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[kel mcguire]

Well, not mine but at a venue I mix for all summer for the past Seven years. Six EV TX1152m, 15" monitors. Probably 300 shows. They've really been outstanding performers. The bands love them. Sure, we've lost a few diaphragms, maybe one or two 15" woofers.

A few of them just sound different, a bit darker, or a bit brighter. That's taking the same speakon with music or voice & mic and testing back to back.

So, Do Xovers change? What might the effect be of an out of phase horn to woofer relationship? I suppose an aftermarket diaphragm might sound different? Would a power amp(that has the same amount of shows) change tone? RMX1850HD amps. DBX 31 EQs.

Ideas?

[Art Welter]

A few of them just sound different, a bit darker, or a bit brighter. That's taking the same speakon with music or voice & mic and testing back to back.

1)So, Do Xovers change?
2)What might the effect be of an out of phase horn to woofer relationship?
3)I suppose an aftermarket diaphragm might sound different?
4)Would a power amp(that has the same amount of shows) change tone?
5)Ideas?

Unit to unit variation can easily make even "brand new" units sound different and require an individual correction EQ .

1) They can- resistors can burn, capacitors drift, solder joints can go "cold", or even missed being soldered in the first place.
Aside from crossover variations, speaker surrounds can "dry out", and cones may "soften up" over, changing their response over time.
2) A deep "hole" in the response in the acoustic crossover range.
3) Usually. Gaps also need to be cleaned completely before new diaphragms (whether stock or aftermarket) are installed, and diaphragms must be properly aligned.
4) Not likely, unless using tube (valve) amps.
5) Lable the wedges and use them on the same mixes and stage positions, the corrective EQ needed for each will change little.
If you typically use pairs of wedges, it also helps to "match" their response before numbering.

Art

[Caleb Dueck]

How much different?  A dB or two, or more? 

Sent from my VS980 4G using Tapatalk

[Chris Grimshaw]

How much different?  A dB or two, or more? 

Sent from my VS980 4G using Tapatalk

A subtle difference between wedges would be a dB or two. Obvious differences would be >3dB IMO.

FWIW, a venue I used to work at had a big pile of SSE Betamax (EV Deltamax derivatives) which were quite variable in sound quality. Some of them got heavily abused, others had a slightly easier life - the ones at the top of the pile would go out most often, and the ones near the bottom would only get used for larger events. All the Crown MA2401 amps driving them were equally old and abused, but there were definite differences between the wedges.
I suspect cones softening up with age, although I'd also recommend going around and checking all the screws are torqued up correctly as routine maintenance.

Chris

[Tim McCulloch]

We have 16 EV xW15 and after 10 years or so they all started sounding different.  In the end we decided to replace every HF diaphragm with brand new EV parts (from the same production batch, too!).  Before you go this far you might want to do a deep cleaning of your HF drivers.  Remove them from the horns, remove the back cap and then remove the diaphragm.  Take a really good look through the phase plug and in the VC gap (bright lights time) and inspect the debris screen (uh, it does have the screen, right?) at the driver exit.  You'll probably go "yuck" at least once.  Trust me.  Clean it out, clean it up.

Inspect the diaphragm and voice coil, reject any with physical damage, clean as needed.  Check DC resistance, should be fairly close to published spec.  Mark the drivers and diaphragms as you go, log the resistance and you can deal with the outliers later.  Reassemble, sine-wave sweep to check for rubs and rattles.  Install compression cap and mount to horn.

After we did the HF, we gave a good listen to the LF and decided to re-cone all the 15s.  And we almost did that but ended up replacing them as the cost of new, delivered to our door was only $50 more, ea. than paying for the cone service and freight 2 ways.

We cleaned up and repainted the grilles.  For about half the cost of buying xw15A, we have xW15A and they all sound the same. 

[Stephen Kirby]

>>, solder joints can go "cold", or even missed being soldered in the first place.<<

Small pedantic rant.  I hate the term "cold solder".  There's no such thing.  Unless you're dealing with a solder pot, all solder is cold.  And they certainly can not "go cold".

The term derives from a dewetted or non-wetted condition resulting from insufficient thermal energy (heat).  There's no way to create a solder joint coldly.  Compression bonding is not soldering.  By definition soldering is the joining of two metals by wetting a low temperature metal between them.  Brazing is joining with a higher temperature metal but still with a lower melting point than the base metals.  Welding is a fusion of the two metal parts above their melting points.

Having done countless solder joint reliability and extended life tests a solder joint can fracture from a number of causes.  Fatigue from stress, either from differential thermal expansion and contraction, vibration or slow cycle steady state stress.  Diffusion of elements into different intermetallic compounds.  The net result from these is a partial or full fracture.  A full fracture will create issues when the fractured surfaces oxidize and become poor contacts with each other.  Until then, unless you pass so much current that a partial fracture behaves like a fuse, you have a completed circuit.  I have fought for years with so called "failure analysis engineers" who chalk an electronically non-functional unit to an "insufficient" solder joint.  Show me on a TDR plot where that joint is and how it caused the failure.  Outside of high power pole top radios, I've never seen a few square microns of cross sectional area difference in a solder joint create failures.  Even in RF test equipment.

So,  a solder joint can be de-wetted - meaning the solder hasn't completely stuck to the surfaces.  Non-wetted, meaning that it didn't stick at all.  Not soldered at all, as Art mentions.  Typically referred to as a "skip".  More commonly occurring in wave soldering or a sloppy shop that forgets to solder every connection.  Occasionally in an SMT connection when the solder paste wasn't deposited on the termination (a printing skip).  It can be overheated, leading to a grainy and easily fractured joint.  Disturbed during solidification with a similar result.  And finally, a fracture.  Ranging from a superficial crack to a completely broken joint and open circuit.

We now return you to your likely fatigued cones and diaphragms. 

[John Roberts {JR}]

Small pedantic rant.  I hate the term "cold solder".  There's no such thing.  Unless you're dealing with a solder pot, all solder is cold.  And they certainly can not "go cold".

The term derives from a dewetted or non-wetted condition resulting from insufficient thermal energy (heat).  There's no way to create a solder joint coldly.  Compression bonding is not soldering.  By definition soldering is the joining of two metals by wetting a low temperature metal between them.  Brazing is joining with a higher temperature metal but still with a lower melting point than the base metals.  Welding is a fusion of the two metal parts above their melting points.

Having done countless solder joint reliability and extended life tests a solder joint can fracture from a number of causes.  Fatigue from stress, either from differential thermal expansion and contraction, vibration or slow cycle steady state stress.  Diffusion of elements into different intermetallic compounds.  The net result from these is a partial or full fracture.  A full fracture will create issues when the fractured surfaces oxidize and become poor contacts with each other.  Until then, unless you pass so much current that a partial fracture behaves like a fuse, you have a completed circuit.  I have fought for years with so called "failure analysis engineers" who chalk an electronically non-functional unit to an "insufficient" solder joint.  Show me on a TDR plot where that joint is and how it caused the failure.  Outside of high power pole top radios, I've never seen a few square microns of cross sectional area difference in a solder joint create failures.  Even in RF test equipment.

So,  a solder joint can be de-wetted - meaning the solder hasn't completely stuck to the surfaces.  Non-wetted, meaning that it didn't stick at all.  Not soldered at all, as Art mentions.  Typically referred to as a "skip".  More commonly occurring in wave soldering or a sloppy shop that forgets to solder every connection.  Occasionally in an SMT connection when the solder paste wasn't deposited on the termination (a printing skip).  It can be overheated, leading to a grainy and easily fractured joint.  Disturbed during solidification with a similar result.  And finally, a fracture.  Ranging from a superficial crack to a completely broken joint and open circuit.

We now return you to your likely fatigued cones and diaphragms.

An odd pedantic complaint... Indeed solder joints can't "go" cold over time, but can be marginal cold from the start, and then whatever minimal solder attachment was present fatigues and breaks over time causing the insufficient joint to fail open circuit.
----
Over time a solder joint can be overheated, possible with passive crossover resistors dissipating a lot of heat. I have also seen this on 3 terminal regulators run without heatsinks that run hot as a firecracker but don't fail and eventually degrade their solder joint integrity.

[/pedantry]

Bad solder is unlikely to cause a subtle sonic difference.

JR

[Art Welter]

Bad solder is unlikely to cause a subtle sonic difference.

JR,

A bad (open) solder joint in a series component could cause an obvious lack of the LF or HF driver, but joint failure of parallel components can be pretty subtle.
For instance, a failed Zobel circuit could result in a single very narrow band change, or an open joint on a HF bypass capacitor could reduce HF gain at 16 kHz by only 3-6 dB, resulting in about the same effect as a layer of dust on the HF bug-screen.
Compared to a 10 dB spike at 4kHz caused by a performer wearing a ball cap, those changes can seem pretty trivial ;^).

Art

[kel mcguire]

Thanks for all the ideas. I hadn't thought of some of those. Things to check after the series is over, which is tomorrow, Perhaps some new diaphragms, and input plates need to be ordered. Or maybe I mark the darker/lighter sounding wedges for next season.

Some seem up or down in brightness by 2-4dB but I don't know which ones have aftermarket parts in the DH3 drivers.

[Stephen Kirby]

An odd pedantic complaint... Indeed solder joints can't "go" cold over time, but can be marginal cold from the start, and then whatever minimal solder attachment was present fatigues and breaks over time causing the insufficient joint to fail open circuit.
----
Over time a solder joint can be overheated, possible with passive crossover resistors dissipating a lot of heat. I have also seen this on 3 terminal regulators run without heatsinks that run hot as a firecracker but don't fail and eventually degrade their solder joint integrity.

[/pedantry]

Bad solder is unlikely to cause a subtle sonic difference.

JR

The point is that there's no such thing as "cold" in the first place.  Marginal cold or otherwise.  The term means nothing to a manufacturing engineer or a metallurgist.  By overheated I was referring to excess heat during the soldering.  This leaves a large grain structure that's easily fractured.  It looks like a piece of metal that's been bent back and forth and is about to crack.  Long term heating will cause a lesser degree of this but has more effect at the boundaries of the solder and termination where the metal gets brittle for metallurgical reasons.  Contaminated or oxidized terminations will cause various degrees of dewetting.  The closest you can get to "cold" would be a non-wetted joint where either things were too contaminated to wet at all or there wasn't sufficient thermal energy (time and or temperature) to get things to wet.  Typically one surface is less contaminated than the other so if it wets one but not the other it's a contamination issue, if neither wets then the process didn't have enough heat.

For people in the soldering industry, the term "cold solder" is roughly equivalent to "Can I get my mike to sound more lively?".   

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