DIY subwoofer for 75 GDN

In order to do something with your own hands, it is necessary: ​​that these hands are present and that they are not sharpened, you yourself know why.

We will assume that both of these conditions are fulfilled in you. Well, so much the better, then I continue. What prompted me to this. From what, in fact, oak, so I decided to make this very subwoofer. So, question-questions. Complicated.

You can blame everything on what, as one lady said about my behavior, like it is unmotivated. As if I have nothing to do, I have a good Yamaha V496RDS receiver, good acoustics, JAMO floorstand fronts and a set from the center and two rear, called JBL HMX. The fronts give out good bass, like, what else is needed? I join here about the fact that there is no limit to perfection, a normal sub is from 6 tr. and above, and in order to decide on your hard-earned money to buy it, you need at least these 6 tr. to have on hand.

And this, in general, is already a luxury that is impermissible for me in the light of my recent purchases. However, everywhere in the magazines they impudently write, not 5, but 5.1, hinting that the right guys must have this “Stradivarius drum”, aka 0.1, aka a subwoofer. And like, if they don’t have such a device at home, then they are not the right guys at all, but big-eared fuckers.

Somehow a new Russian comes to an antique store, well, buy something, stand out in front of the lads. He approaches the sellers – they say so and so, I will not stand for the price. They quickly grasped the topic, took out a drum from the closet and said:
– Here you are. This drum was made by Stradivari himself.
– Yah!
– Exactly, exactly. Our company is respectable and does not fool customers.
Well, HP, of course, bought it, brought it home, put it in the most prominent place. Once he invited guests to his place. Well, during the buffet he says:
– But my pride is the drum that Stradivari himself made.
The gang will all laugh at HP:
– Well, you also screwed up. Stradivarius did violins!
HP immediately went to that store. Half an hour later he returns and with a satisfied look declares:
– Eh you, damn it. You don’t know the history at all. Stradivari made violins for suckers, and for NORMAL KIDS he made DRUMS!

Thus, each owner of a set of five normal columns gradually comes to the idea of ​​his own inferiority, without the presence of the sixth column. Trips to the store begin, conversations with sellers, which are of different types.

Some of them, looking at your frayed jeans, say that an inexpensive active yamaha is the most optimal solution for you, others say that the right sub, which makes your breath freeze, start at $ 300 and more, and everything that is cheaper is full bullshit for those who have cheap bookshelf Soviet acoustics. In general, one can agree with each of them.

Two thoughts appear. The first is why buy not the best thing, for a lot of money. The second – the toad chokes to lay out $ 300 for some kind of low-frequency speaker, when for these bucks I can cut the list of my planned priority purchases by a third.

From two thoughts, a third is obtained – why is everything so expensive.

If you develop the last thought, then it will turn out something like this: why some kind of plywood box with one speaker and an amplifier, which is written not to amplify frequencies above 200Hz and can be a crossover filter, is it worth such crazy grandmothers? I can understand why conventional acoustics are expensive. There is a case that is cleverly designed so that all the speakers sound good, which also cost a lot of money because of their characteristics.

And all this garbage has to play frequencies from 30 to 20,000 Hz. Then various clever people test it and write in their magazines, they say, in this column for $ 600 there is not enough emphasis, that for $ 550 does not emphasize something there, but this one for $ 900 and accents everything has and emphasizes , all you need.

You read such articles, and you think that they are probably smart guys, they hear everything, understand everything, well done, in a word. Considering that there are probably no obvious sound defects in acoustics for $ 500, we can assume that they must have ears like an elephant in order to hear all this.

Finishing the preface … 🙂

Rough work, box construction

As for the subs, they have such a narrow frequency range that the requirements for the frequency response of the speaker are not so high, and the design should not be so complicated that it could not be repeated. What difficulties can be. Well, first of all, you need to find a subwoofer. This is the least of all problems.

There is such a 75GDN, which is very popular because of its good characteristics and low price. Maniacs can buy some kind of imported copy for 100 bucks, but is there any point in overpaying if the difference is most likely not to be felt.

The main problems can be when choosing and calculating the design of the box for this speaker. But here the excellent program JBL SpeakerShop comes to the rescue. It contains many ready-made examples of different types of acoustic design for subwoofers. Download the program, select the type of box. I chose Bandpass 6A. This is such a box.

The picture is taken from the Internet from an article about a sub for 75GDN. I only have slightly different sizes.

I stumbled upon a thread in the forum at www.ixbt.com, just about building a sub, this is almost what I need. I recalculated the dimensions again, it seems like what I was going to do, just a little more.

When I sawed off the first blank of the left wall, I realized that the box would turn out to be not at all small, but there was nothing to do, everything was marked out. The final dimensions are as follows:

• Height 640mm
• Length 410mm
• Width 280mm
• Height of the upper volume 160mm
• Upper bass reflex length 70mm (diameter 70mm)
• Bottom bass reflex length 240mm (diameter 70mm)

The pieces of chipboard were 20 mm thick, I thought that the thickness was the most suitable. I sawed everything with an ordinary hacksaw on wood, and by the time all the walls were ready I was really bored. At the same time I got calluses on my hands from a hacksaw.

Due to the fact that I initially took 2 days to make the sub, all weekend I was screwing the screws into the walls, collecting the box. By the end of Sunday, the box was ready and secured with screws around the perimeter.

Further, all week, I thought over the assembly order. It turned out that the top wall will be the last one, the back one will be the last but one. Without installing these walls, it was possible to work normally with the case inside, which I did the next weekend.

I missed all the joints with Olga Savalova’s favorite glue – “Moment” and installed the inner wall in the slot for the 75GDN speaker, which I bought on the market for 1000r. The wall was properly secured by tightening a bunch of screws from the outside.

Having tried on the rest of the walls again, I began to glue the inner surface of the box with 6 mm thick expanded polypropylene. For this I used the same “Moment”. I let each layer dry under the load.

To cut round holes in the back wall, I had to use a special drill bit, which did its job well and soon I had a back wall with two perfectly round holes with even …