TH-18 Flat to 35hz! (Xoc1's design)

[CRESCENDO]

Originally Posted by weltersys

Unlike the PLX series, the QSC PL380 is also a good LF amp.

PL340 as well (same series)? I ask because I'm using 8 ohm drivers (PL380: 8000W bridged into 4 ohms seems a bit too much for my drivers).. That amp looks like it would've been a winner had I purchased 4 ohm drivers (PL380: 2500W/ch @ 4 ohms).

The PL340 would give me 4000W bridged @ 4 ohms, which seems like a better bet. Still not the 6000W I was looking for, but like you said, this amp would probably give me more of what I need with similar (read 300W more per driver w/PL340) "on paper" PLX specs.

[SonicXtasy]

Hi Guys! All I have to say is OMG!. I have spent the last 2 plus weeks reading this thread from begining to end (slow reader, bad reading comprehension and lack of time) and have learned alot and but now have some questions.

First about the TH-18. I realize that this is a compromise between output/size/efficiency/extension. There are drivers that work ok and drivers that hold up well under extreme xmax. Due to AC limitations I am not too worried about max SPL per cab and more concerned with efficiency/depth/driver cost. If I read correctly I should wait for the finalized version with the additional throat comprssion for cheaper drivers. I believe the 18 Sound 18LW2400 is a good buget driver for this cab.

This might sound somewhat stupid but how low will this play. My gigs are mostly DJing school dances with pop music but my system gets used by other DJs that play mostly hip-hop. I occasionally play dubstep but realize that the extra cab volume needed to get the that low is just not worth it to me. Will this cab (driver dependent) play the bass in these songs?

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The 2nd song I cant stand. All I am concerned with is the first bass drop of that song. I understand there is some lower stuff in it but I am not worried about that.

The "amp talk" from Art was very infomative. I Have 2
PLX3402s, 1 runs subs which are 1 reflex loaded with 2 RCF L18P300's and I add a 2nd reflex loaded with 2 P-Audio SD-18's on bigger gigs. Amp runs bridged and both cabs are wired in series (16 ohms). 2nd amp runs highs. I originally wanted to replace the sub amp with a RMX4040 or something similar but that changed on friday when I stumbled into a deal which consisted of a QSC PL218 and a PL 236, both for $525 out the door at a pawn shop. I was going to dedicate both PLX's to subs and use the PL236 on highs but after reading what Art has to say about the plx's I will probably replace them. Anyway that gets me to how much power can I run on a 15 amp ckt? I have run both PLX3602's close to clipping (one 4ohm stereo and one 8 ohm bridged) and a PLX2402 about half power (4 ohm stereo) from a 15 amp ckt but the voltage drop was pretty low and the sub amp did "brown out" at extreme levels as Art mentioned.

Sorry for the rambling, I am sure I will have some other questions soon.

Thanks and keep up the good work.

Dave

[CRESCENDO]

Ah, just read the PL380 uses Class D and PL340 & 325 use Linear Class H

[NEO Dan]

Seems like for the $ the iTech is the one that fills the bill best as, it'll run 4-6 cabs, has good DSP, Class I/D... PL380 and SW115-4's would be a nice rig too.

[CRESCENDO]

4 @ 2000W/ea, 6 @ ~1000W/ea. I'm still looking for 3000W/ea (or just more LF from the amp than my PLX3402's), but you're right - for the money the I-T8000 is difficult to steer away from. Especially weighing less than 30lbs.

[NEO Dan]

You are basically looking at 3 8Ω TH per bridged I-T8000 then. And considering this is the lowest cost(1amp & 1woofer to buy) way to find out if it'll work. The limiters go to 255V, you only need 220V p-p/155V RMS to get 3KW per box, there are also AVG power limiters to CYA...

Looks like the I-Tech 8000 is 400V p-p capable, that would explain the current limiting. This amp will easily drive your woofers to 220V p-p/you will need the limiters to CYA.

[CRESCENDO]

That would give an approx impedance of 2.66 ohms. The I-T8000 may not have trouble, but it's not rated for a bridged load less than 4 ohms.

CYA = Cover Your Amp?

[NEO Dan]

IF you use the limiter(220Vpk) to keep the amp from pwn'ing the woofers it'll have no trouble running the load, even if you ran it in stereo you'd get 200Vpk before the amp hit clipping. Basically this is the only option presented so far that can get you even close to what you want. You can monitor all the vitals in system architect...

It'll run 6-8Ω 18's on one channel aparrently

[CRESCENDO]

Nice! And I'd probably still gain a little more SPL if I add a 4th sub to that equation for 2 per channel, even w/less power per cab, if I'm thinking correctly..

[CRESCENDO]

SO... REW on my Mac:

My only options under "Output Device & Output" with my AudioFire4 plugged in before start-up and System Preferences set to AudioFire4 are:

Default Device
Java Sound Engine (when selected, "Wave volume" is adjustable)
(I've tried both)

I've got "Output 2" on the rear of the interface connected to "IN 2" on the front of the interface. A 0.1dB change in the I/O of the digital console will be the difference between -14dB and complete clipping in REW, so I have to balance the faders to avoid that (lowering "In A2" on the console quite a bit and raising "Out A2" on the console gets me close). "IN 2" gain knob on the front of the interface doesn't really 'help' this balance - it just moves the dB level/position at which the dramatic level change occurs. I can't even get a good calibration reading without getting the corrupt measurement warning box.

Images of both default output and java sound output windows are below, as well as corrupt measurement warnings, 0.1dB difference comparison, fader combos and windows during calibration.