Why bother?
I enjoy a technical challenge, and have a limited budget, and figure I can get better bang for buck building my own .

Besides, it's easier to spend money gradually, and avoid the other half  querying why I need to spend that much money on "just speakers".

I  also have random woodworking and other audio buddies, so I have access to routers, saws, mics, preamps, etc, etc. So tool budget is about zilch.

Why not build an existing design?
Basically, I'm stuck with a bunch of constraints that make my life difficult. The speakers need to sit in the bookshelf below, roughly where the current little JBLs sit.


Don't laugh too loudly at the massive 14" TV, heh, I listen to music more than I watch (i.e. squint at) TV.

So I'm stuck with speakers against the wall in the shelf, and have strict limits on size, e.g. max height approx 36cm (14"). Not exactly optimal, but I have little other options. Most of the designs out there are either too big, or are rear ported, or both.

In the begining....

I fiddled around with Boxy Cad, and came up with the following PDF, just to get some ideas on how big a vented two-way enclosure, I could reasonably squeeze into the space I had. The smallest hole in the baffle is the port. So it looks like I can squeeze a 6 1/2" mid-woofer on the front of a roughly 17L box.


Driver hunting...
I initially was looking at the Peerless 830883 and the Vifa XT25, until I discovered the local SEAS dealer (but more later). After hunting around the net, I realised the XT25 is a little bit of a beast to tame, but I thought I would go through the whole process on "paper" just to convince myself I had any clue at all.

The fun part

Given I had not bought anything, I used the manufacturers data and SPLtrace from the great FRD collection (assuming I'd use real measurements later down the track). I used unibox to actually do a "serious" design for the Peerless with a 16lL box, Fb 45Hz, and got the response.

I added the phase to the impedance from SPLtrace using FRC from the FRD collection.

Next, I played around with the baffle diffraction simulator to optimise the driver placement on a 14"x10" baffle, to minimise the ripple after the initial hump. I combined the SPL traces,  a guestimate of the manufacturer's measurement baffle and box size, my box and baffle response to get a response to work with in "Passive Crossover Designer".

I aimed for an LR4 roll-off at around 2.5K or above to keep the XT25 happy, but also to try keep the peerless down at 4K. I got the following response which in theory looks okay to me, given my experience :-)




The cross-over transfer functions are as follows, the woofer is a 3-order electrical with the stretched knee to act as BSC. The woofer roll-off helps here to get LR4. The XT-25 is actual 4-th order electical, as the XT25 rolls off much lower than the x-over frequency.



So after getting this far, I'm starting to feel a little more confident of starting.

Hmmm, things I missed.

• The simulations assume the accoustic centres are aligned, they won't be on a flat baffle, I need to factor that in. I've played a little with the Assymetric Response Pattern Estimator, will probably see what it says next time around.
• Room gain and gain from the bookshelf will change the BSC required (if any).
• The cross-over frequency is probably too high for the Peerless, I'd like to go lower (say 2K), so I'm thinking of switching the tweeter to a SEAS 27TDFC, which seems to go lower than the XT25 distortion-wise.

So, at this point I'm thinking I might survive the experience and be satisfied with the result. I'd be very happy to hear your opinions if you think otherwise :-)

Cheers, and thanks for reading this far.

    - Kevin