass outside of the linear zone.

So I want to give myself the ability to select 1, 2 or 4 speakers to cover gigging and home use at down to very low levels to remove another issue with low level "life" in the sound. That's an easy switching issue and I have a PCB design to offer that. I can post a schematic of what is going on if anyone is at all interested. And yes, of course the Fryette will need to be changed between 8ohms for 1/4 speakers and 4ohms for only 2. One oddity which I have noticed is that the top two speakers are mounted closer together than the bottom ones. The horizontal pairs align on their right hand edge when viewed from the back but there is then a 1"/25mm difference in the spacings of top and bottom pairs. I can't see any reason as to why that should be so but it remains there to clearly see.

I now need to mount the PCB in the amp. I want to do it by using the central 4 speaker mounting screws as a base for a couple of brackets with the PCB mounted on them. Getting an accurate idea of the dimensions between the screws is doable but not too easy to be very accurate. It would be much better to know what Fender did with them in the first place. Does anyone have or know where I can get an accurate set of drawings of the cabinet with dimensions for the speaker mounts in the front panel? Failing that, is there available an accurate drawing of the 048832 10" Eminence speaker used in them?