The Audio Equipment Corner

[ejman]

Quote:

Originally Posted by NW-Bound I dunno. People are entitled to their opinion. And who knows, perhaps these guys happened to listen to the speakers that had been blown up, and they really sounded as bad as they heard. I don't think I need to join any more forum. I have caused enough trouble on this one, not about audio per se but spilling it into other threads. However, in looking for ideas to revive my vintage speakers, I surfed the Web a bit to look for replacement parts. That was when I ran across these forums. Some of the posters on these forums are really, what should I say, unusual. Here are some examples. One guy claimed that he spent 5 years to find the perfect placement of his speakers, such that the listener could have perfect stereo imaging anywhere in the room. When he showed off his set up to his friend, the latter said "Wow". And then, to demonstrate how critical his set up was, he moved one speaker 2 inches. The stereo image collapsed, and that huge sweet spot was gone, he claimed! And then, there was a guy who kept his speaker cords off the ground so that they did not pick up static! He also said that his cords would also pick up all kinds of radiation from cell phones, and wireless devices from the neighborhood and that ruined the sound. Aye, aye, aye...

You mean to tell me you don't wear one of these when listening to your gear?

[NW-Bound]

Hey, that guy's got an HP Spectrum Analyzer similar to mine, perhaps in the same series - the one on the shelf, not the one he's got his hand on. My baby cost me $25K in 1999, and it was nowhere near top of the line. It's for microwave work, not audio stuff though.

Anyway, back on audio thinggys, all of the speakers that I have are inexpensive point-source kinds.

I love speakers. I do not care much about amps, because to me they should be flat and distortion-free and that's that. Speakers have different radiation patterns. I know that tall column speakers and the Maggies are line-source, and they do have different characteristics than the ones I have. I may have to get a pair just to see hear for myself, but one thing at a time.

Another thing is that the room acoustics account for a lot. My homes all have wood floors now, and I do not have room nor care for a home theater. I guess that's why I do not consider myself an audiophile, and perhaps will never be more than a dilettante.

I will be showing you what I have been doing with my vintage speakers soon.

[NW-Bound]

OK, I will show you my first baby, the Pioneer CS-88, circa 1968-1970. Following are some pictured linked from Web sites. It weights 50lbs, and has a diecast woofer basket as most of them did in those days.

Front and back photos:


Here's the inside:

[Keim]

Sweet. Looks like a good project. Whetes the crossover? Back of the box?

[Nodak]

In the early days of CDs (mid 80s) there were people that used a green magic marker to put a green edge on their CDs. They claimed that it made a tremendous difference in the sound. There were also places that sold rubber bands to put around the edge of a CD to improve its sound. There has never been a shortage of weird ideas on how to improve the sound of stereo systems.

[NW-Bound]

Here's my own photo of the front with the grill off.

As you can see, it's a 3-way bass-reflex, with a 12" woofer, a mid-range of 5" inside its own metal enclosure, and 3 tweeters. The center one is the main tweeter, a 2" horn of 13 ohms, I think, cannot measure because both speakers got them blown out. The two side tweeters are 2.5" paper cone, with impedance of 7 ohms. The side tweeters are wired in series, then in parallel with the main horn. That brings the impedance close to 8 ohms, and that makes sense.

The arrangement of 3 tweeters is controversial, I think, because of phase cancellation when the listener is off-axis. My Sansui of the same vintage also has 3 tweeters! Did they do that for better dispersion?

[NW-Bound]

Here's the photo of the blown original horn tweeter, along with the new Vifa that I found for replacement. That little horn is diecast; no cheap plastic there. It weighs perhaps 10X the new Vifa which is all plastic. However, that Vifa's got a heatsink in the back. Maybe it won't burn out like the original.

[NW-Bound]

As posted yesterday, I had a hell of a time with checking the crossover responses due to ground loop between the PC I/O, the amp, and the speaker. So, I took time off to build a little differential amplifier which will make the measurement more "precise". Well, it really does not matter much, but if I publish a curve that looks goofy, people will say that I do not know what I am doing.

So, here's that little differential amp. Connections to the crossover and the PC input port are via the little headers.

[NW-Bound]

So, Keim asked for the crossover. Here it is, being hooked up for measurements.

Note the big aircore inductor. No ferrite there to avoid saturation and non-linearity.

[NW-Bound]

Quote:

Originally Posted by Nodak In the early days of CDs (mid 80s) there were people that used a green magic marker to put a green edge on their CDs. They claimed that it made a tremendous difference in the sound. There were also places that sold rubber bands to put around the edge of a CD to improve its sound. There has never been a shortage of weird ideas on how to improve the sound of stereo systems.

And they can "hear" the difference too.

[NW-Bound]

And here's the response curves of each section of the 3-way crossover. They are all 2nd-order, but there's some extra "stuff" to cancel out the woofer's coil inductance, and an obvious padding of the midrange to attenuate it.

The above padding is strange, because they already put in L-pads in the back for listeners to attenuate the mid and high range. You can see the obvious 5-dB down for the mid-range. Was it because the enclosed midrange driver had too much sensitivity?

Also note how the woofer's section comes bouncing back after 4KHz. It does not really matter much as the woofer cannot move at that frequency, but why? In the end, I think it is a side-effect of the inter-turn capacitance of the coils, the internal series resistance of the caps, and the inductance of the wire-wound resistor that they use for impedance control.

The curves show crossover frequencies of 800Hz and 5.5KHz. How do these compare to specs? I need to surf the Web!

[ERD50]

Quote:

Originally Posted by NW-Bound ... However, in looking for ideas to revive my vintage speakers, I surfed the Web a bit to look for replacement parts. That was when I ran across these forums. Some of the posters on these forums are really, what should I say, unusual. Here are some examples. One guy claimed that he spent 5 years to find the perfect placement of his speakers, such that the listener could have perfect stereo imaging anywhere in the room. When he showed off his set up to his friend, the latter said "Wow". And then, to demonstrate how critical his set up was, he moved one speaker 2 inches. The stereo image collapsed, and that huge sweet spot was gone, he claimed! And then, there was a guy who kept his speaker cords off the ground so that they did not pick up static! He also said that his cords would also pick up all kinds of radiation from cell phones, and wireless devices from the neighborhood and that ruined the sound. Aye, aye, aye...

Yes, some people go to some real out-there extremes. I'm hesitant to poo-poo some of it, who knows what others can hear? But I can't help rolling my eyes when they get into areas where my electronics knowledge just tells me - 'no way!'.

The stereo imaging story is at least plausible. Years ago, I made a small portable 'boom-box' style speaker system as a project to work on with my son. We used some car speakers, and mounted them in a mid-sized box, and I ran him through some of the reasons the box needed to be this shape/size, etc (he wasn't that interested, but played along politely). So these were not great speakers, and they ended up in the basement hooked to my receiver. One day, I had it tuned to a classical station, and as I walked by as I was working on some other project, I walked in one spot and I was astounded by the stereo imaging. I actually stopped in my tracks and moved around to get back in that 'sweet spot'. I've never heard anything like it. It was maybe a combination of the source and everything else, but it was remarkable. When I spoke to a friend of mine about it, he said that small speakers can sometimes give an imaging that is hard to get with larger systems. I don't know what all makes up the difference between good/bad imaging, but I've heard it!

But putting speaker cables up on little Styrofoam cups (or $$$$ magic 'isolation systems' from some high end vendor, made from moon rocks or something) to isolate them from the floor, that just doesn't make sense to me. Speakers are such a low impedance, and so inefficient, I just can't imagine static inducing any audible signal on those wires, and if it could be heard why lifting them off the floor would change anything. I'll call snake oil on that one. Signals getting induced into the pre-amp side is a concern, but I just don't think decent equipment and reasonable cables are very susceptible, though certain setups could have problems.

The high-end magazines are much like the 'financial porn' magazines. If they kept it simple, I guess they feel they wouldn't have much to write about. I disagree, with all the real issues and all the various equipment out there, I think there would be plenty. But talking about the 'pace & rhythm' of a power amp is probably easier than doing real engineering work on the subject. When I would read one those mags, I had to have the mindset it is 99% 'entertainment', and maybe I'll get something worthwhile, maybe not.

Another that makes me say WTH? is when they review a $15,000 power amp, and then later talk about how the 'sound-stage' and the way 'sounds came out of a velvet blackness' were all greatly improved when they replaced the power cord with an after market one that supposedly had superior properties. Really? A $15,000 power amp scrimped on the power cord? Gimme a break!

Quote:

Originally Posted by NW-Bound ERD50 talked earlier about a bit of even-harmonics making the sound better. Now, this is something that I understand, and can agree with to some extent. As I explained earlier, I have never had a good tube amp, nor listened to one. But I recalled this experience. It used to be that when one bought a DVD-burner for the PC, there was usually some freebie software thrown-in. With one version of Nero, I got a utility (forgot its name), which would enliven some MP3 that had been ruined by low sampling rates. I tried that, and it seemed to work. I remember distinctly that what that program appeared to do was to run an FFT to get the spectral content, then add some even-harmonics, and reconvert it back from the frequency domain to the time domain. So, something like that has some basis, and I would have no problem with. Of course, if the program material is sufficiently rich and close to the original recording, one would not need that, right?

Yes, I remember having some demo tapes that showed off how the "Aural Exciter" (I was afraid to google that one!) could be used to enhance voices and especially cassettes that had some high-freq roll off. This was done in circuitry at the time, no DSP, so basically, they ran some signal to the side, filtered out a spectrum they wanted, ran that through an amplifier that would intentionally distort in a specific way, subtracting the original signal so they had only the distortion. Then, filter, maybe phase shift that distortion, and add it back to the original signal. The following article says it was dynamic, they added in more at low volumes, and almost none at high volumes. The demos I heard were very effective, and I may look into a 'plug in' for Audacity to enhance my recent cassette transfers. Overdone, it sounds awful.

Apparently, some big name singers used it to get a little more sparkle in their recorded voices. I recall hearing Andrea Bocelli on TV and being super impressed, so I got one of his CDs out of the library. I couldn't stand it - his voice was so processed, it sounded all 'tizzy' to me - like someone humming an aluminum foil kazoo along with his voice. Terrible, hurt my ears.

Aphex Model 204 Aural Exciter


-ERD50

[ERD50]

NW-B - that sure is a lot of drivers!

From what I recall from investigating building a speaker, the placement of those tweeters does affect dispersion. Lots of considerations in order to optimize it, distance from the mid-range and each other, the effective plane that each driver sits in, the surrounding surfaces. Sometimes the speakers are wired in what would seem to be out-of-phase, to compensate for some other phase-shift or delay. I have no idea how much this affects the sound, but speaker builders go on about it, just like investments and withdraw rates.

-ERD50

[NW-Bound]

Well, that's just two extra side tweeters. If I disconnect them, then I have a standard 3-way speaker, and some manufacturers still make these.

I may experiment a bit, after I am sure I have restored the speakers back to as close to original condition, and listened to them for a while. The problem with experimenting is that I need to open the back (with two dozen screws!) to change the wiring. Well, perhaps I can run the wires through the vent hole.

Anyway, I have not gotten to my Sansuis, which is a 4-way with 6 drivers!

Oh, I am going to go sweep the speakers in the back yard with the new tweeter. May drive the neighbors nuts! Heh heh heh...

[Keim]

If you think you will experiment soon don't put all 24 screws in...

[NW-Bound]

Well, the back cover rattled at low frequencies if not tightened. Even at 1W. This baby has high output.

[ERD50]

Quote:

Originally Posted by NW-Bound Well, that's just two extra side tweeters. If I disconnect them, then I have a standard 3-way speaker, and some manufacturers still make these.

Yes, but 5 drivers is 4 more than I'm accustomed to!

Quote:

I may experiment a bit, after I am sure I have restored the speakers back to as close to original condition, and listened to them for a while. The problem with experimenting is that I need to open the back (with two dozen screws!) to change the wiring. Well, perhaps I can run the wires through the vent hole.

Yes, I would definitely mount the cross-over external if you even think you'll be tweaking things (and I expect you will).

-ERD50

[Animorph]

I hated tubes. All I ever did with them is test and replace in our family's TV's. I was happy to go all transistors for my amps and work on getting that right.

I'm using a Tact TCS preprocessor and three Tact stereo class D power amps, with coax digital interconnects between them. The only D/A for a digital source is right at the amp output. I love them, but tinnitus is making really great audio just about useless for me.

The Tice Clock was my favorite BS audiophile item. $250 or so for an ordinary clock that they had "specially treated". It was supposed to favorably align the electrons or something like that. Just plug it into a nearby outlet. They had a complete technical description, but I never did see how they were able to tell how the electrons were aligned.

[NW-Bound]

I think tube amps can sound great too. I have not listened to one, but looking at the specs of the Jolida that ejman mentioned, it was impressive; I did not know they could get that frequency range. The tough part with tubes is the output transformer, which is the main limiting factor.

By comparison, the typical solid-state amps have very low impedance due to the heavy internal feedback. They act more like the ideal voltage source and can handle the load impedance variation a lot better, such as that presented by 3-way and 4-way crossover networks.

ERD50: Yes, I like to get that perfect single driver that covers the entire audible range. Failing that, I am thinking that I will eventually set up a simple two-way speaker system: two columns with "full-range" drivers as line sources, with the low frequencies handled by a subwoofer(s). I will use bi-amping, with electrical crossovers which will be adjustable and more precise than these coils and caps.

Just something to think about the days far ahead. And who knows, I may build my own like Keim.

[springnr]

A lot to be said for full range, aka single driver, with older ears we might not miss some of the highs either ;>)

I cheat a little as my speakers are 1.5s = 6" modified transmission line with a capacitor cross at 5K to the tweeter. A common comment from listeners is about hearing new things in music that they have listened to for decades. Coherent is good too.

Gemme Tanto Babinga, Audio Research 100.2, Audio Horizons Tube Pre