1/4 to SpeakON??

[dincz]

So you don't know.

Because basic knowledge of physics would say the coupling that handles more current would allow for higher SPL in a high-current application. That is pretty basic.

Please explain how that would not be the case.

Because the contact resistance at the current levels in practical use is not significant enough to cause a voltage drop that would in turn cause an audible reduction in SPL.

 

[HolmeBass]

Because the contact resistance at the current levels in practical use is not significant enough to cause a voltage drop that would in turn cause an audible reduction in SPL.

From the wiki, I quote a referenced assertion:

"Speakon connectors are rated for 40 A RMS continuous current, higher than 1/4-inch TS phone connectors, two-pole twist lock, and XLR connectors for loudspeakers. [4]"

Maybe 40 A RMS is not practical - I know I don't play that loud - but for metal, doom, playing large cavernous places, who is to say? I do not see how you can make that blanket statement in the face of such evidence. I usually agree with what you post, I am surprised to find you digging in on such an apparently, to me, indefensible point.

 

[dincz]

Maybe 40 A RMS is not practical

Definitely not practical for bass use - that's PA territory. 40A through a 4 ohm cab would be 6400 watts - or through an 8 ohm cab 12600 watts.

 

[popgadget]

Definitely not practical for bass use - that's PA territory. 40A through a 4 ohm cab would be 6400 watts - or through an 8 ohm cab 12600 watts.

This sums it up.
Prior to speakon, high powered amps used binding posts with banana plugs rather than 1/4" phone plugs.
I can't think of a single high powered amp that used 1/4" output connectors.
With current (no pun intended) production, the use of 1/4" output connectors is limited by code to what we now consider "low powered" amps. There is a voltage threshold that determines the limit.

And as far as wire gauge, open up your 800 watt cab and see what gauge the internal wiring is.

 

[B-string]

1/4" plugs really have a 300 watt limit in audio. Even at that, have I done loud gigs not in the PA with a 300 watt amp and pulled a pretty warm 1/4" from the speaker cab at the end of the gig. Heat means wasted power. [Grandpa ahead] In the old days we were overheatin' plugs and jacks in PA stuff and with nothin' else good we used AC twistlocks for speaker cabs. One a jack gets hot it loses spring tension (loose feeling) and can't perform well, at that point you must replace, rinse and repeat.

 

[HolmeBass]

I am becoming motivated to do this test. Unfortunately the only suitable amp I own, that is one with both 1/4" and speakon outputs, tops out at 260 W into 4 ohms. That probably is not be enough power to notice a difference.

 

[beans-on-toast]

1/4" plugs really have a 300 watt limit in audio. Even at that, have I done loud gigs not in the PA with a 300 watt amp and pulled a pretty warm 1/4" from the speaker cab at the end of the gig. Heat means wasted power. [Grandpa ahead] In the old days we were overheatin' plugs and jacks in PA stuff and with nothin' else good we used AC twistlocks for speaker cabs. One a jack gets hot it loses spring tension (loose feeling) and can't perform well, at that point you must replace, rinse and repeat.

I've seen hot plugs as well.

A commonly used ¼" jack for the output in amps is the Switchcraft 12A. The specs are attached. The contacts are a nickel silver allow. One reason why oxidation builds up on them so easily. The contact plating is rated for 10,000 insertion and withdrawal cycles. Interesting that there is a military version that can withstand 20,000 cycles. This means that the plating is better. But now for the money spec: the contact rating is 1A 25V DC. Conveniently for them, don't provide an AC rating. But people don't run DC through a Switchcraft 12A jack.

Take a 300W amp into a 4 Ω cabinet. At rated power this is 35V and 8.66A AC. With peaks, this will be higher.
(P=V * I = I * I* R. So the current is the square root of the power divided by the resistance: the square root of 300W/4 ohms = 8.66A. Also V = P/I so 300W/8.66A = 35V).

So the question is, can a jack that is rated for 1A@25V DC be used for an 8.66A@35V AC application? It's complicated. Contacts have a resistance as seen in the data sheet. Oxidation adds contact resistance which means more heat. Power and heat factor in to the current capacity. Heat lowers the current capacity rating. If you want to compare an AC voltage rating with a DC rating, to be conservative, you'd want to look at the peak AC voltage. With an AC sine wave, the peak is 1.414 times higher. So the 35 VRMS of the 300W amp above is about 50V peak. Having said that, often the RMS AC voltage rating is used as an equivalent of the DC voltage rating. So the 25V @ 1 A DC rating of the jack can be accepted as 25V RMS @ 1A AC. As I said it is more complicated, this is based on some assumptions. The AC, 50% duty cycle current capacity of the jack is actually higher than 1A. Let's be very generous and say that it is 2A.

If we accept this, is it is safe to use a jack rated at 25V RMS @ 2A AC in an application that requires at least 35V @ 8.66A AC? It is the current that is important, more so than the voltage.

By comparison, the Speakon NL4MP contacts are rated at 40A for a 50% duty cycle --sine wave AC, 250V.

It's a no brainer when it comes to higher powered amps.

 

[dincz]

It's a no brainer when it comes to higher powered amps.

It's a no brainer even without considering voltage and current ratings. The momentary short circuit while inserting or removing the plug is not healthy for amps, exposed live tip when unplugged and the live shell when running an amp bridged - not healthy for the user.

Can't think of any redeeming features.

 

[Bassamatic]

1/4" plugs and jacks were never intended to handle power - they were for telephone switchboard connections (that's why they are called phone plugs and jacks) and later for line level signals. The thought that they even work at all for instrument amps is amazing to me.
You have the circle of the plug touching the flat surface of the jack - how much surface area could there possibly be?
Banana plugs would have been better as they have considerable surface area but would still have the pullout problem. Even XLRs would provide much more contact area and locking, but they are a PITA to install.
Note that 1/4" was never used for consumer audio - binding posts, screw terminals and banana plugs only.

It is likely that the transient nature of instrument audio keeps the 1/4" from getting too hot, plus the jacks are usually mounted to a metal plate that acts as a heat sink so you may notice any heat.

I could not find a definitive audio comparison of 1/4" vs. Speakon - anyone? I do see that the rating on 1/4" is 1A and Speakon 40A HUGE difference.

 

[agedhorse]

Wait a minute guys, all this bantering about of 40 amps continuous is not correct. The rating of 40 amps is at 50% duty cycle, which is only 20 amps continuous. The 30 amp rated continuous (thermal limit) is greater than this which means that 40 amps is a peak limit for contact current density purposes (audio).

From my experiences in double-blind listening tests, there is no audible difference between 1/4" and SpeakOn, but there are differences on long term reliability, especially at very high power levels.

There were other factors that made the SpeakOn desirable, specifically that they are locking, do not short the amp when not fully engaged at the speaker end, and that they satisfy the requirements for a touch-proof connection for safety agency approval.

 

[beans-on-toast]

It's a no brainer even without considering voltage and current ratings. The momentary short circuit while inserting or removing the plug is not healthy for amps, exposed live tip when unplugged and the live shell when running an amp bridged - not healthy for the user.

Can't think of any redeeming features.

Not to mention what happens when there are spikes sent through the amp. Those loud pops when you plug in are never good.

 

[beans-on-toast]

Wait a minute guys, all this bantering about of 40 amps continuous is not correct. The rating of 40 amps is at 50% duty cycle, which is only 20 amps continuous. The 30 amp rated continuous (thermal limit) is greater than this which means that 40 amps is a peak limit for contact current density purposes (audio).

Specs can be vague which leaves you having to make assumptions when interpreting them. I like that Neutrik provides a 50% duty cycle audio current AC rating. Too bad that they all don't do this.

The big advantage as far as I'm concerned is that the Neutrik mating connectors lock. I had people step on cables with ¼" plugs and pull them out. In one case, it resulted in damaging the amp at an inopportune time.

 

[agedhorse]

Duty cycle is important, but so is current density because UL/EU only requires a minimum of 1/8-rated power duty cycle, which leaves room for mis-interpretation. It's all engineering gray area stuff depending on the application.

 

[Munjibunga]

How do you know? It handles much higher current. Seriously, how do you know?

Because the typical current flow doesn't exceed the capability of the ¼-inch plug, which many of us used for decades before the advent of Speakon™ connectors. It's a moot point.

 

[agedhorse]

I can think of countless amps that survived 1/4" speaker plugs, but most were <500 watts/4 ohms

 

[Munjibunga]

I can think of countless amps that survived 1/4" speaker plugs, but most were <500 watts/4 ohms

My old WT-800A had ¼-inch and banana plugs. I used the ¼-inch all the time, even into 4 ohms. No prob. I did end up buying some ProCo Guardian Fat Max 8-gauge cables with bananas on one end and ¼-inch on the other. It might be overkill, but I was going on Pascal's wager. I still have one of those that I put Speakons™ on the ends. Don't ask how - you won't like it. It's very dumb. Cool, but dumb.

 

[beans-on-toast]

No question that there are a lot more amps out there with ¼" output jacks than there are with speakons. It isn't like they are exploding because they have ¼" jacks.

I recently installed some new connectors on an old set of PA cabs. The ¼" jacks were worn and oxidized. The sound really opened up, like lifting a blanket off the cabs. A little maintenance can go a long way.