What's to chat about?

[Seth]

I tried testors model cement when I put together my piezo arrays. Utter failure (like a cow jumping over a barbed wire fence...or is that an udder failure?) Ended up using PVC pipe cement, thickened up with my tweeter cutoffs just like Bill said in the plans, and it worked well. I put on an extra gloppy coat and laid in some of the long cutoff pieces on the backside which yielded a really rigid array. I think there may be a picture in my build thread somewhere.

I'm pretty sure it was your story I read that had me looking for alternatives in the first place. Was it regular PVC cement you used, or the ABS stuff Bruce linked to?

I'm seeing guys on YouTube make their own home brew goo, simply by melting trim scraps into a bit of Acetone, creating various viscosities from thick to thin. I'm looking for quick set up, a strong bond that wont snap, that's also able to be sanded and painted.

[Bryan Cox]

...they're gonna really crap themselves when they find out I'm running all four subs on ONE 450 watt @ 8 ohm amp.

What amp make/model are you going to use?

I'm using two of the the Behringer NX3000D; one for the OTops and the other for T39s. The data sheets says they produce 900 watts at 4 ohms. I assume that's around 500 watts at 8 ohms. Should be more than enough to reach the 50v (625 watt) limiter.

Never owned much Behringer stuff. I used to swear by Crest for subs and Crown for tops but decided I don't want to lift that heavy iron anymore. I haven't really put the NX3000D through its paces but what little I have done sounds great.

[Bruce Weldy]

I'm using two of the the Behringer NX3000D; one for the OTops and the other for T39s. The data sheets says they produce 900 watts at 4 ohms. I assume that's around 500 watts at 8 ohms. Should be more than enough to reach the 50v (625 watt) limiter.

Unfortunately, the Behringer specs are utter bullshit. I've run voltage checks on them before and the only way you'll get the advertised voltage is by running them into solid clip. The NX3000 is fine for the tops.....I even use the 4 channel one for monitors. But, not for your subs. Especially if you are running the premium drivers. To keep the same airflow, you could use a QSC GX7. It's rated 1000 watts at 4 Ohms and will handle 4 T39s with premium drivers. And it's not very heavy.

I use all Crown XLS for my mains and subs....but, I utilize one 1500 bridged for two subs.

[Seth]

I'm using two of the the Behringer NX3000D; one for the OTops and the other for T39s. The data sheets says they produce 900 watts at 4 ohms. I assume that's around 500 watts at 8 ohms. Should be more than enough to reach the 50v (625 watt) limiter.

Never owned much Behringer stuff. I used to swear by Crest for subs and Crown for tops but decided I don't want to lift that heavy iron anymore. I haven't really put the NX3000D through its paces but what little I have done sounds great.

I have an NU4-6000 in my collection of amplifiers. I'm not sure if there were any functional changes made between their NU and NX series. My intuition is telling me it's just a cosmetic change. Anyway, the 4-6000 is essentially two 3000's in one 2U chassis. Don't quote me on this, but my memory is telling me I was able to get 51v per channel before clipping and I had to bridge (and limit) to get my desired 2 x 60v channels out of it. My existing subs are rated 450 rms.

I like the amp, it's been reliable. And, for the most part, plenty of power without too much quirkiness. I also have one of their 1000's with built in DSP, which I have set up to run my dads practice/rehearsal PA consisting of a super cheepo ported 12" sub and Fender Passport tops. It's realistically probably not more than a couple hundred watts and isn't overflowing with headroom, but the DSP allows ample control over the signal and there's enough power for what he does. Thinking about upgrading his speakers to a couple SLAP's, maybe shorties, and a T39 slim.

I don't think the 3000 will put out and meet the full 55v potential of of the 3012LF in the T39. However my bet is, those amps will serve you pretty well. I'm not sure whether you'd actually miss the last 5v or not.

[himhimself]

himhimself wrote: ↑
Wed Jan 22, 2020 7:44 pm
I tried testors model cement when I put together my piezo arrays. Utter failure (like a cow jumping over a barbed wire fence...or is that an udder failure?) Ended up using PVC pipe cement, thickened up with my tweeter cutoffs just like Bill said in the plans, and it worked well. I put on an extra gloppy coat and laid in some of the long cutoff pieces on the backside which yielded a really rigid array. I think there may be a picture in my build thread somewhere. I'm pretty sure it was your story I read that had me looking for alternatives in the first place. Was it regular PVC cement you used, or the ABS stuff Bruce linked to?

I'm seeing guys on YouTube make their own home brew goo, simply by melting trim scraps into a bit of Acetone, creating various viscosities from thick to thin. I'm looking for quick set up, a strong bond that wont snap, that's also able to be sanded and painted.

It was just regular PVC cement for plumbing. The kind with the cotton ball on the wire attached to the underside of the lid. Downside was of course the time to set. That was my hope with the model cement - that I could just hold the pieces for a few seconds and they'd bond. I'm sure some of those other options would work, but with the jig to hold the piezos and time on my side, I just went with the gooey fortified stuff.

[Bill Fitzmaurice]

Ended up using PVC pipe cement, thickened up with my tweeter cutoffs just like Bill said in the plans, and it worked well.

Yep, if in doubt read the plans again, it's probably in there.

[Seth]

Ended up using PVC pipe cement, thickened up with my tweeter cutoffs just like Bill said in the plans, and it worked well.

Yep, if in doubt read the plans again, it's probably in there.

I read through the plans again.

All the DR's, Jacks, and standard Otop plans say to glue the array together with model airplane cement, and after the initial glue up to seal the joints with a couple coats of pvc pipe cement.

The Otop J Array plans say the PVC cement can be tinted with the piezo cutoffs, but still is only used after initial glue up with model airplane cement.

[Bill Fitzmaurice]

Model airplane cement always worked for me for the initial glue up, but the last time I did an array was at least ten years ago.

[Seth]

Yeah, it looks like it's no longer what it used to be. My guess is to keep kids from huffing the stuff. But, who knows what the real reason is. It's not rocket science, I'm sure I'll figure it out. Liking the black ABS cement option Bruce posted up. Lelands description is awfully compelling...

ABS Glue, medium bodied. Tough to find. Black, thick, glues pizeo tweeter arrays like nobody's business. No need to reinforce arrays. Put on another coat after about 30 minutes. Needs to set overnight. If you glob it on the front, it's black just like the tweeters!

[Bruce Weldy]

Yeah, it looks like it's no longer what it used to be. My guess is to keep kids from huffing the stuff. But, who knows what the real reason is. It's not rocket science, I'm sure I'll figure it out. Liking the black ABS cement option Bruce posted up. Lelands description is awfully compelling...

ABS Glue, medium bodied. Tough to find. Black, thick, glues pizeo tweeter arrays like nobody's business. No need to reinforce arrays. Put on another coat after about 30 minutes. Needs to set overnight. If you glob it on the front, it's black just like the tweeters!

That's what I used when I did mine....

[Seth]

That's what I used when I did mine....

Any comments on it's handling? Set up time, finish appearance, sand-ability, paint-ability?

[Bruce Weldy]

That's what I used when I did mine....

Any comments on it's handling? Set up time, finish appearance, sand-ability, paint-ability?

Setup time? Don't remember. Cut your piezos on a good jig and build 'em on a good jig and you don't need much setup time.

Didn't sand 'em. Didn't paint 'em. Put 'em behind a grill - just how all professional speakers should look.

[Seth]

Hahaha... nice

I appreciate it Bruce.

[Bryan Cox]

I'm using two of the the Behringer NX3000D; one for the OTops and the other for T39s. The data sheets says they produce 900 watts at 4 ohms. I assume that's around 500 watts at 8 ohms. Should be more than enough to reach the 50v (625 watt) limiter.

Unfortunately, the Behringer specs are utter bullshit. I've run voltage checks on them before and the only way you'll get the advertised voltage is by running them into solid clip. The NX3000 is fine for the tops.....I even use the 4 channel one for monitors. But, not for your subs. Especially if you are running the premium drivers. To keep the same airflow, you could use a QSC GX7. It's rated 1000 watts at 4 Ohms and will handle 4 T39s with premium drivers. And it's not very heavy.

I use all Crown XLS for my mains and subs....but, I utilize one 1500 bridged for two subs.

I've read in several places that Behringer severely overrates their output figures. I don't think I was planning to push the full 50v out of them because I've read on this forum several times that their war volume is nowhere near that. In one hand I'm hoping that the overrated power figures won't matter much; their decent amps and the DSP is easy to use. In the other, I'm not holding my breath. And if I do get near 50 volts and the T39s won't keep up with the Props then I'll build more T39s.

I don't think I'll hang my hat on Behringer amps. I'll probably go with the Crown XTIs in the future. But with no gigs, deploying for a year, then retiring and starting all over, I couldn't justify the Crown price tag.

With all that said, the first thing I'll do when I get a chance is test the output of the NX3000D. I'll happily share what I find. On that note, if I test for voltage with no load on an amp what does that do to the results? Or is voltage constant no matter what?

[Seth]

I'm not altogether convinced a Crown XLS1500 would outrun a Behringer NU/NX3000D. I think it would be a pretty close match.

Bruce, how many volts are you getting from your XLS1500's per channel & bridged? I was getting over 100v when I bridged the NU4-6000 channels with a 60hz sinewave.