Our new baby

Sam,

If I can comment on your thoughts. These speakers are never going to compete with a conventional large PA, but not every application requires megawatts of power.

Tony and myself have exchanged a number of emails about this type of design since before Christmas. I forget who mentioned it first, but I had been interested because my wife wants a simple system that she can use when I am not about to set the equipment up. She has a friend who uses a Fishman solo performer system and asked if I could make something similar. From my point of view the system needed to amplify an acoustic guitar and vocals and would be used for a solo performer. Tony expressed an interest so one or two ideas were batted back and forth.

A broken leg before Christmas (I was discharged by the hospital last month) and an impending employment tribunal case in the New Year stopped any activity on my part, but Tony pressed ahead and ordered some drive units; so I get the benefit of listening to them before spending any money.

After measuring the speakers we listened to some acoustic material that I had recorded live. We know the 12” sub can pound with the best of them and were interested in how the two speakers integrated over the crossover region. The design has great promise for something so simple, with the ability to increase the number of drive units or stack cabinets if required.

We also discussed some further development ideas but you’ll need to watch this space regarding those. 

Uncle Steve here, to add a little to what the proud dad has already mentioned.

The set up and measurement that produced the above graph was done very quickly and could, depending on taste and time, be tweaked a little more. The amount of eq applied was minimal, Just three bands used. Two were very gentle with Qs of about 0.4. One to pull down a small lump centred around 2KHz and the other to compensate for a slight roll off below 400Hz. The only narrow bandwidth filter was to tame the peak at 10KHz. With no mics involved the original 10K peak might provide a little zing that some may like, but in live situations I always consider such peaks to be tempting fate re: feedback. For a mainly speech system the natural response could improve intelligibility.

For speed of set up (The cab was fitted with a 20mm threaded stand adapter which I didn’t have handy) the cab was placed on top of step ladders with the sub directly underneath. As such it represents closely a typical sub with pole mount positioning the little cab about 1.2m above the sub (single 12” bms reflex loaded)

The measurement mic was on axis between the two centre drive units. With this set up the phase alignment between the sub and mid/tops was achieved by simply flipping the polarity on the sub. No delay was used. Obviously for absolute phase on the kick the phase could be reversed on the mid/tops not the sub. That’s the thing with phase it is relative. The alignment without recourse to delay means that using a simple analogue crossover would be possible. With more time I would explore a variety of different cross-over slopes, mainly to look at how lower order filters would work with a view to using passive cross-overs. Last night was to give an idea how they worked with the 12” sub and the result was positive.

A quick,” that looks about 45 degrees off axis”, showed a gradual roll off in response above 8KHz.