Charles Jenkinson wrote:Ok, thank you. I've had a think about it, seems pretty straight forward without any cutting jigs to me (just using the rip fence AND keeping the blade low), using Anton's method of alternating the elements. On that score, I've just tried unscrewing an element from the plastic horn surround and the screws came out no probs, but the element seemed 'stuck' in the housing, and the wires from the cap didn't seem up to the job of pulling the element out. Is this typical and is there a way to 'pop them out'?
"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."
I found, say 1 in 5 were less inclined to leave the housing than the rest.
They all came out eventually, and worked afterwards...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel. Bunter's Audio and Lighting "like"s would be most appreciated...
Ok, great info., thank you. I thought I had better check out the piezos I bought to find out what type of cutting and assembly patterning I will need to do. I checked 4 out of the 40 that I have bought. All 4 had backs/caps that felt like they were glued on a portion of their perimeter. The backs came off with a little effort. I pulled the first two caps off and nothing they were connected to, via the wires, would move. I pulled the 3rd and there was a paper like tearing sound, so I stopped. On the 4th one, one of the soldered wires onto the piezo disc was soldered short, in length, so in pulling the back off, it ripped the piezo disc off the paper cone. Hey ho. So, how to move forward...
Am thinking: frequency sweep them individually to check function, cut/make up 32 that are good into the arrays, without turning the elements as per Antons method, so that means cutting through screws on the table saw, but it also means a higher blade setting. I think I'd rather cut with the blade lower, alternate the piezos and zigzag the wires on the back when soldering up....? Also, get some more piezos which will hopefully not be glued, for fixing broken elements in future.
I found the construction of the piezo elements to be interesting. The piezo disc vibrates the paper cone by simply being glued to it, i.e. the disc is not 'grounded' to anything. I've included the piccies of the one I broke - haven't properly looked at the wiring in an unbroken one to see if this one with odd soldering (i.e. the short wire is soldered on both sides of the disc) would actually work. ....Also, not the phone camera this time, better pics done on macro.
Attachments
2xJ12L (3012HO) switchable/melded
2xT30
Words&graphics - Audio&Acoustics - Hardware&DSP; 3 different paradigms.
Sounds like a plan to me, Charles. Before cutting you may want to mark all positives with a red dot. Makes it easier on the old brain to wire correctly once these are cut & glued in the proposed alternating pattern.
Ok. Well, I was thinking of checking polarity by doing a phase comparison test against a 'master' aswell. I've already bared the wires on a stereo cable, to power it up from the headphone socket of my lexicon alpha in/out usb device on the laptop. I mean, I can follow the simple +/- printed on the housing fairly easily but if + is - and vice versa that would screw my head up, so yes i agree to marking them.
P.S. I've just checked the other piezo's and they all have one wire, internally, that is soldered to both sides of the disc, on the '+ve' wire. The 'short wire' on the one i broke is because these same wires are fed through the +/- lugs and soldered on the outside of the lug, i.e. that wire was just pulled through more than any others I'd looked at.
2xJ12L (3012HO) switchable/melded
2xT30
Words&graphics - Audio&Acoustics - Hardware&DSP; 3 different paradigms.
A bit of an odd one tonight. I tried phase testing my piezos with the arrangement in the picture, using white noise. Overall, after doing about 9, I think I found that having to swap the wires caused confusion in the comparative sound level. It was very hard to distinguish which way round was louder. I was also convinced it was blowing windy outside, and when I tried a 2kHz sine wave and moved my head around, well, it was like sonic psychedelia. I think I'm gonna call it a day for 'phase testing' (according to a spanner wielding monkey: read mechanical engineer). The only real way to do it is the proper A/B switch arrangement (electrical engineer, I'll have you know) test set up so the comparative noise level increase or decrease is easier to discern at the flick of a switch. I have a feeling i might run out of steam sweep testing aswell (my ears run out after 14k, and around 9k is ear splitting) or is that more critical than phase testing....?
Attachments
2xJ12L (3012HO) switchable/melded
2xT30
Words&graphics - Audio&Acoustics - Hardware&DSP; 3 different paradigms.
No need to go loud. I had it hooked up to the earphone output of an old transistor radio playing softly while tuned between FM stations. Worked for me. I didn't do sweeps. Mine were Monacor tweets.
When I was level testing my pizzers, the pink noise made me nauseous after a little while. With that high-pitched static/whooshing noise, you get ear-fatigued very quickly. I did not do any polarity testing for mine. Just hooked the + to the + and - to the - to check that they were all working and playing at relatively the same volume. My arrays sound fine to me.
A note on cutting the pizzers and not cutting the barrels. You will find that the barrel parts and screws hit each other when gluing up the melded arrays. I wound up having to grind mine down. It is safer however, than having the table saw blade sticking up 3" and running the pizzer through.
No need to go loud. I had it hooked up to the earphone output of an old transistor radio playing softly while tuned between FM stations. Worked for me. I didn't do sweeps. Mine were Monacor tweets.
Hi Anton, I remembered your tester from some time ago when I was looking at this whole thing, and was inspired. I am ok with the mechanical bits and soldering, but struggle with understanding switches/switching to swap the wiring round on the slave piezo. Can I use my 3-way miniature dpdt switches I got for the half-on/full-on/off switching of the piezo arrays and do you have a sketch of how it is wired in this tester, to the terminals of the required switches? Sorry for such a lame question.
2xJ12L (3012HO) switchable/melded
2xT30
Words&graphics - Audio&Acoustics - Hardware&DSP; 3 different paradigms.
No worries Charles, it is a valid question indeed. You would need a DPDT for the phase switching. I have no time today or tomorrow, will see if I can draw something up later in the week. If someone else can do it and has time before then, please go ahead.
Man, you're quick! I was half thinking that it's a valid question, and half thinking 'Charles, you're a lazy sorry arse, sort your sh1t out'. Anyway, I typed 'how dpdt switches work' into google and the top result, some blokes site called music from outer space, explained it perfectly. I was hesitant as to what the question was, about switches.
2xJ12L (3012HO) switchable/melded
2xT30
Words&graphics - Audio&Acoustics - Hardware&DSP; 3 different paradigms.
I've bought 2 of these, then I don't need to break to phase test rig down afterwards to use the toggle switches on the jacks. I figure it's worth keeping the master piezo on one side or indeed fixed to the rig should any breakages occur in the future.
