Auditioning and choosing speakers

[g1]

I've read stories of the 32-ohm load in the "ultimate attenuator" causing damage to high-powered output stages, so I'm personally not keen on the idea of a 100-ohm resistor being sufficient protection.

I think these are 2 quite different scenarios, mis-match that sounds correct vs. no-load, audible fault condition.
Most (though not all) guys using attenuators are doing so to get power amp clipping. The amp in this case gets sustained high power use and as far as the user can hear, it is all working right. I don't think the mismatch makes it blow up right away, and probably not all that often or Ho would have re-designed by now or have a lot of angry customers.
In the case of the 100ohm across the output for protection, even the most dim user should clue in pretty quick that there is a problem (no sound). Worst case a couple windmill power chords.

[Enzo]

I had a guy in my shop once demo-ing some problem, and I was in the rear of his Twin Reverb disconnecting one speaker at a time. We played through one speaker, then I told him to stop as I disconnected that speaker and hooked up the second. Unfortunately, as I was holding the hot lead of hte second about to put it on the speaker, he decided to do one of those windmill chords. Did you know you can get quite a poke holding an unterminated speaker wire when they do that?

[J M Fahey]

You bet.
Even an SS amp can tickleyou big time, but Tubed ones are *much* worse because of the OT inductive kick.

LOTS of tens of volts, wouldnīt be surprised by them reaching 100V peaks if fully unloaded.

Of course that translates up to a couple KV at the plate side and thatīs what punchesn through insulation , arcs sockets o tube guts..

[Gnobuddy]

In the case of the 100ohm across the output for protection, even the most dim user should clue in pretty quick that there is a problem (no sound).

I mentioned this on another thread, but it may be worth repeating here: I have taken to using a switching output jack on my DIY valve guitar amp builds, and wiring an 8 ohm power resistor to it, so that if nothing is plugged in, the amp sees an 8 ohm load. Then I wire a pair of anti-parallel high brightness LEDs and a protective series resistor across the 8 ohm resistor. If I forget to plug in a speaker and play something through the amp, the LEDs flash brightly (in addition to lack of sound) to remind me that I've screwed up.

I've toyed with the idea of wiring a diode bridge across the same 8 ohm power resistor, and feeding the rectified DC from the bridge to a loud piezo buzzer, but I've never actually bothered to try it. But this should get you loud beeps along with the flashing LEDs to let you know the speaker isn't plugged in. It might not work on a loud stage with the rest of the band already going, but short of that, should be noticeable.

My interest is in low-powered amps, so it isn't hard to find an 8 ohm resistor that can cope with the full output power of the amp for a reasonable length of time, certainly long enough for me to realize there is a problem, and fix it. Might not be so easy with a 200 watt monster.

Then again, a 200 watt amp is already heavy, bulky, and expensive, so it may be worth adding this sort of protection, with an appropriately large and heavy dummy load. Maybe four 12-volt, 50 watt, automotive headlamp bulbs in series or something similar.

-Gnobuddy

[Gnobuddy]

I don't think the mismatch makes it blow up right away, and probably not all that often

I would guess the design around the screen grids is the big factor here. Using a bigger anode load lets the anode voltage drop lower on negative peaks, and screen grid current wants to shoot up as the anode becomes less effective at collecting electrons.

But if there are conservatively large screen grid dropping resistors in place, and/or a conservative screen grid DC bias voltage, no harm should be done, because those measures will limit screen grid power dissipation to tolerable levels.

The thing is, conservatively designed valve guitar amp output stages are not exactly universal. Just ask the 6V6 bottles in my Princeton Reverb reissue - the factory schematic shows around 440 volts on the anodes.

-Gnobuddy

[nickb]

Nope, in my original post I pointed out that an electronically controlled switch that senses load impedance is what is needed. It was you who suggested that a dumb (mute) switch at the input would be all that was required!

-Gnobuddy

Ah! My bad. I had jumped into the middle of the thread without reading the whole thing through. Now I see whee you are coming from.

[Gnobuddy]

Ah! My bad. I had jumped into the middle of the thread without reading the whole thing through. Now I see whee you are coming from.

No worries. On we go!

-Gnobuddy

[Steve A.]

That warning could be applied to just about everything sold in a music store.

Yes, but there would be a considerable investment with a store installing various speakers in identical cabinets just for the benefit of a small fraction of their customers. AFAIK Guitar Center stopped stocking raw speakers in their stores many years ago.

With me, I just find a speaker I really like and use it as my go-to replacement. And like tubes I will swap them around until I find a combination that works really well.

10 years ago my go-to speaker was the Eminence Red White and Blues. Nowadays it is Warehouse Guitar Speakers ET65, their version of the Celestion G12-65. (For reference I like the sound of vintage Fender combo amps not Marshall stacks.)

https://wgsusa.com/et65

Steve A.

P.S. The original suggestion might work better with on-line shootouts using high quality audio recordings. A particular cabinet (several of them actually) could be modified as necessary to accomodate quick speaker changes. A few selected guitarists could record loops with a looper plugged into various amps and high quality recordings made of those amps using the speakers in the blowout.
I only mentioned audio recordings so far. Video could be recorded simultaneously of the guitarist recording the loop but YouTube compresses audio so anyone seriously interested would want to download video files with high-quality audio. Or just download the lossless audio files and close their eyes...

[Steve A.]

I don't think so, Mark. I tried setting up a high fidelity system running my computer output into a stereo system, then a pro-sound system. While it was better than listening though cheap PC speakers, or even a decent set of small monitors, there was a nagging problem that nullified remote hifi auditioning a practical exercise, namely that there isn't any consistency in how people record, and even if they make a good recording, Youtube is going to crappify it. Unfortunately there's enough recording variability that it's nearly impossible to make meaningful comparisons. that's how it worked out for me, anyway. I have to do my comparisons in person.

I strongly agree with your concluding sentence but lossless audio files can be downloaded and played through a good stereo for accurate comparisons if the shootout was conducted properly. But like guitars and amps listening to recordings of speakers just isn't the same as checking them out in person.
In addition to the actual sound characteristics I really need to feel how the equipment responds to my playing, how it reacts to what I've always called "finger english." I like to be able to get different sounds and tones just by how I use my fingers... but that is just my own personal preference.

Steve A.

[Steve A.]

Brick and mortar shops should apply a 20% restocking fee on stuff returned for NO reason, which about covers "online discount" price difference.

Well, I would leave that decision up to the store owners. I have bought a hell* of a lot of gear from Guitar Center because of their 30 day "no questions asked" return policy (recently extended to 45 days... woo hoo!)

For on-line purchases from eBay et al I don't mind paying shipping costs both ways if the item is as described but I just don't like it.***

Steve A.

*** eBay has improved their money back guarantee and if the item is NOT as described and they rule in favor of the buyer then the seller pays for shipping costs both ways. They will issue a refund within a few days after the seller receives the return shipment so it is up to eBay to get paid by the seller. I assume that they would suspend the seller's account if the seller tries to stiff eBay.

(A few years back I found out the hard way that the eBay Money Back Guarantee was essentially worthless at that time if they could not persuade the seller to pay. Now they reimburse the buyer first and deal later with the seller. Woo hoo!)

[J M Fahey]

Guitar Center can safely offer "back if you donīt like it" because their price is rock bottom anyway, no third party online purchase can beat that once you add shipping.
My comment was relative to regular physical shops which are used as testbeds for products which will later be ordered online, not the same because they can not meet GC prices.

And if GC loses a sale to MF , hey, they are the same parent company , so money stays in the family.

That said, even GC is in DEEP financial trouble, shoud have crashed long ago, itīs just that manufacturers and importers canīt afford to lose that massive outlet, but thatīs not a fair comparison.

[Gnobuddy]

GC is in DEEP financial trouble

Very true, but at least part of the problem is that they fell prey to "vulture capitalists", who loaded them up with so much debt that there is probably no way they can escape.

I've bought a fair amount of stuff from GC over the years, and never found a reason to hate the shopping experience the way a lot of people do. Most of the employees I dealt with were musicians who did it for the love of the thing, but were paid quite shabbily for their work. That was the main thing I didn't like about GC, they did not treat their employees well.

-Gnobuddy

[Justin Thomas]

That's the kind of crap that killed my favorite local shop... people go in, try the gear, then go online to save a few bucks... then when they get the item, there's parts missing, poor set up, stuff doesn't work, etc. To me, the individual attention I got was always worth the extra few bucks - both at Sale time and later Not to mention, the employees KNEW what I liked, and often recommended me a USED piece of gear, even if they made less money on it. One time they even sent my parents elsewhere because they didn't have what I (thought I) wanted, and had the integrity to not make advantage of my parents's ignorance. The owner had an amazing ear and was a great player, and I would buy on his recommendation without hesitation. And you know what?

I never had to return a damn thing. Maybe I'd resell it after two years...

He also knew what used gear was really worth, as a player, and didn't inflate prices just because something was "vintage"

It was worth every damn cent and second I spent in that store - the Michael Jackson jokes, the great deals, the chances to play really rare amps... And they would send me work, because they knew a lot of working musicians who couldn't afford the official town tech, and because I would treat their amp as a tool, not a reference for factory specs.

But, we got what we wanted (everything as cheap as possible, in every way), and now I have my strings and picks shipped in from a few states away, (because the only two local stores seemingly don't really want my business), from a different mom&pop string shop, for only a few pennies more than Amazon. Because, guess what - not even my local GC carries MY strings in stock. So I'd rather wait a while and custom order them.

Yeah, I may be an effing dinosaur who can't adapt to a modern world, but at least I'll go down fighting and voting with my wallet. And if I ever buy another instrument, I'll try it at GC & buy from my string vendor.

Justin

[bob p]

Part of the problem in shopping at brick and mortar stores is that it's often not a Mom & Pop experience any more. A lot of the time it's a chain store with national presence, and their inventory policies are set by an MBA. To an MBA inventory shouldn't be stocked if it just sits on shelves. It needs to turn over "X" many times per year or it's not worth the shelf space it takes up in the retail outlet.

I even see this with car parts. At my local NAPA an item has to turn over 3x in a year or they won't stock it. A 1970s Corvette dual master cylinder is widely regarded as the "standard" customization product among hot-rodders who do brake work. My local NAPA guy is a rod & custom guy, having had 3 cars on the cover of magazines. When he used to own the store he'd always keep one of those master cylinders in stock. Consolidation in the industry forced him to sell to a multi-store conglomerate, so he's the operator now, but not the owner/operator any more. Now somebody above him has decided they won't let him stock the 70s Corvette master. Even though it's a standard item, some bean counter has decided that it doesn't turn over often enough to warrant the shelf space. So if anyone ever wants one they have to special order it out of the warehouse. The days of walking into the store to buy it are long gone. Everything that comes out of the warehouse has a UPS charge associated with it now. In that context, what's the point of supporting my local NAPA when Rock Auto can deliver it just as fast at a lower cost?

If you get lucky, an independent Mom and Pop might stock a product that they really believe in, even if it's something that doesn't turn over. Mom and Pop shops can tolerate a bit more in the way of inefficiency, as they don't have the MBA constantly looking over their shoulder. If you can find something that's odd in a store like that then it's important to realize the value that they've added to the experience by stocking that product, and it's worth paying a premium for the service they provide. When enough people don't support the VAR model then the stores stop providing value added services. When it's not worth their effort then they quit and we're stuck with buying on the internet.

It's not surprising that most GC stores don't stock much in the way of speakers. They want standardized items that move fast and are easy to flip. This isn't really new though. When I wanted to buy EV speakers in the 1970s I couldn't buy them locally. I had to special order them back then and wait for delivery by UPS.

Maybe expecting any store to carry a zillion types of replacement speakers just isn't realistic. 50 years ago we just paid our money and took our chances. The funny thing is that today everyone wants their shopping experience to be risk free *AND* provide rock-bottom pricing. In many respects consumers here in the USA have been spoiled. We want it all and we want it on a silver platter. Those demands seem a bit extreme when you recognize that there are many places in the world where the shopping options are a lot worse.

[Enzo]

50 years ago you didn't HAVE a zillion speakers to choose from.

Here we can find a bunch of guys who want to horse trade speakers, but in the real world, the percentage of amp owners who want to buy a loose speaker is TINY. I don't expect a store to carry them.