8 Audax AP130G2's...what to do?

[nubbins]

Hey guys and gals.


I've got 8 Audax AP130G2's at hand and trying to think of what to do with them.

I'm looking at a stereo pair of speakers but really confused about what sort of arrangement to go for. I have eyed up a pair of Vifa D27TG-45-06 as an accompliment and would like to not have to purchase any other drivers so it's down to the AP130G2's to run the mid-bass.

What kind of driver arrangement would be good for such drivers...TMMMM, MMTMM, TMMBB...list goes on...a little. :P



A couple of desing considerations:

Speakers will be used with a 50watt 6ohm Valve amp.
Speakers will be placed almost next to the walls due to small room.
Maximum foot print is 300x300mm but height isn't much of an issue (although I'd like to keep them under 150cm)
Choice of additional drivers limited to what I can get in the UK (I only know of Wilmslow, Maplin, CPC for driver choice).



Any input greatly appreciated.

Many Thanks.

[pinkmouse]

Well, the Vifas go quite low, so that gives you a lot of flexiblity in driver positioning. If you can afford four I would go for MMTTMM to keep the sensitivities balanced. You actually have quite a decent box volume with your required footprint, so you might well get a decent response down to about 50Hz.

You could have a look at the Pearless XLS drivers for bass, possibly side firing, that way you could keep the front baffle narrow, with those Audax speakers I think it would look better. You can get the XLS from BK Electronics.

How does that appeal?

[nubbins]

Thanks for your input PinkMouse.


The double tweet idea is tempting..but after a quick mockup I've almost settled on a max height of 130cm and using two tweets with regard to optimal listening height would put the end speaker height far above what I want.

With the 4 Audax units in a series-parallel wiring they would have a sensitivity of 93.9dB. The Vifa D27 is rated around 91dB so padding down the Audax units may not even be necessary after the crossover is factored in.

With the room being 7ft x 8ft and using a 50watt valve amp it's not necessary for super efficient speakers and I think an overall speaker rating of 91dB or there abouts would be quite adequate.


With regards to bass if I can get anywhere near 50Hz that'll be more than acceptable. If lower than that is needed I'll look at seperate bass enclosures utilising some sort of TL design....but that's another project for another time.


Here's a quickie I knocked up about what I've currently got stewing in my mind. MMTMM design, 18mm MDF construction.


Imagine that the whole thing can stand within a 300x300 box and the front baffle is 160mm wide. The front baffle is slanted mainly for aesthetics (speakers are less intimidating in the room this way) but I imagine it'll help align the drivers accoustical centers to some degree.





Bottom:


Top:



With this design and accounting for volume taken up by drivers and the use of 5cm spikes I calculate approximately 56liters of useable volume.


Tuned to ~56Hz I should be able to get roughly an F3 of just under 52Hz and F6 of 47Hz.



Initial crossover slated around 2400Hz from old notes but can go up to 5K as the Audax are pretty good up till there.




What do you think?


Thanks.

[pinkmouse]

Looks good!

Looks like my memory is still ok as well, with my guess of a 50Hz F3.

Just a quick thought, you might want to think about a 2 1/2 way with the outside drivers just set up for baffle step compensation. Though you mention close wall spacing, it doesn't hurt to be aware of the possibilty if needed.