it_ITHomemade 2×9″ stereo cabinet for electric guitar with less than $ 100 video tutorial:
Hello everyone, at the end of the video tutorial concerning the modification that allows the use of external passive speakers with the Yamaha THR30 amplifier we are left with the promise that I would design, build and test some speakers ad hoc that respected the specifications that I consider fundamental for the outdoor use of the amp, that is ease of transport, sound performance in terms of fidelity and volume, and why not, a pleasant aesthetic. Mission accomplished, I present to you this realization that has exceeded all the most optimistic expectations of the initial project.
Let’s start by explaining the reasons that led to the choices:
OPEN BACK OR CLOSED CABINET?
Open, no doubt.
First because it allows us to reduce the volume and therefore the bulk and weight, in fact an open case has the sole purpose of providing physical support to the drivers.
Second, having no Vas constraints we will not be forced to use large quantities of sound-absorbing material with the exception of a few grams that we will insert in the two small compartments that will be created behind the rear bulkhead, this device will serve to avoid that any refractions of sound interfere with the freedom of movement of the cones. I decided to place a panel that partializes the rear opening to 50% with the aim of giving greater strength to the whole, in addition a central partition will prevent the two drivers from interfering with each other.
Third, open cabinet because if we find ourselves playing behind the cabinet we will not have to be content with listening to the sound reflected from the nearest surfaces but we will hear exactly as much as the speaker is propagating on the front, in essence it will behave like a monitor with only a negligible drop in higher frequencies, this more “circular” sound diffusion will also benefit any listener positioned outside the frontal plane.
Fourth, the open back cabinet is more rock!
For the construction of the homemade stereo cabinet for electric guitar I used 2 cm poplar plywood because I trusted the suggestion given to me by the carpenter who had built a quantity of it in his career as a speaker, I have not regretted it. case is light and resistant, rigid just the right and the wood is pleasant to handle and work. I covered it with black adhesive carpet, and protected with plastic corners, I added a handle with a circular stainless steel section, similar to that of the THR30, positioning it on the side so that we can place the amp above the speaker, as you may have noticed. the upper surface of the cabinet is exactly the same as the base of the THR30 to the advantage of the overall aesthetics.
WHICH SPEAKERS TO USE?
I must admit that the choice was not easy, going step by step I immediately discarded the 8 ohm drivers because while maintaining excellent reproduction fidelity they paid the price of a noticeable decrease in sound power at this point , thanks to the fact that the home studio audio market does not offer much of 4 ohm speakers and what little did not shine for its robustness, let’s remember that our speaker must be transported without the fear of damaging the speakers, I came in I help the hi-fi car market, 4 ohm is practically a standard, resistance to stresses too, you simply had to choose powerful, faithful, sensitive drivers with a frequency response as wide as possible and generous in size. The choice fell on a pair of mighty JBL STAGE2 9634 elliptical 6 ”x 9” speakers. What a goal guys, HARMAN KARDON, owner of the JBL brand, did an excellent job equipping these 3-ways with a simple but effective crossover placed on the same speaker frame, sizeable inductance in series with the copper-wound woofer and a good electrolytic in series with the tweeter, the care with which these speakers have been built, without any savings in terms of materials used almost out of place with their selling price, they could have asked for 3 times as much and it would have been a good buy anyway. Just to say, they also provide Thiele-Small parameters, which are the prerogative of drivers of a very different category. The sound they produce is already a show in itself, it is precise, clear, punctual and fast, without any smudging but here the good quality of the Yamaha amp is also due to the good quality of the Yamaha amp, the basses are portentous, if by chance you forget to play the guitar silencing the low E, in a chord where it should not be played, will be heard, and how. In practice, these speakers perform like a 20 cm diameter driver but with the lateral dimensions reduced to only 6 “allowing us to place them within the 42 cm width we have available so as not to exceed the size of the amplifier, at all. advantage of aesthetic proportions. I placed the speakers vertically because we are not interested in propagating the sound upwards or worse downwards, we are interested in having the sound “widen” horizontally to reach any audience at best.
A funny detail, at the end of the recording of the rehearsal, played with the electric guitar on very dynamic backing tracks, I immediately listened to check the result but, what a disappointment! It sounded like the sound produced by a shoe box and I immediately tried to identify the technical fail that caused that disaster, only to realize that these speakers have such a wide and dynamic frequency response that no laptop or mobile phone is able to faithfully reproduce. Listening to everything with my Mackie monitors the result was completely overturned, we had almost entered the hifi field despite the fact that the recording was made with a simple Samson Q2U microphone, I am putting the link in description of this microphone because in its field it is not knows rivals, has a digital USB interface, an analog XLR, an internal sound card and is good for practically everything from podcast to live so to speak.
One last tip, if you need to build this box because it is really successful and will not fail to give you satisfaction, of course the measurements are not written on the stone, thanks to the fact that it is an open back you can adapt them without problems for the use to which you want to use it that is not that of exclusive use with the YAMAHA THR30II amplifier.
Now I leave you to the tests, you will notice, by observing the spectrographic graph, that these speakers respond even below 36 Hz despite the specifications set as a limit of 50, what else to say if not spectacular for their quality / price ratio?
I’ll briefly summarize the material you need to make the homemade stereo cabinet for electric guitar:
- SPEAKERS JBL STAGE2 9634 elliptical 6 ”x 9”
- CABINET:
2 cm thick poplar plywood with the following measures:
1 Panel 420×330 mm for the front;
1 Panel 420×150 mm for the rear;
2 Panels 420×110 mm for the upper and lower surfaces;
3 panels 260×110 mm for the sides and for the central bulkhead.
You can find all this in a DIY shop that will also cut it for you.
The screws are 3.5 x 35 mm
- COVER
Black adhesive carpet very easy to place.
Carrying handle in inox.
- CONNECTIONS:
Neutrik NMJ2HF-S 1/4″ Panel Mount Mono Jack, Non-Switched, Solder Tabs.
If you want to avoid milling the housing hole, take the long size version.
1 Foot – Guitar Bass Instrument Cable x2
- MICROPHONE
Samson Technologies Q2U USB/XLR Dynamic Microphone Recording and Podcasting Pack (Includes Mic Clip, Desktop Stand, Windscreen and Cables).