8 ohm cab question

[Old Garage-Bander]

500 watts into a 4 ohm load will be around 250 watts into an 8 ohm load, probably slightly more, something like 275 watts, since the load is an impedance and not pure resistance.

The PF-500 is rated for 300 watts into 8 Ohms. I believe the GK is rated for 350 watts. You will barely hear the difference of 50 watts into the same speaker. However different speakers or different arrangements of speakers will be louder or quieter depending on other factors even if the power is exactly the same.

250 watts does not become 275 watts just because you make the leap from resistance to impedance.
An amp with a load of X will produce the same amount of power if X is a resistance or an impedance.

All resistances are pure. To say "pure resistance" is being redundant. If it is not "pure" there is an impedance involved.

 

[Tim Skaggs]

The PF-500 is rated for 300 watts into 8 Ohms. I believe the GK is rated for 350 watts. You will barely hear the difference of 50 watts into the same speaker. However different speakers or different arrangements of speakers will be louder or quieter depending on other factors even if the power is exactly the same.

250 watts does not become 275 watts just because you make the leap from resistance to impedance.
An amp with a load of X will produce the same amount of power if X is a resistance or an impedance.

All resistances are pure. To say "pure resistance" is being redundant. If it is not "pure" there is an impedance involved.

I was attempting to give the OP a rough estimate answer to this question; if this cab is rated 400w at 8ohms....what do you think I’m really putting into it wattage wise from the PF500? The link to the PF-500 Owner's Manual on the Ampeg web site is glitched up so I couldn't look up the specific wattage of the amp into an 8 ohm impedance. I made a guess. My apologies to the OP for my mistaken guesstimate.

 

[Wasnex]

Probably over 50% of all reasonable quality 410's out there are plenty adequate. There's more negative comments being made out of this format than it deserves IMO. Vertically stacking does not automatically make for a better format.

Depends upon what the player wants to hear. 410 flat on the ground is good for a player who keys of the bass and low mids. A pair of vertically stacked 210s is better for the player who wants to hear more of the full range of the instrument. It should be noted, the vertical stack will not be tall enough to get your earz into the dispersion pattern for all frequencies unless the cabinets are elevated significantly or the top speaker is tilted back a bit.

Another argument for the vertical stack is the superior horizontal dispersion allows the player to roam around a bit more with less changes to their tone.

I used to have an Eden 410XLT and 210XLT. Most of the time, I ran the 210 vertically on top of a rolling case that was the approximate height of the 410. I put a Countryman Type85 under the 210 so the speaker was aimed at my head. For a short time I ran both the 410 and 210 on top the rolling rack. I loved the sound but only when I was standing immediately in front of it. Unfortunately the tone was way too punchy for my drummer who wanted a big pillowy low end. The solution was to put the 410 on the ground by the drummer and the 210 on the rolling rack behind me. I was running stereo at the time and ran the volume of the 410 to carry the band while the 210 was run at a very low volume for my personal monitoring needs.

Personally I wish I had a set of four Genz 1288Ts to stack vertically. I am sure that would be glorious.

 

[Old Garage-Bander]

I was attempting to give the OP a rough estimate answer to this question; if this cab is rated 400w at 8ohms....what do you think I’m really putting into it wattage wise from the PF500? The link to the PF-500 Owner's Manual on the Ampeg web site is glitched up so I couldn't look up the specific wattage of the amp into an 8 ohm impedance. I made a guess. My apologies to the OP for my mistaken guesstimate.

I too found that I couldn't access the manual at the Ampeg site. To me it acted like they wanted me to sign in.
That would suck if it were the case. I used to be able to look at their manuals.
I did a little extra searching and found another place that had it available.

Cab power rating has no bearing on what the amp will deliver.

IMO...
Trying to give a power output number of an amp while playing through it is non issue.

First, too many people are hung up on that one parameter.
Speakers and cab design play a larger part in this than does the amp's output.

Then even if the manufacturer where giving honest numbers, the numbers they actually measured, how do you know the conditions under which those numbers are derived.
Then are they talking RMS, peak, "music power"? What is the context of the power numbers?

Getting power numbers are done under test conditions. There is no correlation between those tests and actual playing conditions, and even if you could do that, no two people play the same way.

Finally, and the point I tried to make in my first response is that there is no calibration involved in where the knobs point and how much power an amp is putting out. Halfway up is not necessarily half power. Even with the pot at it's electrical midpoint there may be no correlation between where the pointer points and how much power (however you define it) is coming out of the amp.

What people should concentrate on is how a given amp works with a given cab. Once you know that, and the particulars of a cab you can make some estimates about how other cabs might work with that amp. If the amp and speakers do the job then what else is there? The only consideration for power is if you are playing 100 watts into X speaker arrangement and it's not enough, then you best start looking at upwards of 1000 watts and hope you don't fry your speakers.

 

[ashtray]

You blew the speaker in your combo because your 210 cab was getting the same wattage as your 410 cab - but each speaker was seeing double the wattage in the 210 than the 410.

I might recommend replacing the combo speakers with a pair of 8 ohm speakers wired in SERIES*, this way the combo is 16 ohms. When you combine that with the 8 ohm 410 cab, each speaker will get the same amount of watts, allowing you to push the whole rig harder.

If you like high mids, elevate the cab closer to your ears. Pointing all those high mids at your ankles won’t do much to help you hear them.

*If you wire your combo speakers in parallel by mistake, you could fry your amp when you hook up a second cab. Wiring the combo as 16 ohms total will have an effect of reduced output when used alone.

 

[Stumbo]

Hi all,

Previously I was running a GK210mb combo into a GK410MBX cab.

[email protected] of power even for outdoor gigs. !!!

People, it's 500w combo like the Fender Rumble. Running a 4x10 extension cab should be okay. 250w to each cab. Possibly too much bass did the speakers in.

I suggest replacing the speaker in the GK210mb combo and adding an adjustable HPF to your signal chain. Try testing it at about 60hz to start.

Tightens up the low end, protects the speakers, tames venue acoustics and you'll get back the 2x10 at ear level.

Also consider a compressor.

 

[JeezyMcNuggles]

Hi all,

Previously I was running a GK210mb combo into a GK410MBX cab.

[email protected] of power even for outdoor gigs. I blew a speaker in the combo, and wound up buying a PF500. I LOVE THE TONE. First gig with it went really well.

However I’m noticing at practice I’m cranking the midrange, and then switching the midrange selector more and more to high mids. This was at our guitarist house with my 410. I use an old 810e at a local rehearsal studio, but it’s not mine.

I’m starting to think my cab is underperforming me....if this cab is rated 400w at 8ohms....what do you think I’m really putting into it wattage wise from the PF500? Typically gain @11 o’clock. Bass at 9-10 o’clock at most. Mids @2-3 o’clock...lately I’ve been moving the midrange to 4th position...volume is around noon before the red light kicks in....compression is barely above OFF..

Thanks for any help!!!

How close are you to the cabinet? You wanna be at least like 6 ft away from it if you want to hear yourself. If you're to close, you get trapped in a sort of pocket where the sound doesn't quite make it to your ears. You could be too loud, or too bright and not even know it. But, the 810 is 4 ohms (half the resistance), taller, more powerful in general. And, with the speakers going higher up, it's just way easier to hear yourself regardless. But yeah, fix your speakers and you should be fine once again. What the one guy said about the 16ohm speakers is brilliant though. But you gotta find ones with the same specs, or they'll sound like crap in your box.

 

[JeezyMcNuggles]

The question is not addresed to me but, personally I read this question asked as kinda trick question.
Honestly, the 410 format on its own provides some benefits that you can't get of from a different driver alignment. That's nothing but pure science and is independent of any brand or distinct sound design goals for the 410 driver alignment

I like aluminum Hartkes

 

[Eddie LeBlanc]

Your PF 500 is a class D amp, Rated at 500 watts into a 4 ohm load. It is generally estimated as a 250 to 300 watt output into an 8 ohm load. That is not much these days considering the competition and also competing volumes of guitarists' amps.

Either get another 8 ohm cabinet to connect in parallel with your existing 8 ohm cabinet, or get a good 4 ohm cabinet, in order to get the 500 watts out of the PF500. It's all about the ability of the amp to push watts. If you keep pushing the amp to do more than it is rated into the Speaker load you are presenting it with, it will strain to provide, at the expense of clipping the amp and possibly damaging it, or damaging the speaker cabinet.

I run two Schroeder 8 ohm Neo cabinets, a 12-12 L (dual twelves), and a 12PL (single 12"). Both are 8 ohms each, I push them with a Genzler MG800 (800 watts into a 4 ohm load). Both cabs have a very similar SPL rating 103 SPL and 102 SPL (the loudness per watt), so they react similar when connected together to give a 4 ohm load to the amp. And that set up will get loud.

BTW SPL rating can be important to understand when selecting a cabinet. It is the perceived loudness of the cabinet when operating or how efficient the cabinet can react to wattage input. A 103 DB per watt is a large perceived improvement in volume versus a 98 DB per watt cabinet. So to understand a cabinet one must not only understand wattage rating, and frequency response, but all Efficiency rating too, in order to compare cabinets.

 

[Eddie LeBlanc]

BTW the GK 410 MBX is rated at 100 SPL with a 400 watt rating, (it uses 4 - 32 ohm speakers all wired in parallel.

The GK 210 Combo amp is rated at 500 watts into a 4 ohm load. So the amp is a 500 watt amp into a 4 ohm load.

 

[Eddie LeBlanc]

Oh yeah, my little lite weight Dual Neo Schroeder cabinets and the Genzler MG 800 are more than adequate to keep up on stage with my guitarist's Dual Mesa Lone Star amp set up with dual 12" extension speakers on each amp (a total of 8 twelves with his Lone Star Amps). His total rig weighs a ton, and he moves it with dollies Mine is about 70 lbs total With wires.

Its all about efficiency and lite weight for me these days. Too old to be schlepping huge heavy cabinets. There are too many better options and advances in design and technology these days.

 

[el murdoque]

I’m starting to think my cab is underperforming me....if this cab is rated 400w at 8ohms....what do you think I’m really putting into it wattage wise from the PF500? Typically gain @11 o’clock. Bass at 9-10 o’clock at most. Mids @2-3 o’clock...lately I’ve been moving the midrange to 4th position...volume is around noon before the red light kicks in....compression is barely above OFF..

So with no boosted bass and the master around noon, a 300W amp puts out a lot less than half of its rating.
Have a look at the Quilter Bass Block 800's writing on the master pot - every amp is different, but this should give you a rough estimate. That amp is rated 800W and the master noon position says 160W.

Keep in mind that the bass signal is HIGHLY dynamic with peaks well above average and dips that go, well, to zero.

You should gauge what the cab can take. Be alone in the room and play - now increase the master until the cab starts farting out. That's too much. Now back down on the master a bit until you can't bring the cab to fart out any more, no matter how you play. That is where your cab's max is. If you can't bring it to fart out with the master dimed, try adding more bass.
And work CAREFULLY! Approach the cabinet's maximum in tiny, careful steps - you don't want to overshoot and blast the cones around the room.

As long as your cab is not farting out and the amp is running without heat issues, you're fine, no matter what the settings are.
I've been playing tiny cabs with powerful amps that could not be turned past 9 o'clock and I've been playing full stacks with amps where I had to max out the master and gain to get every last bit of juice the head would give without melting. Be reasonable, use your ears and you'll be fine.
Know the limits of your stuff from safe testing. When there are two guitars blasting the room with distorted amps and 4x12 cabs, you might miss the sound your cab makes when it's about to cross the styx.

 

[chris_b]

Hi all,

Previously I was running a GK210mb combo into a GK410MBX cab.

[email protected] of power even for outdoor gigs. I blew a speaker in the combo, and wound up buying a PF500. I LOVE THE TONE. First gig with it went really well.

However I’m noticing at practice I’m cranking the midrange, and then switching the midrange selector more and more to high mids. This was at our guitarist house with my 410. I use an old 810e at a local rehearsal studio, but it’s not mine.

I’m starting to think my cab is underperforming me....if this cab is rated 400w at 8ohms....what do you think I’m really putting into it wattage wise from the PF500? Typically gain @11 o’clock. Bass at 9-10 o’clock at most. Mids @2-3 o’clock...lately I’ve been moving the midrange to 4th position...volume is around noon before the red light kicks in....compression is barely above OFF..

Thanks for any help!!!

Firstly I don't believe you blew the speaker because you "over powered" it. . . . unless you have a few pedals boosting the signal into the red!! If not, then the combo is 500 watts with 250 watts into the 210 at 8ohm, and at 4 ohm, when paired with an extension cab. That's what it was designed to do and that's what you did. Components can fail. So nothing sinister there.

Are you saying the cab is "under performing" because it isn't loud enough or because you have to alter the EQ so much? You can search as much as you like but IMO these amps will always sound different. My guess is that you could be experiencing the difference in EQ voicing between your old GK amp and your new Ampeg, or maybe the Ampeg doesn't match well with the GK cab.

I'd describe a cab as under performing when it isn't loud enough. If that's the case get another cab, a matching 210 for instance, and you'll get more volume and tone. You like the tone of the Ampeg, but another GK amp might match better with the cab. . . there are so many solutions but you have to know exactly what the problem is.

 

[agedhorse]

So with no boosted bass and the master around noon, a 300W amp puts out a lot less than half of its rating.
Have a look at the Quilter Bass Block 800's writing on the master pot - every amp is different, but this should give you a rough estimate. That amp is rated 800W and the master noon position says 160W.

Keep in mind that the bass signal is HIGHLY dynamic with peaks well above average and dips that go, well, to zero.

You should gauge what the cab can take. Be alone in the room and play - now increase the master until the cab starts farting out. That's too much. Now back down on the master a bit until you can't bring the cab to fart out any more, no matter how you play. That is where your cab's max is. If you can't bring it to fart out with the master dimed, try adding more bass.
And work CAREFULLY! Approach the cabinet's maximum in tiny, careful steps - you don't want to overshoot and blast the cones around the room.

As long as your cab is not farting out and the amp is running without heat issues, you're fine, no matter what the settings are.
I've been playing tiny cabs with powerful amps that could not be turned past 9 o'clock and I've been playing full stacks with amps where I had to max out the master and gain to get every last bit of juice the head would give without melting. Be reasonable, use your ears and you'll be fine.
Know the limits of your stuff from safe testing. When there are two guitars blasting the room with distorted amps and 4x12 cabs, you might miss the sound your cab makes when it's about to cross the styx.

This is not at all true on just about every amp out there. The Quilter is a little bit different.

In general, the master volume has little relation to how much power an amp may be delivering to a speaker.

 

[jcerio]

I once owned a PF500. I liked the amp, but found a couple of things that made me sell it. First, I found that it was rather anemic compared to my Aguilar Tone Hammer 500 at any setting in to the same cabs. I really only liked the tone when I had the "Ultra Bass" engaged. But that setting scooped out enough mids that it really hurt the performance of the amp IMO. If I have to then boost mids to make up for it, what's the sense? I would consider a PF800 down the road, but for right now I'm happy without it. My advice - don't use Ultra Bass.

 

[el murdoque]

This is not at all true on just about every amp out there. The Quilter is a little bit different.

In general, the master volume has little relation to how much power an amp may be delivering to a speaker.

Agedhorse, I bow to your wisdom.
I just wanted to elaborate that most master pots do not work in a linear fashion with 0% power at 0, 50% power at noon and 100% power fully dimed.

Could you elaborate a little further on the internal workings of an amplifier regarding these matters?
Is there a way to roughly determine the used wattages from the settings of gain, EQ and master?

 

[Eddie LeBlanc]

Oh yeah, at one rehearsal studio there is an Ampeg PF500 there for my use. I never did like it that much. Never could get any punch out of it to suit me.

I had a GK MB500 in another studio that I moved to that rehearsal room. The GK plays rings around the Ampeg PF in my estimation. This is into the same dual 10" - 8 ohm cabinet. Just saying.

 

[Old Garage-Bander]

Could you elaborate a little further on the internal workings of an amplifier regarding these matters?
Is there a way to roughly determine the used wattages from the settings of gain, EQ and master?

I also await the true wisdom.
In the meantime, while waiting for the corn to pop, I invite you to view rant #24.

 

[el murdoque]

I also await the true wisdom.
In the meantime, while waiting for the corn to pop, I invite you to view rant #24.

I would, but I regret to inform you that you make way too much sense!

One thing, though:
You actually CAN use the numbers printed on the cabs. At least if you know how.
Firstly, you need to eliminate all the BS numbers. An example would be the Bugera cabs (2x10 with 1600W and 1x15 with 1000W), where obviously someone in the lab fell on the voltmeter and broke the display.
When you're left with brands that seem to have a clue what the numbers they print on their cabs mean, you're still left with the thermal rating of the voicecoil. But since you have no clue whatsoever how much juice you are pumping into the cab, the number does not matter that much.
But let's say you're in the range of one brand and you own two 8 ohm cabs, each ratet at 600W and a head that is rated at 500W at 4 ohms, it is fairly safe to assume that you can turn up your head pretty far, if not all the way without causing harm - as long as you're playing bass and not pumping a square wave at 25Hz in there.
Most numbers from respected brands work well as a rough guideline.
My head says 300 and the cab says 250? better watch out.
My cab says 800 and the head 200? I probably can do what I want.
Your ears should always be the last line of defense before a speaker spills its innards, as you can pretty much hear the farting long before that happens. If you're forced to max out what you got - get more.

 

[agedhorse]

An amplifier's power output depends on the input level and the overall voltage gain of the amp, that's all there is to it. If you reduce the voltage gain (say turning the master volume down) by 50% (6dB), you reduce the power by 75% (6dB) but if you increase the signal level to the amp by the same 6dB then the output voltage and power will be identical to the original conditions. Same thing applies if you decrease the master gain by 6dB and bring up the channel gain by 6dB.

Knob positions mean absolutely nothing, they are set be the designer to meet their goals for the way they feel that the range of conditions the amp is designed to operate under. Different gain structure and control taper alone can result in identical knob positions yielding very different results.