bumnote Posted February 20, 2019 Share Posted February 20, 2019 3 minutes ago, binky_bass said: I'm not great with the wattage/ohm equation. Does daisy-chaining two 8B 4 Ohm cabs then present half that load to the amp? With potentially a 2 Ohm resistance would I be right in saying that the cabs are then much more vulnerable to damage as with half the ohmage it essentially doubles the recieved wattage into the speakers? With each cab being 400w and the head being 600w would it then stand to reason that I could in theory push the 600w to say 2/3 power (say 400w equiviance) based on the 2 ohm resistance effectively halving the joint cab wattage to a combined 400w instead of 800w? So really, I suppose the question is, am I safe enough with running the Markbass at no more that 2/3 volume into both these cabs if they present a joint load of 2 ohm? Techy stuff! If you connect 2 x 4 ohm cabs up, you will get a total impedance of 2 ohms. This wont affect the speakers, but could well potentially damage the amp, depending on the spec of the amp. Quote Link to comment Share on other sites More sharing options...
Jack Posted February 20, 2019 Share Posted February 20, 2019 4 minutes ago, binky_bass said: I'm not great with the wattage/ohm equation. Does daisy-chaining two 8B 4 Ohm cabs then present half that load to the amp? With potentially a 2 Ohm resistance would I be right in saying that the cabs are then much more vulnerable to damage as with half the ohmage it essentially doubles the recieved wattage into the speakers? With each cab being 400w and the head being 600w would it then stand to reason that I could in theory push the 600w to say 2/3 power (say 400w equiviance) based on the 2 ohm resistance effectively halving the joint cab wattage to a combined 400w instead of 800w? So really, I suppose the question is, am I safe enough with running the Markbass at no more that 2/3 volume into both these cabs if they present a joint load of 2 ohm? Techy stuff! Yes, daisy chaining 2 4R cabs is a 2R load whether they're both linked to the head or whether it's one cab into the other. Either way they're still wired in parallel. There are some misconceptions in your post though, the amp is still 600W, so split between the two cabs they're only getting around 300W each, the amp doesn't magically double in power to 1200W just 'cos there are more cabinets on it, it's still a 600W amp. The cabs couldn't care less, the cabs are and will always be 4R each, the problem is your amp which I don't think is supposed to go down to 2R. It's the amp that stands to be damaged by this, not the cabs. 1 Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 (edited) I'm after an education here, so any thoughts would be happily received... What's the potential damage to the amp? From a logical point of view I would see the amp as feeding the cabs, so where does damage to the head come into the equation? And yes, I understand the slightly condecending statement of "The amp doesnt magically double in power to 1200w", I was more inferring to the potential load being recieved by the cabs if functioning at 2 ohm the the resitance is halved. So, with two 4 ohm cabs coming into the amp at 2 ohm, whats the risk of damage if the amp is rated at 600w on the rear panel with the handbook rated power being 500w into 4 ohm? Edited February 20, 2019 by binky_bass Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 Am I right in saying running these cabs at 2 ohms pushes the head beyond it's limit by a factor of 2? So would the head need to be run at a max of half power before hitting the danger zone? Quote Link to comment Share on other sites More sharing options...
Jack Posted February 20, 2019 Share Posted February 20, 2019 It wasn't meant to be condescending, sorry if you took it that way. Yes, the head is only safely rated down to 4R (as far as I know) so giving it a 2R load is outside of its rated safety specs and potentially dangerous. Like any safety spec, there may well be no long term consequences to running the head at 2R. Most safety specs have a margin of error and the amp will have safety features, so it might be fine. Just like if you put 510kg on a crane rated for 500kg you might well be safe, however that spec is what it is for a reason. Best case, all is fine. Worst case, amp fails catastrophically and explodes in a fireball. There are a lot of very possible scenarios in between those two examples, most of which aren't much fun. Quote Link to comment Share on other sites More sharing options...
Japhet Posted February 20, 2019 Share Posted February 20, 2019 (edited) 28 minutes ago, binky_bass said: Am I right in saying running these cabs at 2 ohms pushes the head beyond it's limit by a factor of 2? So would the head need to be run at a max of half power before hitting the danger zone? Your amp will have a minimum load. It's most probably 4 Ohm in which case you'll fry it if you try to run 2x 4 Ohm cabs. Running at half power makes no difference and you'll still fry it. Don't do it. Edited February 20, 2019 by Japhet Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 I've run the rig as in the picture for a good 3 weeks now, probably a total of 10 hours use, running the gain at circa 1/3 and the volume and about 1/2 with no issues at all. No overheating, no stuttering, nowt... The amp definitely says 500w @ 4 Ohm on the rear, and these cabs are definitely 4 Ohm a piece. Running these cabs together, supposedly at 2 Ohm into a 500w @ 4 Ohm head, should I expect derterioration over time or more of an instant death? As I certainly havent experianced the latter. Obviously I don't want to kill the amp, but as yet (in my blissful apparent ignorance!) I have had no problems whatsoever running the rig as is. Quote Link to comment Share on other sites More sharing options...
Jack Posted February 20, 2019 Share Posted February 20, 2019 (edited) 10 minutes ago, binky_bass said: The amp definitely says 500w @ 4 Ohm on the rear, and these cabs are definitely 4 Ohm a piece. Running these cabs together, supposedly at 2 Ohm into a 500w @ 4 Ohm head, That's definitely a 2R load then, and that's definitely below the rated safe impedance for your head. I just quickly checked the manual on my lunch break and it says: 'DO NOT connect amp to a load of less than 4ohms, outputs are wired in parallel'. 10 minutes ago, binky_bass said: should I expect derterioration over time or more of an instant death? As I certainly havent experianced the latter. Obviously I don't want to kill the amp, but as yet (in my blissful apparent ignorance!) I have had no problems whatsoever running the rig as is. Good question. I dunno, both? neither? one then the other? As I said before, most safety ratings are overly cautious, there may in fact be no repercussions at all. The speed rating on my car tyres is V, which is 149mph. What will happen if I go over 149mph? They might be fine, they might wear out faster and not last as long, or they might catastrophically fail and explode. The same is true of your amp. It's a bad idea. Edited February 20, 2019 by Jack 1 Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 Right, yeah I've had a read of that and you are indeed correct. So with these cabs being wired in parallel at 4 ohm each, because of the nature of parellel wiring the load becomes 2 ohm... so if one cab blows the other is still alive. Is it possible to re-wire them as series? This then would see them function at a joint 8 ohm right? ...But with the drawback of them both cutting out if one dies? My brain is trying to absorb everything here! Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 So similarly, it would be equally unwise to run four Aguilar DB112 cabs (300w 8 ohm) into a TH 500 (500w @ 4 ohm, 250w @ 8 ohm) as that would also be a 2 ohm load? If the amp has two dedicated inputs for speakers, I assume daisy chaining two DB112 cabs into each input (4 cabs in total) would then be running a 2 ohm load? (I dont have 4 DB112s, I'm just getting my head around safe loads etc.) Quote Link to comment Share on other sites More sharing options...
Jack Posted February 20, 2019 Share Posted February 20, 2019 (edited) 50 minutes ago, binky_bass said: Right, yeah I've had a read of that and you are indeed correct. So with these cabs being wired in parallel at 4 ohm each, because of the nature of parellel wiring the load becomes 2 ohm... so if one cab blows the other is still alive. Is it possible to re-wire them as series? This then would see them function at a joint 8 ohm right? ...But with the drawback of them both cutting out if one dies? My brain is trying to absorb everything here! Basically, yes. Not to confuse you even further but obviously a cab isn't really a thing, it's speakers n a box, right? So the speakers inside each cab are wired in either series or parallel too (or both), so what would actually happen if you broke a speaker is the total impedance of one cab (and so the whole system) would change. The electrons flying around the cables don't really know or care that there are even two separate cabs, it's just one load created by all of the individual speaker drivers. Clear as mud? 🙂 The easiest way to hook up two speaker cabinets in series is to use a series wiring box. It's a pretty simple DIY project, and if you can't do it I'm sure a local university student reading electronics would do it for beer money. In a mathematically perfect you wouldn't need to do this, as the 3dB increase you get from doubling speaker area would be cancelled out by the 3dB loss you have from halving amp power. So (again, in a perfect world) you amp with 500W into one of your cabs is the same as running into 8R with 2 cabinets. It normally isn't that simple though.... 45 minutes ago, binky_bass said: So similarly, it would be equally unwise to run four Aguilar DB112 cabs (300w 8 ohm) into a TH 500 (500w @ 4 ohm, 250w @ 8 ohm) as that would also be a 2 ohm load? If the amp has two dedicated inputs for speakers, I assume daisy chaining two DB112 cabs into each input (4 cabs in total) would then be running a 2 ohm load? (I dont have 4 DB112s, I'm just getting my head around safe loads etc.) Yes. This is why I made the point above about it being thought of as a total load rather than the cabs being thought of as being discreet. Do you theoretically have 2 cabinets, each 8R with 1x12" speaker each, or one 2x12" cabinet that's a total of 8R as the two speakers in it are wired in parallel? It doesn't matter! Either way there's 2 drivers, 8R each, so 4R total. 4 of those DB112s cabs is a total load of 2R, just as if it was one massive 4x12" cabinet. Edited February 20, 2019 by Jack Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 So 3 Speakon connectors and 4 bits of wire, wired in series, housed in a non conductive box would essentially do the trick? Weekend project... 1 Quote Link to comment Share on other sites More sharing options...
Skinner Posted February 20, 2019 Share Posted February 20, 2019 Two 8 ohms cabs will present a 4 ohm load to the amplifier. Quote Link to comment Share on other sites More sharing options...
jrixn1 Posted February 20, 2019 Share Posted February 20, 2019 (edited) 2 hours ago, binky_bass said: the amp is rated at 600w on the rear panel with the handbook rated power being 500w into 4 ohm? I think the 600W is the power consumption of the amp itself. The power the amp delivers to the speakers is something different (as mentioned, 500W into 4 ohms or 300W into 8). 1 hour ago, binky_bass said: I've run the rig as in the picture for a good 3 weeks now, probably a total of 10 hours use, running the gain at circa 1/3 and the volume and about 1/2 with no issues at all. Regarding wiring the cabs in series: will 300W into two cabs (receiving 150W each) sound any louder/better than 500W into one? You said yourself you're running it at lowish volume. Perhaps using just one cab and turning the master up will be easier/sufficient. Edited February 20, 2019 by jrixn1 1 Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 I used one 8B cab for a good year or so, no volume issues there to be honest. I recently got the other 8B from eBay as it was silly cheap hence the second cab. There is no real benfit to using both for the purposes in which I use them other than having two looks better than having one! Purest self-indulgence I know, for which I could easily have been punished with the blowing up of the MarkBass... So knocking up a series box from about £15 in parts would allow me to continue my (somewhat pointless) amp vanity. Either that, or get a second head for the second cab, or god fobid, SELL the second cab... 1 Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 I still don't feel quite at Ohm with all of this, but I'm learning! (awful I know...) Quote Link to comment Share on other sites More sharing options...
bumnote Posted February 20, 2019 Share Posted February 20, 2019 The reason I posed the question in the first place is I have effectively the same cab set up as you have [total load 2 ohm impedance] but havent run it with the the phil jones D400 because the spec on the amp says 4ohms minimum. The best bet for you is to phone whoever is the markbass distributor and ask them what would happen if you connected your amp to a 2 ohm load. Then you would have hopefully the definitive answer Quote Link to comment Share on other sites More sharing options...
Muzz Posted February 20, 2019 Share Posted February 20, 2019 5 minutes ago, binky_bass said: I used one 8B cab for a good year or so, no volume issues there to be honest. I recently got the other 8B from eBay as it was silly cheap hence the second cab. There is no real benfit to using both for the purposes in which I use them other than having two looks better than having one! Purest self-indulgence I know, for which I could easily have been punished with the blowing up of the MarkBass... So knocking up a series box from about £15 in parts would allow me to continue my (somewhat pointless) amp vanity. Either that, or get a second head for the second cab, or god fobid, SELL the second cab... Yep, them's is your options. There are a few amp heads which will run under 4 ohms loads (the Mesa 800s, Genz Magellan, etc), but the vast majority have a 4 ohm limit. As above, I don't know what the exact repercussions might be of running a lower impedance load and what triggers there might be, but if the manufacturer says don't do it, they mean 'If it goes click/boom/fizz, don't call us'... Quote Link to comment Share on other sites More sharing options...
jrixn1 Posted February 20, 2019 Share Posted February 20, 2019 4 minutes ago, binky_bass said: There is no real benfit to using both for the purposes in which I use them other than having two looks better than having one! You could take two cabs, but only plug one in It does look better, I agree! Quote Link to comment Share on other sites More sharing options...
binky_bass Posted February 20, 2019 Share Posted February 20, 2019 Before I ran this rig I actually did send both MarkBass and Phil Jones and email asking if it was safe to run both cabs into the Markbass... No response from either. As such I did it anyway, in hindsight a potentially foolish manoeuvre, but hey, now I know! Quote Link to comment Share on other sites More sharing options...
Muzz Posted February 20, 2019 Share Posted February 20, 2019 One analogy is if you're driving along at a reasonable speed, and you keep the accelerator where it is, but start to depress the clutch (i.e. reduce the load on the engine), then the revs will rise higher and higher, potentially damaging the engine... Quote Link to comment Share on other sites More sharing options...
Skinner Posted February 20, 2019 Share Posted February 20, 2019 The cabinet or cabinets should never present a lower load than what is specified from them amp outlet/outlets or you run the risk of serious amp damage. If you have more than one amp you could just use the right configuration of amps to match cabs. Peavey used to have a bass amp that output down to two ohms which I used with a 4x12 cab (2 ohms). Krampera kvb 800 runs down to 2 ohms, also Genz Benz shuttle Max 12.2 has twin amps and outputs at 4 ohms so that's another potential fix? Quote Link to comment Share on other sites More sharing options...
Skinner Posted February 20, 2019 Share Posted February 20, 2019 Also. . don't try this at ohm ! Ha ha Quote Link to comment Share on other sites More sharing options...
itu Posted February 20, 2019 Share Posted February 20, 2019 First I write shortly about speaker load and amp, then I will offer you a possible, if not a working solution. Amp can push volts and amperes to a load (speaker). If the load is optimal, the most volts and amperes (multiplied together: watts) from the amp go to the speaker. Now the Ohm's law tells, that current equals volts divided by impedance (I = U / Z). When the impedance gets smaller, the current rises. Sometimes people think that lowering the impedance brings you more volume. Although the amp may see less impedance it may be not powerful enough to push that load anymore. Think it like that you go to a gym. There are two springs that you need to push. The other is short and thick (lower impedance) and the other is longer but more slender. Because of the thickness of the spring wire the shorter is harder to push. Yes, it would only need shorter distance to be pushed together but it is uncomfortably heavy for the user. What happens in the amp is that the current starts to rise and it heats up the power section. If the parts can handle heat, they survive, if not, you get lots of melt metal. It not uncommon, that the power section pushes less power to the smaller (and harder) load. So you get less volume. My slightly unorthodox option to your two cabinet issue starts from opening the cabinets. If the elements are wired in parallel (two 8 ohm elements in parallel = 4 ohms), you might change their connection to series (two 8 ohm elements in series = 16 ohms). Then it would be easy to just use one or two cabinets in the amp. I suppose that your amp is not tube. Tubes love exact matching. Usually transistors like similar or larger impedance in their outputs. 1 Quote Link to comment Share on other sites More sharing options...
Pea Turgh Posted February 20, 2019 Share Posted February 20, 2019 4 hours ago, Skinner said: Also. . don't try this at ohm ! Ha ha Ohm-my gosh these jokes are getting bad. ... I’ll get my coat. Quote Link to comment Share on other sites More sharing options...
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