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[Tim McCulloch]

25,000 sq ft...117' x 214' deep....either way the client is expecting to see 4 tops and 4 subs

You can take what the customer expects (did they order it or did you propose it?) and it's up to you to send a signal to the parts that provide the best coverage and meets the client's actual need, as opposed to the client's visual expectation.

So stack 'em up, wire 'em up, but turn down/off the amp channels that aren't needed.  I'd run any "unnecessary" boxes at a low level just so they're on and working if the client decides to put his/her head in front of one.

[Tamar Ghobria]

Putting that aside my question is about the I-techs and running them at 2ohms....

[John Rutirasiri]

....I would be happy to here suggestions of different amps if the I-techs don't perform well in this configuration...Or if I need to upgrade to a I-Tech 8000....Thanks in advance

Itech amps have no problem driving 2 Ohm loads all day long.  I normally run 4x TH118s per IT12000 doing summertime outdoor EDM shows.

I believe in having ample headroom and not driving your amp near clip.  The IT6000 is rated at 2500W/ch into 2 Ohm.  I would get another IT6000 for your two other TH118s.  You could sell your IT6000 and get an IT8000 or IT12000, but having two amps is better than relying on one.

John R.

[Scott Carneval]

The amps will be fine. You could use some more power to the subs, but realistically if you double the power you stand to gain 3db. If 3db will make or break your show you have the wrong setup. Center cluster your subs and you'll make the 3db right back


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[Mike Pyle]

25,000 sq ft...117' x 214' deep....either way the client is expecting to see 4 tops and 4 subs

I don't think 2 SM80s per side is a good setup for a room 117' wide and 214' deep. If the PA were on the long wall it would make sense. How high is the ceiling?

The iTechs current limit into 2 ohm loads, so at full amp output the power available to each cabinet is greatly reduced compared to running fewer cabinets with a total impedance of 4 ohms. You would definitely need another amp to properly power 4 of the subs.

[Tim McCulloch]

I don't think 2 SM80s per side is a good setup for a room 117' wide and 214' deep. If the PA were on the long wall it would make sense. How high is the ceiling?

The iTechs current limit into 2 ohm loads, so at full amp output the power available to each cabinet is greatly reduced compared to running fewer cabinets with a total impedance of 4 ohms. You would definitely need another amp to properly power 4 of the subs.

The ITech is optimized for use at "4 Ohms".  They will current-limit there, too.   If you can run them on 208v-240v you get more no matter the load impedance.  If you have actual impedance (not just nominal rating) below 4 Ohms I'd really want the higher mains voltage (or another ITech on another AC circuit).

[Art Welter]

Putting that aside my question is about the I-techs and running them at 2ohms....

The I Tech 6000 only puts out 2500 watts at 2 ohms compared to 3000 at 4 ohms. 3000 watts peak is a reasonable amount of power for the TH-18.
1250 watts per sub is a reduction of a bit more than 3 dB, so the 3dB you gain from doubling the cabinets is nullified by having less than half the power available to them. A pair of TH-18 run off the amp would actually be slightly louder (not allowing for power compression) than four run off that amp.

Get a second amp for the additional subs to get a 6 dB increase in level.

[eric lenasbunt]

I don't think 2 SM80s per side is a good setup for a room 117' wide and 214' deep. If the PA were on the long wall it would make sense. How high is the ceiling?

The iTechs current limit into 2 ohm loads, so at full amp output the power available to each cabinet is greatly reduced compared to running fewer cabinets with a total impedance of 4 ohms. You would definitely need another amp to properly power 4 of the subs.

Would it make more sense to use the second pair as delays halfway down the room?

[Tamar Ghobria]

I don't think 2 SM80s per side is a good setup for a room 117' wide and 214' deep. If the PA were on the long wall it would make sense. How high is the ceiling?

The iTechs current limit into 2 ohm loads, so at full amp output the power available to each cabinet is greatly reduced compared to running fewer cabinets with a total impedance of 4 ohms. You would definitely need another amp to properly power 4 of the subs.

Not enough coverage? Or because of the amps?

[Tim McCulloch]

Not enough coverage? Or because of the amps?

I'm guessing Mike is thinking "2-wide" on the SM80.

Eric brings a good suggestion about delay speakers and it has merit.  It's going to be very loud up front if you try to make it 200'.  While the Danley boxes "hold together" nicely they don't have a way of negating the inverse square law (yet, anyway).  Clear sound is good but it's got to get above the crowd buzz in the back of the room without nailing the folks up front.

Regarding amps:  what's the program material?  Here's the dirty little secret:  if you put 2500W continuous into your speakers you'll have a very short show.  If you put 600W continuous into them, you're likely to be in power compression by a couple dB after about 15-30 minutes of operation and throwing more continuous level at them will generate disproportionately more heat than SPL.  Ivan can probably give you specific information about power compression that applies to the TH118; mine is intended for general discussion.

Also another thought about current limiting - this is done to keep the UL rating for the 20 amp supply cord and power inlet.  If you finagle 240v service to your ITechs you'll get 3dB more output before current limiting kicks in.

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