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8 to4 ohm

#22
SanDiegoHarry said:
bad idea.
rather than change your driver, get a 2nd 1x15" running at 8ohms for a fine load of 4 ohms on your amp. Plenty of air shall then be pushed.
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Why is it a bad idea? If an additional 3dB of SPL is adequate, and the OP is happy with the system, I don't see anything wrong with the change.
 
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#23
agedhorse said:
Why is it a bad idea? If an additional 3dB of SPL is adequate, and the OP is happy with the system, I don't see anything wrong with the change.
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I see it as a bad idea from the general economics and outcomes, filtered with the assumptions money is short [peavey near as old as me] and [near] universality of wanting big bass. For the little extra a whole old cab costs, compared with just the driver, you get the whole enchilada. Bonus not driving anything remotely hard.
 
#24
Downunderwonder said:
I see it as a bad idea from the general economics and outcomes, filtered with the assumptions money is short [peavey near as old as me] and [near] universality of wanting big bass. For the little extra a whole old cab costs, compared with just the driver, you get the whole enchilada. Bonus not driving anything remotely hard.
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Black Widow baskets run under $100 new in the US, and are an easy user swap. Old Peavey cabs are seriously heavy too.
 
#27
Downunderwonder said:
That's enviable for us Downunder. But so is the supply of $150 used cabs in good condition.
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Yep, I know that things are very different in many other countries , but I'm sure there are many compensations too.

I used to work on a lot of the Mark III and Mark IV series amps. IME the play feel is much nicer at 4 or 2 ohms than at 8, and if I were going to haul an anchor around I'd want it to at least pay its own way as much as feasible. A 4 ohm driver in the present cab and another one in a separate cab would be a fairly classic backbreaking rig...Link Removed
 
#29
It's up to the OP, however, a second 8 ohm 15" would give a bigger 6dB kick in the pants, which would probably be a more satisfying upgrade than merely switching the single 15" from 8 to 4 ohms.

I have a 4 ohm Black Widow in a Peavey 1516 and it doesn't take a lot of power below 100Hz to make it cry for help.
 
#30
Something that people often fail to take into account is that needs change over time: What seems adequate now might well not be a few months from now. Add a second cab now, even it's more than you currently need, because somewhere down the road you'll be glad you did.
 
#32
basscooker said:
Farting out isn't necessarily related to watts. It's about using more low end than the speaker can reproduce. Any speaker can be pushed too hard for it's physical limits without reaching its power limits.
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I have a related question: if a speaker is pushed to its physical limits by the user turning up the bass eq and the volume, will adding a second (identical) speaker allow for more bass or just more volume at that level of bass?

e.g. if my cab farts w/ bass at 2oclock and vol at noon, will adding a second cab allow me to turn the bass to 4 (leaving vol the same), or will I have to keep my bass at 2 and just turn up the volume?

Also, does farting for just a short amount of time hurt the speaker? I wanted to feel out my limits at home so I have an idea of how far I can push, I was gonna take it up to fart volume just for a second to find out the threshold.
 
#33
I suggest comparing the efficiency rating and T/S parameters of each driver. Also, based on what I have seen with some manufacturers is that their 4 ohm version is approx. 3dB less efficient than their 8 ohm version making for a zero sum gain.
 
#34
Coolhandjjl said:
I suggest comparing the efficiency rating and T/S parameters of each driver. Also, based on what I have seen with some manufacturers is that their 4 ohm version is approx. 3dB less efficient than their 8 ohm version making for a zero sum gain.
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Good point. Here is an overview of the available baskets for Black Widow 15s: Invalid Link Removed

There are some recommended applications that only apply to certain 4 ohm variants, so a little more input from the OP on specific wants and needs would be useful.
 
#35
+ 3dB of amp output is barely detectable, if at all. It takes +10 dB (ten times) the amp power to sound twice as loud to your ear (perceived loudness).
As stated above - it is a much better idea to get a second cabinet and double the cone area.
 
#38
Zigman said:
This is what im doing, im going to 4ohm on the 15 and adding a 210 8ohm on top to kik it down to 2. 6ohm 133wats to the 210 and the rest. Of the 400 gos to the 15
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I'd suggest getting a decent 4 ohm 2x10" instead as it does a better job of distributing power to each driver and doesn't require swapping the 15"; plus it would make a nice standalone cabinet. Guessing that you already have a line on an 8 ohm 2x10".
 
#39
Most 4 ohm drivers are roughly 2.6-3dB greater sensitivity on a constant voltage basis, 0.4 -0dB less sensitive on a constant power basis, so when you calculate at the net SPL gain, you use the constant power model which results in the expected net gain for the OP's situation of roughly 2.5dB

Regarding 3dB being barely detectable, it's the same as the difference between going from a 250 watt amp to a 500 watt amp... a significant increase in SPL. If it wasn't significant, we wouldn't spend the effort that we do designing to achieve that lest dB or two of output and my job would be a hell of a lot easier ;)
 
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#40
Zigman said:
I am useing a peavey mark 6 head to a 8ohm 115 black widow, im going to trade it out for a 4ohm black widow how big of a diff. Will i hear? My amp is rated at 400 watts at 2 ohm about 250 at 4ohm and im gessing about 150 at 8ohm?
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Add another 8 ohm 1x15 and then run 2 8 ohm cabs for a 4ohm load and you will notice a difference
 

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