First (not too) easy project for a two way bookshelf

[Giovanni1968]

Hello everybody,

glad having found this forum which looks rich of contents and skilled people so I couldn't skip the chance to pose a (long) question

I still own my old stereo system which I started building when I was 14 (loooong time ago) and which, partly, still works but having been updated in the recent few years there only are the JBL4311B (which will hopefully soon be standing onto decent stands), Sony CD-P X505ES CD player, the power amp being a twin KT88 chinese Aeron AP890 (bought almost new here on site off a friend as well as the preamp and turntable), preamp an AR SP9 and turntable the Gyrodec MKI (with a few tonearms and a step up which are gonna be sold hopefully).

A few years ago I saw a project on a forum called TNT-Audio and thought I might have given it a try as to have a second setup (I still own an Adcom pre and power amp which could still do well), I went straight in and bought the speakers, binding posts (is this correct to indicate the connectors in the back?) and some of the components, the project is not difficult at all but never had time to work onto it because of other priorities but I had to take the box with the speakers off of the storage and as such thought to give it a try provided I will ask a carpenter (is this how you call the artisans who work wood?) to cut the pieces to assemble the boxes.

I don't like the original project look at all and here we start with the questions:

- internal volume should be 14 liters, I'd like to have a non parallel box like this in the picture, is it going to badly affect sound quality or, marginally, increase by eliminating box resonances?

- placement of reflex port, I'd like it being hidden on the back of the box but this would force the placement of the speakers at a certain distance off the back wall, if I only had a couple feet off of the walls would it be better to move the port on the front rather than the back?

- speakers alignment wise, I won't bother too much about aligning the emission centers, too complicated and dunno how (and if) worth, would not even to attempt to cut the tweeter flange to move it closer to the woofer like in the original project but should they still be placed the closest to each other?

- wood wise, I would like them to look nice and would ask my man to look for walnut (noce in Italian) for the sides (to be curved shape on the exterior and straight into the interior) and top/bottom but which wood could I use for the front and rear panel to be darker and close to the look into the pic linked above (maybe applying a tint like I do on my doors at home would somehow work into darkening...)?

- crossover wise, I am trying and attach a picture of the components I have, I am pretty sure the inductances are not good, I remember that over their values to achieve the desired one I had to unwire a certain number of rounds but I forgot if I did it correct or not and as such would need to buy new ones, now, given I have to order these I'd like to know if the other (few) components (resistors and capacitors) are fine and how would you mount them, if on a PCB or glued on a small piece of wood?

I think this is way more than enough to start with, I know you will tell me not worth to throw so much money for such a case with the speakers I bought but if this works I might then in the future think of a better quality project so, please, be nice

Grazie a tutti

Giovanni

[system7]

I don't see much wrong with a monkey coffin, TBH. That is, a squarish box. It's the front baffle that should be kept constant and same as the model design, and that does most for the sound. If you change it, the bass flatness is affected.

But don't let me stop you going exotic...

Quite tricky efficient 6" polycone woofer that. Very awkward frequency response. See how it goes on the simple crossover, I suppose. You'd need quite a complicated LCR bass circuit to fix the big bump at 1.5kHz.

Crossovers can be built lots of ways. A simple one could be just hardwired and soldered on a bit of board. I sometimes do this sort of thing:



Inductors aren't expensive. You can buy a 2.2mH or 2.8mH ferrite for £5 in the UK, and either would do well enough here, I'd guess. Otherwise borrow a good multimeter from an electrician to measure inductance. It's the square of the number of turns, isn't it?

Port can be at front or back, but front is more versatile. Time alignment here is both drivers on flat baffle.

But have a go. Might be OK. Monitor Audio used to do designs like this with simple two element crossovers. The R852 or R952 IIRC.

They just stuck components on as with this R352. But make sure you like the sound before applying the hot glue!