RS 40-1285D results

I posted a couple of months ago about finding a pair of NIB Realistic (Radio Shack) 40-1285Ds. After checking around the basement, I realized that a pair of flats I had cut for what was to be my first speaker project (BR's -w- FE167E's) would be a decent size sealed box for them. Based on some TS params GM had, they model to be -3db at 90 or so with a Q of about .8. As the boxes said they were designed for "Acoustic Suspension" I figured I might as well try it. I've attached a crummy pic. It's tough to get a pick of black things, as it throws the cameras metering for a loop.

Surprisingly, I'm fine with the quantity and quality of bass. They have no BSC, as I plan to use them in real bookshelf/against a wall situations. They're destined for my studio, as I really don't like the little old B&W mini monitors in there. They only get to 12K, but that's high enough for me and most music. A supertweeter sure wouldn't kill them. Surprisingly, the midrange is the weakest part. It's tight, gritty and uninvolving. I gave the raw drivers tons of break in. They entirely lack the Hemp/BIB's expansive beauty.

I wonder if part of the reason is the cabinet construction. I used 3/4" MDF. They are damped on the back, top and one side. The enclosures are finished in a couple coats of Hammerite (over primer.) (Do not use the Krylon Hammer finish by the way. It is a PITA. Get the real thing.) Sometime I'll make some adapter plates and mount them in the BIB's, as the specs indicate it might almost work. That would be eye opening.

pj
edit: forgot to add pic
 

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Here is an earlier thread where GM posted some measurments:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=109224&highlight=

I know mine could be considerably different, but for what I'm using them for I'm sure the reasonably sized sealed box is close enough. I got them installed in my studio tonight. They are a big improvement. I hear some whizzer peaky-ness. I'll try the 99 cent tweak when I have the chance.

pj
 
Greets!

If your camera has any manual adjustments, hold it close to the dark object and let it select a setting, then manually reset it to this when you're in position.

I was really impressed with this driver some time ago, so dug it out and perched it in the top lip of one of the Altecs with a winter coat draped over the horn mouth to limit the cavity resonances and proceeded to loosen it back up with a little Pink Floyd. My RTA crapped out on me a couple of years ago, so am limited to just a bass/treble control, but wound up with the bass at 9 o'clock and treble maxxed out, though I imagine someone with better HF hearing would dial it back a bit. Anyway, the point is that even without a baffle it needs minimal bass boost to sound ~tonally balanced, so needs plenty of space to 'breathe' or it begins getting congested/overly focussed and why I designed an acoustically large ML-TQWT for it. Note too that it needs the $0.98 tweak to help open it up and damp the whizzer's 'shout', but obviously it's never going to be a Lowther.

Anyway, I played full sets of Bill Evans, Linda Ronstadt, Chet Atkins, Norah Jones, Frank Sinatra among others and was once again impressed with its horn-like presentation, so yeah, it's a bit 'tight' and lacks a Jordan's unnaturally smooth (flat) response, but uninvolving? Clearly a difference in set up and/or personal preference.

GM
 
I know I could have gotten it right using the exposure compensation, but I would have had to choose a different background. Metering the dark speaker would have made the wall and ply background nasty bright. I also have a tough time getting it to focus and eliminating weird flash reflections. Basically, I was just too lazy to do it right. Proper light, background, and settings would have made it work fine. Thanks for the tip though. It's always best to meter the subject.

I think your "plenty of space to breath" comment is right on the mark. I liked them better in the thin cardboard OBs, even though the bass wasn't there. The midrange still wasn't perfect, but they sounded pretty good. I know I can tame the whizzer shout. I need to get out and buy some new foam weatherstrip. Little sealed boxes make great sense to me in terms of limiting excursion and cabinet colorations, but in practice it just isn't right. I think back to the difference between the Hemps in little sealed and BR enclosures versus the BIB's. Also, it's quite possible that the Taiwanese and Thai versions are different sounding beasts, is it not? I know you mentioned the Taiwan versions hitting 20K, and mine certainly don't come close. Perhaps the midrange differs too?

pj
 
Hmm, forgot this driver had multiple country vendors. Yeah, if the HF's not there, then the mids will definitely be perceived differently. I know the two 40-1354 variants have a completely different character. Oh well, bottom line is you tune a driver with no cab to find out how much loading they can handle, then design a cab to suit and typically use various forms of EQ to fix the rest as best you can and/or BW limit them and add a (super) tweeter. I don't recall the measured response of mine beyond the RTA showing adequate output to 20 kHz.

GM