Craig Sawyers

Well, I got a response from the P&G factory - the guy I've been dealing with is called Steve Collard. He checked their manufacturing system, and they have no record of ever having made any 20k or 50k audio taper RF15's. The practical limit of 10k is down to their manufacturing process. So no different alas to the response you guys have got via the US distributor.

If you want to have a look at mine (the workbench, that is ), there are links to pics on the woodworking types: old lumber thread

Your neck of the woods too? Been raining stair-rods here for the last two days and 10C; tomorrow supposed to be good though.

That sounds really great - good handmade workbenches are a real heirloom treasure. It is right and fitting that they should go down the generations. I've heard it said that a craftsman is only the custodian of a bench, and I hope your great grandfather's one follows that tradition through another generation at least.

This is really interesting. I'm not a bike rider (well, I was at one stage, but got fed up with how much it hurt falling off), but it is clear how a bike can be instrumented to measure and record a whole host of parameters that describe what the cyclist is doing - including power output. What there doesn't seem to be is an equivalent system for runners - in fact there is very little information on the typical power output of a runner. Anyone know if there is anything equivalent in the running world that I've missed?

Heh. My worst transgression was going to a 9am lecture after an all night drinking session (long story...). I sat plumb in front of the lecturer, fell flat asleep on the desk and snored loudly for the duration. You can bet that I was noticed! Massively amused the rest of the class.

Happens all over the world. The countryside we used to play in as kids and chill as teens first became an open cast coal mine, was infilled, and then a four lane road put through. Life sucks when they erase your childhood.

Probably a good idea - you've seen the movie Fatal Attraction?

During measurement of the bass, and curing the various buzzing and rattling in the earlier post on this, I found out why although the imaging in most of a female voice was perfect, sibillants were skewed towards one speaker. Very careful measurement revealed that although the response of both treble panels was very close in shape and extension, one of them was between 4 and 6dB lower in output. I'd got a pair of old-stock panels from One Thing Audio near Coventry UK to replace the burnt out ones originally in there. So I phoned them up. Yes, he said, that can happen - there is a progressive degradation of the coating on the mylar (perhaps through sunshine?) that leads to panels of different vintage having markedly different sensitivity. So they are building me a new pair of panels, built onto original stators. They are going to charge me the difference between the price of the old panels (

Have a good one, Kevin!

I've used these guys before Stainless Steel Fasteners, Microscrews, American Threaded Fasteners . They are extremely responsive, and cover all the head styles and lengths in both metric and US thread sizes. If you don't see what you want, get in touch with them - not everything they have is on the website. I'll be using them once I decide what I need specifically in US thread sizes for the T2. Craig

London Marathon day yesterday. Well actually a personal worst time, but I'm massively pleased with it. This was the first race I'd taken place in since a knee operation three years ago, so it was a real journey into the unknown. 58 minutes slower than my PB. The good news is that there was not so much as a single twinge from the knee. Plenty of twinges from elsewhere, of course! 19 miles onwards was the usual mind over body battle, where the body keeps telling you to stop this nonsense and stop hurting it, and you have to play all sorts of mind games to keep going. This clearly worked, because in spite of feeling really bad my five k split between 35k and 40k was my fastest at 27 minutes (you have a tag that registers your time every 5k, plus half way and at 26 miles). So flat mile splits by the clocks, flat 5k splits - pretty much mission accomplished. Feel like I've been beaten with a length of lead pipe today of course

Ditto Craig

The el cheapo WM61A (a couple of dollars/pounds each - in fact you buy ten of them and have plenty to play with) does not come with any calibration data, other than what is in the datasheet. In any case, measuring in a listening room renders any quantitative measurement meaningless, which is why it is appropriate to use a cost effective measurement method rather than a calibration standard mike. The best you can hope for is a subjective peer at the data and look for obvious problems. I was actually more interested in the bass end since I'm building subs, and at least doing the measurement identified a few rattly/buzzy problems (now cured).

Did some sine wave tests with the ESL57's in preparation for designing the active crossover to the dipole subs. Microphone was a modified Panasonic WM61A (Digikey plus many other places). Flat from 10Hz to 20kHz+ and pennies each. Mod is on Linkwitz's site. Anyway, even measured in-room at 1m they were astonishingly flat - within +/-5dB from 55Hz to 20kHz. Drops like a stone below 55Hz. But - quite a few buzzes and rattles from 300Hz and down. Turned out to be two things - wiring behind the signal transformer in contact with right hand bass panel dust cover, and the hessian mat stuck to the rear grille sagging into contact with the bass panels. Wiring was easily sorted out by unbolting the transformer, moving foward and pulling the wiring well out of the way (tucking down the side of the transformer). The hessian was more interesting. Originally it was stuck on with dobs of pitch/bitumen, presumably applied hot. In my case it has lost grip over the years at the top - hence the sag into the bass panels. I took the mats out of both speakers, carefully removing it from the bitumen dobs with a craft knife blade. I then hand washed them gently, since they are rather fragile (unbelievably filthy) and dried on the washing line and airing cupboard. Cleaned the rear grilles (unbelievably filthy). The hessian mat was then attached to the grille using spray carpet adhesive. I sprayed that onto the rear of the grille, and then applied the mat. That has sorted the problem a treat, and has the added benefit that now the mat is firmly stuck over its whole area onto the grille, it damps it nicely. Craig

Thanks guys! The interesting conundrum was that to build a bench, you need a bench. Problem is, the other bench is a metalworking bench, and the only way I could handle the size of timber was to take the metalwork vice off. So everything was constructed by making endless holding jigs to clamp the pieces to the surface of the bench while handplaning, routing, mortice chiselling etc. Plus the shed is 8 foot x 11 foot, into which is squeezed my machinery (on wheels so I can pull it out when needed). God knows how I managed to build the bench in that space from raw lumber. Needed careful planning for sure. Next project is to convert the garage into a half way decent sized shop - the shed is just too small

I don't think it is beech. These are some pictures of my modified Klausz bench. The top is constructed entirely out of European beech, with several coats of Danish oil, and the underframe is Sapele. Took quite a while to build it - 7 foot long 4" thick beech planks are exceptionally hefty to put through a planer/thicknesser, and then edge joint (with 1/2" plywood splines to locate and strengthen). Every type of joint going - blind, through wedged and fox wedged tenons, half blind and through dovetails, dowel and spline joints. All on a bigger scale than I have ever done them before. Finished just before Christmas 09. A joy to work on. Total weight including the vice hardware is (calculated) 350lbs. http://www.tech-enterprise.com/Saws/Benchfinished1.jpg http://www.tech-enterprise.com/Saws/Benchfinished2.jpg http://www.tech-enterprise.com/Saws/Benchfinished3.jpg http://www.tech-enterprise.com/Saws/Underframe.jpg Craig

Looks to me like ceramic lampshades with a speaker shoved in one end Not like those Transmission Audio beasts. Bewildering selection of products when you look at their site - but as pointed out the subs are truly outrageous. The Ultimate that is shown above costs $2m, needs 51kW of power amps and produces over 140dB - pretty close to a space rocket at launch and enough to make your ears bleed

I'm getting hot and sweaty about this damned thing already. Only comment - given the legendary resolution of the basic Curl design, the mute relay needs careful consideration.

More running stuff happening. Did 18 miles yesterday and basically siezed up once I'd finished. Forgot how painful it was when your calves go into spasm. Felt like crap all evening, walking around like a geriatric. But something must be going all right because this evening went out for a short run and ended up doing a very crisp 4 and felt fantastic. First time doing decent milage since a knee op three years ago it's holding out fine touch wood.

I haven't used or listened to supertweeters, so this thread is kind of interesting to me. I did however come across a reference in The Journal of Neurophysiology Vol. 83 No. 6 June 2000, pp. 3548-3558, entitled "Inaudible High-Frequency Sounds Affect Brain Activity: Hypersonic Effect". The web link is Inaudible High-Frequency Sounds Affect Brain Activity: Hypersonic Effect -- Oohashi et al. 83 (6): 3548 -- Journal of Neurophysiology . The full text link works perfectly. Basically these guys used Gamelan music, which has a lot of spectral content from 20kHz to 50kHz. They tested subjects with full range, up to 20kHz and just 20kHz to 50kHz. They used EEG and PET scanning. What they showed was that areas of the brain lit up specifically when the full bandwidth music was played - so something is happening when there is music coherent frequencies present outside the range of normal human hearing. In their conclusion they say that they have no idea what the actual mechanism is.

Daughter needed a new exhaust on her car, but ended up not having enough money with her. Of course, the outfit (Kwik-Fit in the UK) do not have the capability to take a credit card payment by me over the phone. Go figure. Some sort of head office secrity thing. So rather than driving to Oxford, it was a nice day so I ran in - good additional training for the London. Almost excatly 13 miles along the Thames path. Felt really good - the techs in Kwik-Fit treated me like some sort of hero when I trotted in - which was quite a ego boost. Fortunately my daughter gave me a lift back! She's now off to visit her brother, and then back to Uni.

After chickening out on a really long run on Sunday, got out yesterday on a route that I used to do years ago. Start at Eynesham, and pick up the Thames Path. Follow said path to Abingdon, then 3 miles further to home for 19.7 miles total. The Thames Path is a long distance path that starts (or finishes, depending on your point of view) at the Thames Barrier in London and goes all the way to the Source near Cirencester, 185 miles away. Not as the crow flies, or the car drives, because the Thames twists and turns and packs a lot of miles in to a much shorter distance. The state of the path on my route is either paved near Oxford, or like a skating rink with mud and lake-like puddles. Plus a 20mph wind. So pretty hard work. Which is my excuse for why the wheels came off pretty badly at 17 , and I had to phone my wife for rescue. Hydration was really an issue - it took four pints of fluid back home until I was half way topped up. Bit of a masochist really.

The crossover is somewhat naiive in the SW63. The dipole subs are rolled off at 18dB/oct and the ESL63's at 12dB/oct, which is never going to work. They need to be properly integrated with a +6dB/oct boost to compensate for dipole behaviour at long wavelength. They need a Linkwitz Transform to properly deal with the bottom end, and then a 2nd order L-R crossover with the ESL63. Yes that is a good version, references Linkwitz's treatment of dipole speakers including subs, but like most of Linkwitz's recommended drivers the ones used are no longer available. There is a good article on making the SW63 work properly here Homepage MT Audio Design and navigate through to Quad ESL tweaks. I've chatted by e-mail with this guy, and he knows his stuff. I've got the circuit schematic for the SW63 as delivered if anyone is interested.