Risk damage with Speakon to 1/4”?

[DoctorZee]

I recently picked up a Tech21 VT Bass 500 head, and the owners manual specified that it should only be used with Speakon cables. It says that using a Speakon-to-1/4" cable risks damaging the cabinet and head.

Is this a real risk? I've never heard of this type of damage before. Should this really limit my choice of cabinets?

 

[Goatrope]

Sounds to me like it's just an awfully conservative warning. The advantage of a locking connector is certainly a plus when it comes to tube amps, but still, the only damage I could imagine is accidentally pulling out the 1/4 end while that tube amp is running.

 

[DoctorZee]

Sounds to me like it's just an awfully conservative warning. The advantage of a locking connector is certainly a plus when it comes to tube amps, but still, the only damage I could imagine is accidentally pulling out the 1/4 end while that tube amp is running.

Thanks, I was thinking similarly. This isn't a tube amp anyway!

 

[Redbrangus]

A lot of Class-D amps use a bridging topology at the output stage; this means that neither speaker cable conductor is at ground potential and shorting either conductor to a grounded conductive surface (like the chassis of the amp itself) is likely to fry the output devices. The fact that one of the conductors on a quarter-phone is on the shell of the connector makes it especially vulnerable to exactly this kind of unintentional, casual shorting to ground. If you have a well-made Speakon-to-quarter-phone speaker cable, you'll be OK as long as you never (i.e., NEVER EVER!) plug or unplug the quarter-phone end while the amp is turned on. Putting a layer of insulating tape or heat-shrink tubing around the barrel of the quarter-phone plug is also advised.

A far better (and safer) solution would be to change out the connector on the speaker cab -- it's easy enough to do and costs almost nothing. If you go that route, the NL4-MPR is the one with the large, round flange -- it mounts directly to an enclosure more easily and securely than the smaller, rectangular ones (NL4-MP).

 

[DoctorZee]

A lot of Class-D amps use a bridging topology at the output stage; this mean that neither speaker cable conductor is at ground potential and shorting either conductor to a grounded conductive surface (like the chassis of the amp itself) is likely to fry the output devices. The fact that one of the conductors on a quarter-phone is on the shell of the connector makes it especially vulnerable to exactly this kind of unintentional, casual shorting to ground. If you have a well-made Speakon-to-quarter-phone speaker cable, you'll be OK as long as you never (i.e., NEVER EVER!) plug or unplug the quarter-phone end while the amp is turned on. Putting a layer of insulating tape or heat-shrink tubing around the barrel of the quarter-phone plug is also advised.

A far better (and safer) solution would be to change out the connector on the speaker cab -- it's easy enough to do and costs almost nothing. If you go that route, the NL4-MPR is the one with the large, round flange -- it mounts directly to an enclosure more easily and securely than the smaller, rectangular ones (NL4-MP).

Very helpful! I mean, I understood very little of what you said, but still helpful!

 

[Redbrangus]

In that case, maybe just go with this:

...the owners manual specified that it should only be used with Speakon cables. It says that using a Speakon-to-1/4" cable risks damaging the cabinet and head.

 

[DoctorZee]

In that case, maybe just go with this:

I was mostly joking. Tell me if I'm wrong, but my takeaway is that I shouldn't let it limit my cabinet choices... but if I get one with 1/4" connectors, just be sure to use a high quality cable, be careful with it, and look into replacing the cabinet's connector down the road.

 

[beans-on-toast]

¼" jacks have limitations. 500W is pushing it. The company is covering them self with the statement in the event of damage.

Can you get away with using a cab with a ¼" jack in this case? Sure. I prefer speakon connectors. Better to modify a cab and install a dish with a speakon connector.

Why you shouldn't use ¼" connectors for speakers.
Disadvantages of 1/4 speaker connections.

 

[Skillet]

You can buy some speakon connectors and rewire your cables. You don't even need to solder, just use a screwdriver.

 

[Ewo]

My .02: change out the jack on the cabinet. Use a Speakon, and you'll be worry-free.

As @Redbrangus, @beans-on-toast and others pointed out above, the modern class D amps don't want to work into a 1/4" phone plug.

 

[RSBBass]

I have a modern Class D head, a Traynor SB200 and it has both Speakon and 1/4" phono plug outputs. While I agree that Speakon connections are better, they both do the same thing, they carry a signal and a ground. The idea that a 1/4" plug can't handle the power is belied by the decades of use doing exactly that in thousands of venues.

 

[Redbrangus]

they carry a signal and a ground.

This is exactly the point -- they don't carry a signal and a ground; in bridged topology, both conductors are 'hot' and neither is referenced to ground. And the quarter-phone plug was never intended to carry any current at all -- it's a happy coincidence that it works ok enough with a few hundred watts, but there haven't been decades of use carrying heavy current because amps capable generating more than a few hundred watts haven't been available all that long. If quarter-phones were a workable solution, they would have been included on pro power amps, which they haven't been since the PV CS-800 era. Nowadays, I don't believe an amp larger than 500 watts with a quarter-phone output can receive a UL certification, but I could be wrong.

 

[Peteyboy]

I have a modern Class D head, a Traynor SB200 and it has both Speakon and 1/4" phono plug outputs. While I agree that Speakon connections are better, they both do the same thing, they carry a signal and a ground. The idea that a 1/4" plug can't handle the power is belied by the decades of use doing exactly that in thousands of venues.

While I kinda agree with you, I think they're talking about connectors/cables that deal with 500 watts. Your amp is 200 @ 4ohms.

 

[agedhorse]

I have a modern Class D head, a Traynor SB200 and it has both Speakon and 1/4" phono plug outputs. While I agree that Speakon connections are better, they both do the same thing, they carry a signal and a ground. The idea that a 1/4" plug can't handle the power is belied by the decades of use doing exactly that in thousands of venues.

On most class D amps, the speaker output is bridged and both terminals carry signal (the tip carries the non-inverted signal and the sleeve carries the inverted signal). If the sleeve contacts a real ground (ie. the chassis, the sleeve of another cable that's connected to ground, etc.) the short circuit that results can damage the amp and even the other device that may be connected to it.

Another challenge, especially on larger amps like the Subway 800 series, is that the voltages and currents are high enough that SpeakOn connections provide added safety. On large amps, the voltage on the sleeve can be as high as 50-70 volts peak referenced to ground and 100-140V from tip to sleeve. This presents a hazard to somebody that may come in contact with the speaker plug. The current can also be quite high, I believe the current limit for the Subway amps is around 25 amps peak, which is well in excess of the safe current handling of a 1/4" connection and because this jack is considered a "PIS" by the safety agency regulations, the additional safety ratings of the SpeakOn jacks/plugs with regard to flame spread (specific to the material used) comes into play. Different countries and regions interpret this differently, and since we ship globally we need to address the strictest interpretation as "best engineering practice".

It looks like most pro level amps have been migrating to SpeakOn only over the past few years, especially at the higher power levels.

This question comes up often enough that IMO, it's important to understand WHY many companies have migrated away from using 1/4" speaker connectors.

 

[devnulljp]

A lot of Class-D amps use a bridging topology at the output stage; this means that neither speaker cable conductor is at ground potential and shorting either conductor to a grounded conductive surface (like the chassis of the amp itself) is likely to fry the output devices. The fact that one of the conductors on a quarter-phone is on the shell of the connector makes it especially vulnerable to exactly this kind of unintentional, casual shorting to ground. If you have a well-made Speakon-to-quarter-phone speaker cable, you'll be OK as long as you never (i.e., NEVER EVER!) plug or unplug the quarter-phone end while the amp is turned on. Putting a layer of insulating tape or heat-shrink tubing around the barrel of the quarter-phone plug is also advised.

A far better (and safer) solution would be to change out the connector on the speaker cab -- it's easy enough to do and costs almost nothing. If you go that route, the NL4-MPR is the one with the large, round flange -- it mounts directly to an enclosure more easily and securely than the smaller, rectangular ones (NL4-MP).

On most class D amps, the speaker output is bridged and both terminals carry signal (the tip carries the non-inverted signal and the sleeve carries the inverted signal). If the sleeve contacts a real ground (ie. the chassis, the sleeve of another cable that's connected to ground, etc.) the short circuit that results can damage the amp and even the other device that may be connected to it.

Another challenge, especially on larger amps like the Subway 800 series, is that the voltages and currents are high enough that SpeakOn connections provide added safety. On large amps, the voltage on the sleeve can be as high as 50-70 volts peak referenced to ground and 100-140V from tip to sleeve. This presents a hazard to somebody that may come in contact with the speaker plug. The current can also be quite high, I believe the current limit for the Subway amps is around 25 amps peak, which is well in excess of the safe current handling of a 1/4" connection and because this jack is considered a "PIS" by the safety agency regulations, the additional safety ratings of the SpeakOn jacks/plugs with regard to flame spread (specific to the material used) comes into play. Different countries and regions interpret this differently, and since we ship globally we need to address the strictest interpretation as "best engineering practice".

It looks like most pro level amps have been migrating to SpeakOn only over the past few years, especially at the higher power levels.

This question comes up often enough that IMO, it's important to understand WHY many companies have migrated away from using 1/4" speaker connectors.

That was very informative and succinct. Thanks both of you. learned something useful today.

 

[fdeck]

As for damaging the speaker... I'm sure Andy has seen more in a year than I've seen in my lifetime, but a potential failure mode is for an output device on the amp to fail, causing the output to deliver DC at high current to the speaker. (Devices can fail "off" but they can also fail "on"). This can be particularly a problem if your amp is more powerful than the rating of the speaker.

I have no design experience on real commercial bass amps to know if they are protected against this potential fault, but I know that in my hobby prototyping, I've made mistakes leading me to think that it's possible.

 

[J-Bass RMR]

Interesting... and something I wasn't aware of...
I converted anything I could to speakon 30 + years ago.

But, most my new cabs only have one speakon and one 1/4" ??!!!
I often use a speakon to 1/4" cable to connect 2 cabs, apparently putting the system equally at risk?
I do it this way - mostly at home, because it simplifies swapping out different heads. I guess I'll have to re-think that...

I make my own cables, and use shrink-wrap, but mostly as additional strain relief - it doesn't cover the entire "barrel". Easily modified, but still doesn't sound like a good idea...

 

[rtslinger]

I use the adapter on my TC Electronics Thrust 500 never had an issue

 

[sawzalot]

I use the adapter on my TC Electronics Thrust 500 never had an issue

Just because you're lucky doesn't mean it's a good idea.

 

[Lobster11]

This has been interesting and educational, and leads me to a follow-up question. Suppose you have an amp with two speakon outputs, and want to connect a pair of (8 ohm) cabinets that only have 1/4" jacks. From a safety/risk perspective, does it make any difference if you hook up each cabinet to a separate output (via two speakon-to-1/4" cables) versus daisy-chaining (i.e., speakon-to-1/4", then 1/4" to 1/4" from cab to cab)? Usually people say it doesn't matter which way you do it, but I suspect they're usually thinking only in terms of impedance matching rather than risk/danger. And is the answer different depending on the wattage of the amp?