• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Preferred Power Ratio/Passive Cabs ??

tjh

tjh

Mar 22, 2006
6,381
2,721
Minnesota
#1
We currently use a pair of Yamaha Club Series S115IV passive speakers (specs below, 8 ohms each), and have been driving them with a small Yamaha powered mixer (400 watts per side @ 4ohms, one side to Yammies, other to monitors) ... we are increasing the capabilities of the system by switching to a non powered mixer ( MG166CX), and then either the Crest ProLite 2.0 I currently have, or a Crest ProLite 3.0 ...

I have seen where sound RI cabs 'should be' driven at 1.5-2X the rating of the speakers, and I think I understand the reasoning. One question is, with a cab design such as the Yam Club Series is the same type of power ratio desireable seeing their is no external crossover, etc, or do extra precautions need to be taken (to protect the internal x-over and HF driver) when using the higher power rating amps?..

The choices I have are to power the Yamaha's with a bridged 2.0 ProLite which would be 2000 watts to the pair @ 4 ohms (1k each), or to use one side of a 3.0 and 900 watts @ 4 ohms for the pair (450 each)...

I might know the (which is the best) answer here (but thought I would run it out there for the more experienced that have forgotten more about sound RI than I will probably ever know) ..

.. one positive of using just one side of the 3.0, is that we can then use the other side of it for monitors, and only need one power amp ...

Yamaha S115IV Specifications:
Enclosure Bass Reflex Type
Speaker unit (LF) 15" cone
Speaker unit (HF) 2" V.C.driver
Frequency Response 55Hz-16kHz
Power Capacity (Noise) 250W
Power Capacity (Program) 500W
Power Capacity (Maximum) 1000W
Nominal Impedance 8 ohms
Sensitivity 99db SPL (1W, 1m)
Nominal Dispersion (Horizontal) 90°
Nominal Dispersion (Vertical) 40°
Crossover Frequency 1.7kHz
Input Connectors 1/4 " Phone Jack
 
#4
tjh said:
I have seen where sound RI cabs 'should be' driven at 1.5-2X the rating of the speakers, and I think I understand the reasoning. One question is, with a cab design such as the Yam Club Series is the same type of power ratio desireable seeing their is no external crossover, etc, or do extra precautions need to be taken (to protect the internal x-over and HF driver) when using the higher power rating amps?..
Click to expand...
It's actually 1.5 to 2.25x the RMS rating of the speaker. And, absolutely the same power ratio, as any external crossover in a passive system would be BEFORE the amps not after.

tjh said:
The choices I have are to power the Yamaha's with a bridged 2.0 ProLite which would be 2000 watts to the pair @ 4 ohms (1k each), or to use one side of a 3.0 and 900 watts @ 4 ohms for the pair (450 each)...
Click to expand...
The S115V's are 500w program @ 8-ohm.. so they should be powered by an amp that produces between 625w and 1125w. That upper wattage range is to let the amp handle audio transients - as in peaks - not long-term levels. I ASSUME you are running both speakers in series (daisy-chained) and that's where you get the 4-Ohms?

If you don't have close control of the mixer, using the ProLite2 in bridged mode might be pushing the envelope for use with the 115's. That said, as long as you gain-stage your system properly, you should be OK with it, as you will probably never hit the 1000w peak per speaker. The knobs on the front of the amp are not volume controls, but input level attenuators. Any Solid State amp can reach its peak out levels with those knobs at low levels, IF the input voltage is high enough. Setting the knobs at max, means less voltage is required to drive the amp to rated power.

The more conservative approach would be plan B - the ProLite3 - with 450w going to each.
 
#5
s0c9 said:
It's actually 1.5 to 2.25x the RMS rating of the speaker. And, absolutely the same power ratio, as any external crossover in a passive system would be BEFORE the amps not after.

The S115V's are 500w program @ 8-ohm.. so they should be powered by an amp that produces between 625w and 1125w. That upper wattage range is to let the amp handle audio transients - as in peaks - not long-term levels. I ASSUME you are running both speakers in series (daisy-chained) and that's where you get the 4-Ohms?

If you don't have close control of the mixer, using the ProLite2 in bridged mode might be pushing the envelope for use with the 115's. That said, as long as you gain-stage your system properly, you should be OK with it, as you will probably never hit the 1000w peak per speaker. The knobs on the front of the amp are not volume controls, but input level attenuators. Any Solid State amp can reach its peak out levels with those knobs at low levels, IF the input voltage is high enough. Setting the knobs at max, means less voltage is required to drive the amp to rated power.

The more conservative approach would be plan B - the ProLite3 - with 450w going to each.
Click to expand...

... yes, both cabs would be run parallel (daisy chained) to arrive at the 4 ohms

... you have a good point with the 'close control of mixer' comment ... there could very well be a less than 'qualified' son or friend of guitar player sitting there from time to time ... those may be good times to use the conservative 'plan B' approach, and save the bridged 2.0 option for when needed with a better board operator ...

Scott and Ranger, thank you for your comments as well ... ;)
 

Latest posts

Top Bottom
Back