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Puzzled about this amp combination...

N

numpty

Oct 29, 2011
8
0
#1
Hi everyone, I'm a total newby to this and I have tried my best to read previous threads so I wouldn't bother anyone, but I didn't seem to find an answer...
I am an upright player, and if I ever had to use an amp, I used my little combo. However, I just joined a loud band and needed a loud amp...
So, in my local area I found 2 great deals:
1) an old Hartke HA3500, which has 2 x speaker outputs labelled at 8ohm each and produces a total 350w at 4ohms
2) a custom Flite 4x10 cab, advertised at 600w at 4ohms.
However, this Flite cab is very unusual, in that it is really a 2x2x10 cab. Each 2x10 side has separate inputs at 4ohms.
So you can use only one side at 4ohms and produce 300w, or use both sides by the 2 separate inputs.
I'm getting to the point...
I thought, If I use both outputs of the Hartke, I can use the 2 inputs in the cab. So, I'll split the 350w at 4ohms into 2 2x10 (each at 4ohms).
BUT
I just came home, having bought bought, and I started having terrible doubts....
1) if I plug the Hartke into one side of the flite only, I am plugging a 350w amp into a 300w cab: that's bad isn't it....
2) What if by using both sides of the flite cab, I produce a load of only 2ohms (4ohms cab + 4ohms cab) and blow up the amp?? Or does that happen only if you connect the 2 speakers in parallel (instead of using the 2 sides separate inputs...)
Guys, i'll stop now, because I am starting to confuse myself.
If anyone has any advice I would be really grateful.
And if all of the above is a stupid query, I humbly apologise...
 
#2
Yes you will have a 2Ω total load. You probably have 8Ω drivers in the cabinet each pair wired in parallel to give you 4Ω per side. In your shoes I would rewire the cabinet to have 16Ω per side with the drivers in series pairs. That will give you 8Ω when combined.
 
#7
numpty said:
Thank you very much Paul. That makes a lot of sense. Whilst I'm waiting for someone to help me rewire the cab, can I use one side only or best not?
thanks again very much.
Click to expand...

If the two cavities are separate you'll be fine.

Wiring: tip of input socket to driver1 positive. Driver1 negative to driver2 positive. Driver2 negative to input socket sleeve.

Repeat for the second section.

Polarity can be checked using a 9V battery touched against the drivers terminals. Positive battery terminal to positive driver terminal will cause the cone to move out away from the magnet structure.

Polarity IS important the cabinet will never work properly if you get it wrong.
 
#8
Good advice from BassmanPaul and k31bassman.

Your amp can have a higher power rating than your cabinet as long as you use your ears. If the speakers sound stressed, turn down.

Conversely, a cabinet power rating equal to or greater than the amp rating does not make you blowout-proof, because (as is often mentioned here) bass cabs are often limited by excursion more than power. This is especially true if you like to boost bass, and/or use a lower tuning.

I'm not familiar with that speaker. I assume they wired it that way to allow for use with a stereo power amp. Would be interested in knowing the weight.
 
#9
1n3 said:
I'm not familiar with that speaker. I assume they wired it that way to allow for use with a stereo power amp. Would be interested in knowing the weight.
Click to expand...

I believe Flite makes very light cabs: this is 'only' 50pounds in weight.
Here's their website
Flite Ultralite Speaker Cabinets - About Us
The guy who sold me it had got it second hand from the guy who had had it made (or that's the story...) I wonder if it was wired in parallel and series so that it gives you 4ohms even when both sides are used...or that would be wishful thinking...
Of course the best thing would be to ask the people at Flite, but I bought it third hand, so it would be a bit cheeky...
 
#10
numpty said:
I believe Flite makes very light cabs: this is 'only' 50pounds in weight.
Here's their website Flite Ultralite Speaker Cabinets - About Us
Click to expand...

Thanks. The website lists the 410 at 52/45 lbs for std/neo drivers. Still nice to have corroboration from an owner.

I wonder if it was wired in parallel and series so that it gives you 4ohms even when both sides are used...or that would be wishful thinking...
Click to expand...

From your original description, it's dual parallel wiring; no series. You'll need to make it dual series to get your 8ohm load. If you were ever going to use it with a stereo power amp, it might be worthwhile to add a switch, to toggle both sides between series and parallel.
 
#11
Ok thanks guys, I found a good diagram for wiring in dual series. Just one more thing (like lieutenant Columbo): once I rewired it to get my 8ohms load, how much wattage am I likely to lose if any (currently is rated at 600w)?
 
#12
numpty said:
Ok thanks guys, I found a good diagram for wiring in dual series.
Click to expand...

It should match BassmanPaul's instructions in post #7. And the battery test is always a good idea.

Just one more thing (like lieutenant Columbo): once I rewired it to get my 8ohms load, how much wattage am I likely to lose if any (currently is rated at 600w)?
Click to expand...

Your cabinet rating doesn't change. The amp is rated at 240w into 8 ohms. You lose a little power with the higher impedance, but doubling your speakers should be a net win.
 
#13
The Flite probably was configured as it is for use with an amp like the Ashdown Superfly, which has two separate power amps both rated for 4 ohm operation. It's a useless configuration with the Hartke or any other single power amp head. Assuming the drivers are eight ohm rewire them as series/parallel pairs, giving you an 8 ohm cab.
how much wattage am I likely to lose if any
Click to expand...
None, since you can't make use of the amp into all four drivers as it's presently configured.
 
#15
As my double bass preamp system is pretty sophisticated and already has all the controls I need, could I plug my preamp into a simple power amp, and then run each channel of the power amp into a separate side of the cab? Would I maintain 4ohms in that case?
P.S. thanks very much for the wiring diagrams
 
#16
numpty said:
As my double bass preamp system is pretty sophisticated and already has all the controls I need, could I plug my preamp into a simple power amp, and then run each channel of the power amp into a separate side of the cab? Would I maintain 4ohms in that case?
P.S. thanks very much for the wiring diagrams
Click to expand...

Yes, you could run it as is with half the cab on one channel, other half on the second channel. You could also run it as is with a 2 ohm stable amp but I'd rewire it as an 8ohm cab and use it that way. You don't gain anything by running the low ohms and just put more stress on the amp. The power difference is pretty much meaningless.
 
#17
numpty said:
... could I plug my preamp into a simple power amp, and then run each channel of the power amp into a separate side of the cab? Would I maintain 4ohms in that case?
Click to expand...

Yes, and yes (4 ohms per channel). This was probably the intended usage for that cab. Again, if you want to be able to do this AND use your Hartke with the full cab, you'd need a switch to toggle each side between series & parallel wiring.
 

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