Created on 05/29/2015 20:09.
Last updated on 17.02.2020 21:10.
Author: Gray Hamster.
There are two pieces of 30GD-2-8 isobaricom, bandpass of the 4th order: front chamber 27 liters, rear 33 liters, resonant phasic 64 Hz (diameter 77mm, length 18 cm, two pieces). Not lazily, we read history.
A colleague at work, Andrei, depicting mournful physics, said: I want a homemade subfuver in the car. And quietly added: to the ball. Khe-khe, I replied and remembered about two 30GD-2-8, it seems that is their name. Well, 8 ohms is not ours, you have to push two. Measured with one TS, oh, how sad. Even without counting, I realized that the trunk is over, there is no more of it – it’s a sub. He immediately twisted it face to face and measured the Thiel-Small parameters again. Wo, this is it. Figured in LspLab3, sort of like a bandpass coming out or a closed box. Even a small closed box comes out.
But greed won out, given the awful sensitivity of the heads, the bandpass got out. 6 dB per ball, and the basket sticking out of the box was embarrassing. Yes, and ZYa’s quality factor turns out to be a rapper, or an unhealthy rise to the bottom. Although an option. With FI, quiet horror.
Without spinning, I hummed 50 Hz for a couple of minutes to knead-warm up and measured TC, right as there are, two heads at once, a couple of times, to be sure that I was not deceived. Modeled again. Frequency response with a small stroke, the car will still bend a lot more, the GVZ is not small, but not large either. There was no long scratching in the forehead, even in LspCAD I did not go to model, why wrinkle my head, there are still no other heads, but SPL-greed shouts: LET’S GO! And so he did.
A 19mm thick laminate was filed with a circular saw, the ballerina screwed the holes. Well, everything is assembled: the walls are glued together with capitalist PVA, the bottle says that it is waterproof, no clamps were used, he just drove a couple of screws in each direction, which he left to live in a box. I am firmly convinced that screws as permanent fasteners are self-indulgence, glue rules! Only the top wall is removable, given the reliability of the heads. For its tightness, I smeared a thin layer of plasticine on the ends. Well, we made a little more.
Two pieces of cardboard pipe were cut off on the bass reflexes, on which the Oracal film was previously wound. I really like cardboard tubes: a bunch of diameters, it is easy to cut (I cut it either with a manual or stationary pipe cutter with a mental machine – very soulful, it just stinks a little). Well, to the ball! Also an important argument, right?
I twisted it, measured the ICH, yeah by, it turned out with the calculated phasics just below the setting, we don’t need such happiness, shortened it. I think the mistake was due to the fact that I incorrectly calculated the volume of the GG and the phasics. When calculating, I used a new especially complex technique “by eye”. According to this technique, three liters came out. In general, I cut it off for a couple of santas and that’s it.
I put the microphone into one of the tubes and measured it. As in the simulation picture, it is not even interesting. Everything. Yes, no vibration isolation was used: it will sit in the trunk of a sedan, and such a great honor is a great honor.
To assemble the subwoofer, we used: 30GD-2-8 – two pieces, domestic plasticine – one block, three squares of chipboard, half a meter of acoustic cable, a bit of glue, a piece of cardboard pipe. Time spent: one evening TS and calculate, the second evening twist-tune. It was not me who sawed. Everything except the chipboard – the ball. Only mushrooms in the forest are cheaper.
How does it play? He plays like that normally. Only subsonic would be good. He chooses a move quickly, there could be more. And so there are no complaints. I was even surprised that it was not buzzing at all, only smeared a little. Another undoubted plus of bandpass – well, you can’t pierce the diffuser with a screwdriver! Firewood, again, can be transported or potatoes. And what is more difficult to manufacture, I do not think. One extra wall does not make the weather. Difficulty setting up? It is not more complicated than FI, if it is of the 4th order.
The couple carried me away. Let’s draw the line. This story is not about a subwoofer. Why did I write all this? Yes, because I’m tired of reading on the forums: help! I want a sub on the Riga speakers dear to my heart, I don’t know how. Well, want to continue.
To read a book by Vinogradova (loudly, damn it, it says – a book, a brochure) – an hour, if a die-hard then a couple. Master LspLab, another hour. Wrinkle your forehead for a long time, measure TC, then one head, another hour. Cut the chipboard, if there is a machine for 5 minutes, if not, then from the straightness of the hands and the presence of a jigsaw-hacksaw.
Or, in the peak case, Uncle Vasya for a couple of beers. A can of glue, 30 screws, another hour, if there is a screwdriver or calluses and a couple of hours, the whole product is ready for use. Well, it will not work the first time, to hell with it, but experience will be gained.
In short, one should not shout “for help” half of life and engage in theorizing until retirement, but do it. Only if the GG is left, such as the same 30GD-2 or China-Poland, then no passports dance, even for estimates, only measurements of the T-C of the living head. Brand passports are closer to life and you can take risks without measuring, but there is a chance of making a mistake. And if you don’t want to be wrong, you can buy Infinity, or something else for real money, and see how to cut a box in your passport.
Or go and shop a ready-made subwoofer to buy. But this is not our path, is it? Really friend? Making a subwoofer with your own hands is our true path.
Good luck! More music!