Pirellithecat Posted October 19, 2023 Share Posted October 19, 2023 (edited) Looking for informed comment on a "thought experiment" which I'm going to have to take in stages ............ unless the answer is so obvious when explained that I run for cover ....... Hyperthetically, let's say that I have a 400W 8Ohm cab. Has a sensitivity of 100dB @ 1meter Nominally it has a Max output of 120 dB Actually, I have 2 identical cabs. When used together, giving a 4Ohm load, what is their combined sensitivety and Max Output. (dB AND Watts)? Edited October 19, 2023 by Pirellithecat Quote Link to comment Share on other sites More sharing options...
Newfoundfreedom Posted October 19, 2023 Share Posted October 19, 2023 Calling our resident expert @Bill Fitzmaurice 1 Quote Link to comment Share on other sites More sharing options...
BassBunny Posted October 19, 2023 Share Posted October 19, 2023 Or @Phil Starr 2 Quote Link to comment Share on other sites More sharing options...
Pirellithecat Posted October 19, 2023 Author Share Posted October 19, 2023 When I say "Watts" in the last sentence, I mean The nominal max wattage of the pair/ the nominal max wattage rating of an attached amplifier? Quote Link to comment Share on other sites More sharing options...
spyder Posted October 19, 2023 Share Posted October 19, 2023 As fair as I understand... 4 ohms 800 watts 106 db due to coupling of the two cabs. 2 Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted October 19, 2023 Share Posted October 19, 2023 OK most of the answer is: it depends. So I'm assuming you are looking to drive both speakers on one side of the PA and close coupled, ie close enough that the wave front is entirely in phase. You don't say if they are active or passive If they are the power is doubles and the radiating area is doubled so you'd gain 6db, in practice if they are passive the amplifier will be limited by the current the power supply can er.. supply so the power won't quite double but a 1db difference would probably not be noticeable. In practice it's more complex because they won't be close enough to couple perfectly and you'll get some cancellation. If they are active cabs then obviously you have two amps each 'seeing' an 8ohm load, if you are driving two 8ohm passive cabs from an amplifier and you are wired in parallel then the amp is driving into 4ohms and in your example the power handling is doubled to 800W. Quote Link to comment Share on other sites More sharing options...
Pirellithecat Posted October 19, 2023 Author Share Posted October 19, 2023 Sorry Phil - I can see I'm going to have to start giving you a fee for consultation work! The Speakers are my "hypothetical bass cabs", so passive and usually on stage, vertically stacked, under an 800W Amp. I should have been more clear ... oops! Quote Link to comment Share on other sites More sharing options...
Pirellithecat Posted October 19, 2023 Author Share Posted October 19, 2023 OK - Thanks for the info - I'm re-assured. Reason for asking. I have 2 Mesa Subway cabs (115 and a 112) and as the person who transports and unloads/loads/sets up the PA, I was thinking of changing from 2 cabs to a single cab to reduce carries into/out of the car/venue/home and to (albeit marginally) reduce set up complexity/time. Space is at absolute premium in the car - just about room for me once I get the bass Rig/PA/Monitors/lights etc in, so I've been looking at single cabs which don't reduce the overall wattage/potential volume. I've used a Barefaced BB2 in the past, but on it's own it just isn't sufficiently "big" - I've also tried the LfSys Monaco (which I prefer over the BB2) but again I'd need 2 which rather defeats the purpose. I've also found counterintuitive ratings for cabs which I assume are just doubled up versions of their single unit versions. Choice seems limited if I need an 800+ Watt cab that's not too heavy - there's a limited Barefaced Supertwin, a GRBass AT 212 Slim, or a Mesa Subway 2x12 unless anyone can suggest something else. So many thanks for the reality check 👍 Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted October 21, 2023 Share Posted October 21, 2023 Right I misunderstood. Obviously the physics remains the same in terms of impedance and power handling. I'm wondering why you need to be so loud? I've just upgraded from the LFSys Silverstone to the Monaco, I had two Silverstones and never ever used the second cab. The Monaco will go louder than the Silverstone and one cab was all I needed to match any drummer. In terms of on stage monitoring and/or your sound out front being louder than the drummer just creates problems because you'd then have to mic the drums and put them through the PA. Is this actually a problem with your over-loud guitarist I wonder? I'm also concerned that if you are pushing 600W through a Monaco generating peaks of 125db then your stage levels are high enough to damage your hearing. If space is at a premium then you wouldn't want to be carrying two cabs where one will do. Why do you want 800W handling? is this to match an amps quoted output? Who isn't hearing the bass? Is it you or the audience? Quote Link to comment Share on other sites More sharing options...
Pirellithecat Posted October 21, 2023 Author Share Posted October 21, 2023 The LfSys Monaco is indeed a brilliant cab. I prefer it to all the 1x12" cabs I've tried. Probably a bit louder and certainly much better dispersion, so easy to hear yourself on stage. I just wish there was a 2x12 as this might fit the bill to replace 2 400 Watt Cabs with a single cab to make for fewer trips between car/venue/ home and simplify set up a little. I think my original question was just seeking reassurance that there wasn't going to be significant reduction in headroom should I replace e.g. 2 Mesa Subway single driver cabs with a single Mesa Subway 2 driver cab or similar. Rather than taking one or two cabs depending on venue I now think it's better to have a single cab with sufficient headroom for all gigs and use volume control as appropriate.🤔😄 2 Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted October 21, 2023 Share Posted October 21, 2023 I've been gigging with single 1x12's for years. Even with a loud drummer I've never struggled for volume except at open air gigs where I take a second cab. Looking at the specs on Mesa's web site these look to be very capable cabs. Their specs are really helpful and so specific that I assume them to be the result of measurements rather than made up figures. (375W @ 74.3 Hz is such an oddly specific figure to choose it must be a measurement) So 97.5 db/W and 400W for the Subway 112 means the maximum output should be a genuine 123.5db. That's a really loud cab and should be much more than you'd need on stage. Any more than that and I'd be looking to put bass through the PA anyway. All this assumes your amp can drive 300W into the cab at 8ohms. Have you tried doing a gig with just one cab? If not why not try it, you might be pleasantly surprised. If you need reassurance then why not take both cabs but only plug one in (preferably the one on top) and see how you get on. Obviously you'll have to turn the volume up a little to get to your usual volume but the cab should be fine. I'd be interested to hear how you get on. 1 Quote Link to comment Share on other sites More sharing options...
moley6knipe Posted October 25, 2023 Share Posted October 25, 2023 I'm fascinated to see the outcome of this thread. I've gigged a single BB2 for years and if I cranked the volume on my GK amp to full I'd drown out drummer, both guitars and the PA! Quote Link to comment Share on other sites More sharing options...
tauzero Posted October 25, 2023 Share Posted October 25, 2023 On 19/10/2023 at 11:01, Pirellithecat said: Looking for informed comment on a "thought experiment" which I'm going to have to take in stages ............ unless the answer is so obvious when explained that I run for cover ....... Hyperthetically, let's say that I have a 400W 8Ohm cab. Has a sensitivity of 100dB @ 1meter Nominally it has a Max output of 120 dB Actually, I have 2 identical cabs. When used together, giving a 4Ohm load, what is their combined sensitivety and Max Output. (dB AND Watts)? Going back to that original question - 400W with a sensitivity of 100dB@ 1 metre for 1W = c. 128.5dB for just the one cab for the full 400W, c. 125.5dB if the output is 200W with an 8 ohm load. So a single cab pushed to 400W would be as loud as an entire concert. I'm another one who gigs happily with a 1x12 (BB2 until a couple of years ago, then a GR Bass combo). Quote Link to comment Share on other sites More sharing options...
Pirellithecat Posted October 25, 2023 Author Share Posted October 25, 2023 (edited) Our "total" output PEAKS at 115dB - so I guess our average is in the "School Dance" category. We do not put bass through FOH I've used a single BB2 gen 3 and a single LfSys Monaco in this situation and as I don't like driving cabs too much, they are not loud enough (according to the Guitarist and drummer and me). If I add another cab (1 x12 or 1x15) to spread the load, I'm much happier and the sound, tonewise, is more pleasant. So, "yes", I'd like to use a single cab to help set up and carrying "time" but so far am unconvinced that a single 12inch or 15inch cab will be sufficient. Tonight, as per Phils suggestions, I shall try out a singel 12inch cab and a single 15inch cab and report back. I might even take some dB readings. Edited October 25, 2023 by Pirellithecat Quote Link to comment Share on other sites More sharing options...
moley6knipe Posted October 25, 2023 Share Posted October 25, 2023 I've never worried about driving my BB2 hard. I know numbers and website blurb are sales pitches, but it's rated as good to 800w and the point of the design is to get heat out, provide proper porting etc so it can handle what's thrown at it. My GK gives 320W @ 8 Ohms and I tried turning the master up to 12noon once and I soiled myself, as did the rest of the lads 😃 I'm not posting here to in any way decry or belittle what you're asking / trying to achieve, but for me a GK into a BB2 gives as much vol and tone as I could ever want for any situation... I'm just tickled to find someone who finds a BB2 insufficient is all! 1 Quote Link to comment Share on other sites More sharing options...
Pirellithecat Posted October 26, 2023 Author Share Posted October 26, 2023 Update. Limited time last night but ...... Tried single 12 and 15 inch cab. Added 15 to 12 in combo. Confirms that what I like is more sq cms of speaker cone. The combo is far more authoritative. The 15incher does pretty well (raised up on other speaker), didn't drive it to breaking point, but at a volume I could hear myself playing "the notes" above the volume of the band. All good but lacks thump/scale etc. The 12 incher I'd be more worried about in terms of subjecting it to undue "stress". In a situation with bass in PA/FOH the single 15" would probably be OK but you'd need someone out front to let you know how the sound was. So OK as a stage monitor for the Bass Player. Useful experiment. The new Guitar Speaker is a mixed blessing though - fantastic in terms of getting to hear what the guitar is doing at all locations on "the stage" , but it is much stronger in the low mids, which makes it much more difficult to hear the notes on the bass. It's also much louder ........... The very unhelpful aspect of all this is the Catch22 scenario where to protect their ears, the drummer and guitarist use ear plugs. They then tend to play more loudly. Watched the dB meter ........... Peaks still at 115, but the range is in the region of high 90's to 115 peak - I'd say that the average SPL are in the region of 105. Work to do! Quote Link to comment Share on other sites More sharing options...
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