The rationale behind this project is to reduce the number of my ScanSpeak 18W/nnnn stock drivers. I have some 10+ pairs of SS 18W/45-85nn drivers and cleaning the attic I found a box of pre-veneered MDF sheets made more than a year ago, ready cut for a 13 liter vented design, actually the 18W/8542-00 + SEAS 27TFFC, the classic compact studio monitor from a producer than shall remain nameless here.
The 18W/8542-00/27TFFC will be the final construction for sale, including the mahogany veneered cabinets seen here.

When the 18W/85nn drivers came about some 15 years ago, everybody was impressed from the design, the "ugly" looking carbon-paperpulp membranes and the huge magnets. The rather slim chassis allows a 145 cm^membrane area from an overall 177 mm diameter, quite impressive. All 18W/85nn have copper plated polepiece, symmetric drive, and a vented centre polepiece. The huge magnets and low Qt suggests drivers suitable for 10-15 liter cabs and a few small monitor designs were launched immediately after the release of the drivers. Since then numerous designs have been produced and often we see the classic 18W/8545-00 driver used in up to 24 liter vented or transmission line constructions despite really suited for smaller cabs. My Amish speakers are examples of this.
The 18W/8545-00 has an aluminium voice coil former, where the 18W/8545-K00 has a kapton voice coil former.

Why build small speakers when we can have bigger sound for the same money from a bigger cabinet? Well, the answer is simple: Because sometimes they must to be small due to how they will fit in with a given idea about how our living rooms are going to look. WAF is high from small speakers. Even if a slim floorstander doesn't not take more floor space compared to a mini on a stand, the WAF is higher for the latter. Not much we can do about it. Thus this range of Compact Studio Monitors. "Studio" because it started with the 8542 driver for studio use, by request from a Norwegian studio ingeneer. The result was the 8542/9500/9700 design, released last year. Not exactly a studio monitor suitable for placing on the mixing console. Sorry it took so long.

How small is small? Well, the W15CY001/OW1 is small, the Ellam a little bigger (10 litres) and delivers a bass performance leaving the W15 behind. When we add 2-3 litres we may have room for a 6-6½" driver, a significant increase in membrane area and we can get a decent bass response down to 50 Hz. Comparing a 18W/8545-00 to a 15W/8530-G00 in 13 litres and 10 litre respectively, we get this picture:

The 15W/8530K00 may produce a slightly more extended bass response, but at the expence of ~2 dB efficiency. Listening to the bass response from W15W/10 litres and the 18W/13 litres - side by side - leaves no doubt which driver is most comfortable in this area. I'm not talking about midrange quality here, only bass.

Selling kit#4 I had the question whether the kit would fit into an existing cabinet with tweeter placed center. Standard is what's seen on the drawing above. So, I made a test set-up from a 205 mm wide cabinet, tweeter placed center and I added fillets to make 75, 95 and 105 mm to top. Usually we have to avoid having the exact same distance to all three edges, so 105 mm is not recommended. What center placement does is rasing the response - a little - around 4 kHz. I still recommend 75 mm to top, but 95 mm will go too. Based on simulation, I don't think this is audible at all, so take your pick. The XT25TG is an easy driver.

Tweeter test set-up with a 15W filling the hole.