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Copyright 2009-15 © Troels Gravesen Click image to view large View driver specs:,, The Accuton has a new name: C50-8-044 and from private correspondence with Accuton, this is exactly the same driver. I always liked the and seeing the large ScanSpeak D3806/8200 dome getting out of stock here and there, John/US came in handy with a pair of Accuton C 2 44-8 inverted domes and a pair of HIQUPHON OWI tweeters as well, thus the SP44 project was on track. We could also call it Ekta-Accu, but SP44 it will be. Comparing SP44 to the Ekta is obvious and despite not having them side by side, I'm afraid the SP44 will beat the Ekta from a less coloured upper mid/lower treble. These ceramic domes are something special.

Now, what can the C44 do the D3806 can't? Well, it goes deeper and it goes higher and it has a remarkable flat response all up to 20 kHz where a serious cone break-up occurs. 20 kHz is really high and nothing to worry about in a 3-way system. The C44 is not particularly sensitive, around 85-86 dB/2.8 volts - but all the same a good match to the 18W/8531 driver that usually can be tuned to a system sensitivity of 86 dB/2. C Program To Calculate And Print Student Grade Using Structure. 8 volts. Looking at C44 horizontal dispersion, 6 kHz seems like a good starting point for crossing over to the tweeter, thus the C44 is really able to handle all of the important treble range, because we can go even lower compared to the D3806. From simulation 900 Hz looks ideal, but no guarantee this will also sonically make the best transition to the 18W midbass. Has to be tried.

Last but not least, the C44 has the most clean cumulative spectral decay I can remember, i.e. Distortion is really low. The 18W/8531 and OWI drivers are well known from numerous constructions, so not much to add here.

8531 still one of the best 6-7' midbass available and the OWI is the 3/4' dome where everything seems to have been done right! We need some 28-32 liter volume to please the 18W driver the best. From 32 liter we get an F3 = 39 Hz.

Not many 6-7' drivers can do this. The price to pay is sensitivity being on the low side. Vent tuning is a never ending topic and anything from 28-38 Hz may do depending on taste.

The higher we go, the more response we get in the 50-100 Hz range, where 28 Hz renders an almost flat response. 28 Hz is not all that easy to achieve as we need a long port in a 32 liter net volume cabinet. 70 x 290 mm - or 60 x 210 mm, the latter actually OK if we flare the vent to reduce port noise. So, why should you possibly try a design like this? Well, first of all enjoy the world of diy loudspeakers and enjoy something you'll have to pay at least 6,000-8,000 US $ for over the counter. Finished speakers with the current set-up come with serious price tags. Mostly thanks to the C44, this speaker will merciless tell you if you amps and musical sources are less than - well, really good.

I do not have a state of the art solid state power amp, but my tweaked Rotel RB981 at least has the power to make the 8531 bass drivers going. Do not run this speaker on low-wattage anything. The 8531 bass driver can go deep for the size like no other bass driver, but it likes lots of amperes to perform its best. I ran the SP44 from my 20 wpc AM amps and the sound is great - much better than the 100 wpc Rotel, but bass grip is lacking as soon as I crank up volume.