First post: Questions regarding ALTEC 612 enclosure - DIY

[Tralalalala]

Hello !

I have now started to build my 612 DIY cabinets.

I have choosen 19mm MDF as material for these cabs.


Any other people out there that has built or heard Altec Duplex speakers in MDF cabinets ?

Reason for using MDF instead of Birch plywood :

1. Birch plywood in 19mm (3/4 inches) thickness is almost not possible to find where I live.
2. Birch plywood compared to MDF in price : you can triple the amount between the MDF and the birch plywood.

I will paint the cabinets battleship grey

Will add pictures later on !


- tralalalala

[Geekstar]

Battleship Gray is the only choice....Chicks love battleship gray, definitely...

After all of the work and expense you already invested, don't let a few Kroner influence your material choices.

Arguments can be made for MDF or plywood. I'd go with the ply. Might even be tempted to go with the 15mm. I find that Altecs sound good in somewhat live plywood boxes, although I had a pair of very heavy MDF Onkens that worked well.

I don't now how many people soaked in modern design practice will agree with me but, within limits, I say "Lively cabinet equals lively sound."

[Altec Best]

Hello !

I have now started to build my 612 DIY cabinets.

I have choosen 19mm MDF as material for these cabs.


Any other people out there that has built or heard Altec Duplex speakers in MDF cabinets ?

Reason for using MDF instead of Birch plywood :

1. Birch plywood in 19mm (3/4 inches) thickness is almost not possible to find where I live.
2. Birch plywood compared to MDF in price : you can triple the amount between the MDF and the birch plywood.

I will paint the cabinets battleship grey

Will add pictures later on !


- tralalalala

Your leaving out the Biggest consideration. Of What sounds the Best.. I also agree that (Baltic Birch) Plywood is what sounds the Best IMHO...

Good Luck with your project.

[GM]

Any other people out there that has built or heard Altec Duplex speakers in MDF cabinets ?

Yes.

?? MDF cabs have a low Fs due to their higher mass, damping, usually in the lower mids BW, so tend to ?suck the life out? of some speaker?s critical mids, especially low Qt ones like most Altecs.

If driven with a ~matching impedance or the driver has a high Qt though, the cab?s damping tends to reduce any under-damped driver ?ringing?.

19 mm BB or similar no-void ply OTOH tends to have a high enough Fs due to its extreme rigidity to be above the cab?s gain BW, so only minimal damping is required to keep the driver from exciting the cab, ergo any ?liveliness? in the response is all driver generated and most Altecs are known for their ?liveliness?.

A decent compromise is to make the baffle and top out of 19 mm no-void ply and the rest out of MDF and use some ply scraps to reinforce the MDF panels. If stand or wall mounted, then make the bottom out of ply also.

GM

[Tralalalala]

Hi again people

Thank you all for the response !

GM: thanks !
I will take into consideration your suggestion about building the front and top ( maybe the bottom also ) plates in 18 mm baltic birch x-finer.


Will keep you updated !


- tralalalala

[Tralalalala]

OK. Done some research: I will need one birch x-finer 18mm to do what GM suggested.

I have some questions:

1. frame ( blue surface on the first attached photo below ) : I have seen DIY 612 cabs with this type of construction before.

a good design ? ( will be built out of 18mm birch ply)



2. front frame ( made out of MDF ) mounted to the the front baffle with wood pins.

again - the design - will it work ?




all inputs will be appreciated !


- tralalalala

[GM]

1] Yes, ?window? bracing is excellent/quite popular for non-high aspect ratio cabs such as the 612. The main thing is to not make the cutouts any smaller than necessary and of course add back its bulk to maintain the design volume [net Vb] as it can be > the original bracing?s.

2] Don?t see why not.

GM

[Tralalalala]

Hello,

OK - so I have bought myself two plates of (1220mm X 2240mm) birch 18mm ply

This is the last drawing plans I will post in this thread ( just deleted previous drawing plans so I don?t make any confusion...) - These new drawings are the ones I will use to FINALLY build my own 612 cabs.

Regarding the frame : I have done some calculations : Thanks to GM for telling me about this in his last post.
the frame inside this DIY cab should be almost the same in volume ( a bit less ) as the construction inside the original 612C cabinet. - I also have to thank Altec Best for giving the dimensions of the original frame !

All measurements are in mm.

The inside volume of this DIY cab has exactly the same dimensions as the original 612 C cabinet.

































- tralalalala

[alancohen]

I think that if you are going to rear mount the driver frame, proper form would dictate beveling the hole, kind of like a mini horn.