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fEARful™ Part Ten (10)

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The IPR DSP 3000 are now shipping; the IPR DSP 4500 ship in mid April. The 3000 will run mono, but it's not clear if the 4500 will.

From everything I've gleaned, the 4500 and 6K won't run bridged.

The good news is that you probably won't want to run it bridged:

4500 - 825w/8ohms; 1500w/4; 2250w/2
 
From everything I've gleaned, the 4500 and 6K won't run bridged.

The good news is that you probably won't want to run it bridged:

4500 - 825w/8ohms; 1500w/4; 2250w/2

That's a fEarful amount of power. Can't really imagine needing that much, certainly not more. I'm on the fence between getting the 3000 DSP now or waiting for the 4500. Let us know how your 3000 works out; are you using any sort of outboard hi pass filter on your rig?
 
Thanks, man!

Funny you mention it, I have a 3K arriving supposedly in the next half hour from UPS...Cooler heads prevailed...er...or sort of prevailed...and I decided to try the 3K. Its available now, and for $399 with no tax and no shipping. If I decide it's waaaay overkill, I'll keep it as a PA use only amp. If its underkill (which is probably not going to happen), I'll sell it and bump up. If the DSP versions end up being all that, I'll consider that at a later point too. I figure its a win-win-win situation. I'll let you know how it goes.


Let me know how it works out. I was reading up on it, the crossover function it has, does that mean you can dial in one range for the woofer for one channel, and dial in higher range for the mid driver for the other channel?
 
Well I finally got around to putting grills on my fEARfuls. They are aluminum grills with 1/4" holes and have a 58% open area. I'm not sure if I like them yet. I can't see as much of the blue baffle as I would like. I might switch to an expanded metal grill.

Invalid Link Removed
 
Well I finally got around to putting grills on my fEARfuls. They are aluminum grills with 1/4" holes and have a 58% open area. I'm not sure if I like them yet. I can't see as much of the blue baffle as I would like. I might switch to an expanded metal grill.

Where'd you pick them up? I've been looking for aluminum grilles just like that. Do they come in black?

Robby
 
I work for a home builder and the company that supplies our structural steel carries sheets of perforated aluminum. The pieces were covered in oil and dirt. So I cleaned them up and bolted them on. I might paint them the color of my baffles. I payed $50 for the two of them.

If you have a local steel supplier give them a call and see what they carry. If you're not sure call a couple of home builders and see who supplies their structural steel. We have two suppliers in my general area.

Wade
 
That's a fEarful amount of power. Can't really imagine needing that much, certainly not more. I'm on the fence between getting the 3000 DSP now or waiting for the 4500. Let us know how your 3000 works out; are you using any sort of outboard hi pass filter on your rig?

I would be very very careful when running an amp as powerful as this with bass cabs. With that amount of headroom, you'd certainly want to think about a hi-pass in your chain and you'd want to be a light touch on the power amp's attenuators. You're looking at the 700-850 range per cab if you're running either one channel at 4 ohms or one 8 ohm cab per channel. I seriously considered this amp, but was strongly cautioned to consider carefully. In the end, I decided if I wanted REALLY big power, I could bridge the IPR3000 at roughly 3kw, and I could my whole rig off of either one or both sides as needed.

This amp for me will double for PA duties as needed, when we show up to a gig and find a practice PA for the front end, or no monitors, or both. On a loud stage, it may double as keyboards on one channel and me on the other...or it might be a side fill amp for the drum riser. If its a really dodgy situation, we can use it for both small front end and monitors and I'll just use my LMII.

I'm going to see if I can get away without a high pass, but it's definitely a back burner option for me right now. The fEARful cabs are less prone to the kind of failures that many speakers suffer from the sub-30hz set, but its not immune.

Let me know how it works out. I was reading up on it, the crossover function it has, does that mean you can dial in one range for the woofer for one channel, and dial in higher range for the mid driver for the other channel?

Unfortunately, due to our singer being on 'African time' he didn't show up at my house until over an hour after practice began, and of course it takes 20 minutes from my house...so running late, my IPR sat in its cardboard box in the trunk of my car, along with my Kern preamp. :( I saw this coming, so swung my shoulder bag full of LMII over my arm and used that for the evening. Man, even though I've only used the Kern once, I REALLY missed it.

The crossover on the IPR isn't really suited to fEARful purposes, more for PA usage. The 100hz crossover is too low to effectively split signal for these cabs. You'd want a dedicated crossover unit that you could program, or you could wait for the IPR-DSP amps to come out and have that function built in. As it is, that switch is designed to allow subwoofer use on one or both of the sides, or to high pass at 100hz if you're driving the non-sub parts of your PA.
 
I would be very very careful when running an amp as powerful as this with bass cabs. With that amount of headroom, you'd certainly want to think about a hi-pass in your chain and you'd want to be a light touch on the power amp's attenuators. You're looking at the 700-850 range per cab if you're running either one channel at 4 ohms or one 8 ohm cab per channel. I seriously considered this amp, but was strongly cautioned to consider carefully. In the end, I decided if I wanted REALLY big power, I could bridge the IPR3000 at roughly 3kw, and I could my whole rig off of either one or both sides as needed.

Exactly. The DSP provides the hi pass filter; I would think 33hz would be a good starting point. I believe Peavey recommends setting the attenuators up all the way, and controlling the output from the pre.

I prefer to have lots of power in reserve, and an amp not even close to maxxed out. The loudness of the cabs would be the main governor in this situation; can't see being in an environment in which I need the cabs to be louder than they they can safely do, and doubt that I'd be able to tolerate speaker damaging volume as well.

I'm also thinking that the 3000 would be just fine for my purposes, but I'm waiting to hear your experience before I make any decision. Hope it kicks butt!
 
Matt916,

If you worked from the current plan - with 1.5" bracing "sticks" - I strongly suggest you cut new bracing WITHOUT any holes drilled in it. That just isn't going to do the job. Other than that, what you cut looks really NICE.

Thanks for the input. Yeah, I don't know what I thinking at the time. I was recently helping my son reduce weight in his CO2 racing car for science class using some forstner bits. The forstner set was still out on the workbench. I just had to open them and admire them once more and then next thing you know I had holes in my braces. :rollno:

Unfortunately I woke up early Sunday and started assembly before reading the forums. I got the whole thing assembled and even managed to get the crossovers built. Man that day flew by.

I ended up using Titebond III for the wood joints and then ran a bead of PL along all the seams. The T-nuts were installed on the baffle ahead of time and have some PL on them to help keep them from falling out. The bolt holes were really close to the cutouts so one tooth of the T-nut protrudes into the cutout. There's plenty of room to clear the drivers though. I glued all the bracing on first. I've built furniture in the past so I went for the mad dash to glue up the panels for final assembly.

Here's some assembly pics:
Glued and Clamped
Clamped.jpg

I also added extra bracing to the bottom panel. That panel seemed too big not to have any.

Clamps Removed
FinalGlue.jpg


Low/Mid Crossover
LowMidCrossover.jpg


HF Crossover
HFCrossover.jpg


Greenboy,
Your comments really got me worried. So I decided to use my engineering skills to run some mechanical tests and calculations.

I made two more brace pieces, each 10" long, one with holes and one without. I tested them at work using tensile/compression equipment. I ran a flex test with a 7.5" span. The full sample deflected 0.021" with 225 lb load (the highest load cell available was rated to 225 lb). The swiss cheese sample deflected 0.052" with 225 lb load.

I used that information to perform some deflection calculations for some possible modifications to my foobar. Assuming that the plywood strength is the same perpendicular to the plys as it is in the plane of the plys (which it isn't), then I could get the same deflection as the spec'd braces if I glued a 0.25" x 0.75" flange to the top of my swiss cheese brace.

I decided to glue a 0.5" x 1.0" flange instead to account for the fact that the plywood is weaker perpendicular to the plys. I also glued the same flange to my test sample so I can run a flex test to compare to my calculations and the correct brace. I have to wait until Wednesday to give the glue enough time to cure before I test it.

Extra Bracing Support
ExtraBracing.jpg

I put a dado on the bottom of the flange for extra gluing surface. No room for clamps so cable ties will have to do (I have thousands of these, my company makes them).
 
The crossover on the IPR isn't really suited to fEARful purposes, more for PA usage. The 100hz crossover is too low to effectively split signal for these cabs. You'd want a dedicated crossover unit that you could program, or you could wait for the IPR-DSP amps to come out and have that function built in. As it is, that switch is designed to allow subwoofer use on one or both of the sides, or to high pass at 100hz if you're driving the non-sub parts of your PA.

Thanks BurningSkies. My Peavey Pre has a crossover on it, and I've also got a Rane AC22 active crossover. Just trying to see what all my options are. The price on the standard 3000 seems attractive. Since my bi-amp plan is to run a ss amp for the woofers and a tube amp on the midrange, the added DSP feature of the new model may be wasted money for my purposes. Otherwise, it seems like an SWR, QSC, or Crown will suffice. It will most likely come down to price and availability.
 
I ended up using Titebond III for the wood joints and then ran a bead of PL along all the seams.
PL used like this will provide no strength, at all. Nothing wrong with using it as caulking except the price. Two big advantages to using pl are strength and expansion. The Titebond is fine glue, but as a butt joint glue it's not as good as the pl. In a biscuit or dadoed cab where you have additional surface area, no biggie, as long as you get it air tight.


The T-nuts were installed on the baffle ahead of time and have some PL on them to help keep them from falling out.

Use epoxy. Pl does not adhere to metal well. It needs porosity. If you should pull hard enough to spin the nut the pl won't help. Epoxy makes them virtually spin proof.
 
hmmm.. I just realized I put the port divider in without putting those 3 holes in it that are in the plans. Is there any reason outside of weight for those? I'm not really concerned about weight with the 12/6

I made the same mistake with my 1st 12/6 and just realized that the (early prototype) flatpack I got from Speaker Hardware doesn't have them, either.
 
Extra Bracing Support
ExtraBracing.jpg

I put a dado on the bottom of the flange for extra gluing surface. No room for clamps so cable ties will have to do (I have thousands of these, my company makes them).

I had hoped my warning reached you before you got any further. But that didn't work out. I probably would have glued a strip of 1/4" plywood against the face of each holed segment in areas nearer the center of each panel and let it be nearer edges.

The way you did it will probably be fine though, since this is a 12/6 with its smaller panels.
 
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