Killed some brand new speakers... help me make better choices

[wheresthefbomb]

So I got this pair of Eminence Beta 15a speakers rated at 300w each. According to everything I've read, they should be able to handle 600w wired together. Well, today my GK 700RBII (rated at 480w according to the rear panel) came in and while I was testing it through the 2x15 both speakers failed. There was a burning plastic smell and now they both read zero resistance with my multi-meter, I'm assuming I cooked the voice coils. I was admittedly pushing the amp pretty hard when this happened, but I figured I should have been safe based on their power rating. What do I need to do to be able to run this amp safely? How much power handling should I be looking for to avoid doing this again? The bass we are using is in B standard/drop A also.

 

[odibrom]

... the "together" thing was in series or parallel? Because the watts' and ohms' total will change depending on the mix type...

When finding speakers for an amp, the rule of thumb is that the speakers' total watts and ohms should be equal or higher than the amp's output.

If one is mixing several speakers, one should do the math... don't ask me what math...

 

[wheresthefbomb]

... the "together" thing was in series or parallel? Because the watts' and ohms' total will change depending on the mix type...

They're in parallel, I'm definitely aware of how series/parallel effects impedance, but what I read said that the total power handling is additive regardless of series/parallel. I'm no expert though, so that could very well be incorrect...


also as I'm reading more, I'm realizing I know very little about loud bass signals. The speakers were definitely pumping hard when they died, lots of excursion, and the amp's clipping light was on a lot. I'm 100% sure this was user error, I'm just trying to figure out exactly what error(s) I made and what I can do to get a good, loud bass sound without destroying more expensive shit.

 

[Wiltonauer]

1.) What was the nominal impedance of the speakers? Before you killed them.

2.) That 480W rating on the amp… the manual I found says that’s at 4 ohms.

 

[wheresthefbomb]

1.) What was the nominal impedance of the speakers? Before you killed them.

2.) That 480W rating on the amp… the manual I found says that’s at 4 ohms.

8ohms each in parallel for a total of 4ohms, tested and confirmed with a multi-meter.

 

[SalsaWood]

That suuuucks. Make absolutely sure you split the load, I say that just because it seems like you did them in series and cooked them- even though that kind of doesn't fit either since they both popped their circuits. I always believed it best practice to over spec your speakers (cone headroom) and respectively under spec your amp wattage.

Of course IDK bass stuff, you guys do shit differently and I do hardly anything right anyways, so school me if I'm wrong please.

Also might have peaked well past the RMS wattage rating of the speakers for too long, but again I'm not sure how this would have caused this exact malfunction and in both speakers to boot.

 

[Wiltonauer]

Since the amp’s power rating when changing from an 8-ohm load to a 4-ohm load increases by only 50%, I’d be curious about some other numbers, too — like the bandwidth and distortion ratings under those conditions. It’s obvious the amplifier wasn’t happy about the situation that blew the speakers. It was clipping, for one thing. Also, most amplifiers can deliver power levels far in excess of their nominal ratings for short durations — but the distortion goes up and the sound goes to hell. Distortion in the power section of a solid-state bass amp is something to be avoided.

Finally, power handing ratings for speakers are highly suspect. What kills speakers are things like heat buildup in the voice coil and excessive excursions at the wrong frequency — like DC, for example. It’s difficult to say that a certain number of watts is “safe” while any higher number isn’t. Speaker manufacturers know all this, and they try to be helpful with their power handling ratings, but there just aren’t any guarantees that you can’t damage a speaker just because numbers implied that it should have been okay.

 

[Spinedriver]

Back when I was playing bass, I don't think I ever turned up past half way. I ran a Markbass LMII into a Peavey TVX 410 and even at 4 or 5, it was PLENTY loud. I can't imagine being in the same room with it turned up to 7 or 8.
I guess the lesson is that it's not always a good idea to push your amp so hard that the clipping light is almost always on.

 

[odibrom]

Back when I was playing bass, I don't think I ever turned up past half way. I ran a Markbass LMII into a Peavey TVX 410 and even at 4 or 5, it was PLENTY loud. I can't imagine being in the same room with it turned up to 7 or 8.
I guess the lesson is that it's not always a good idea to push your amp so hard that the clipping light is almost always on.

In some rehearsal rooms I've been to, the bass amp had to be just slightly bellow the clipping zone so the bass could be heard. Some bass amps are really low volume... or badly setup...

 

[Baelzebeard]

I warned you.

Since they are open circuit, they overheated, which means they got too much wattage for too long.

If the amp was clipping, it was likely putting out in excess of its rated power. The Eminence Beta has a relatively small voice coil and magnet structure for its thermal power rating, and in this case it was not able to dump the excess heat. Sustained low notes, square waves and the like cause massive heat build up.

Now let's talk about cab design, and speaker compatibility. When you want to drive a low frequency signal,(below 100hz.) with authority, you need to be much more deliberate about the design of the cabinet and specs of the speaker. I suspect, for whatever reason, your cabinet/speaker combination was inefficient, requiring you to dump more power into the cab to get the volume you wanted.

Is the cab sealed? Ported? If ported what is the tuning frequency? What is the internal volume of the cabinet?

Since you are tuning to A/B, you are asking a lot of the speaker system ,(and amp) to reproduce those low notes at high volume. You definitely don't want a ported cab tuned too high for the signal. So you might benefit from a High Pass Filter set just above the tuning frequency of the cab/ports.(if you can't modify the cab)

 

[tedtan]

Amps are rated by the amount of watts they deliver before they begin clipping/distorting, so a 480 watt amp can deliver that cleanly, but can put out more than that if pushed into distortion. If you had it dimed, it could have been putting out 600 to 1,000 watts into the speakers.

Keep in mind that those 100 watt Marshall heads were designed to push two 4x12 cabs with four 25 watt speakers each (200 watts total power handling). When people started diming their amps into a single 4x12 cab, it was common for the speakers to blow, so they started bumping up the speakers’ power handling abilities to 30 watts and eventually 50 watts and above to keep them from blowing.

Ideally, I want to see a speaker cab with at least double the power handling ability as my amp is rated for, though if part of your sound is speaker distortion/cone cry, then you’ll want to stay with lower wattage speakers.

 

[TedEH]

When it comes to bass I've always been really paranoid about pushing the gear. I had one cab - a 4x10, with a cheap amp, start to catch fire when it was cranked. I've come across plenty of speakers that were clearly pushed past their limits. Given how amp and speaker ratings tend to be a bit of a crap shoot, I generally try to intentionally overshoot my needs and trust that the gear will protest if I push it too hard. My last setup was 1100watts bridged into two 4x10s for a total of 1200w handling, so in theory they were matches - but I never pushed the volume above half of what I had available.

I know a guy who uses a 2x10 for shows and plays it LOUD. Those cones are a-movin'. I'm pretty paranoid they'll only last so long under that kind of usage.

If I wanted to be as certain as possible that my bass rig was "safe", I would:
- Always overshoot what you think you need.
- Don't use a "scooped" sound. Cut through with mids and highs, don't try to shake the bajeezus out of everything with B A S S.
- Use physically big cabs. Wattage doesn't tell you about volume. Number of speakers doesn't tell you about volume. But so far, the bigger the cab, the better luck I've had.
- If you can't use physically big cabs, look for ones with a reputation for being loud. My Peavey cabs couldn't cut it. My Mesa cabs could bring down buildings at similar sizes and ratings. My friend who pushes his cabs uses Markbass. Either he's lucky, or they can take a beating.
- If you have a HPF, use it. I've used a bunch of stuff into a Crown power amp, and the crown amp has a HPF that is always on, regardless of what I use as a preamp. Lowest it goes is 80hz, which sounds high, but you reaaaaally don't need much below that point most of the time.
- Remember that a HPF is not a sharp cut off at the point of the filter - setting it to 80hz doesn't mean that you have nothing below 80 anymore. Set it higher than you think you need, or as high as you can get away with while still getting the low end you want.

 

[youngthrasher9]

I feel vaguely responsible for this result as I gave some input in the thread encouraging you to buy these.

Thinking more about car subwoofer applications is probably the more sound direction to go, I’d heed what baelzebeard and tedtan said.

Also, for car audio they generally say: you want your amps’ wattage to represent 75% of what your speakers can handle.

 

[Moongrum]

So I got this pair of Eminence Beta 15a speakers rated at 300w each. According to everything I've read, they should be able to handle 600w wired together. Well, today my GK 700RBII (rated at 480w according to the rear panel) came in and while I was testing it through the 2x15 both speakers failed. There was a burning plastic smell and now they both read zero resistance with my multi-meter, I'm assuming I cooked the voice coils. I was admittedly pushing the amp pretty hard when this happened, but I figured I should have been safe based on their power rating. What do I need to do to be able to run this amp safely? How much power handling should I be looking for to avoid doing this again? The bass we are using is in B standard/drop A also.

I'd reach out to Eminence. I doubt they can do anything for the blown speakers, but they can probably give a more objective answer as to what went wrong. Maybe even hit up GK, maybe there is something non-intuitive about their power ratings.

 

[Spinedriver]

I feel vaguely responsible for this result as I gave some input in the thread encouraging you to buy these.

Thinking more about car subwoofer applications is probably the more sound direction to go, I’d heed what baelzebeard and tedtan said.

Also, for car audio they generally say: you want your amps’ wattage to represent 75% of what your speakers can handle.

Exactly what I did with the Markbass amp. It has a max output of 500 watts @ 2 ohms, so I got a 4 ohm cab that's rated for 600 watts. No way in hell I intended on cranking the amp in the first place but at least the cab should be able to handle volume spikes even if I did have to turn it up to 5 or 6.

 

[Rubbishplayer]

This sounds awfully like a case of mixing up RMS ratings with peak power ratings, with some confusion over the impact of speaker impedence.

It used to be the case that the Root Mean Square rating is what's used with most amps and speakers, giving a maximum continuous power rating. However, amp makers (especially cheaper ones) often quote the peak number, confusing matters further. This is important as an amp can often produce double its RMS at peak, and this is especially true for instrument amps, more so for bass amps.

I always worked on the principle of working with speakers rated twice the RMS output rating of the amp when I made bass cabs and never had a problem. But even here you need to be careful:

1. Firstly, make sure you know the impedence rating for your amp (e.g. 480w at 4ohms or 8 ohms?). If it is at 8 ohms, try to keep your speaker solution rated the same, because your 4 ohm rating is likely to be much higher (probably double) that of your 8 ohm rating.
2. Remember that parallel wiring of speakers halves the effective impedence of the overall solution. So, two 8 ohm speakers wired in parallel will have a total effective rating of 4 ohms, which in our example, will induce your amp to dump in more power.
3. Series wiring adds the impedence, so the same two speakers in series would have a combined impedence of 16 ohms.

Remembering the rule above of doubling the RMS rating to get peak power, let's do a couple of worked examples:

Example 1: Amp RMS rating: 480w at 4 ohms
Required solution: a 4 ohm speaker set rated at 1000w
Solution: 2x15" 500w 8 ohm speakers wired in parallel.

Example 2: Amp RMS rating: 480w at 8 ohms
Required solution: a 8 ohm speaker set rated at 1000w
Solution: 2x15" 500w 16 ohm speakers wired in parallel.

Finally, it is difficult to assess what exactly went wrong here, but two 300w speakers does not sound like a good start: they should be 500w. Also, if you mismatched the speaker impedence compared to the amp rating (e.g. your solution was 4 ohms when your amp is rated at 480w at 8 ohms), then that would have exacerbated matters (e.g. you might have been dumping as much as 900w RMS/1800w peak into a 600w RMS rated solution).

Hope this helps.

P.S: Don't chuck the speakers, cos they may be repairable (may be cheaper than a new set).

 

[Rubbishplayer]

I feel vaguely responsible for this result as I gave some input in the thread encouraging you to buy these.

Thinking more about car subwoofer applications is probably the more sound direction to go, I’d heed what baelzebeard and tedtan said.

Also, for car audio they generally say: you want your amps’ wattage to represent 75% of what your speakers can handle.

That 75% rule may be fine for recorded audio, which has a limited dynamic range, but is no good for instrument amplification, especially bass, where the dynamic range is wider. Speakers with double the RMS rating of the amp's RMS rating is the usual rule.

 

[Rubbishplayer]

This sounds awfully like a case of mixing up RMS ratings with peak power ratings, with some confusion over the impact of speaker impedence.

It used to be the case that the Root Mean Square rating is what's used with most amps and speakers, giving a maximum continuous power rating. However, amp makers (especially cheaper ones) often quote the peak number, confusing matters further. This is important as an amp can often produce double its RMS at peak, and this is especially true for instrument amps, more so for bass amps.

I always worked on the principle of working with speakers rated twice the RMS output rating of the amp when I made bass cabs and never had a problem. But even here you need to be careful:

1. Firstly, make sure you know the impedence rating for your amp (e.g. 480w at 4ohms or 8 ohms?). If it is at 8 ohms, try to keep your speaker solution rated the same, because your 4 ohm rating is likely to be much higher (probably double) that of your 8 ohm rating.
2. Remember that parallel wiring of speakers halves the effective impedence of the overall solution. So, two 8 ohm speakers wired in parallel will have a total effective rating of 4 ohms, which in our example, will induce your amp to dump in more power.
3. Series wiring adds the impedence, so the same two speakers in series would have a combined impedence of 16 ohms.

Remembering the rule above of doubling the RMS rating to get peak power, let's do a couple of worked examples:

Example 1: Amp RMS rating: 480w at 4 ohms
Required solution: a 4 ohm speaker set rated at 1000w
Solution: 2x15" 500w 8 ohm speakers wired in parallel.

Example 2: Amp RMS rating: 480w at 8 ohms
Required solution: a 8 ohm speaker set rated at 1000w
Solution: 2x15" 500w 16 ohm speakers wired in parallel.

Finally, it is difficult to assess what exactly went wrong here, but two 300w speakers does not sound like a good start: they should be 500w. Also, if you mismatched the speaker impedence compared to the amp rating (e.g. your solution was 4 ohms when your amp is rated at 480w at 8 ohms), then that would have exacerbated matters (e.g. you might have been dumping as much as 900w RMS/1800w peak into a 600w RMS rated solution).

Hope this helps.

P.S: Don't chuck the speakers, cos they may be repairable (may be cheaper than a new set).

P.P.S: If you do get the speakers repaired, assuming they're 8 ohm, one option to reuse them with this amp is to wire them in series, which will give you a 16 ohm solution. The downside here is that you'll likely halve the output of your amp (around 240 watts, compared to 480), but that'll be well within the total RMS rating of your repaired speakers (600 watts).

 

[GunpointMetal]

Those clip lights on bass amps mean stop there, and go back a little bit. I feel like if it wasn't loud enough everything else was too loud. Volume isn't tone.

 

[wheresthefbomb]

Really appreciate everyone who has shared their knowledge here, it has been very helpful and instructive. I've got a pair of 500w/8ohm Deltas on the way. We've got a couple backup cabs we are using in the meantime. The cabs aren't mine (they belong to our drummer) and so I'm very hesitant to keep using them, but we've been using them safely since I made this thread by keeping the amp well below clipping, keeping the -15dB pad on, and focusing the EQ on mids while scooping the bass. We will continue to operate it that way even when I get the new speakers in, but I'll be a lot more confident about using it with my own cabinet.