Sad cab day - possible dying speaker in Mesa PH410?

[trjh2k2]

Actually, I'm going to take back my "might still be cheaper than the cab new" comment - 170 x 4, then adding tax, shipping, etc, is gonna creep right up to $800 or so. That's an oof.

 

[trjh2k2]

So I stuck the speaker back into the cab and as soon as I played an actual instrument through it, the scratchy sound came back. I guess that's that then.

If anyone's interested, I took a quick clip with my phone. It's hard to hear what's going on, but it's definitely there:

 

[trjh2k2]

For whoever is still following - I think the one thing I'm left with that I'm not entirely clear about:
Lets say I replace two speakers now, and two later. And we're working on the assumption that all four of the original speakers have at least some damage. Does having two good and two bad speakers in the same cab put the two good ones at risk?

I'm thinking two scenarios:
- Worst case scenario is one of the two bad speakers dies completely, which spells bad news for everything connected to it, since impedance is thrown off, those cab parameters are all thrown off, etc.
- More likely, none of the speakers die, but the way the bad speakers interact with the cab is still thrown off, which puts extra stress on the new speakers and shortens their life span.

Do I have the right idea, or am I being paranoid? In other words -> is replacing only two speakers a bad idea?

 

[agedhorse]

If the speakers are damaged and the parameters have shifted significantly (that's one way we determine if a speaker has been driven past its mechanical limits and has become damaged), then yes it could jeopardize the new speakers if driven hard. At low volumes it's not going to matter.

 

[trjh2k2]

Thanks aged, the feedback is fantastic and appreciated.

 

[trjh2k2]

So I finally got my chance to put a bit of serious volume into the cab, which I know isn't the smartest thing to do when the speakers are damaged, buuuuuuut I don't think the damage is quite in "is going to imminently explode" territory yet, and I wanted to know what it was going to sound like, if it would actually get as loud as I would need it to, etc - and I figured this could inform me on whether or not I'd want to sell vs. repair it. For some context, it was me, our drummer (he's pretty loud), and one guitar through a Roadster+Recto cab, and we only played two songs. The room itself is pretty terrible sounding too, which I find leads to more volume from everyone, so that's a thing. Posting my thoughts, because why not. Sorry for the wall of text.

What I observed:

• It's definitely loud, but definitely not as loud as my usual cab. I think 2x of these would be insanely loud though.
  
• It seems to have a bit more low end than the previous cab though.
• I can kind of understand how the previous owner wouldn't have noticed the noise. It's hard to spot when at low volume, but as soon as you get some volume though it, the noise is completely buried, and the speakers aren't farting out or anything (that I can tell), so you could convince someone (based on the sound) that there was nothing wrong.
• I can kinda see how volume could murder these speakers though. At home volume everything stays pretty much in place. We started song 1 and I was at my "usual volume" on the amp, based on the other cab, and you couldn't see a ton of movement on the cones, but it was there - but I also was getting buried under the guitar, so I added just a bit more from the amp and once I was at audible volumes the cones were really moving - which is something I'm not used to seeing. With my other cab (tc808), I don't know if it's just because the grill covers it up well enough, or maybe there's enough speakers/power available that they don't have to really flex, but I've never noticed cone movement like that before. It kinda freaked me out for a moment.

I know some bass cabs/speakers do that, but it caught me off guard. I tried to do some reading about what to expect from this. There wasn't a maaaaassive amount of excursion happening, and it was only when playing reasonable low or hard, but it's enough to be very visible, and enough that I wasn't willing to give any more volume to it. I later googled the numbers for the CA10 and feel a bit better knowing that xmax (3.02mm) and xlim (7mm) are..... well, that to me seems like huge numbers. I definitely didn't move those things by 7mm, that seems like some holy-crap movement. 3mm is a possibility though.

If this is normal, then how loud must the previous owner have run this thing to damage the speakers?

I kinda wish I had filmed the thing going so I could get some more professional eyes on whether or not that amount of movement is normal for these speakers.

I was also trying to think about whether or not the amp I'm using is overkill for the cab, but I don't think it is. I've got a Crown XLS1000 I'm using for power, and at 8ohm, bridged, it shoooould be 700w of "average power" (whatever that means.... is that rms? Or similar? I have no idea). I had the preamp set pretty loud, but the master volume stayed just above half way, and I thiiiiink the volume knob on these is pretty linear to my ears, so I know I wasn't pushing out as much as that amp can do. I'm thinking that with a cab that really moves the speakers around, it's probably smart to turn on the hi-pass, which I normally leave off.

Anyway, that was my cab adventure. I've got some recording I want to do soon, and I kinda want a real cab in the recording for a change - so I'm leaning towards the speaker replacements reasonably soon-ish.

 

[agedhorse]

by the time you have hit 7mm, you will have experienced that damage. Over time, beyond 3-4mm on the CA type driver, the spider is beginning to experience fatigue and as the spider's fiber structure decays, the compliance of the driver increases, the cabinet is no longer tuned for the drivers, and for a given amount of power the displacement increases until something "breaks".

If you are seeing a lot of motion, and you are using the 30hz(?) HPF on the XLS amp, this is a prime indicator that the creased cones go hand in hand with damaged suspension. Generally, even though you see the creased cones on 2 drivers (at this point), the damage is present in all 4 speakers.

I see this often, there's nothing mysterious about it. It's a 600 watts RMS thermally rated cabinet that's good for about 400 watts RMS below 50hz. No different (in reality) than many other 410 cabinets of the era.

 

[trjh2k2]

I wasn't using the HPF at the time I saw that movement - more that when I saw the movement, I thought it would be smart to turn that filter on, but by the time I had that thought, we had already shut stuff down. I assume a lot of bass amps have a filter like that built in with or without indicating it, to help protect speakers, but a PA amp like the Crown isn't going to do it by default. I normally don't use it, cause it starts at 50hz, which seems kinda high. If it was 30, I probably would have left it on. Maybe another point on the list of reasons I've been considering trying to replace the Crown with something more bass-specific.

I could be exaggerating how much I saw the speaker move (and more and more I wish I had recorded it so I'm not going on my fuzzy old man memory). For as long as I've played bass, I've only ever really used the one cab I've got, so I don't have a reference point for what most 4x10s look like when being used with a healthy amount of volume. I assume some movement is ok, and expected, since how else do you move that air.

It keeps making me wonder - are most 4x10s just too little to compete with a loud drummer in a bad room? Do I just have poor expectations of what a 4x10 should be able to do? I could swear I've heard some 4x10s that can shake buildings, but every time I try to use one it struggles to keep up. Maybe I've actually just got a bad sound that doesn't cut well, and it makes me want to crank volume more than I should?

Here's a dumb thought:
You know how tube amps "seem to be louder" when rated at a much lower wattage? I've always assumed that this was some kind of psychoacoustic thing or a difference in what kind of harmonic content ends up in the sound or something - would that also mean that a tube amp is "safer" for a speaker? I mean, if you're getting the same "perceived" volume while putting less wattage/energy into your cab, I assume that would be healthier for the cab. Unless that's all nonsense.

 

[beans-on-toast]

Tube amps that offer rich harmonics and non-linearities can sound louder. Higher frequencies do not extend the speaker cone like lower frequencies do.

 

[trjh2k2]

Sure, but it doesn't say much about the difference you'd get using those two setups in terms of the abuse the cab is going to take. Say you have a 1000+ watt class D amp, and a 300 watt tube amp, dialed as close as you can get them, and you play them both at the same perceived volume - is the cab going to take the same amount of abuse from both?

I felt a bit dumb yesterday, trying to search youtube for videos of bass cabs being played at volume so I could compare what I saw to what other people see and.... there was just nothing. Nobody films their cabs this way, I guess. Lots of videos of home theater and car audio people pushing subs to see how far they can make their speakers move because that seems to be fun for them - but that's not helpful to me.

Maybe it's fine and what I saw was actually pretty normal - maybe it's a ported vs. sealed cab thing where some ported cabs just have more visible movement and I'm not used to it. But if not, I'm paranoid about investing more money into a cab that I'm just going to kill again if they're not really meant to handle being loud. And by loud I mean "audible in a metal band with two rectos in a small room" kind of loud. Am I wrong to expect any 4x10 to be able to do that comfortably?

 

[agedhorse]

A well designed 410 is quite capable. It’s all about reasonable expectations.

 

[trjh2k2]

I understand, but at the same time, it's hard to know what's reasonable or not.

If I go with my gut, I think the cab could handle more than I gave it, and it would probably be fine, and I'm overreacting to the cone movement because I'm used to a cab that doesn't do that in a way that I can see it. I don't normally play with a ton of low end - I generally rely on high end to cut through, so I don't think of myself as the kind of bassist whose sound is abusive to gear, but who knows.

The usual advice is "the speakers will tell you if something is wrong", except that it's been said a bunch of times that people are damaging their speakers long before the speaker makes an obvious noise to tell you. I didn't hear any distortion from the cab even though they're already damaged, so my ears tell me nothing. And the cones definitely moved, but I have no way of measuring it, and I don't have the experience to eyeball what "healthy cone movement" is.

So that just leaves me with... try it and find out I guess? I mean, I could buy a whole new set of speakers, they work great, the cones move but it's normal, it lasts for decades and I never have to worry about it again. Or, I could buy all new speakers, and fry another one of them in 2 jams.

I kinda wish there was a video or something out there demonstrating examples of what a cab looks like when it's being abused. "See how that cone wobbles instead of just pokes out on transients? It's about to implode" or "Hear that kinda growly sound that pops up here? You might think that's cool speaker distortion but that's actually the cone telling you it's about to fold in on itself."

If those videos are out there and I haven't found them, I'm all ears.

 

[6thplanet]

I will say, you never forget the sound of a voice coil former hitting the back plate.

If I can remember I'll get a video of my cab at practice Saturday.

 

[trjh2k2]

Do you have a similar powerhouse cab? If you're willing to video that so I have a picture of what they normally look like, that'd be fantastic. If I end up getting this one up to volume again any time soon (it's unlikely though), I'll try to remember to film it as well. I think the visuals will help the conversation along better than any of my whining will, hah.

 

[trjh2k2]

It's occurred to me just now - xmax, xlim, etc are from the centre position, right? As in - if your xmax is 3mm, you're actually talking about 6mm of total travel in both directions, right? That seems like a lot of movement to me. Maybe I really am just paranoid of something that's pretty normal and I just never noticed before.

 

[6thplanet]

Not a powerhouse cab, but should give you a comparison of what normal excursion looks like.
As for Xmax numbers, should be noted whether peak or peak to peak (p-p). One can't really assume with just a number.

 

[trjh2k2]

The eminence website describes it as the greater of "Voice coil height minus top plate thickness, divided by 2" or "the excursion point of the woofer where THD reahes 10%". Which..... I guess is not super useful to the average bassist who isn't equipped to measure those things, but that sounds to me like they mean the number is in one direction.

Understanding Loudspeaker Data | Eminence Speaker

I guess something that maybe makes some sense is that if I consider these to be "beater" speakers, I can continue to experiment a bit when I get the chance, to see how much they can handle so that once I get the new speakers I already have a sense of what to reasonably expect from the cab. If I'm going to learn where those limits are, I'd rather do it with speakers that are already beaten up than with new ones.

 

[agedhorse]

I give up trying to help with science, data and real world service experience.

 

[trjh2k2]

I'm not disagreeing with or dismissing anything you've contributed, aged, I'm just rambling and thinking out loud because I can. ¯\_(ツ)_/¯ Just documenting my thought process, where people can give me feedback.

What have I done or said that went against your recommendations? Is it that I turned it up to see what would happen?

Honestly, your insight is super helpful - it is difficult to apply though, especially without the experience that someone like yourself has to put that information into context. "Quite capable" could mean a lot of things, just like "reasonable expectations" can mean a lot of things. Maybe my expectations aren't reasonable and this cab isn't appropriate for me, but how do I know that without trying it? And it's not like I'm just going to drop $700 on replacement speakers without thinking it through and rambling on about it for a while. That's not impulse-decision amounts of money. I want to understand what I'm doing and what I'm dealing with so that I can go forward with said reasonable expectations, or decide that the cab isn't going to meet those expectations so that I can save myself the money and the hassle.

Edit: One takeaway I definitely got from this is that I should probably be engaging the HPF on the crown, which I hadn't been doing until now.

 

[agedhorse]

Umm, well ok then. Carry on.