I just finished my time alignment tool.
I built this heavy stand in order to keep in position 1" and 2" compression driver unit with dedicated horn. Basically it can be used with every midrange unit.
The purpose of this tool is to have an accurate control over time alignment and spatial position of the driver. It could be used on every large size bass speaker.
My purpose was to have the following settings:
- long stroke time alignment (delay)
- full adjustable feet, height, camber
- rotating tower
- translating slide left right.
Coupling: cork discs between driver unit and brass. Steel balls from a bearing, with dedicated brass support.
Materials: Brass, soft aluminum, 7075, stainless threaded bars M10. All screws stainless. I decided engine turning for the front plate.
I will engrave in the future vernier style graduated scale. A next improvement could be a remote controlled unit, with motors instead of knobs.
I'm traditionalist, I prefer manual action mechanisms.
I upload a couple of pictures of the unit, I don't know why but I can't use the automatic loader, I have to put one picture each time.
That's the link of my FB album, with full construction if someone is interested.
That's one fine tramming cradle. Is a bubble somewhere to regulate level, is tuning focused on the speaker alone? While the pic is a little oblique the engine turning is a nice touch. If this was in a shop window, no one would see homemade.
...we'll learn more by wandering than searching...
Thank you very much!
I have tubes with colored liquids, I'm undecided about fixing on the rest or use just as bubble level for the first implementation. I have also to print a label for the rotating turret, I'm still not able to engrave good lines, it's better to not destroy the surface
The best tuning options are:
- total height: useful to raise the distance between woofer and mid unit, I found interesting modifying this parameter to increase the voice and scene height.
-rotation and inclination useful above all with horns, aiming the listening position.
other minor adjustments are good in order to find the best position of the driver
-time alignment setting needs more way to be done, like a woofer or tweeter. The purpose is to adjust the distance between units. it helps accuracy and response. A pretty useful way is also to use a sound processor with active crossover, Dcx2496 for example has time alignment auto setting with microphone, pretty accurate also considering that's a PA unit.
I tried to give it a good finishing and above all, a good weight and stability.
I made also the horn with lathe. I tried a fast measurement without setting the scale, the result is pretty impressive compared to original data from RCF brand (first picture). The second picture is the response at 1m, from 1 to 20khz. Considering the size of the diaphragm 1,75" with 1" exit I think it's a great result to have the possibility to use the driver up to 10khz with only a little equalization. With original PA horn it would be terrible for hi fi use.
The sound is awesome, acurate, fast, and not tiring at all. I tried a fast 2 way active with my 15" onken bass enclosures. I'm not a fan of 2 ways, too many compromises, in my opinion a large 15" should operate from 20 to max 500hz, I prefer cut from 150 to 250hz. A fullrange or a true midrange unit gives better performance in listening ina a critical area of fq. But that's only my taste
Here is an engraving method.
Process might have a name...a description will do. Does head of your mill tilt 45° along X or Y?
A 4 flute end mill can produce a shallow 'scratch'. A little deeper will make something like an eyebrow or elongated arrow. You could index straight or round with just a little engineering, [AKA trial & error]. Use the knee for depth control, most quills deflect on their stop.
Far as speaker dynamics, literally had no clue of all those considerations or adjustments. My best speakers were stacked Advents' directly on floor in typical California raised frame house. The crawl space can be one heck of a resonant chamber. Top speaker was inverted for adjacent tweeters, floor and ceiling carried bass. Anyway, I still only know one tuning adjustment; TURN IT UP!
...we'll learn more by wandering than searching...
Very impressive build Stephano with impressive and excellent results on a PA amp! You've become quite the Audio Engineer on top of all your other mad skills. Most people barely consider the concepts of Time Alignment let alone acoustic lobing. It can make all the difference in the world if done properly and increase efficiency drastically.
Most mid to high end systems come with a dsp based acoustic optimizing algorithms, but if the speakers are not designed with these things in mind, all that does is balance the sound to the environment in some format or the other.
Thanks for sharing this build.
‘‘Always do right. This will gratify some people and astonish the rest.’’
Thank you all very much!
I know that's a pretty strange tool for the forum
It's uncommon to find people with the need of tuning a multi-way speaker system at home.
PJs you're right about time alignment and lobing, it's an undervalued concept, even in common production speaker. I'm trying to collect the best methods to make a system sound better.
Surely Dsp and sound processor with active crossover are powerful devices to play, my inexpensive dcx2496 has an autotune program (with microphone) pretty accurate for short and long delays, phase and correction. I think in a passive system it would be an hard job to solve the problem, above all if all drivers are inside the same cabinet.
Good idea Toolmaker about using the 45° mill head with a 4 flute end mill, I want to try!
I'm still working on plasma tweeter, I will modify soon the prototype, hoping the results will be enough this time, I want to try also a powerful oscillator with GU81 tube.
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