Optimus Prime

Hi ,

I've been playing around with different arrangements for open baffle, I thinks i've finally found what i wanted.

Here are a few pics - Optimus after the Radioshack Optimus Dipole Linaeum Tweeters, Prime because its the first speaker i've built.

Still have to sort out the mounting for the tweeter and tidy up and of course paint.

Measurements later.
 

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Quick update,

finished wireing and testing, pretty decent response but the mids aren't doing much below 500hz and ideally i'd like them to go down to 300 ish , the tweeter is what i expected it to be it's about as dipole a tweeter as i can get on my budget.

believe it or not the subs are actually really good - in a previous post i mentioned that they are 15" skytronics in room i'm getting flat to 30hz :) this is measured with a calibrated ecm800 mic.

the tweeter start to roll off around 2k and also around 18k but thats fine i cant hear past 17k (old enough to afford the speaker too old to appreciate them :rolleyes: )

so after a bit of tweeking im fairly happy although i think im going to try a different midrange to see the difference.

I wont post my measurements as im not completely happy with them yet.

I reckon it's time for a larger nude midrange.
 
hi twest

The linaeums start to roll off around 2.5 k strangely enough that was where the original 1st order crossover was before i removed it and set them up with digital crossovers.

I'd like to do some more tests on the tweeter but they do sing beautifully. there is a known issue with this tweeter in that it doesnt sound particularly good on axis but since i have my speakers equalised for the listening position i.e. about 35 degrees off axis they do sound very nice.

I want to do a fully 360 degrees 1m measurement to see what i'm getting from all sides, in theory i should be able to get close to perfect off axis performance.

My spl requirements are not particularly high i would reckon most of the time i'm listening at around 70db ish so excursion on all speakers is minimal. I can't see any movement of the woofers however i do plan on doing a max spl test and according to basta each pair in parallel per side should be able to do 100db @ 1m on the 100w per channel tk2050 amp.

The linaeums aren't particularly efficient but i'm driving them with a 30w per channel amp which is more than enough to make me cover my ears. Its a real shame that the linaeum style technology has all but died i think aurasound own the patent now but there has been no further research on the technology.

the mids do sound very good but i just have this feeling that i need to cross the woofer lower - maybe its just that something in my head is saying woofer don't run that high and i can't say there is any glaring issue to running them high.

I have a pair of very old 8 inch full rangers and ill try them out hopefully tonight and see what i get.
 

twest820

Member
2009-06-24 10:49 pm
Yes, do the measurements and see what the Linaeum's directvity and distortion look like. Without that you don't know where the TM cross should fall and hence can't size the mid for matching directivity and front to back wave symmetry. Eight is a nice size for a dipole mid but good front/rear symmetry usually requires a cross around the dipole peak, which is usually about 1.3kHz on a nude eight and rather demanding of the tweeter.