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4-Ohm load vs. 8-Ohm load - benefits to amp?
- Thread starter esa372
- Start date
epilogue
I went with the 4-ohm cabs, and I couldn't be happier. They roar, and sing, and punch, and rumble far more than their 8-ohm brothers. I was really surprised at the difference; the 4-ohm cabs are noticeably louder, fuller, and more harmonically rich. (Their gig-debut will be this Wednesday night!) Plus, it's nice knowing that the 4-ohm cabs are using the amp's full potential.
Thanks, everyone, for all of the input - TB is a great community with a wealth of information!
~esa
I went with the 4-ohm cabs, and I couldn't be happier. They roar, and sing, and punch, and rumble far more than their 8-ohm brothers. I was really surprised at the difference; the 4-ohm cabs are noticeably louder, fuller, and more harmonically rich. (Their gig-debut will be this Wednesday night!) Plus, it's nice knowing that the 4-ohm cabs are using the amp's full potential.
Thanks, everyone, for all of the input - TB is a great community with a wealth of information!
~esa
Glad that you've achieved your goal.
However, the differences in volume may be unrelated to impedance unless comparing exactly the same cabinet designs (i.e. one 4 ohm, one 8 ohm). Could be that the new cabinets are also more efficient than the older ones....
However, the differences in volume may be unrelated to impedance unless comparing exactly the same cabinet designs (i.e. one 4 ohm, one 8 ohm). Could be that the new cabinets are also more efficient than the older ones....
Thanks!
That's what I did - identical cabs; different ohm ratings.
Certainly true. But, whatever the reason, I love the new rig!
Okay...I'm having some issues...I have a shuttle 6.0 and which is 375watts at 8ohms and 600 watts at 4 ohms...
I have a GB NeoX 112 which is 300 watts at 8ohms and an Avatar Neo 212 which is 500 watts at 4ohms...
When using the 212 it still seemed like I had to push the master volume and preamp gain further than I should have— well past 3 o'clock on both and my volume on my onboard preamp was all the way up.
I have an electric jazz trio that played outside yesterday and I though i'd have plenty of head room...but I didn't...
The only other thing i can think is that I need to swap out my battery on the onboard pre...
But barring that I am just setting up my rig incorrectly?
I have a GB NeoX 112 which is 300 watts at 8ohms and an Avatar Neo 212 which is 500 watts at 4ohms...
When using the 212 it still seemed like I had to push the master volume and preamp gain further than I should have— well past 3 o'clock on both and my volume on my onboard preamp was all the way up.
I have an electric jazz trio that played outside yesterday and I though i'd have plenty of head room...but I didn't...
The only other thing i can think is that I need to swap out my battery on the onboard pre...
But barring that I am just setting up my rig incorrectly?
Don't be concerned about the position of the knobs, as it means very little; some amps are out of steam at 1/3, while others (like the Shuttle) use the whole range of rotation.
For maximum headroom, try cranking the volume to maximum, then adjust the gain to taste, using the master for setting the overall level. As mentioned in many previous threads, the clip/lim light is just letting you know that you're entering into limiting, not that you're out of power and need to back off, so don't worry about pushing into the limiter.
Also, in case you don't know, the amp is rated for 4 ohms minimum, so either of those cabinets are fine, but not both together.
Remember a cab power rating has very little to do with anything. It is a loose suggestion of maximum power, not an indication of how much power a cab 'needs' or how loud a cab will go.
Your Avatar cab could be a bit low in SPL (especially in the frequencies that you might be interested in), resulting in you having to turn up a bit more. Also, be aware that the Genz heads don't use those pure linear master volume pots, that reach 'full on' in the first have of their range. Don't use your eyes regarding the pre gain setting (which is also set at a very low gain level) or the master regarding 'how loud the amp is'. With a moderate output passive bass, some actually run the Shuttle input gain all the way up.
Finally, your Shuttle's power amp 'clip' indicator, unlike most other circuits, does not indicate the amp is at 'full power', but rather that some 'tube emulation limiting' is kicking in. Therefore, that clip light flashing a bit does not in any way indicate you are at full power, nor does it require you to turn the amp down.
Edit: Also just noticed you were playing outside. Depending on the situation (i.e., if you didn't have a wall behind you and/or were playing to a wide open space), that context will require HUGE amounts of power and cone area to work sometimes. Don't judge a rig's performance based on playing outside. That is a can of worms regarding getting a full bass tone at even moderate volumes.
we were fortunate to have a wall behind us...I guess it's a little frustrating to move from 1x12 to a 2x12 and have the amp running the exact same way with not that much more volume...
I was a little surprised. What you guys are saying makes sense, but the end result still doesn't make sense to me...
I was a little surprised. What you guys are saying makes sense, but the end result still doesn't make sense to me...
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
- 278
- 76
- Disclosures
- Owner, Bill Fitzmaurice Loudspeaker Design
Wattage ratings tell you next to nothing. Unfortunately that data which is pertinent is not made available.
On average it takes twice the speaker complement outdoors to get the same perceived level as indoors.
Make sure you compare the output of the 112 to the 212 in the same room and situation. Again, playing outside will bring any rig to its knees. Even if the Avatar is lower SPL than the GS112, doubling the drivers and almost doubling the power should sound at least somewhat bigger than a single 112 at 8ohms. However, Avatar is a good but low cost box, and the couple I've heard have been less than impressive regarding low end extension and absolute volume.
Basically how loud a cab will get per watt. SPL is typically measured and reported at 1K, so it is kind of a measure of the voicing of a bass cab (at least one and two way with tweeter cabs, since a driver that really pumps it out at 1K will probably not really pump it out at 50hz).
It takes a LOT of energy to reproduce deep bass, so if you have a cab that is voiced very deeply, it will almost by definition be voiced politely in the mids (unless there is a mid driver or whatever). So, a lower SPL cab measured at 1K USUALLY sounds softer and deeper versus a higher SPL cab with the same head, bass and player.
SPL means Sound Pressure Level, it is usually measured in dB
http://en.wikipedia.org/wiki/Sound_pressure
It is not a measurement of efficiency.
The efficiency of a speaker enclosure (your good old cab) is usually measured by db/1 watt @ 1 meter or (db/2.3 volts @ 1 meter). You should look for the frequency at which it is measured as well. Actually a FR (Frequency Response) graph is more meaningful, as it will show you the efficiency of the speaker across the spectrum; not just at a single point.
http://en.wikipedia.org/wiki/Sound_pressure
It is not a measurement of efficiency.
The efficiency of a speaker enclosure (your good old cab) is usually measured by db/1 watt @ 1 meter or (db/2.3 volts @ 1 meter). You should look for the frequency at which it is measured as well. Actually a FR (Frequency Response) graph is more meaningful, as it will show you the efficiency of the speaker across the spectrum; not just at a single point.
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
- 278
- 76
- Disclosures
- Owner, Bill Fitzmaurice Loudspeaker Design
That is sensitivity. Efficiency is a percentage, acoustical watts output compared to electrical watts input. It averages about 2%.
It's not just more meaningful, it is the only valid method of comparing the sensitivity of cabs. It's also not available from any major manufacturers.
I have a 1980 ev 215 cab that is now wired to 2.9 ohms dc restistant on a tester at the speaker jack, I am running a 4 ohm load from my ampeg svt vr head ( all tube) for 6 months now with no problems is this correct to have the ohms switch on 4 ohms or 2 to drive the 2.9 ohm cab correctly. the evm 15 L's read 8 ohms each on the back but because they are high efficent they read 5.4 for 1 and 5.3 for the other I run them inside the cab to make them read 2.9 ohms. it has been a dilema to use the 2 ohm switch vs the 4 ohm . thanks for you help
You are measuring DC resistance, not AC impedance with your meter. The DC ohms indicates they are 8 ohm nominal impedance and you have them wired for a 4 ohm nominal AC impedance. Use the 4 ohm tap from your amp. DCR is most always less than the nominal AC impedance.
