'LGT' Construction Diary

[SunRa]

Hello,

I'm following this thread with most interest. I have to say that shinOBIWAN's progress is just fantastic. The reason I was that intersted (besides catching some woodworking and cabinet building tips ) was the fact that intrigued by AT's midrange linearity I was dreaming of using them in an open baffle with a higher crossing point (say more than 3Khz, a la Sonus Faber Stradivari). So the thread became more intersting when shinOBIWAN reported the great results with ob and higher crossing point. The higher cross point I think it's ok using just one mid, but in appolito configuration I guess the things will get somehow different.

Now, I was just wondering, why exactly the mid's would be best in a closed box as Mr. ScottG and holdnet seems to report? I always thought that the best advantage of open baffle is not only in bass but midrange too. And another problem, what is the radiation character of an OB compared to a closed box that favours the last one? I am somewhat intrigued mainly reading the last articles on linkwitlab and the older ones on musicandesign which seem to favor actualy a dipole configuration all the way to 22Khz by adding a rear tweeter. Of course dipole character and open baffle are quite diffent as jussi mentioned in the 4-way open baffle thread, but still...

I just hope I'm not just threadjacking here with my questions .

Best regards!

[Salas]

Originally posted by holdent
Getting past the "are ribbons the best" argument (a big step for me!), I'd like to add a caution to the mixed box/OB suggestions. I've never built one due to the difficulties optimizing them reported by others such as Tony Gee and his Modulus (ribbon & OB mid & sealed woofer - see http://www.humblehomemadehifi.com/Modulus.html). In the 6Moons review of the Bastanis Prometheus Mk II they also note set-up problems (http://www.6moons.com/audioreviews/b...rometheus.html).

I've built a number of fullrange, TQWT boxes, several BR and sealed designs, and most recently, two OBs. I think the sound from the OBs are the best I've heard (and, of course, they are remarkably easy to build!). But OBs, as ScottG points out, need to be pulled out from the wall. In my living room they really need to be at least 1.0 m out. I would also agree with what I think ScottG is suggesting -- OBs function best if the bass is OB and the midrange+tweeter aren't.

To me the most interesting combination to experiment with would be OB bass and cardioid mid-high.

[LineSource]

APRE tool 8" + 5" + ribbon WMTMW
300, 2000, 3rd order
time aligned baffle offsets

[LineSource]

APRE tool 8" + 5" + Dome WMTMW
300, 2000, 3rd order
time aligned baffle offsets

[LineSource]

What's running at my house
APRE Tool 3-way 90" ribbon linesource
15" woofer line array, 3" mid, 0.4" tweeter
80Hz, 3200Hz 3rd order

[Salas]

pictures?

[ShinOBIWAN]

Thanks for that Linesource, I'm working hard to lessen those problems but not at the expense of subjective quality.

[ShinOBIWAN]

Does anyone know what the thickest MDF available is?

Ideally looking 50mm(2") or even better, 75mm(3"). I've seen 36mm but is there anything thicker?

[ShinOBIWAN]

Kind of a weird question but does anyone know if contact cement reacts with 2 part or single part paints?

What I'm going to be doing is veneering over all these problematic joints that were created after cutting the angles in the baffles:



Without the veneer its near impossible to stop them from creeping back through the gloss finish - believe me I have tried!

So the plan is cover them up with a plain and stable veneer (0.6mm thick Beech), use contact cement to stick the veneer and then spray over as normal. But the thing that has me worried is will the contact cement react or be broken down by the chemicals in the paint? I hate to do all that work and then find the veneer starts to blemish at a later date.

This is the contact cement:

http://www.tooled-up.com/Product.asp?PID=2561

I guess the sensible thing to do is a test piece but if I could get a little insight from someone who's tried this then even better.

Thanks for any advice!

[pinkmouse]

Contact adhesives certainly react with various oil based finishes. I'd knock up a test piece and try it, that way you know for sure.