|lowell||10/12/2017 11:48 AM|
|Matchless Chieftan - WTH|
So this combo came in with low volume and distortion. I checked the bias and was shocked. 70ma per EL34. Plate volts are 430v. So I figured these tubes are toast and put a new pair in. Same result.
I subbed in an OT, and checked the Rk' s etc... all this only to see on the schematic that this is CORRECT! So...WTH.
In the schematic it has 24v/270ohm on cathode. 89ma!! At 430v Ra that's 38watts!!
Please someone tell me there's a reason for this. They have "special" EL34 they use from the factory right? 藍
|TimmyP1955||10/12/2017 12:02 PM|
|I'd think that there ought to be a resistor after C9 and C18 (if I am reading the numbers rightly). As it is, when the master is at zero, V5A and V5B are driving each others' plate resistors in parallel with their output impedances. Seems as though this would compromise the performance at low MV settings.|
|Leo_Gnardo||10/12/2017 1:12 PM|
I've tried increasing the cathode resistor but by the time plate current is brought down to a sane level, the output is in deep crossover distortion. Can you tell, they're not my favorite amp?
|Justin Thomas||10/12/2017 1:16 PM|
|Not to mention, that "Master Volume" is just a courtesy. It was never really intended to be used below "10" anyway... |
All joking aside, it was meant for shaving off a little bit, not getting Rawk in the living room.
|Leo_Gnardo||10/12/2017 2:36 PM|
|Enzo||10/12/2017 2:39 PM|
|Think of it as a class A amp, and then you ignore the high current.|
|J M Fahey||10/12/2017 3:07 PM|
|Killer sounding amps, they are what they are, and if you donīt like them, just donīt buy them.|
I do regular maintenance on the few available in Argentina (less than a dozen) and players love them.
They run so hot that the plastic front panel bends.
I added a 12V fan fed rectified 6.3V (about 7 or 8 V DC) so they just blow a gentle breeze and owners clip one wire to stop them, claiming "sound is not the same" ... who am I to disagree?
A common problem is that power tube cathode caps dry up , at least once a year, check that.
|The Dude||10/12/2017 3:19 PM|
|One of my favorite guitar tones for a semi-distorted sound is Todd Nichols (Toad the Wet Sprocket), who plays a DC30.|
|J M Fahey||10/12/2017 3:20 PM|
Both plate signals mix ... out of phase.
When MV pot is set to 0 ohms, combined output is also 0 VAC.
Even if it were not, same signal drives both power tube grids ... which again are out of phase so they cancel whatever small signal *might* have survived.
"Brilliance" control does the same, but at high frequencies ... and itīs just the 60 years old VOX "Cut" tone control.
|TimmyP1955||10/12/2017 4:08 PM|
|Leo_Gnardo||10/12/2017 6:02 PM|
|Chuck H||10/12/2017 7:08 PM|
|J M Fahey||10/12/2017 8:54 PM|
|This is one of my customers, listen and judge for yourself:|
by the way, this is not Rock, Blues, Pop, etc. but one of our popular Folkloric songs, just played with electric instruments.
|Leo_Gnardo||10/12/2017 9:34 PM|
|Chuck H||10/12/2017 9:42 PM|
|Justin Thomas||10/12/2017 9:53 PM|
|Mick Bailey||10/13/2017 4:41 AM|
|I won't fit anything other than new-production tubes to Matchless amps. They don't last long at all and I got bitten years ago by fitting expensive NOS and having them come back after three months.|
The killer with these amps is studios leaving them switched on all day long unplayed and not putting them in standby between sessions, or even takes.
Another problem is those tube socket sleeves with the Nomex (or whatever) lining. They cause the base to overheat. I had an amp with an arced socket and when I replaced them got rid of the sleeve and installed a regular bear-trap retainer. I noticed on the last tube swap the bases hadn't discoloured anywhere near as much.
|J M Fahey||10/13/2017 8:26 AM|
|This player, Ricardo Mollo, always had a good ear for tone, and mixes/matches whateverīs needed to get it, just doesnīt follow "fads", only trusts his ears.|
His earlier setup, with which I could not complain, was classic Fenders, "any" Fender as he put it, in fact on every US trip he brought back a couple silverface Bandmaster heads because they were: tube - Fender - simple - available dirt cheap at pawnshops or second hand at standard Music Shops just because they were "the less desirable" ones, since they carried no "fairy dust" , "no Guitar God used them", played full blast so distortion comes from them, each head driving a Marshall 4 x 12" , rewired for 4 ohms to match heads, the whole shebang pushed by an 80īs TC Electronics distortion pedal.
End result was liquid, "clean" distortion courtesy of overdriven Fenders, forward sounding Celestion sound, and looooonnnnnnggggg sustain courtesy of that pedal, a killer combination.
Two local legends apply to his setup:
1) he was going through one of the "big" NY shops (Mannys, Sam Ash or Alexander) and he asked for a Metal Zone pedal, then just out of the oven and all the rage, but store owner after hearing him play told him: "forget it, kid stuff, just try this one" and gave him the TC Electronics instead.
2) much later, when he got into Matchless and found them hard to get, they were out of production and in any case never there were many of them, when he saw through the Net that somebody was selling the 15W one in Florida, a few miles away from Miami.
He grabbed his passport and leather jacket, went to the airport and picked the first Miami bound flight (mind you, some 14 hours away), picked a taxi at Miami airport and went to sellerīs home who couldnīt believe his own eyes.
Tested and payed for it, grabbed the handle and went back to Miami airport, where he had some trouble with DEA or Immigration; they "somewhat suspected" a Rock type guy who travelled 6000 miles, **no luggage** and with cash in his pocket, stayed only for 4 hours and travelled back "with a package".
Of course everything cleared up in a few minutes
|Leo_Gnardo||10/13/2017 8:40 AM|
|Mick Bailey||10/13/2017 3:33 PM|
|I don't know what it is, but I always get stopped at the airport when carrying packages marked 'Tractor parts for export'.|
|Chuck H||10/13/2017 6:26 PM|
I worked a job in Palo Alto, Ca. with a trim carpenter from North Carolina. The general flew him out because he had game. Had some vintage tools and fabricated many custom tools. He told me that when he flew in he had his special tools in a five gallon bucket with the lid duct taped on for extra security. He intended to carry it onto the plane. Security told him "No way. You need to check that." His response was "What!?! It's tools! It's not like it's a bomb or anything!"...
He didn't fly that day
|J M Fahey||10/13/2017 10:30 PM|
|Oh, a friend was stopped at a Brazilian airport, they pulled him from the plane, dragged him to the luggage inspection X Raym,achine and pointing at the screen told him: "explain that loaded pistol in your luggage" ... it was a battery powered drill with a kludged battery pack filled with "1/3 AA" NiMh batteries he got for free at his job.|
Ok, ok, they vaguely looked like .45ACP cartridges and were inside the handle.
Oh well, joys of 1984.
Just remembered: for Ricardo Mollo, being 100% Sicilian stock didnīt exactly help him look like a "safe" passenger.
|Chuck H||10/14/2017 4:50 AM|
|Ok. Since we're a little sideways already...|
My customer that travels international is sort of known for being a hot head. Big, bald, tattoos and a leather vest. Very much a biker look. After 911 and the new airport security measures they stopped him at the X-ray for his grooming kit. They wouldn't let him carry it on because there was a pair of nail clippers in there!?! He went off on the security officer saying something like 'What am I gonna do with these, nibble someone to death!?! Do you know what I could do to you with a pen!?!' He spent the next two hours in the security directors office and had to take a later flight.
|drewl||10/14/2017 8:09 AM|
|Used to work on a Chieftain for this one wealthy guy like every six to eight months.|
thing ate tubes like crazy.
I built one for a friend out of a Traynor Reverb amp.
It didnt run nearly as hot and still has the same EL34's from over ten years ago.
The same 6CA7's it came stock with from the 70's!
Built a Clubman for myself out of stuff a guy gave me.
Changed the preamp to more of a Marshall 18w and am running a pair of old 6K7's I found.
It runs kinda hot, but not as bad as a Chieftain.
|bob p||10/14/2017 9:11 AM|
|Juan, that tone is HUGE. but looking at 2:49 it doesn't look like he's plugged straight into the amp, so I'm not sure that the chieftain abusing a pair of EL34 can take all of the credit for that tone. I don't know what he's got on the floor, I don't recognize most of the pedals. my best guess is that there's a fulldrive down there, and I have no idea what those other pedals may be. who knows what's really in the signal chain, but my ears think there's some transistor edge in that tone.|
|Chuck H||10/15/2017 7:26 AM|
|Chuck H||10/15/2017 7:33 AM|
|From the original post. I don't remember noticing it the first time around.|
EDIT: Apparently it translates as "blue" or "indigo plant" or could be a surname.
|J M Fahey||10/15/2017 12:15 PM|
the whole shebang pushed by an 80īs TC Electronics distortion pedal.
1) the **oooolllldddd* door theory: imagine this old door at an old house, along the years said door has been painted: blue - red - green - blue - brown - green.
The million dollar question: what colour is that door? .... green of course, the last paint layer rules.
If door is chipped you will have glimpses of the earlier colours, but the main one is green, the last one.
By the same token, if you use various distorting stages in your signal chain, but the last one is balls to the wall driven power tubes, going unmolested straight into good speakers, your sound will be "tube", no matter how much sand you used earlier.
* Jimi Hendrix distortion pedal was *awful* buzzy nasty Fuzz Face ... yet he had incredible liquid sustain thanks to the overdriven Marshalls.
Funny things happen when noobs try to use a Fuzz Face into a "Marshall" ... a 30W valvestate on 3 (any louder and the cops come) ... so ugly is the sound that Fuzz Face isnīt used any more.
* similar thing happens with revered Tube Screamer.
Killer sound driving Fenders to death (similar to Ricardo Mollo recipe) , not so cool on its own (although way better than FF)
* Krank Distortus Maximus: killer driving an overdriven Krank full tube amp, nasty buzzy on its own.
|lowell||10/15/2017 12:24 PM|
|ha!!! Y'all are crackin' me up.|
Long story short. Replaced the Rk's with 470ohms. Put them around 45ma. Still hot IMO, but within spec. Amp SOUNDS FINE. Oh and BTW both speakers are blown, oddly enough.
Chuck, that symbol was a on my phone. It turned into an Eastern/Asian symbol after posting
|bob p||10/15/2017 12:51 PM|
|thanks, Juan. can you clarify what those other pedals are in his signal chain? since you know the guy, maybe you can find out, or maybe there are some pedal users here who will know those things. me? i've been out of the pedal thing for so long that i don't even have a clue. i haven't bought a pedal since the 20th century. my only interest is out of curiosity. i seriously dig that tone.|
(I'm showing my age when I say that I dig it, rather than calling it dope.)
|J M Fahey||10/15/2017 2:00 PM|
|Will ask when I see him at some show, or his stage hands bring something into the shop, but he changes pedals *often* in any case.|
The main point anyway is to have a standard Tube amp driven to hell so *it* supplies main distortion, and a somewhat neutral didtortion box driving it.
So yes to that old TC Electronics pedal, an MXR Distortion+ , a Blue Screamer, maybe a RAT if you set "filter" flat (it can become a ball of mud if you overdo it) , probably not a Marshall Guvīnor or any of its derivatives and definitely not strong flavoured pedals such as Big Muff or any Fuzz.
And use good to excellent speakers, he uses basically Celestions, either standard 4x12" boxes or whatever Matchless fit there.
Donīt know whatīs inside the little 15W one, but standard muscle in the DC30, which pushed him upwards thanks to a very favourable Guitar Player shootout was a Celestion Greenback and G1230H , which turned out to be a winner combination.
Matchlessī Sampson was trying to recreate original VOX AC30 sound, but he could not get his hands on a pair of Celestion Blue because they had not been reissued yet and originals were unavailable or horribly expensive, same thing, so he tried a ton of combinations to find which came closest.
Best was what I posted above, with the added twist of degooping: he brushed speaker edge with some acetone and wiped away with cotton balls or toilet paper the sticky solution as much as he could.
I *guess* as a side effect he was *aging* those speakers.
Point is, and I remember reading that on the paper magazine way back then , that said shootout was about "2 x 12" combos" and part of the testing was plugging all of them into a standard Marshall 4 x 12" .
*All* combos improved sound (compared to internal open back 2 x 12") which is not surprising, **except** Matchless DC30 which "had same quality on its own as the full 4 x 12" cabinet" which is nothing short of impressive.
|bob p||10/15/2017 2:11 PM|
|are those Matchless combos open-back or closed-back? nobody ever shows the back side of a Matchless, Matchless doesn't say on their website, and I've never seen one in person.|
their site does refer to the preferred pairing as a G12H30 with a Greenback with some "proprietary treatment" which if I had to guess is nothing more than de-doping the surrounds.
|Enzo||10/15/2017 3:38 PM|
|When one of our stored we serviced for carried the Matchless, I was told they took the new speakers and pounded on the magnets with a mallet to reduce the magnetic charge in them.|
|bob p||10/15/2017 3:50 PM|
(there's a "WTF" just for you, rjb. )
|g1||10/15/2017 5:27 PM|
Why don't we just partially degauss speakers rather than using power attenuators? Something about the sound must fall apart if the gauss level goes too low?
How does Eminence modulate the flux density in their FDM speakers?
|J M Fahey||10/19/2017 8:49 PM|
1) degaussing definitely lowers sensitivity, no doubt about that, but not smoothly across the range.
Same as installing a corolla engine in a fully loaded 18 wheeler truck, you will lower maximum speed but you will *murder* acceleration.
The speaker becomes "slow" (literally), muddy, loses treble, bite, attack.
Also loses damping so you get a boomy "single note peak" at resonance, because it becomes underdamped.
Which in brochure language is described as "smooth" , "warm" , etc.
It definitely is not "the same sound but at lower levels" by any means.
2) power handling decreases dramatically.
If you think about it, voice coil handling is puny, just a small 2 layer coil of fine wire (typically around 0.16 to 0.22mm) wound on a poorly conductive thin sheet plastic or paper bobbin.
Easy to burn with a few Watts if laying static on a table ... or inside an unmagnetized speaker.
Yet Voice coils live standing tens or over 100W because they shake violently all the time, air around them is turbulent (and thatīs an understatement) , VC is 0.1mm to 0.2mm away from a massive (1 to 8 kilos magnetic structure)
FANE measured the turbulent air conductivity and found it "close to silver" , go figure.
So you have a speaker which stands, say, 60W continuous, any waveform including squarewave, you drive it with a 30W RMS amplifier which can give you some 50W RMS squarewave fully overdriven (not the exact double because power supply drops something) ... so far so good.
Now you attenuate it by 10 dB ... and you drive your amp balls to the ball (thatīs the point) ... still 50W RMS squarewave, besides sustain and feedback make your notes, specially power chords last longer ... but speaker voice coil now stands, say, 30W RMS because ventilation is poorer; by definition an accident waiting to happen.
Worst is that attenuation range isnīt that much, will never turn a Club/garage amp into a bedroom one.
I find conceptually better to add a resistive attenuator and let a big, robust (and inexpensive) resistor take the onslaught.
Sound will also change, in fact it will probably appear harsher (Fletcher Munson), but in any case thatīs easier to handle.
Never opened one, but I guess the Eminence speaker adds some variable gap or separates 2 steel pieces or adds a steel ring "bypass" , something to lose magnetic density **at the VC gap** ; the ceramic magnet is a "strong/square" material and canīt be altered itself .
Personally find "best" the variable +V system, which leaves everything exactly the same, just makes amp less powerful.
And second best the Ultimate Attenuator, which passively loads and reamps but in the least intrusive way.
|The Dude||10/19/2017 8:58 PM|
|..... and, to top it off, that square wave you mentioned is holding the speaker at full excursion and incursion for longer periods of time than a sine wave would, so there is even more heat generated and less time for cooling.|
|J M Fahey||10/19/2017 10:46 PM|
|Yes, squarewaves are destructive.|
To boot, clipping SS amp waves are almost perfect squarewaves (Music Man amps too), while regular tube amp ones, not that much.
A 100W SS amp makes speakers suffer more than a 100W tube one, because clipped waveforms are different, even if averaged power is the same.
Now, on a resistor load, that makes not difference.
|pdf64||10/20/2017 7:57 AM|
When measuring the bass resonance impedance peak, it becomes less and less as the field coil voltage is turned down, but it doesn't seem to affect the tone.
|g1||10/20/2017 12:22 PM|
edit: sorry, I missed JM's comments on the eminence which seem the best explanation short of an autopsy.
|Enzo||10/20/2017 12:27 PM|
|One could probably contact Eminence and ask them what the basic process is.|
I contacted them once with a nerdly question about the magnetization process and machinery, nothing to do with using their product, and I got a very nice explanatory response from them.
|J M Fahey||10/20/2017 5:06 PM|
|Well, itīs probably patented, or there would be a dozen copycats by now.|
So somebody skould search for it, where they spill the beans, by definition.
At least the basic working principle.
|Enzo||10/20/2017 5:12 PM|
|Oh just the basic principle. Anyone who wants to steal the idea needs to merely buy one and take it apart.|
|J M Fahey||10/20/2017 5:30 PM|
|Found more than I bargained for, a VERY detailed and advanced analysis at: Test Bench: Eminence Maverick Guitar Speaker|
just as a notable point, this table shows *real* sensitivity, by the way a lot less than what Eminence claims (I routinely substract 3 dB from their SPL "number") but the main point is attenuation is *very* small, a meager 8dB or so.
Might do to fine tune an amp to a drummer, but definitely not enough for bedroom or quiet practice:
the 3 relevant lines for us are:
* SPL: from 95.4 to 87.9 dB , some 8dB ... very little to justify the expense and complication.
* BL from 8.4 to 3.6 <--- this is the main magnetic variation parameter, B is (variable) flux density. L is voice coil wire length which of course does not change .
* Qts , speaker Q at resonance, it shoots through the roof, from 0.99 to 3.90 , a whopping 4:1 ratio, as I predicted (without seeing this but making own design speakers for 40 years), speaker becomes poorly damped and controlled, bass becomes boomy.
|bob p||10/21/2017 1:06 AM|
|Like Juan, I prefer a resistive attenuator. I never thought it was worth the effort to degauss speakers. I prefer EV speakers with their ginormous 4# 13 oz magnets because those big manly magnets will do things that little girlie magnets just won't do.|
|Chuck H||10/21/2017 11:19 AM|
I've built resistive attenuators into some of my amps, but my personal attenuator uses the load design from the Randall Aiken article:
Designing a Reactive Speaker Load Emulator
instead of a resistor. Now, my design uses a rheostat as a sort of parallel valve to tell the amp which load (speaker or other) to play into. So in that regard it's partly resistive all the time. Using my active load attenuator side by side with the purely resistive units I'd have to say that the reactive element in my design sounds better. Especially at low settings. Since tone is subjective, of course, YMMV.
|g1||10/22/2017 1:04 PM|
|OK, sorry about the sidetrack. I did a bit of research, and is often the case, it lead me right back to this forum. |
Seems we had this Eminence FDM discussion before. If anyone is interested in the long (and weird ) discussion, here's the link:
|bob p||10/23/2017 11:55 AM|
|I hate it when that happens -- I'll go looking on the internet for information, only to find that the search engines direct me back to my own threads. It's sad to think that there are topics that I don't know enough about, where the search engines point to my threads as reference material. What's up with that? Search engines don't seem to be very smart when they direct me back to my own posts.|
|Chuck H||10/23/2017 7:52 PM|
|Search engines are using more intuitive criteria for your selections now because they think they know what you want better than you do. They watch what you do and put you in a box. So if you look up fishing rods today, tomorrow when you look up lightning rods you'll get some results that include fishing rods (presumably because both searches include the word "rod"). That is a mild example and it's actually MUCH worse than that. Now that my searches are stuffed with pseudo results of whatever narrow criteria a program has used to determine "who I am" I can hardly find anything because of the pile of crap being thrown at me, that they think I'll like (because, apparently most people do) INSTEAD of just showing results based on the words I put in the search engine. It's stupid technology that's not going to get better as long as there's something to sell.|
|The Dude||10/23/2017 7:56 PM|
|Well, if they're watching my internet history, I dare not type "rod" in the search box.|
|Justin Thomas||10/23/2017 8:50 PM|
Pardon my rant & carry on!
|Chuck H||10/23/2017 9:01 PM|
|bob p||10/24/2017 3:08 PM|
So Chuck, explain something for me --
That Aiken gadget is actually a speaker emulator, right? I mean, it's not designed to be an attenuator per se, it's designed to be a load box for a speakerless amp, right? I'm thinking that if anyone decided to build the Aiken thingy, then it would be used for loading an amp that's being driven hard, presumably with signal being fed to a mixing console or a re-amping input via the amp's line-out jack.
I suppose that you could use this type of emulator in parallel with a speaker, though that'd only get you -3dB. I'm thinking that a variable load resistive attenuator (Airbrake type) or a traditional ladder attenuator, would provide more flexibility with a speaker.
How are you deploying the Aiken thingy? I'm thinking that to get the most bang out of it you'd need to have the ability to variably divide output between it and a real speaker.
|bob p||10/24/2017 3:22 PM|
Search engines SUCK. I hate them. The problem is not that their algorithm does not work, or that it's becoming "more intuitive" -- the problem is that their algorithm places a higher value on their ability to show you and ad and bill a third party for it, than it places on you getting the results that you wanted.
Example: I'll formulate a very specific Boolean request to specifically eliminate some irrelevant items from the search results using the minus sign. What happens? Google ignores my specification NOT to include specific items in the search results and provides them anyway. They're turning a blind eye to what we really want, and they're feeding us the line of crap that they want us to see.
The problem is not that search engine algorithms are inaccurate -- the problem is that search engines make their billions by shoving their ad-shit into your face, fully knowing that you don't want to see it, and not caring that you don't want to see it. They do this because they get to bill an advertiser for being included in the search results. They prefer that the criteria for display are relaxed somewhat, as that allows them to purposefully allow inaccurate results to be co-mingled with accurate results -- if it results in a click through then they've made their money.
|Jazz P Bass||10/24/2017 4:12 PM|
|Ad Blockers work wonders.|
|TimmyP1955||10/24/2017 5:46 PM|
|The Dude||10/24/2017 5:49 PM|
|Understood. However, a speaker does not usually respond to those harmonic frequencies well. It mostly sees it as a square wave. It can't reach top and bottom of excursion that quickly. So, it sit's there at one end or the other for longer periods of time.|
|bob p||10/24/2017 6:37 PM|
|Enzo||10/24/2017 6:51 PM|
|"comprises a bunch of sine waves" not comprised of.|
What would you pay for a non-advertising supported search engine? Either by subscription or by search?
|ric||10/24/2017 7:09 PM|
|Enzo||10/24/2017 7:15 PM|
|Well, the problem is the "of", not the tense. My gear list comprises three amplifiers and two guitars. My gear list comprised three amplifiers and two guitars. No "of". My team comprises four workers. My team is composed of four workers.|
Comprise has a sense similar to include. If you can substitute "include" for comprise in your sentence and have it make sense, then it is right.
My menu includes three omelet dishes, but never my menu includes of three omelet dishes.
SO save the "of" for the next time you need one.
(Just a personal crusade, considering all the other grammatical errors I make daily)
|TimmyP1955||10/26/2017 4:27 PM|
|Depends on where you look it up. Some sources say that comprises and comprised of are both correct. To me, comprises doesn't make sense:A bunch does no make a number of things, a number of things make a bunch.|
Back to my post: The speaker does not spend time at one extreme or the other when reproducing a square wave. Forget what it looks like on an oscilloscope.
|bob p||10/26/2017 5:57 PM|
|Enzo||10/26/2017 6:35 PM|
Depends on where you look it up. Some sources say that comprises and comprised of are both correct. To me, comprises doesn't make sense:A bunch does no make a number of things, a number of things make a bunch.
My team covers the infield, the outfield, and behind the plate. Versus: my team covers of the outfield, the infield, and behind the plate.
|bob p||10/26/2017 6:38 PM|
|I don't want to edit my post after someone "liked" it, as that would be like putting words into their mouth, so I'll just make a new post.|
Maybe some of the difference in opinion here stems from the difference between real world observations and how we like to mathematically model real world situations for study. Fourier theory tells us that any square waveform can be approximated and/or modeled by convolving a group of sine waves of the required amplitude and frequency, but that's not the same as asserting that that's how square waves are actually produced in the real world, outside of the realm of mathematical models, pencil and paper.
We can debate whether or not real world phenomea like square waves actually exist as convolutions of sine waves (the theory) or whether square waves actually exist in nature (observation). To the observer, DC is DC. It's square. A 9V battery and a speaker sure look like square wave behavior. At the level of battery chemistry, we're looking at a combination of high frequency and low frequency events in the battery's matrix, and the power spectrum of those reactions is definitely in the low frequency side approximating DC. But the observed electrical result in the speaker looks pretty square-wave in it's behavior, as long as the chemical reaction can hold out.
Energizing a speaker with a battery is like energizing a relay or a solenoid. You can feed a relay with AC and it will drive it's armature to move and stay put, acting as a Boolean Gate. It sure looks like square wave behavior. Of course, these the behavior of these things looks different if you look at them on the macro vs. micro levels.
|Leo_Gnardo||10/26/2017 7:06 PM|
Meanwhile in the biophysics department we had a brilliant professor who had a study going testing the reactions of frog and clam muscles to being stretched. He used a modified JBL 12 inch speaker - cone removed - as the muscle pulling and sensing device. A square wave applied to a DC amp pulled the cone, and its return to rest position, pulled by the muscles under test was monitored on a scope. Kool frankenstein stuff! One of my apartment mates worked on this project. For a while we got all the leftover clam bits to make chowder once a week. That guy went on to be a pioneering biophysics research prof at U Virginia in Charlottesville. Lesson: clams make you smart!
|The Dude||10/26/2017 7:26 PM|
|That story reminds of the the old ServoDrive speakers. The cone movement was done with a motor and belts. No voice coil.|
|bob p||10/26/2017 7:35 PM|
|as a side note to Leo's comment about impulse response transfer functions, we were once talking on this site about how modelling amps worked, and a few of us diverted off into a discussion about DSP and i commented about how I thought that modelling amps could never be made to sound like tube amps for some technical reasons...|
the next day I got a phone call from a forum member (can't remember who it was) who wanted to talk to me about the impulse-response transfer function theory, specifically relating to my comment that an infinitely high and narrow pulse contained all frequencies. He was an RC model car enthusiast who was trying to solve a battery charging problem, and ended up using high frequency pulses to quick-charge NiCD batteries for the cars. The idea was that the HF charging could more effectively populate the battery matrix, and he got a patent for it.
I can't remember who it was. Anyone want to claim that one?
|potatofarmer||10/27/2017 10:08 AM|
|Yes, sticking DC on a speaker's terminals will cause the coil to jump in one direction and stay there, but the suspension is going to cause it to bounce a bit before it settles. Particularly when we're talking about woofers, the inherent low-pass keeps them from recreating any sort of pure square wave at all. It's basically the same idea as the "underpowering" myth, which is silly enough in the HiFi and PA worlds, but with guitar amps/speakers it's just ridiculous.|
|TimmyP1955||10/31/2017 6:21 PM|
|The Dude||10/31/2017 6:59 PM|
......"An oscilloscope does not show you the frequency spectrum of the square wave."......
Exactly. And neither does a speaker. By comparison to a scope, the speaker is just crude mechanical junk unable to respond to Mhz.
......"Putting a bunch of sine waves together does not create a DC component."
As far as the speaker is concerned, that is exactly what happens.
I'm not trying to argue (and I'm not going to), and I do understand your theory, but it doesn't hold up in practice.
|J M Fahey||10/31/2017 9:28 PM|
A squarewave waveform shows you the frequency response, just does not crunch numbers which is something else.
At the most basic, square wave edge shows you :
* flat response extending to very high frequencies, way higher than test squarewave: perfect sharp edge squarewave.
* rising highs: spike at the front edge.
Spike width and height gives you an idea of how much treble boost you have , and whether it includes low order or high order harmonics.
* ringing front edge shows you high frequency resonances.
You can even know what frequency is ringing by counting small peaks and seeing how many fit in the main squarewave.
* rounded front edge speaks of high frequency attenuation.
How rounded gives you a good idea of how much.
* rising or drooping top/roof/horizontal part of waveform shows whether there is a bass boost or cut.
There are whole books dedicated to squarewave (and other waveforms) interpretation and use in analysis, design or servicing.
Putting a bunch of sine waves together does not create a DC component.
You wonīt create pure DC , but DC components, any day of the week.
Look at it the other way:
*any* waveform, that means any shape, can be decomposed into (or made up of) a mix of various sinewaves.
You may need a single one (a sinewave is made out of *one* sinewave) or a very complex mix of wildly varying ones but the basic principle is the same.
An assymmetrical waveform will have a DC component, whether it is a poorly balanced tube power amp (poorly balanced PI or unmatched power tubes) which would be the mildest case to a narrow high voltage single polarity spike which would be the extreme and can be decomposed in a bunch of sinewaves.
So since you can reconstruct them using the sinewaves we found just above, by the same token we can create them, using the same recipe.
As a side comment, saying "you need an FFT for that" while dissing other methods sounds akin to saying "you canīt tune a guitar without a digital tuner" , or even "you canīt fly NY to Washington without VOR/ILS/GPS/Inertials/Radar" or any other Electronic Navigation aids.
As they often repeat here, "thereīs more than one way to skin a cat"
|bob p||11/1/2017 12:36 AM|
Who would have said something like that?!? Looking at Post #55, it seems that you did:
A square wave is comprised of a bunch of sine waves. Look at one on a scope displaying FFT.
Putting a bunch of sine waves together does not create a DC component.
|Chuck H||11/11/2017 6:54 AM|
I mentioned that my design is partly resistive. I'm using a power rheostat wired like a pot to blend/shunt between the speaker and the Aiken load design. I did have trouble with the .5mH air core inductor in that there is no core to mitigate EMF. This caused my single coil guitars to squeal whenever I was within a few feet of the attenuator. I corrected for this by using two .25mH inductors wired in series/out of phase with a copper plate sandwiched in between. The copper plate reduces mutual inductance and circuit function cancellation but since the EMF from each inductor is out of phase it cancels out in the radiant field. IIRC I just epoxied them together and wrapped the thing in electrical tape. You can probably skip this fussiness if you can find a suitably rated .5mH cored inductor with a low enough DCR.