Adding a third cab...

[chris_b]

4 hours ago, SimonK said:

 

...you trust your cabs more than I do - have you ever connected an ohm-meter to your cabs to see what they actually read? I've had thermal cut-off issues with amps in the middle of gigs before, while if you run two amps simultaneously there is a running backup!

 

 

Eh?

 

I trust an 8 ohm cab to be an 8 ohm cab. You do, we all do! 

 

I also trust an amp to be able to run within its specified ohms range. If that is 2.67 then it is absolutely safe to run 3 x 8 ohm cabs. I have done this for years with zero failures.

 

If you had problems you weren't within spec or your gear had other problems. It was nothing to do with the subject of 3 8 ohm cabs and amps running at 2.67 ohms.

[chris_b]

On 17/10/2024 at 23:47, Downunderwonder said:

But for home use I can't see the need. . .

 

 

Me neither.

 

Seems to me the OP wants better tone and hopes more speakers will deliver. I think that will true on a gig, at stage volumes, but at home. . . . maybe it's over kill.

 

At home I run a Barefaced 110 and my TH500 turned down to 1. Great sound but still too intrusive for playing at night. I'm thinking of switching to a headphone amp for silent playing.

Edited Saturday at 13:07 by chris_b

[Dan Dare]

3 hours ago, bremen said:

Voice Coils impedance varies with frequency; multimeters read DC , that is zero Hz.

 

This. A driver is a reactive, not a resistive load, hence the variation in impedance with frequency. Below is a typical impedance curve. You can see impedance is highest at the resonant frequency (the lowest frequency the driver is capable of reproducing). It drops to around 4 ohms through much of the useful frequency response, rising again at the upper end due to voice coil inductance.

 

I pointed out earlier that the stated impedance of a speaker is an average (the term usually employed is mean impedance). In practice - again as stated above - there is a safety margin with any good quality amp, which means they will drive lower impedance loads as long as you don't push things (either via cranking the volume too much or presenting them with a very low impedance load). That means you don't need to worry as long as you are sensible. The danger signs are obvious - sound gets dirty, volume drops, amp gets too hot, etc.

Edited Saturday at 15:52 by Dan Dare

[agedhorse]

1 hour ago, Dan Dare said:

 

This. A driver is a reactive, not a resistive load, hence the variation in impedance with frequency. Below is a typical impedance curve. You can see impedance is highest at the resonant frequency (the lowest frequency the driver is capable of reproducing). It drops to around 4 ohms through much of the useful frequency response, rising again at the upper end due to voice coil inductance.

 

I pointed out earlier that the stated impedance of a speaker is an average (the term usually employed is mean impedance). In practice - again as stated above - there is a safety margin with any good quality amp, which means they will drive lower impedance loads as long as you don't push things (either via cranking the volume too much or presenting them with a very low impedance load). That means you don't need to worry as long as you are sensible. The danger signs are obvious - sound gets dirty, volume drops, amp gets too hot, etc.

That would be a nominal 4 ohm driver not an 8 ohm driver, by any definition of nominal impedance. 
 

8 ohm nominal would average greate
 

r then 8 ohm’s impedance, with less than 20% of the bandwidth dropping below 8 ohms and dropping no more than 20% below 8 ohms when measured in the cabinet. The cabinet affects the impedance below about 250Hz.

 

This is a good rule of thumb IME as an amp and speaker designer. There are 2 different mechanisms that need to be respected for an amp to work reliably, maximum peak current and power dissipation. Average and minimum impedance affects both mechanisms.

[SimonK]

2 hours ago, Dan Dare said:

 

This. A driver is a reactive, not a resistive load, hence the variation in impedance with frequency. Below is a typical impedance curve. You can see impedance is highest at the resonant frequency (the lowest frequency the driver is capable of reproducing). It drops to around 4 ohms through much of the useful frequency response, rising again at the upper end due to voice coil inductance.

 

I pointed out earlier that the stated impedance of a speaker is an average (the term usually employed is mean impedance). In practice - again as stated above - there is a safety margin with any good quality amp, which means they will drive lower impedance loads as long as you don't push things (either via cranking the volume too much or presenting them with a very low impedance load). That means you don't need to worry as long as you are sensible. The danger signs are obvious - sound gets dirty, volume drops, amp gets too hot, etc.

 

...so mean impedance makes sense - everyone likes a graph!

 

Re trusting cabs, if others are happy running at 2.67 ohms then fine, but I think I am happier to have a bit more of a safety buffer and not go below 4 with my amps. Also, as mentioned, if I did bring more than two cabs I'd rather run two amps as that makes a much bigger difference to the sound than a third cab.

[Bill Fitzmaurice]

1 hour ago, SimonK said:

I'd rather run two amps as that makes a much bigger difference to the sound than a third cab.

Only if one amp lacks the current capacity required to drive three cabs. Speaker output is determined by excursion, excursion is determined by voltage swing, an amp will deliver the same voltage swing into three cabs as it will with one or two. When trouble occurs it's because the amp lacks the ability to deliver the same current into three cabs as it does into one or two. If amps had unlimited current capacity we could use as many cabs as we could haul, with no concerns about impedance.

[Dan Dare]

4 hours ago, agedhorse said:

That would be a nominal 4 ohm driver not an 8 ohm driver, by any definition of nominal impedance. 

 

I know. I was using the chart to illustrate the idea that impedance is frequency dependant. I did point out that the impedance of the driver to which the chart applies would be at or around 4 ohms through much of the useful part of the frequency spectrum.

 

You are correct in all you say, of course. I was attempting, without being too technical, to re-assure the OP that he shouldn't worry as long as he is sensible. In his original post, he informed us that he uses an AG700 (as do I), which is stated to be able to drive loads down to 2.67 ohms min impedance.

[Rob Stevens]

17 hours ago, Dan Dare said:

 

 

 

You are correct in all you say, of course. I was attempting, without being too technical, to re-assure the OP that he shouldn't worry as long as he is sensible. In his original post, he informed us that he uses an AG700 (as do I), which is stated to be able to drive loads down to 2.67 ohms min impedance.

Sorry but I don't understand any of the preceding information in members posts. 

Dan.. In my OP I was considering either the 500 or 700 since they will both run at 2.67 ohms,,,,members have confirmed that I would need that.... I don't have either at the moment, but am thinking the 500 will be better for me, since the 700 is mahoosive for my wants...

Chris.. You say you run 3 without issue and you obviously like it, so I'm thinking... why shouldn't I follow your lead...?

 

I'm sure I'm gonna get another '10' TE cab and the 500 Aguilar head cos aguilar say it runs at 2.67....!. If it sounds 'pants' I can still use the head with 2 and I'll sell the extra cab.

I get the impression from comment that members think it's the wrong thing to do and that it will be a mistake... But I'm sure they made mistakes too at some point.

And I hope that doesn't sound dismissive of advice that has been offered.

Regards. Rob

[SimonK]

20 hours ago, Bill Fitzmaurice said:

Only if one amp lacks the current capacity required to drive three cabs.

 

Maybe from a technical perspective, but more is more when it comes to amps and tone. I know he's a guitarist, but watched this today from Joe "I keep adding amps until it sounds right" Bonamassa! Arguably makes less of a difference to bass, but nevertheless if you haven't tried two amps simultaneously - I would!

[chris_b]

32 minutes ago, Rob Stevens said:

Sorry but I don't understand any of the preceding information in members posts. 

Dan.. In my OP I was considering either the 500 or 700 since they will both run at 2.67 ohms,,,,members have confirmed that I would need that.... I don't have either at the moment, but am thinking the 500 will be better for me, since the 700 is mahoosive for my wants...

Chris.. You say you run 3 without issue and you obviously like it, so I'm thinking... why shouldn't I follow your lead...?

 

I'm sure I'm gonna get another '10' TE cab and the 500 Aguilar head cos aguilar say it runs at 2.67....!. If it sounds 'pants' I can still use the head with 2 and I'll sell the extra cab.

I get the impression from comment that members think it's the wrong thing to do and that it will be a mistake... But I'm sure they made mistakes too at some point.

And I hope that doesn't sound dismissive of advice that has been offered.

Regards. Rob

 

Hi Rob, the AG500 and AG700 are both good to 2.67 ohms, so connecting 1, 2 or 3 x 8 ohms cabs is fine. I did this with the AG700 for many years. The volume you play at is your preference

[chris_b]

If you need the official info. . . . https://aguilaramp.com/pages/manuals

[Bill Fitzmaurice]

1 hour ago, SimonK said:

if you haven't tried two amps simultaneously - I would!

The first time I did that it was with my '65 Fender Bassman and Tom Hamilton's '66 Ampeg B-15. That would have been in '67 or '68.

[SimonK]

7 minutes ago, Bill Fitzmaurice said:

The first time I did that it was with my '65 Fender Bassman and Tom Hamilton's '66 Ampeg B-15. That would have been in '67 or '68.

 

Awesome - how did the two together compare to each on their own?

[Bill Fitzmaurice]

Apples and oranges, mainly due to the different tone stacks. The Bassman bass knob set at 10 was about the same as the Ampeg set at 6. But you really couldn't run the Ampeg higher than 6 anyway, as it would cause the speaker to fart out.

[Rob Stevens]

Hello again.

I took delivery of my new AG500 yesterday..!!

But I'd like advice from 'the collective' as to what 'speakon' cables I need to connect it all up. So..

Do I need NL2 or NL4 cables? It says NL4 1+/1-  on the back of the amp... Does that mean I need NL4..?

 

Also what gauge cable does it need to be as there seems to be various?  Is it that the lower the number the better the cable?

Do I use the same type of cable to 'daisy chain' from cab to cab as the one from the head to the first cab?

 

And lastly does cable length matter?

 

Quite a lot there isn't there.... But thanks.

Regards. Rob

[chris_b]

Rob, check this out.. . .

 

https://audiouniversityonline.com/speakon-connectors/

 

Use genuine Neutrik speakon connectors.

 

So, use NL2 connectors and daisy chain the cabs.

Edited 6 hours ago by chris_b

[Chienmortbb]

On 19/10/2024 at 08:51, SimonK said:

have you ever connected an ohm-meter to your cabs to see what they actually read?

That measures the DC resistance. Impedance includes the AC properties of the speaker or speaker/crossover combination.The impedance will be higher than the DC resistance because you have to add the inductive reactance to that to obtain the impedance and that is frequency dependant.