Falling down with my fiberglass T39 and DR200

[Robby Hoinsky]

While neither of these are complete, I couldn't help but take them out for a listen yesterday. It was lovely autumn day in New England and with the sun setting over the mountains behind my yard, I couldn't think of any better way to enjoy it than with some bfm cabs. I ran some speaker cable from my studio to the yard. That 100' cable that annoys me at bar gigs finally came in handy. I ran them each off a channel of my xti 2000. The T39 is 18" wide with a 3012lf and the DR200 is a beta 8a with melded array and passive xover.

First a few pics.

The cabs:








The testing set up:





Then this happened. I foolishly was carrying the dr200 in the stand and stepped up a 2 ft step onto my patio and kerplat! the dr200 fell right on his face. I made a seasonally appropriate 'fall' joke then checked the damage. Surprisingly just a corner got a little dented and the tweeter array cracked. Probably fell about 7 or 8 feet. Good thing it is made of fiberglass and not yet finished, otherwise I would have been pissed!






You can't really evaluate it after that, but I tried anyway. Still sounded great even with the cracked array.



I set up a measurement mic and set the xover in the xti200 for the T39 for 24dB/oct LR at 40 hz and 24 db/oct LR at 100 Hz. The dr200 was set at hp of 100 Hz. I kept the levels moderate, but loud enough for a party. Outside, the DR200 was outrunning the T39 handily. Inside the dr200 was louder than I would ever want it, so the T39 kept up fine. After setting the xover and matching the level outside, i had planned to take some measurements, but ended up just putting some music on and listening. It sounded too good to play pink noise !

I know this has been said before, but the T39/dr200 combo sounds nice. Very nice. Outside it really opens up. It just has a clarity that is very open. I put some eq cuts at around 10 k and 16 k to tame the top end a bit. I wouldn't say that the sound is 'hifi' but it is not typical pa (and by that I mean overly bright). When I have the chance I will take some more measurements and eq it a bit more. I'll wait until I have another one built to really give it a thorough review though, consider this just a teaser. I have a pair of epoxy/fiberglass oTop 12"s in the works too.

Robby

[Benj Ross]

Thats great stuff Robby! What is the total weight for those cabs? Looking forward to more review.

Benj

[Gauss]

Once you add a diffuser, the highs will be much more natural.

[Robby Hoinsky]

Once you add a diffuser, the highs will be much more natural.

Will the hot spot be reduced too? I notice a strong hi frequency tinge dead center with the array.

[Robby Hoinsky]

Thats great stuff Robby! What is the total weight for those cabs? Looking forward to more review.

Benj

Still haven't weighed them. My business partner for the dj/karaoke business carried the T39 to the car on saturday and I believe his exact comment was 'This is like one of those Styrofoam movie props' and earlier while the bass was playing he said 'Screw my QSC, build me one of these'

I'd guess about 40 lbs for the T39 and 25 lbs for the dr200. The otop12's are even lighter.

Robby

[Gauss]

Yes, the primary purpose of the diffuser was to eliminate the hotspot, the taming of the highs before EQ was a bonus.

[SeisTres]

Once you add a diffuser, the highs will be much more natural.

Will the hot spot be reduced too? I notice a strong hi frequency tinge dead center with the array.

It will reduce to an acceptable level, IMO, but it is still present. Also, at the wider angles, they no longer sound harsh but the the drop off rate of the highs relative to the listening angle seems very natural after the diffuser.

[Zack Brock]

Once you add a diffuser, the highs will be much more natural.

Will the hot spot be reduced too? I notice a strong hi frequency tinge dead center with the array.

It will reduce to an acceptable level, IMO, but it is still present. Also, at the wider angles, they no longer sound harsh but the the drop off rate of the highs relative to the listening angle seems very natural after the diffuser.

+1 - I retrofitted a pair of Jack 10's with the melded array diffuser this weekend and noticed the same results being reported here. Very nice!

I used a 1/2" piece of CVPC with an outer diameter of 5/8", painted it black with Krylon, then used hot glue to glue it to the array. Was done in about five minutes.

[Drey Chennells]

nice to hear Robby. I particularly enjoyed the play by play snapshots of the kersplatting DR scenario lol. Glad to hear it held up!

[gdougherty]

I used a 1/2" piece of CVPC with an outer diameter of 5/8", painted it black with Krylon, then used hot glue to glue it to the array. Was done in about five minutes.

Thoughts on how the hot glue will hold up over time? I've got paint on both the array and the pipe I picked up and was thinking of doing a 1/2" dowel insert that I could screw into place from the top and bottom of the cabinet. Should work, but may be a real PITA to get installed exactly where I want it. Crazy glue or PVC cement would require stripping the paint off the contact points for sure.

[Monomer]

Damn, beat me to the punch on glassed t39's.


Any pictures of the build? Does it rattle/walk without that front brace on?


They both look spectacular!

[Robby Hoinsky]

Damn, beat me to the punch on glassed t39's.


Any pictures of the build? Does it rattle/walk without that front brace on?


They both look spectacular!

Thanks. It doesn't rattle or move at all. The T39 is very solid. I can hear some low midrange resonance in the mouth, like a 500 Hz (just guessing by ear) resonance, but it sounds more like a cavity resonance than a panel one. I'm going to install braces too, so I'll see how that changes it.

Check out the build thread here http://billfitzmaurice.info/forum/viewt ... 30&t=13429

and my photobucket: http://s80.photobucket.com/albums/j193/ ... /?start=40

Fiberglass is the way to go, so light, so strong. Glassing the panels one by one makes it just like building with wood, only lighter. I had no trouble bonding it with pl prem.

Robby

[LelandCrooks]

I wouldn't trust hot glue. Scrape the paint, use 1/2 CPVC and ABS or some similar plastic glue. I'd bet superglue would work for this application. I've played around with mounting these things quite a bit, and the best is cover a 1/4 of the pipe with glue along it's length, stick it in place, use masking tape to hold it while it dries. Otherwise it wants to bow because of the glue.

[tdogg]

I wouldn't trust hot glue. Scrape the paint, use 1/2 CPVC and ABS or some similar plastic glue. I'd bet superglue would work for this application. I've played around with mounting these things quite a bit, and the best is cover a 1/4 of the pipe with glue along it's length, stick it in place, use masking tape to hold it while it dries. Otherwise it wants to bow because of the glue.

i put all my piezo scraps into a jar and covered them with acetone. let it sit over night (do NOT tighten the cover, just set it on). stir it up the next day and you have some awesome ABS cement.

[Gauss]

I also used hot glue to put in the diffuser. It was an easy way to make sure that it followed the slight bend of the piezo array. I kept trying to figure out how to clamp it down while the glue dried. I figured that since I used hot glue to put the crossover in place, it would be strong enough for a light dowel (behind a grill). Plus, when I moved the coil in my crossover, it worked so well that I took up a layer of ply with the glue.