Impedance etc

[Mr. Foxen]

You problem is pretty much definitely lack of sensitivity in the cab. Half the power going to is is wasted on a speaker not touching air, and it is very unlikely that the speakers can convert much more power than you are feeding them into sound. Bigger cab is needed. All the plans for increasing watts are bit meaningless, because at most you can double watts and that is 3db difference, which in the scheme of things, you can just about notice as an increase in volume. The advantage of two speaker cabs is that you've just double the amount of air being moved by speakers, as well as dropping impedance, so you double up the benefits, and get an additional bonus from coupling in the lows, and an additional bonus of elevation for better mid/high audibility.

[flyfisher]

.I need several questions answered.
1. Does the amp automatically deliver the higher wattage to a 4 ohms speaker (there's no switch on the amp)
[b]Yes[/b]

2. can i change the ohmage of the speaker without a 'switch'
[b]You could change the CAB ohmage by messing around with switches and rewiring the SPEAKERS, but not to 4 ohms[/b]
[b]A two speaker 8 ohm cab will have speakers of 16ohms in parallel or 4 ohms in series. You can't rearrange these to give a 4 ohm 212 cab.[/b]

3. Can i daisy chain another 8 ohm cab and will this deliver an ohmage platform for the amp to deliver its higher wattage of 600w or will two 8 ohm speaker still only produce and 8 ohm capacity.
[b]Not daisy chain (that would be in series and give you 16 ohms to the amp), but you could connect another 8ohm cab in parallel to give a 4ohm load to your amp.[/b]

4. Why when the speaker wattage is 600 watts and I presume the amp is only delivering 375watts is the amp clipping.
[b]The speaker wattage is a measure of what the speaker can accept. It has no bearing on what the amp can deliver. The amp will go into clipping if it is over-driven in some way, which is not really a speaker problem.[/b]


5. Can I daisy chain speakers of 8 and 4 ohm
[b]Again, daisy-chaining means connecting in series. This would give 12 ohms and would do no harm but the amp could not deliver full power.[/b]
[b]I suspect you mean connecting in parallel, in which case the amp would see a load of 2.7ohms, which is probably below the minimum for your amp and would therefore not be a good thing.[/b]

6. Should i just admit the speaker and amp are incompatible and buy a 4 ohm speaker with enough wattage headroom
[b]If you really want to get the max power out of your amp then yes, though 375W into a 212 cab should be pretty loud. I guess it depends on the venue but my after a certain size wouldn't you play via the PA as well? 600W on stage seems like an awful lot to me.[/b]

[Mr. Foxen]

[quote name='flyfisher' timestamp='1333795796' post='1606531']
[b]If you really want to get the max power out of your amp then yes, though 375W into a 212 cab should be pretty loud.[/b]
[/quote]

Bear in mind its an SP isobaric job, so it isn't really a 2x12 but a dual motor 1x12.

[flyfisher]

Ah, fair point - hence your point about half the speaker not touching air?

[AMPEG]

[quote name='Mr. Foxen' timestamp='1333798517' post='1606611']
Bear in mind its an SP isobaric job, so it isn't really a 2x12 but a dual motor 1x12.
[/quote]Don't understand 'dual motor' How does an isobaric 212 differ from an ordinary cab? Also to run 2 x 8ohms cabs should i be connecting them via the two speaker inputs on the reverse of the amp rather than connecting the second cab via the dual jack inputs on the reverse of the speakers.

[Mr. Foxen]

[quote name='AMPEG' timestamp='1333803087' post='1606703']
Don't understand 'dual motor' How does an isobaric 212 differ from an ordinary cab? Also to run 2 x 8ohms cabs should i be connecting them via the two speaker inputs on the reverse of the amp rather than connecting the second cab via the dual jack inputs on the reverse of the speakers.
[/quote]

Isobaric means one speaker in in front of the other, the airgap between them is of static pressure, which is what 'isobaric' means. It means the two act as one speaker but with two motors, they sink twice the power but move the same amount of air as a single speaker, the upside is you can get away with a smaller box behind them as you have twice the power to expand and compress the air 'spring' in it, smaller cab is harder spring, larger cab is softer spring style.

[AMPEG]

[quote name='AMPEG' timestamp='1333803087' post='1606703']
Don't understand 'dual motor' How does an isobaric 212 differ from an ordinary cab? Also to run 2 x 8ohms cabs should i be connecting them via the two speaker inputs on the reverse of the amp rather than connecting the second cab via the dual jack inputs on the reverse of the speakers.
[/quote]its not that i want 600watts of power on stage, rather it is to try and avoid the clipping by being able to run the amp without having to put the master and pre-amp volumes right up.

[AMPEG]

[quote name='Mr. Foxen' timestamp='1333803352' post='1606711'] Isobaric means one speaker in in front of the other, the airgap between them is of static pressure, which is what 'isobaric' means. It means the two act as one speaker but with two motors, they sink twice the power but move the same amount of air as a single speaker, the upside is you can get away with a smaller box behind them as you have twice the power to expand and compress the air 'spring' in it, smaller cab is harder spring, larger cab is softer spring style. [/quote] So in essence the drivers although having twice the wattage of say a single 12 are only moving the air of one...meaning they are louder but not as punchy?

[Mr. Foxen]

[quote name='AMPEG' timestamp='1333803691' post='1606718']
So in essence the drivers although having twice the wattage of say a single 12 are only moving the air of one...meaning they are louder but not as punchy?
[/quote]

Bassier/lower for a small box. A single 12 in twice the size box (actually maybe 50% bigger because no space taken up by the other speaker, gap and extra port length) will sound the same and have same max volume. Obviously you lose some power because it will be higher impedance than two speaker in parallel, but the extra power is wasted anyway because it isn't going into moving extra air in the isobaric box. For the cost of twice the price and extra weight, you gain a 1/3 smaller box.

Edit: So for your purpose, the problem isn't lack of power as much as lack of volume, you need more speaker area moving air for your power to be better used.

Edited April 7, 2012 by Mr. Foxen

[StraightSix]

An Isobaric speaker has one 12" driver behind the other so only one is hanging out the front and in contact with the air therefore measurements such as SPL (how loud it can go) will be determined as if it were a 1X12...ie, not very loud.

You need a better cab that is capable of moving far more air...your (effectively) 1X12 cab has an approximate Volume displacement (air movement capability) of around 250cc whereas a properly designed 2X12 would have a Vd around 680cc - almost three times as much.

I will now quote Bill Fitzmaurice from another thread: Doubling driver displacement offers the same increase in volume as quadrupling your power output.

[flyfisher]

[quote name='AMPEG' timestamp='1333803087' post='1606703']
Also to run 2 x 8ohms cabs should i be connecting them via the two speaker inputs on the reverse of the amp rather than connecting the second cab via the dual jack inputs on the reverse of the speakers.
[/quote]
On all the cabs I've seen it these different ways to hook things up are electrically the same. This is because the multiple sockets are usually connected in parallel. I prefer to connect two cabs using the two amp outputs because if they are connected amp-cab-cab then if the connection to the first cab fails for some reason then the second cab will go quiet as well. Also, splitting the power over two cables will, in theory, reduce power losses in the cabling. But, frankly, these are very minor points and in practice there's little difference in these two ways of hooking things up. They certainly won't address the other points you're raising.

[AMPEG]

Thanks for all the replies guys its been really helpful...seems my choice of cab was wrong since whilst i am able to get the volume i want the isobaric cab isn't giving me any punch. I will try hooking up my Ampeg 8 ohm 200 watt speaker along with the 212. Trouble is the clipping on the amp, how is it possible to be 'over-driving' the amp...i'm using an Overwater active bass which by nature is bright and punchy but surely the amp should be able to handle this? Is there any danger that I could blow the amp and if so how do I counteract this?

[StraightSix]

Adding more speakers effectively adds volume.

Therefore you may find that the amp clipping stops because you won't need to run the amp so hard...try it and see what you think.

[BassTractor]

Sorry, haven't read all eight pages, but from what I've seen, and trying to answer your last posting:

Indeed, the amp is not "overdriven" by the Overwater. It's overdriven by that guy from South Wales.

Without going into details:
You are asking one or more of the amp's stages to deliver amplitudes (say volume) that it can't. Having done its very best, it clips (cuts) off the part of the amplitude it can't deliver. This clipping results in both a lower volume than wished for AND the production of a massively awful lot of new higher frequencies. Depending on construction and possible presence of protection circuitry, this might blow up the tweeter(s) in the cab.

If the tweeter indeed is blown up, this will normally not be harmful to the amp, but in some (rare, as far as I'm aware) instances may reduce the impedance of the cab to far below what the amp's power stage can tolerate (typically removing the impedance altogether), and _that_ would possibly ruin the output transistors (or equivalent) of the amp. This too depends on construction and possible presence of protection circuitry.


Without knowing the specifics of your gear or the specifics of that guy from South Wales: you could maybe experiment a little with the gain and master volume settings. Something as simple as that can help a lot.

YMMV, and all that.


best,
bert

Edited April 10, 2012 by BassTractor

[BassTractor]

Knowing full well that YMMV + +, but just to be sure:

Having given this some more thought, I think maybe you've run into a _function_ of the GB, that allows you to set the gain so that the first stage gets slightly overdriven. In case, this is a good thing, and a light is then not a warning sign but an advertisement.


best,
bert

[Brother]

I need to buy a new amp and cabinet and I looking at matching an Orange Terror Bass 500 amp, which has an output of 500 watts (8 or 4 ohms switchable)with an Orange OBC410 cab, which handles an output of 1,000 watts(8 ohms). Orange tell me it will be a good match but some of the threads here are saying that a 1,000 watt cabinet would not work efficiently with a 500amp head. Can anyone advise please??

[StraightSix]

The Terror Bass and that OBC410 should be fine as Orange have said.

According to the specs I've seen, the OBC410 is rated at 600W RMS not 1000W as you say.

If it were my money I would not want a cab weighing 43kg (95lbs), I would probably go with a Barefaced Super Twelve at 18kg (40lbs). The Super Twelve will handle 1000W RMS, is made in Britain and is at the pinnacle of current bass cab design.

[url="http://barefacedbass.com/product-range/super-twelve.htm"]http://barefacedbass...uper-twelve.htm[/url]

It will only cost you around £780 delivered - the Orange OBC410 is £732 plus delivery charge.

Edited May 2, 2012 by StraightSix

[Brother]

Thanks for your comments. According to the techie at orange they used to be 4 x 150w speakers but have been changed to 4 x 250w speakers and the sales information has not been updated so it is in fact 1,000 watts. I have not heard of barefacedbass but looking at some of the reviews it seems to be very well received. Need to do a little more research I feel. It's mind boggling for a newbie!

[StraightSix]

No problem - keep in mind that speaker (and therefore cab) wattage ratings are the limit at which the voice coils melt from thermal (heat) overload.

In many cases, you can realistically halve that wattage rating because the speakers will hit their displacement limits well before their thermal limits.

The Beauty of the Terror Bass is that it only weighs 5kg...why not look for an equally lightweight, modern cab to partner it with...?

Lots more info here:

[url="http://barefacedbass.com/technical-information/understanding-power-handling.htm"]http://barefacedbass.com/technical-information/understanding-power-handling.htm[/url]

[url="http://barefacedbass.com/technical-information.htm"]http://barefacedbass.com/technical-information.htm[/url]

One more thing to consider - Barefaced cabs rarely come up for sale secondhand and when they do, they often sell in minutes which says a lot in terms of how they are loved by their owners.

[Brother]

I opted for the Orange Terror Bass 500 + Orange OBC410 (600 watts @8 ohms). The Terror Bass has an Ohm switch but I am not sure how this works. Can anyone advise what the max output I will be getting from the OBC410 when the Terror Bass is switched to 8 ohms? Thanks.

[StraightSix]

The Terror 500 will put out 500W RMS at 4 or 8 ohms - it must be switched to 8 ohms to use a single OBC410.

The Terror is probably quite capable of putting out over 1000W peak output so your OBC410 cab is not safe if you crank it too much.

As I said before, the cab wattage rating is only the limit at which the speaker voice coils melt - the speakers will run out of excursion well before then and fail.

Best thing is to use your ears - if the speakers are complaining, you will hear it and must turn down. If you need more volume, by a second OBC410 8 ohm cab and run them both with the Terror switched to the 4 ohm setting.

[BigAlonBass]

Here's a (probably) silly question:- I have a Peavey Max 700 Amp with 2 speaker outputs. I have 2 x 8 ohm cabs and 1 x 4 ohm cab. If I 'daisy chain' the two 8 ohm cabs to one output, and the 4 ohm cab to the other output, is it delivering 4 ohms through each output?
Like I say, probably a silly question, but I could never get my head round the Maths for multiple speaker combinations, and I just wondered if it was do-able for an on-stage Rig.
The Peavey goes down to 2 ohms, so hopefully it won't be any lower than that, if I've got it wrong.

[Mr. Foxen]

I think you are picturing ohms wrong, which makes them hard to understand, form the 'delivering ohms' phrase. Ohms are a property of the cabs, how hard they are to push current through, lower is easier. With 2 8ohm cabs daisy chained in parallel (the default if you use the speaker out on a cab to connect to second cab), those two will total 4 ohm, then the second 4 ohm cab brings it down to 2. But half the power will be split between the pair of cabs, and the other half goes to the cab on its own, which causes balance trouble best avoided.

[PauBass]

Not sure about this set up I have in mind for my Aguilar DB750 amp:

If I run two 8 Ohms cabs, one 2x10 cab 350 Watts and the other one a 1x15 400 Watts, that would make them go down to 4 Ohms, right?.... what total wattage I'll be getting?

Edited July 20, 2012 by PauBass

[StraightSix]

Maximum of 750 watts RMS running at 4 ohms.