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How do you determine how much power is enough?

I don't use a fancy formula. A rule of thumb is 3x the output of the guitarists' amp.

That works fine as long as the sensitivity rating of the speaker is relatively high. But if you own something like an Acme Low B, it's not going to work. For example if your running and SVT and an 810...it works. [Log(300) x 10] + 100 = 124.8dB

I had one of the original runs of the Low B2. The power rating was 350W RMS and the sensitivity was 93dB. Acme recommended a 400 to 500W amp.

[Log(350) x 10] + 93 = 118.4dB. Barely got the job done in a cover band. My power amp could make more than 350W, so I had be careful to avoid blowing the drivers.

I think I would have been totally satisfied with a pair if Low B2s and 700w, as the calculated SPL would go up to 124dB...my magic number.

In comparison the Eden D210XLT I used with my last touring rig was rated 103dB 1W/1m. So with my 260W amp the calculated SPL was ~127dB. Always plenty for my needs.
 
If you’re currently rocking an 800+ watt rig, what kinds of gigs would you no longer be able to do, or what kind of musical compromises would you have to accept, if you had to make do with a 500 watt rig? (Or transpose the question to 500 —> 350, 350 —> 200, 200 —> 100.)

We all know that less power = less clean headroom. But how does that actually manifest as a limitation in real-world gig situations for you? Is it little tonal infelicities that only you would notice? Gross farting? Speaker damage?

To actually answer your question, my opinion and experience only, is that 500 watts will do in the bar scene (heck, I rocked a 300 watt GK 800rb for 30 years), 800 watts is nice for headroom and plenty for theatres and small outdoor gigs.

The thing is, once you get past that, you should be going direct with a sound guy and your amp becomes a stage monitor anyway. Once you get into in ear monitors, you don't even really need an amp.

Everyone's journey is a bit different. A lot depends on the genre, the sound you want, how loud your bandmates are, where you play... And playing live is a lot different than being in the studio. Your little subtleties of tone go right out the window when you're playing with a different soundman every night. If you're in an original band, at least half the time you might be playing through a backline or someone else's rig.

I make do with a 500w single 12 combo. In ear monitors and a DI. No compromise.

Good luck in your journey. Try not to overthink it.
 
I rocked a 300 watt GK 800rb for 30 years), 800 watts is nice for headroom and plenty for theatres and small outdoor gigs.

I toured a 800RB biamped into a Bad End S15D and a Ramsa WS-A200 for a couple years. Always plenty loud.

The S15D was pretty lean down low, but rated sensitivity was 103dB 1W/1m. It's rated for 300W RMS but I don't think it can actually make good use of that much power. I thought it got loud fast and then started to fall apart at super high SPL...but maybe it was the amp rather than the cab.

Calculated SPL = [log(300) x 10] + 103 = 127.8dB. I don't feel like I ever got close to clipping this rig, or even pushed it to the point where it started falling apart.
 
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I honestly think most volume issues for bassists are cab issues. I've seen too many run some really ancient or inefficient cabs and wonder why their 'amp isn't loud enough'. The best, powerful efficient cab you can afford and fit in your car plus a crummy head will sound clearer and better than an expensive amp running into a trash cab. Just because guitarists can run anything into any box with speakers, doesn't mean we can too.
 
Since I don’t want to go deaf, I play with bands who have control of their volumes, and even the loudest don’t require me to need beyond maybe 100w into a couple 210s.
If you let the music and the audience be your guide, you can get away with a lot less power.
 
For loudness, the speaker cab efficiency is more important than the amp watts. If one cab puts out 93 db @ one watt one meter and another cab puts out 103 db @ one watt, one meter. A big, big difference in loudness. About 10 times louder.

As far as I know, Schroeder bass cabs are the most efficient and are the loudness.

Forget the watts of the amp and consider the efficiency of the cab!

From a Google search............
Decibels increase exponentially
For example, every increase of 10 dB on the decibel scale is equal to a 10-fold increase in sound pressure level (SPL). Near silence is expressed as 0 dB but a sound measured at 10 dB is actually 10 times louder. If a sound is 20 dB, that's 100 times louder than near silence.

Cabinets | Schroeder Cabinets | Bass Cabinets | California
 
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For loudness, the speaker cab efficiency is more important than the amp watts. If one cab puts out 93 db @ one watt one meter and another cab puts out 103 db @ one watt, one meter. A big, big difference in loudness. About 10 times louder.

As far as I know, Schroeder bass cabs are the most efficient and are the loudness.

Forget the watts of the amp and consider the efficiency of the cab!

From a Google search............
Decibels increase exponentially
For example, every increase of 10 dB on the decibel scale is equal to a 10-fold increase in sound pressure level (SPL). Near silence is expressed as 0 dB but a sound measured at 10 dB is actually 10 times louder. If a sound is 20 dB, that's 100 times louder than near silence.

Cabinets | Schroeder Cabinets | Bass Cabinets | California

As a general comment since this topic comes up regularly, whenever comparing numbers, it's essential that you know how the numbers are derived. There are many different ways to measure sensitivity resulting is very different numbers, without it being clearly defined it's nothing more than number. Sometimes it's simply mistakes made, sometimes it's a lack of understanding of the technical aspects of the subject and sometimes it's intentionally misleading. Just like every other spec, it's the classic case of buyer beware.
 
There are many different ways to measure sensitivity resulting is very different numbers, without it being clearly defined it's nothing more than number.

This is the main reason I mentioned calculated SPL figures are ballpark estimates. Comparing calculated SPL figures should be relatively valid if you are comparing cabs within a single manufacturing product line. But even different product lines under one company may use different standards for their specs. JBL for example uses different measurement practices for different product lines.

Still I think comparing calculated SPL figures is more informative and useful under most circumstances than simply considering how much power an amp makes.
 
This is the main reason I mentioned calculated SPL figures are ballpark estimates. Comparing calculated SPL figures should be relatively valid if you are comparing cabs within a single manufacturing product line. But even different product lines under one company may use different standards for their specs. JBL for example uses different measurement practices for different product lines.

Still I think comparing calculated SPL figures is more informative and useful under most circumstances than simply considering how much power an amp makes.
IF you know when the numbers are not representative of real world results. It's generally more of an issue in DJ, lower end PA speakers and musical instrument speakers, not much of a problem in the higher end PA cabinets however.

There is a big difference in a measurement being made at a favorable point on the response curve versus an average over the usable bandwidth for the application (say for a bass speaker from 50Hz - 5kHz, for a subwoofer this may be better defined over say 35Hz - 120Hz). Some speakers have peaks that are 6dB or more above the average and it's not uncommon to exploit this for marketing purposes.

The same applies to the acoustic space... for speakers that are flown in normal applications they are operating in full-space, yet for speakers that are stacked on a stage they are generally operating (at lower frequencies anyway) in 1/2-space. When operating against a (acoustically solid) wall and stacked on a stage, the radiating pattern will approximate 1/4-space. Why is this important? Because the difference in each halving of the acoustic space results in an increase of 3dB which invites marketing folks to employ liberties which do not universally apply when comparing across brands.

Most musical instrument speakers are used in 1/2-space, virtually none in full space and only a very few in 1/4-space. This is why "most" bass cabinets are specified in 1/2-space, it's how the vast majority are used in practice.
 
Pretty much what the title says. More specifically, if you like:

If you’re currently rocking an 800+ watt rig, what kinds of gigs would you no longer be able to do, or what kind of musical compromises would you have to accept, if you had to make do with a 500 watt rig? (Or transpose the question to 500 —> 350, 350 —> 200, 200 —> 100.)

We all know that less power = less clean headroom. But how does that actually manifest as a limitation in real-world gig situations for you? Is it little tonal infelicities that only you would notice? Gross farting? Speaker damage?

I hope the thread premise makes sense, and I’m looking forward to hearing your responses. (I don’t have any agenda except to learn, I promise.)
I have a number of different amps that I use depending upon the situation. I have a 400-watt Eden Nemesis RS-400 (400-watts into 4Ω) That I bought in 2008 and kept as a backup after I bought my Eden WT500/800 amp (was upgraded to 400-watts per channel into 4Ω or bridges at 800-watts into 8Ω). I actually bought that big Eden amp (weighs about 36-lbs. in its rack) in 2010 directly from David Nordschow (AKA David Eden) after he sold and left Eden to found his new business DNA (David Nordschow Amplification). It's an amazingly versatile amp with clean clear and articulate sound and plenty of power for lot's of headroom. It weighs about 36-lbs in its rack.

I also bought a DNS-410 by DNA in 2015. It handles 1400-watts with a max SPL of 137db. It arrived 2-days before I moved from Virginia to Washington state. My 800-watt amp bridged into it will theoretically drive it to 135db, but I've never needed to push that much power into it. At wide open field-type Music Festivals, I get told to turn down if I turn the master up to 10:30. So 10:15 is the max I use on it. Good news is that I don't need to haul around an 810 cab even for music festivals. So I thought that rig was the be-all/end-all and I would never have to buy another cab...boy was I wrong.

Having an 800-watt big rig like that scares the crap out of owners of small venues. A group I started playing with in 2016 hosted Friday Night Open Mic nights over 40-times per year at a small brewpub. Owner's eyes got huge when I rolled in my 410 for the first time. He shook his head, "NO" and then pointed me to the small Peavey 112 combo on the stage and said, "use that". So I rolled my 410 back out to the car and put it away. I could not get close to my Eden/DNA sound out of that Peavey 112 so I bought an Eden 112 cab in 4Ω (EX-112 handles 300-watts rms) for all of $269 new and used it. It sounded so good that I immediately bought a second one and would use both of those at medium-sized venues into my big Eden amp. After using my RS400 for that 112 at small venues, a friend wanted to sell his Class D Eden TN226 (225-watts into 4Ω) That ended up being about the perfect match for small venues and the sound was excellent.

And then one night, our 5-pc group got more than a little loud in that small venue and I had to turn up. Next thing I know, the power clipping light is flashing (a very bad thing). If I didn't do something quick, it would turn off the amp. Dropping the Bass EQ didn't help and turning down just made me disappear. So I turned on the auto compressor and turned the gain (becomes the threshold control when auto-compressor is on) up a bit to get the gain-set light flashing a lot and that worked perfectly. It stopped the clipping light from flashing and compressed the peaks in my sound without significantly affecting my attack or dynamics. Was far better than the auto compressor on my big Eden amp, which is harsh by comparison, and I was impressed. I could be easily heard after all without hurting the amp.

Honestly, if I knew I was going to use two cabs, I would have bought them in 8Ω and bought the 500-watt TN-501 instead. That would give me 250-watts with one cab in small venues and 500-watts into two cabs (250 each) for my medium-sized venues. I'd probably still used the big Eden amp with my DNS-410 for large, outdoor, and music festivals though.

Then in 2019, when I was accepted into the DNA Endorsing Artist group, I bought a DNS-210 cab (700-watts rms, Max SPL=134db). I found out from experience that I can use that single DNS-210, that I can use it for everything from small to large indoor venues. In 2021 I bought a DNA-800 amp which puts out 800-watts into either 4Ω or 2Ω and I use that with my DNS-210 now for all indoor venues mostly because it weighs all or 4.8-lbs, which is about 31-lbs less than my big Eden amp and I can get the same sound out of it. Even though that DNA-800 amp will only put out 400-watts into 8Ω it still is plenty for all my indoor venues because my 210 cab is a very loud cab while still being clear, clean, and articulate with a very low and focused bottom end. I still roll out my DNS-410 now for outdoor venues and music festivals. But if I'd known then what I do now, I would have bought the 210 first and then added a second one when I needed to play outdoors rather than buy the 410 first and add a 210 to it later.

Conclusion:
After all those years and all that money, my conclusion is YES, you should get an 800-watt into 4Ω class D amp. Buy a quality 210 that handles at least 400-watts (both thermal and mechanical) and that will work for small and medium venues and perhaps for large ones depending upon the cab. Then buy a second 210 cab when you need one for large venues, outdoor venues, or music festivals. Even small venues won't give you the evil eye bringing in a 210 cab and with the right cab you can use it for all indoor venues. My DNS-210 weighs 52-lbs which is not particularly light for a 210, although it is lighter than David's previous Eden designs. But there are certainly lighter 210's around. My DNS-410 weighs in at 79-lbs though and being able to use my 210 where I would normally have to have to use my 410 is definitely an advantage.

If you prefer, an 800-watt amp into a 2 x 115 set-up will also work but is typically heavier and perhaps not as punchy (somewhat slower transients usually). I toured for 3-years in the early 70's with a 215 rig and that was plenty indoors or out, but we were playing for two weeks at each venue (5-nights a week) so moving gear around was a once every two-weeks task and I was in my early 20's then anyhow.

The picture below is from the first time I used my DNS-210 in a large venue. I wasn't sure it would cover it, so I brought my 410 with me and stacked my 210 on top of it. No question the 410 could handle it if I needed it. I only had the 210 plugged in and amp was bridged at 800-watts but the master was only turned up to 10 o'clock. If I needed to, I could quickly unplug my 210 and plug in my 410. Didn't need to as my 210 easily handled it, and the 410 was just an expensive amp stand all night.

1_709x1082.jpg
 
As a general comment since this topic comes up regularly, whenever comparing numbers, it's essential that you know how the numbers are derived. There are many different ways to measure sensitivity resulting is very different numbers, without it being clearly defined it's nothing more than number. Sometimes it's simply mistakes made, sometimes it's a lack of understanding of the technical aspects of the subject and sometimes it's intentionally misleading. Just like every other spec, it's the classic case of buyer beware.

Thank-you agedhorse for your excellent post! I always enjoy, if that is the right word, your intelligent, informitive and experienced comments and advice.

Kind of a tangent but recently I bought a pair of Klipsch Cornwall IV stereo speakers. I bought these based on reviews and specs. So happens that these speakers are rated at 102 db, one watt, one meter. Anyway, not only do these speakers sound great "to me", they are also very, very loud (and dynamic) like having a live band playing in my living room when I play Lps and Cds.

Thus, I made my comment on loudness based on a bass cab's db specs. And I agree with you that........how reliable are any manufacture's ratings? Nothing is to be trusted.

As a 72 year old "wanna be" bassist, I use Acme Low B 2-10 cabs for nice, true bass and a near perfect 41hz open E but the db is lacking but.............I don't care.

Want loud? Bigger amp? More efficient speakers? Whatever float one's boat.

I'll continually read your post as..........I love them!
 
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As I mentioned, my last touring rig was rated to produce about 127dB. This is with only 260W. The key is my speaker had a 103dB 1W/1m sensitivity rating.

[Log(260) x 10] + 103 = ~127dB.
Wise words from a man who knows what he is talking about. I play through 2 RevSound cabinets (a 112 and a 115); both are in the same ballpark; 102 db 1w/1m, either speaker by itself at 8 ohms are more than sufficiently loud for most sized gigs with approx 200 watts.
 
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I toured a 800RB biamped into a Bad End S15D and a Ramsa WS-A200 for a couple years. Always plenty loud.

The S15D was pretty lean down low, but rated sensitivity was 103dB 1W/1m. It's rated for 300W RMS but I don't think it can actually make good use of that much power. I thought it got loud fast and then started to fall apart at super high SPL...but maybe it was the amp rather than the cab.

Calculated SPL = [log(300) x 10] + 103 = 127.8dB. I don't feel like I ever got close to clipping this rig, or even pushed it to the point where it started falling apart.
It's amazing how solid and practical the Bag End S15-D is, even considering its limitations. I have one, and although I've thought about getting rid of it a few times, I'm glad I've held onto it. It's not the most portable cab, nor the most hi-fi or big sounding by modern standards, but it sounds good and it's generally pretty loud for what it is.
 
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When I was in college, I had a head with a whopping 90 watts of power. A couple very efficient 115 cabs rounded out the rig - big enough that they were efficient, and had decent low frequency extension. I got a case of tinnitus from that rig - it kept up with a loud drummer just fine.

Nowadays, we make speakers much smaller, and still efficient - kinda. Those tiny cabinets don't have much low frequency extension, so, you crank up the low end to try to make them shake the pace a bit - they actually aren't efficient at low frequencies. That is one reason why modern rigs need lots of watts - to drag some low end out of them.
 

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