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Stereo imaging and the witchcraft of circuitry design

Nordfors

Member
I thought I understood imaging and setting things up for a good sound stage - good speakers, speaker placement, minimize reflections, good source material with some recordings being better than others. But recently I’ve run into a situation where I’m at a loss. My problem seems to be not the speakers at all.

Last fall I picked up a Hitachi SR703. Was a one owner unit inherited by their children who put it in a box and forgot about it for a few years. Needed a serious clean up, smokers, but under the grime and nicotine was a beauty. Had a bad power button which I couldn’t find a replacement for so took it to one of my two local techs, the one closest who, unlike the other, believes you should only replace capacitors if something stops working. Great tech with a great reputation otherwise. The shops been there since the mid 70’s. He did his usual run through bench test, which he always does before working on anything, replaced the power button with one he had at the shop, and it was back with his clean bill of health. Sounded excellent. Rich and full. I decided to put it in one of my systems to run it a few months.

After a while, despite the generally high quality sound, I began thinking there was basically no imaging, no soundstage, so I set up an A/B with another receiver in the stable, my trusty Kenwood KR5200.

Speakers are Dynaco A25’s, same position, same room, same source, same tracks, 6 that I like, great recordings with lots of known depth and separation both left and right, up down etc.

These are good speakers to me, in good shape, well cared for.

Well, the Kenwood, as usual, was holographic. With eyes closed you couldn’t point to where the speakers were, rather musicians placed all throughout the room in specific locations, but not at the speakers.

The Hitachi. The opposite. Seemingly good channel separation, singer is in the left speaker, guitar player is in the right speaker, etc, but that was it. Everything was “in” the speaker, clearly this one or that one. No sound stage to speak of. Not immersive at all.
I went back and forth like this over two weekends trying to rule myself out as the weak link. No change. Hitachi doesn’t image.

How can this be? I believe this to be a well built, well laid out piece of gear. Certainly on par with the modest Kenwood and 10wpc more power. Is this something a recap would help, are there certain parts of the chain that are more responsible for this aspect of two channel stereo than others? I’m at a loss here.

I’d like to see this Hitachi perform up to its potential. Any thoughts would be greatly appreciated!
 
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Definitely try the speaker phasing. You don't say what the source is but I can imagine problems in the phono stage or tuner that would cause that. You could have your tech run a phase comparison over the audio range for each pair of inputs. It might have a cap that's working well enough for passing signal, but that's wonky enough to play games with phase and response. Good bench tests absolutely can find this.
 
Could it be a speaker output phasing issue? Is the bass lacking as well? Try flipping one set of speaker wires.
Good point concerning phasing. Bass was fuller with the Hitachi but more precise with the Kenwood (its higher damping factor?) I switched these two out several times and I'm fairly certian everything was in phase, but I'll check again! The source is digital in this setup, not my ultimate preference, but through a Fosi Audio ZD3, which I've been content with. Note that while the Hitachi's tuner is the best I've ever had strength wise, (I'm down in a ravine and it pulls stations in clear stereo no other receiver I have even registers) while in FM stereo there is clear channel separation, but no soundstage. No diffference between FM or the DAC run through aux input performance wise in this aspect. Thanks!
 
This is a great question. Speakers out of phase could do this for sure. @ConradH has a very interesting take on the issue. If one was looking for the cap(s) that could be throwing the phase slightly out; would one start with any coupling caps in the output section?
Also make sure that the high filter is not engaged as holographic effects come from directional perception of high frequency sounds.
 
This is a great question. Speakers out of phase could do this for sure. @ConradH has a very interesting take on the issue. If one was looking for the cap(s) that could be throwing the phase slightly out; would one start with any coupling caps in the output section?
Also make sure that the high filter is not engaged as holographic effects come from directional perception of high frequency sounds.
Also a great point concerning the high filter. But, it does seem to be working. Admittingly I'm probably losing some of that end of the spectrum at my age, but sonically I perceived it was functioning........I'll inspect this further as well. Good to rule out the low hanging fruit before comitting to surgery!
 
FWIW, my hearing at 71 isn't near what it used to be, but I still have no problem hearing 90+ percent of everything musical and soundstage is undiminished.
 
This is exactly what made me think speakers out of phase. The description of everything either left or right.
 
I'll probably be lambasted for saying this but maybe the Hitachi has ferrous binding posts and the Kenwood doesn't.
 
Some things are really hard to troubleshoot when it comes to audio in a forum. Speakers out of phase can have the illusion of coming from way outside the actual speakers. I don't know how well trained your ears are to these issues. Sitting in my listening chair right now - I have the voice in the middle and some instruments left and right but if I invert one speaker it becomes very holographic/airy, I can do it with a tap on my pc with a EQ. The voice does shift some but the instruments shift way outside and an echo almost gets injected. On the next recording when I did it the voice separated and came from outside both speakers. Out of phase speakers sound like the instruments/voice are coming from everywhere almost.

I am probably 90% wrong but what someone might think is in phase could be out of phase and they might even prefer out of phase. In phase, in 99% of recordings the lead singer is dead center. Yes the bass is diminished in out of phase but that is sometimes harder to discern. I can tell in 2-3 seconds if speakers are out of phase based on what I hear- especially if I know the recording.

We can not trust the color of binding posts on your amp or your speakers-we have no idea who has been in there. I am going to guess and say reverse the Hitachi connections- but it could be the other.
 
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Also a great point concerning the high filter. But, it does seem to be working. Admittingly I'm probably losing some of that end of the spectrum at my age, but sonically I perceived it was functioning........I'll inspect this further as well. Good to rule out the low hanging fruit before comitting to surgery!
So, curious, do you have a conclusion to this issue you were having?
 
For sure, out-of-phase speakers will have weaker bass than in-phase. Bass tends to sound muddier, less focused, too.

:idea:
 
Quick phasing check is to put the speakers right next to each other and facing you and play a low frequency tone, say 100 Hz. It will be lot softer out of phase than in phase. You can pull a tone out of your phone, just be sure to feed the same signal to both channels. Keep it around a half volt for the line-level inputs.
 
Another factor might be the input and output filter capacitors on an amplifier, they're there to eliminate RFI and stop the amp becoming a radio station. Different amps will have different degrees of doing this, it could be knocking the spacial signal off, and different qualities of capacitor. Suggest have a read of Lampizators article on the benefits of snipping these out.
 
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