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Impedance etc

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[quote name='StraightSix' timestamp='1342811224' post='1741463']
Maximum of 750 watts RMS running at 4 ohms.
[/quote]

So the sum of both cabs wattage then?
That's the same as my current 412 cab, will they feel as loud by being two cabs?

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I would suggest you should exercise caution with those cabs - most cab wattage ratings are based on thermal limits of the speaker voice coils.

This means that they will overheat at approximately the RMS rating but many bass speakers will hit their excursion (movement) limits well before that and be damaged.

As to similar volume levels to your 412, you will have to compare them to know for sure.

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[quote name='BigAlonBass' timestamp='1342736930' post='1740384']
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?
[/quote]

The two outputs are probably connected in parallel, so you'll actually finish up with a load of 2 ohms.

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[quote name='PauBass' timestamp='1342811347' post='1741466']
So the sum of both cabs wattage then?
That's the same as my current 412 cab, will they feel as loud by being two cabs?
[/quote]

No, not the sum of the two cabs wattage. The two cabs will have a total impedance of 4 ohms, the DB750 will output 750W into 4 ohms, 375W into each cab. However, unless you make a habit of running the amp flat out constantly, the fact that it can nominally output 25W more than the rated power into one of the cabs should be irrelevant.

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Tauzero, StraightSix, thanks a lot for your help guys!

Not sure if changing my 412 cab rated at 750 watt is going to be a good idea, with the new rig I'll be losing one speaker as I'll have a 115 and a 210 cab...will I
lose volume?

Edited by PauBass

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[quote name='PauBass' timestamp='1342818991' post='1741620']
Not sure if changing my 412 cab rated at 750 watt is going to be a good idea, with the new rig I'll be losing one speaker as I'll have a 115 and a 210 cab...will I
lose volume?
[/quote]

Hmmm, how long is the piece of string that you use to tie up your apples and oranges?

Speakers differ in efficiency as well as in impedance and power handling. Total speaker cone area will be smaller but if the speakers move further (higher Xmax) then the volume of air moved might be the same or more.

How often do you actually run it flat out?

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[quote name='tauzero' timestamp='1342819786' post='1741633']


....Speakers differ in efficiency as well as in impedance and power handling. Total speaker cone area will be smaller but if the speakers move further (higher Xmax) then the volume of air moved might be the same or more.

How often do you actually run it flat out?
[/quote]

Well I do play in a very loud rock band and I need the power/volume for this gig.
The cab I'm thinking of replacing is a Bergantino NV412, just because I want to make the rig a bit more portable for smaller venues.

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[quote name='PauBass' timestamp='1342865400' post='1741971']
Well I do play in a very loud rock band and I need the power/volume for this gig.
The cab I'm thinking of replacing is a Bergantino NV412, just because I want to make the rig a bit more portable for smaller venues.
[/quote]

The Berg outputs a sound level of 103dB at 1W at an ear located 1m from the speaker (if Berg's figures are to be believed). What you need to do is find the SPL for the other two speakers. Things start getting rather convoluted due to the logarithmic nature of sound levels, but, taking a simplistic approach, if they're both around the 103dB 1W/1m level, the volume will be around the same. A 3dB difference in sound level means a doubling in power, so if they were both around the 100dB level, you would need to turn the amp up a bit. How much is another of those piece of string questions, volume/output level controls are nominally logarithmic so on a scale of 1 to 10 you might turn it from 5 to 6, or you might have one of the more biassed controls that have most of the power increase over the first half of their travel which would mean you had to go from (say) 4 to 8.

There may well be someone a bit more knowledgeable than me along in a bit to correct any mistakes I've made.

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[quote name='tauzero' timestamp='1342880138' post='1742311']
The Berg outputs a sound level of 103dB at 1W at an ear located 1m from the speaker (if Berg's figures are to be believed). What you need to do is find the SPL for the other two speakers. Things start getting rather convoluted due to the logarithmic nature of sound levels, but, taking a simplistic approach, if they're both around the 103dB 1W/1m level, the volume will be around the same. A 3dB difference in sound level means a doubling in power, so if they were both around the 100dB level, you would need to turn the amp up a bit. How much is another of those piece of string questions, volume/output level controls are nominally logarithmic so on a scale of 1 to 10 you might turn it from 5 to 6, or you might have one of the more biassed controls that have most of the power increase over the first half of their travel which would mean you had to go from (say) 4 to 8.

There may well be someone a bit more knowledgeable than me along in a bit to correct any mistakes I've made.
[/quote]

Thanks again for your advice...I've found out they they output at and I assume there's going to be a bit of a drop in volume there:

[b]Sensitivity:[/b][color=#000000][font=Arial, Helvetica, sans-serif][size=3] 96 dB 1W 1M For the 115 cab[/size][/font][/color]
[b]Sensitivity:[/b][color=#000000][font=Arial, Helvetica, sans-serif][size=3] 98 dB 1W 1M for the 210 cab[/size][/font][/color]

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I think you may need to look for another alternative - EAD Foundation 212, Tech Soundsystems ND212 or ND410 perhaps.

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[quote name='alan_01_uk' timestamp='1346584183' post='1790749']
does this mean I can not at a later stage add a second cab[/quote]

Yes - you can use two 8 ohm cabs or just one 4 ohm cab with that amp.

Edited by StraightSix

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[quote name='alan_01_uk' timestamp='1346585472' post='1790781']
Thanks for the reply but that is my point I would have to buy two more 8 ohm cabs as if I had bought the 2x10 8 ohm cab I would have just had to buy the 1x15 8 ohm cab so I can't use the 2x10 cab I have got and just add another cab I will have to buy another two 8 ohm cabs?
[/quote]

I'd sell (or take back to shop & exchange) the 4Ω cab & get the 8Ω 2x10 & then you can add another 8Ω 2x10 when needed (or any other 8Ω cab).
With your amp the most you can use is 1 4Ω cab or 2 8Ω cabs (or 4 16Ω cabs).

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How long have you had your cab? Might be worth having a word with where you bought it if recent.

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You'd probably be as well to just hold on to it & sell or swap it if you get to a point where you need to.

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You should give the MB rig a try in your full band. You might be well surprised.

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[quote name='alan_01_uk' timestamp='1347193357' post='1797840']
Thanks for your advise I played in a medium sized pub last night with the band and I have only ever used the markbass for my duo gigs where I di through the pa and it really worked well and the band were well surprised and it means when I am playing a small to medium venue I will not have to break my back and take my Dynacord 4 x 10 300 watt combo.
[/quote]

Might be worth considering selling the 2x10 & the combo & getting a couple of 8Ω 2x10s?
Did you stick the 2x10 vertical?

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[quote name='alan_01_uk' timestamp='1347229589' post='1798388']


Yes I did have it vertical so the speakers would be one on top off the other rather than next to one another is that a good or bad idea?
[/quote]

I'd say it's a good idea as the cab designers on here recommend it for 2 reasons.
It brings one of the drivers closer to ear level & it gives a better dispersion from left to right.

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Need a bit of help as my brain is frazzled at the moment!

Amp = Hartke LH1000[list]
[*]Dual Parallel Mode: 2 x 225 watts @ 8 ohms, 2 x 320 watts @ 4 ohms, 2 x 545 watts @ 2 ohms
[*]Bridge Mode: 1 x 750 watts @ 8 ohms, 1 x 1100 watts @ 4 ohms
[*]
[/list]
Cab = Ashdown 8x10 1200W @ 4 ohms.

I am looking at adding a 500w, 8 ohm 1x15 cab.

Can this be done safely without loss of life to amp or cab???

Any pointers would be greatly appreciated and sorry if this dumbass question has been asked a thousand times previous.

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[quote name='hunt the shunt' timestamp='1364651435' post='2029231']
What on earth do you think you will achieve adding a 1x15 to a kilowatt 8x10 rig???
[/quote]Good point. A 1x15 is a good addition to a 2x10. Adding one to an 8x10 is about as useful as putting a sail on a cigarette boat.

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[quote name='hunt the shunt' timestamp='1364651435' post='2029231']
What on earth do you think you will achieve adding a 1x15 to a kilowatt 8x10 rig???
[/quote]

He just wants his roady to hate him more.

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[quote name='alexclaber' timestamp='1219072784' post='264689']
Although this analogy is full of holes it does make some sense given a bit of tweaking. If you take a normal car onto a race track and try to achieve consistently fast lap times then your brakes will give out, guaranteed. Take that car back on the road and those same brakes will be more than capable of decelerating the car as required for many thousands of miles, even if you like to drive fast.

Consider the amp the engine and the speakers the brakes - in normal use your amp can have significantly more power than the speakers can handle and you will never ever have a problem. Push your amp to the point where things are not sounding nice, just as driving a car fast round a track will seem rather brutal compared to driving quickly on the road, and you risk speaker damage. And just as a low powered car has enough power to wreck its brakes on a track, so too can a low powered amp wreck a speaker if abused.



The wattage delivered to the speaker depends on the voltage output from the amp and the speaker impedance at that frequency. The voltage output from the amp depends on the voltage input to the amp from your bass and the gain within the amp. Play hard and use a hot bass with the volume on the amp set at 2 and more voltage will be output than with a quiet bass and a light touch but the volume set at 11. See the other thread about gain vs volume for more information.

Alex
[/quote]

I'm pretty sure Alex is the first person in the thread to identify a pertinent issue: That speakers have different impedance ratings at different frequencies. I believe I understand correctly that this is the real reason why tube amplifiers appear louder for their wattage. They are able to output a variable current to match the changing impedance of the speakers over varying frequencies thus applying full wattage regardless of the frequency, which isn't true of solid state amps, so they have a fuller more balanced and efficient transference of energy across the frequency range. Does this sound correct?

D.

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[quote name='polyrythmmm' timestamp='1369314226' post='2087643']
I'm pretty sure Alex is the first person in the thread to identify a pertinent issue: That speakers have different impedance ratings at different frequencies. I believe I understand correctly that this is the real reason why tube amplifiers appear louder for their wattage. They are able to output a variable current to match the changing impedance of the speakers over varying frequencies thus applying full wattage regardless of the frequency, which isn't true of solid state amps, so they have a fuller more balanced and efficient transference of energy across the frequency range. Does this sound correct?

D.
[/quote]

Not really. Valve amps cope less well than SS one with uneven impedance, part of the reason why some consider them to disagree with ported cabs, and I suspect quite a lot of the reason why they disagree with multi driver cabs with crossover that have weird impedance spikes (nicely designed ones are probably less of an issue)

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Hi guys,

I have just bought a Hartke ha5500 rated 550w @ 4ohms (my ashdown mag c210 just wasn't loud enough!). Anyway I have a [email protected] Ashdown mag extension caninet and for the short term I may use this with hartke till I get a decent cab.
From what I have read, am I right in saying that because the speaker is 8ohm the wattage to the speaker will be less (closer to the 250w speaker rating).
With regard to buying a new cab, I will probably only buy & use 1 - should I ideally get a 550w or above at 4ohm?

Cheers

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The Hartke will probably be putting out something like 315w at 8 ohms. You can still use your 250w cab with it, but you'll have to use your ears for signs that it's complaining. If it is, turn down the bass and/or the volume.

The volume increase you'll get by unleashing the extra wattage using a 4 ohm cab is... well, disappointingly small. Should you ever feel the need for more volume you'll get a much bigger increase by adding a matching 8 ohm cab.

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