Fender 400 Pro 2x10 cab (ohms question)

[svoncampe]

I just acquired this nice-sounding cab: 350W at 4 ohms and 500W at 2ohms.

I understand generally speaking that this amp will deliver 350W if the single cabinet (or combination of two) run at 4 ohms. I also understand that the head will deliver the maximum output of 500W to a single 2 ohms cabinet or any combination of cabinets totaling 2ohms.

The 400 Pro is made up of the head/amp and the 2x10 cabinet:

Amp: Output: 350 Watts @ 4 ohms, 500 Watts @ 2 ohms
Cab: 8 ohms impedance (2-10" Fender® Special Design Cast Frame Eminence® 16 ohm, 175 watt Speakers)

This is my confusion: I would have expected the single 2x10 to draw 350W, thus shouldn't it have an impedance of 4ohms? Instead, however, it has an impedance of 8ohms. Thus, how many watts are being delivered to this 2x10 cabinet? Isn't itless than 350W because the impedance on the cab is 8ohms and the amp requires 4 ohms to deliver 350W? What am I missing here?

I understand that there is a 1x15 cabinet created to combine with this 2x10 to deliver maximum power: Fender Pro 115 Bass Cabinet with 8 ohms impedance.

So, if I combine both cabinets: (8ohms x 8ohms)/(8ohms+8ohms) = 4 ohms, meaning the amp is delivering 350W. Correct? Why wouldn't the designed combination not deliver 2 ohms to draw the 500W of power?

This is confusing me. I appreciate any help. I am considering ordering the 115 Pro cab but am open to get a 4x10 instead and either run it alone (unplug the 2x10) or both, if the ohms allow.

Thanks.

 

[Old Garage-Bander]

You have a combo and it has 2 speakers that are 16 ohms each.
This means the combo is operating at 8 ohms.
If it is rated for 350 watts at 4 ohms and 500 watts at 2 ohms, then you are probably getting something less than 350 watts with just the combo alone.

If you add another 8 ohm cab you'll have a 4 ohm load on the amp and it will then be able to produce 350 watts.
If it indeed is rated for 500 watts at 2 ohms then you can add two more 8 ohm cabs and be at 2 ohms, or one more 4 ohm cab and be at a bit more than 2 ohms. Or any combination of cabs that will keep the total load on the amp at 2 ohms or above.

I cannot speak to reasoning behind Fender engineering or marketing as to why they do what they do.

 

[BassmusM6674]

+ to what Old Garage-Bander said.
I don't think you're missing anything.
It seems like a bit of a mismatched ohm pairing of built in speakers to a 2 ohm capable amp. A set of 8 ohm 10's would have gotten the load to 4 ohms and then adding another 4 ohm cab would get it to 2 ohms and the full 500 watts. I would find a matching 4x10 versus a 1x15. No problem with ohm load if the amp can handle 2 ohms.

 

[Stumbo]

IME, you'll get more volume with more speakers to move more air. More watts give you more headroom. You're in a position to do both.

 

[svoncampe]

I appreciate the responses. Thanks -

One other question came to mind relating to watts. I have the ohms thing down, I think; I cannot/should not use any combination of cabinets that lowers the ohms below the minimum required by the amp. The lower the ohms, the more power it can draw.

If to this Fender amp I add a cabinet in my current collection, such as for example another 2x10 (Carvin 4 ohms 600W total), then I'd be OK I think: 350W being drawn from the amp and delivered to both 2x10's, the Fender receiving the max it is designed to receive and the Carvin receiving less than what it can handle, but OK and no damage to speaker or amp.

What if I use an amp that can handle more while maintaining the same cabs? I have a Carvin B800 head:
300W at 8 ohms
500W at 4 ohms
800W at 2 ohms

I plug my Carvin 2x10 (600W at 4 ohms) and Fender Pro 2x10 (350W at 8 ohms) to it:
(4 x 4)/(4 + 4) = 2 ohms. In this case I am drawing the full 800W from the amp but more than each speaker can handle. Will this blow the speakers? Will it only do so if I go past a certain point on the master? The Fender would obviously go first.

Thanks again for the help.

 

[Old Garage-Bander]

I appreciate the responses. Thanks -

One other question came to mind relating to watts. I have the ohms thing down, I think; I cannot/should not use any combination of cabinets that lowers the ohms below the minimum required by the amp. The lower the ohms, the more power it can draw.

If to this Fender amp I add a cabinet in my current collection, such as for example another 2x10 (Carvin 4 ohms 600W total), then I'd be OK I think: 350W being drawn from the amp and delivered to both 2x10's, the Fender receiving the max it is designed to receive and the Carvin receiving less than what it can handle, but OK and no damage to speaker or amp.

What if I use an amp that can handle more while maintaining the same cabs? I have a Carvin B800 head:
300W at 8 ohms
500W at 4 ohms
800W at 2 ohms

I plug my Carvin 2x10 (600W at 4 ohms) and Fender Pro 2x10 (350W at 8 ohms) to it:
(4 x 4)/(4 + 4) = 2 ohms. In this case I am drawing the full 800W from the amp but more than each speaker can handle. Will this blow the speakers? Will it only do so if I go past a certain point on the master? The Fender would obviously go first.

Thanks again for the help.

The amp's power is split proportionally between cabs based on the impedance (ohms) of each each cab.
If all of the speakers are the same impedance the total output will be divided equally between each cab.
If your amp is putting out 100 watts and you have two cabs of equal impedance, each cab gets 50 watts.
If you have an 8 ohm cab and 4 ohm cab, 2/3 of the power goes to the 4 ohm cab while the 8 ohm cab gets 1/3 of the power. In this case you had a 2:1 cab impedance ratio so the power is split by a 2:1 ratio, or 66 & 2/3 watts to the 4 ohm, 33 & 1/3 watts to the 8.

 

[svoncampe]

Copy, I understand and I appreciate the help. I want to make sure though: I assume that at some point if I turn the gain or master volume up too high, I could blow the speakers if a use an amp with wattage rated higher than the speakers/cab even if ohms are within the minimum. I have two 2x10 cabinets.

The options I have now are:
1) running my B800 Carvin amp (300 w @ 8 ohms, 500w @ 4 ohms, 800w @ 2 ohms) using the Carvin BRX10.2 (600w at 4 ohms) and Fender Pro 2x10 (350W at 8 ohms), or
2) Running the same two 2x10 cabs but with the Fender 400 Pro amp (350w at 4 ohms, 500W at 2 ohms)

If I use the Fender amp, then I know the cabinets/speakers will be OK.

If I use the Carvin amp, could I damage the Fender cab?

Thanks again -

 

[Old Garage-Bander]

Copy, I understand and I appreciate the help. I want to make sure though: I assume that at some point if I turn the gain or master volume up too high, I could blow the speakers if a use an amp with wattage rated higher than the speakers/cab even if ohms are within the minimum. I have two 2x10 cabinets.

The options I have now are:
1) running my B800 Carvin amp (300 w @ 8 ohms, 500w @ 4 ohms, 800w @ 2 ohms) using the Carvin BRX10.2 (600w at 4 ohms) and Fender Pro 2x10 (350W at 8 ohms), or
2) Running the same two 2x10 cabs but with the Fender 400 Pro amp (350w at 4 ohms, 500W at 2 ohms)

If I use the Fender amp, then I know the cabinets/speakers will be OK.

If I use the Carvin amp, could I damage the Fender cab?

Thanks again -

Since, under some circumstances, it is possible to blow the speakers with amp power that has less power than the speaker ratings, then yes it is possible to blow speakers with an amp rated more than what the speakers can handle.
You always need to listen to your rig. If things start to sound funny you will need to back the volume down.

 

[svoncampe]

I appreciate all of the help. Thank you.