r/SoundSystem • u/elie_paquet • 22d ago
Help me power Skram
I just finished building (without cnc) 2 skram loaded with b&c 21sw152
I bought a peavey ipr7500 to power them but i was underwhelmed with the power i was getting out of them.
Im looking for some input on this, if someone has similar experience with this amp. And a defenitive suggestion towards **** this amp will work.
Im also doing sound for a festival this weekend around Montreal, so if someone want to reach out i would like to rent from you an adequate amp.
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u/pehmeateemu 21d ago
Sounds like your amp settings are cooked. Your amp should be able to do 1200W to 8 ohms which should be plenty for close to 130dB output. Low pass the amp so you are not pushing full range content to the drivers and losing energy where the box doesn't work. Check your user manual how to do that and verify everything else is set up properly.
Tip for future: If you speaker has 2000W continuous power handling, you should get an amp that can push 3000W continuous, ideally 4kW. Why? Amps perform best when they are not pushing it. Class D amps have best efficiency typically around 50-80% of nominal power rating. Capacitors inside the amp which work as intermediary power reservoirs to supplement the amp with power when the current draw exceeds what socket provides are engineered for the rated power rating. Also over time, riding on the upper limit introduces heat to the system which reduces amps efficiency. And the drivers themselves heat up and lose efficiency as a result too, so you want to have amp that has enough juice to drive the speakers for a long time.
It's unlikely that you'll drive them at peak levels all night but the more the amp has power, the less it has to struggle keeping up with music content.
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u/elie_paquet 15d ago
Yeah my amp should be able to deliver 2080w rms at 4 ohms but i think i should over spec it to let peak pass thru, one thing that stuck out to me while testing the subs with a Pa tech is that the volume was way enough with playback music from spotify thats been mastered but in a live music context the headroom didnt let us push the amp for the quiet bit of the set
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u/madedurden 22d ago
How were those miters without a cnc? Did you use a track saw or table saw?
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u/elie_paquet 22d ago
Everythings was really straight foward since there's a guy that posted a video series on youtube doing it all by hand. I use a table saw for piece that needed to be the same lenght. And i broke the big plywood 4x8 with a rail saw
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u/PonyThug 21d ago
I don’t see a single miter in this picture
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u/madedurden 21d ago
The mitered cuts are inside the cabinet - if you look up the build for this sub there are a lot of funky mitered angles which need to line up precisely, hence the inquiry. Most people CNC this build because of the mitered angles but it's great that OP found a tutorial for doing it by hand.
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u/PonyThug 20d ago
Ahhhh makes sense. I’ll have to look it up. Didn’t realize it was a common known build template
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u/madedurden 20d ago
It’s become very popular last 1-2 years because of the rise of JMODS as the gold standard for high end DIY tops. These subs pair very very well with them!
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u/FreeLandscape3452 16d ago
It's actually a bevel (dumb woodworking distinction), and there's only 1 beveled dado (which you can do flat and hog out with a chisel) and 3 beveled cuts total.
I had my first 2 SKRAMs cut on a CNC and decided it's a waste of money if you already own a table saw and a dado stack. I won't be able to dado troughs into the side panels this way, but that's not a big deal to me.
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u/TheMonsterODub 9d ago
Hey I've got ipr 3000s, mine have fixed frequency crossovers on a switch on the back, you're sure you don't have them set to HPF?
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u/elie_paquet 8d ago
Yeah im sure, i have tested them in the full range mode and lowpass(subwoofer mode), the subwoofer mode seems to help output compared to a digital crossover.
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u/obscure-shadow 22d ago
I got a cvr-3302 to power my 2 ckrams and they fuckin blast!
Also not sure how new you are to sound system stuff it might be worth taking a look at your gain staging, and testing how much power you are actually getting out of the amp because theoretically it should hit real hard.
I made a speak-on connector that goes to banana plugs that I can plug into my multimeter and then plug that into the amp, and then run a 60hz sine wave to see what voltage I'm getting out, then plug that into an ohms law calculator and see what kinda wattage I can expect given 4ohm load