The thing you wrote sounded backwards, so it was necessary to look at it more carefully. Sorry.


You know, this whole discussion started with a repair tech not really knowing what he meant when he repeated what the other repair guys told him: check to speakers and wiring.  The guy who's putting the Denon back in has two front channel speakers... is one of them a "known good sample"?


Marantz.  1979-1981.  They made hundreds of speakers at that time.


Documentation was tops, factory staff was great, but somehow every once in a while a group of crossovers or speakers had a reversal somewhere.  The sad yet amusing thing was that it happened most often in the totally cheap-ass speakers that they hot-glued together.  When the line tester showed a frequency response anomaly, we had to kick in the backs of the speakers to see what was wrong.

Re: a known good speaker- no, it isn't known because it hasn't been tested and found to be within an acceptable range of parameters. It may make sound under various conditions, but it's not known if it, or the speaker wire, has some kind of problem that could bake the Denon again.

When an amp needs repair, it's just good policy to recommend that the speakers and cable be checked. I don't know of any service techs who wanted to make a career of repairing one person't receiver and since they have a service warranty, it costs them less if it doesn't come back within 30 days, or whatever period the warranty covers.

Were the drivers rear-loaded or glued in from the front? That's a bold way to build speakers- if they needed work after they left the factory, a dealer was supposed to submit a warranty claim and scrap them. I remember a lot of crappy speakers of that quality, complete with 1/8" glued-in Masonite back and full 1/2" particle board box. Oh, boy. Add a 1-1/2 pound Sony turntable and an 18 Watt/channel receiver and you had one fine audio system.

For those who care:

[Link: bkprecision.com]

[Link: bkprecision.com]

[Link: bkprecision.com]

Also FYI MLSSA is an Acoustical and electrical measurement system.

[Link: mlssa.com]

With hardware that the software controls. With an instrumentation grade mic it does acoustical measurements and with options does electrical measurement as well as thiele small parameters etc.

Data from MLSSA can be exported into programs like LEAP, which is a crossover optimization suite, etc. I own that as well.

I used to be a speaker system manufacture. I used to have lots of technical discussions with Dick Pierce, Ken Kantor and others on Compuserve back in the day. So I do know enough to be dangerous!

PS I was not suggesting to use MLSSA for this particular situation. lol

Measures resistance using a test frequency that can cause an inductive reactance

I only have the time to tackle one of these:


The description on the linked page includes


Isn't that what I said? It won't measure just resistance; inductors will also affect the reading. Series inductors will increase the reading. Parallel inductors will decrease the reading, but they will do that with a DC meter as well, since you'd then be reading the DC resistance of the wire.

They totally ignore capacitance, which might be fair but is not accurate. It might be fair because capacitive reactance at frequencies as low as 120 Hz require HUGE capacitors for the reactance value to be low enough to affect measurements unless you're measuring resistances in the tens of thousands of ohms or greater.

This meter is NOT intended for general resistance measuring. On Page 8 you read (or maybe don't)


That is, this inductance will add 3.14 ohms to the measurement. Other examples involve capacitive reactance, though the word reactance is not found in the manual.

Also note that resistance is measured using 1 kHz. The references to 120 Hz are on P 11, series mode capacitance; and P12, parallel mode inductance. All other measurements use 1 kHz.

I'll look at the others after I go earn some money.

edit: a graph of the impedance of a "nominal 4 ohm" speaker.



Since driver manufacturers know we want speakers that are 4, 8, or whatever impedance, they design the drivers to have those values seen to the right of the big bump. It is not at all the total crapshoot that Timmy implies it to be.

That big bump on the left is the bass resonance. The cabinet is designed to modify the load on the speaker at different bass frequencies for flattest response and actually changes this.

The "trough" is where the nominal impedance value comes from.

This is not a speaker system. A system will have another one or two such curves, shifted to the right, for the tweeter or midrange and tweeter. The impedances of those sections are in parallel with this one and modify the overall impedance so the curve doesn't just go up and up as shown. A Zobel network can be added to an individual driver to flatten its impedance (as the amp sees it) in the upper rising section, too.

The crossover components ARE all part of the speakers impedance (as are the connecting wires to the drivers). If course inductors have a resistive component to them. (Reactance usually causing the value to rise with frequency) So do capacitors have resistance all of which must be considered in a "speaker system", So Ernie I am not quite sure what your point is regarding the LCR vs a VOM. Do you want me to measure for resistance of a DUT with the B&K LCR and compare it with a Fluke 87 VOM to see what the differences are? I think the answer will be "close enough" for a speaker to determine if a "hard short" is present.

I am saying what the driver engineers call the "nominal" impedance and the marketing department may be two different things. THAT is the marketing crapshoot! That is all.

Talk soon.

My point is to understand what's going on. If you use your meter, which measures resistance using a 1 kHz tone, you won't be on the same page as anyone who uses a normal VOM or ohmmeter because those use DC. The measurements might be the same, but might be ain't is.

Yes, it will be close enough. But then if you have some kind of weird DC problem in a 70 volt amplifier and you try to measure the resistance of the load just to see how horrible it could be to the DC component of the amp output, you'll have an unclear answer and, again, that answer won't tell another person using DC equipment what to use.

I once saw Leo Kottke in performance. He was a great guitar player, mostly self-taught, who fiddled around (yuk yuk) with string tuning, coming up with very different-sounding music. After the performance, he put on a master class. It turned out to everyone's surprise that he could hardly play a blues or any other simple tune with anyone else. He had gone off in his own direction and did not have a common base of tuning, nor experience playing with others, and so seemed not so talented in a crowd.

Measure ohms with DC so you can play with others. Yes, your meter will give you useful information and that's fine as long as you're dealing with things without the need to communicate the information.

I completely disagreewith you about the impedance spec, though. A marketing department has zero reason to call a speaker an 8 ohm speaker when it's a 4 ohm speaker, or any other combination of misnaming. I've seen an 8 ohm speaker system with a 2 ohm dip below 100 Hz, but it was accurately named an 8 ohm speaker per standard practice. It shut down amps left and right (also yuk yuk), and it was taken off the market about a week after it was issued, redesigned, and returned to the owners.

I used to sell these high end ribbon speakers by Apogee. They were "nominally" 8 ohm loads but could dip to 2 ohms in the low end.


Look I know you guys love to explain how a watch is made - if some one asks you the time...

I have been f**king repairing and building speakers since 1972. I currently repair approx 30 speakers a week, that come into our shop.

Don't take something so simple - so complicated.
Take off your propeller caps.

"I've seen an 8 ohm speaker system with a 2 ohm dip below 100 Hz, but it was accurately named an 8 ohm speaker per standard practice."

Holey smokes. So the DC resistance at 0Hz was say 6 ohms and the Nominal impedance at the "trough" before the rise was 8. and there was a 2 ohm dip at 100Hz? WTF happened there?

Apogee Scintilla's were rated at 4 ohm, but would dip down to 1 ohm!!!

We sold those Speakers (my all time favorites), with big Levinson amps (before they went digital). You could arc-weld with those monsters!
 

I sold a few of those Apogee Scintillas back in the day. Usually paired with the "50 watt" ksa50 krell. And since they were ribbons the load was purely "resistive".

I guess us propeller heads are having fun. lol

Another way to check to see if a speaker is bad...


...Do a background check!!!


8>)

Hey Mr Stanley,

Do you do re coning? all brands? Can you elucidate?

PS. I just checked. Scintillas were 1 ohm !! or some had a 4 ohm position that did not sound as good.

Yes we do! All major brands.
 

TimmyS,

It is amazing to me - some of the speakers we repair! People become very sentimentally attached to the speakers of their younger days.

I mean we see some nice speakers, and we see some total POS's that should be tossed - but Nooooooooooooooooo! I WANT THESES SPEAKERS repaired!