Today, I decided, was the big day. I measured all 6 of my LX55 speakers in a consistent, hopefully repeatable way. Unlike the way I measured 3 speakers yesterday.
I adjusted an Athena speaker stand I haven't used in years to the maximum height. That turned out to be what was needed to align the bottom of the speaker with the UMIK-1 measurement microphone in my microphone stand. Fortunately I had previously obtained the correct adapter to attach the UMIK-1 microphone coupler to the stand (along with a few others). This was a bit over 3 feet from the floor.
I actually adjusted the microphone to be at the height of the center of the woofer, believing that to be a pretty good spot for these speakers. Actually, in my near ceiling surround positions, I'm way below that axis, which I'm pretty sure is suboptimal for these speakers. But I think they are supposed to be on fairly high stands so you are not too far ABOVE the tweeters.
The microphone and speaker were adjusted to be 1M (39 inches) appart, plus or minus an inch or two. This is far better than the 10 inches yesterday.
I put the microphone toward the back corner to be out of the soundpath of the refrigerator, and the speaker in the middle of the room facing towards it.
I've never done a series of speaker measurements with such a serious set up. And now, including a calibrated microphone and the industry standard program REW.
One big surprise was that the improvements I made to the right surround speaker, called previously and still unit number 1, still didn't seem to have made it a very flat speaker. It's too much work now to go back and restore the factory out-of-phase tweeter, but previous measurements showed that to be horrifically cut off above 5kHz. But it's still pretty much shelved down, starting at 3kHz, making this speaker fairly useless without further modification:
I had to go back and double check that it was this speaker I had actually modified.
Meanwhile, I hadn't for a long time measured the two speakers with the complete AudioGeorge (tm) modification, which I bought directly from George himself. This modification consists of correcting the tweeter polarity (as I just did for unit #1), and also bypassing the choke which normally rolls off the woofer, as well as damping materials on the tweeter and straws on the port. (I have sealed the ports on all my surround speakers, which is a more drastic measure, to help compensate for near ceiling corner locations.) I had previously disliked the choke bypassing, feeling it produced some hump in the upper midrange around 2kHz. In fact, it does, but it also seems to contribute to a generally flatter or at least more extended upper frequency range from 1kHz to 10kHz. Though we can't tell exactly yet how much of this may be due to drivers with better response than in unit #1. Here is LX55 number 2, which has these modifications.
This looks greatly preferable to the partly modified #1.
Meanwhile, #3, another AudioGeorge unit, looks pretty similar to #2, which is a good thing, maybe even more extended and better in the highs, before the seemingly inevitable 10kHz roll off.
Unit #4, which is a stock unit whose woofer I damaged in January (the woofer surround was so flaky a mere touch of a screwdriver caused it to break into pieces). This still looks far better than unit #1 even after having done the phase correction on #1. Which begs the question, has unit #4 had the phase reversal mod? Not as far as i know.
Unit #5, had been in storage, climate controlled storage, until I damaged the woofer in unit #4. Then I brought #5 out of storage to replace #4 as the left side surround. This is another stock unit, I think, but measures the best of all the stock units I've had for over a decade.
Now, I recently acquired a sixth unit, with a mind to ultimately expanding to a "9.1" system, and also doing lots of tests, experiments, and modifications. This new unit #6 is clearly the best measuring unit of all, the most extended high frequency response anyway, with only about 5dB of decline at 10kHz, and only 12dB at 20kHz (at which point, it might pick up, according to the wider bandwidth LX5 measurements by John Atkinson).
Well, except for that hump in the bass, which I had not dealt with until today. After stuffing the port with the same polyurethane foam backing rods I used for the other speakers, I got flatter bass:
Now for unit #6, I don't imagine the phase reversal to have a positive effect. The response 200Hz to 5kHz is virtually flat! Changing the tweeter polarity and especially bypassing the woofer coil is going to cause elevation in the 3-5kHz response.
So if something ain't broke, don't fix it, I decided. I decided to use Unit #6 as s drop in replacement for the funky unit #1, which can't seem to achieve extended flat response regardless of tweeter phase, as the right side surround. Meanwhile, the here-to-fore hardly used unit #5 is the best of the remaining unmodified units, on the left side surround. And with the existing AudioGeorge units in back, I have a full set of pretty good LX55's.
That solves the immediate problem, and right away the surround setup no longer has a dark sound like it did before (just one dark sounding speaker can do that). I had to readjust the level for the right side surrond a little, and it is very reassuring the speaker now sounds pretty much like the others.
As to what is going on here, one thing seems to be pretty obvious. There is high variability in the drivers is these inexpensive speakers, just as John Atkinson noted, which can cause excessive rolloff in the highs above 3kHz. In some cases, but not all, it might improve matters greatly to provide the AudioGeorge modifications, which tend to boost the highs. But not always, and that's all I can say now (though I suspect speaker aging, and the woofer dustcap resonances, are critical factors).
It may be, that the now useless unit #1 could be salvaged with the AudioGeorge modifications. It's worth pursuing, but now that I have a great set of 4 for my "7.1" system that are all pretty good, I feel that the important work is done here for now.
It may be more interesting to see what the modification does for unit #4, since #4 has virtually identical response to the now-in-use #5. It's a decent way of doing the experiment without messing up my now better-than-ever (as of Friday morning, all channels leveled within 1dB, something I'd never been decently able to do before) surround sound system. #4 is currently more rolled off than the new #6, could the AudioGeorge modification bring them both to the same level? I'm currently disinclined to mess with #6 for many reasons, including how much of a pain it is to get back on the wall again, and also it just seems to work best of all right out of the box. But if I get favorable results with two other speakers first, that could be the third. If.
The long term plan for #4 and #1 is woofer and even tweeter replacement experiments. At least #4 has a messed up woofer that needs replacing anyway. It could be the tweeter on #1 is defective somehow.
But meanwhile, also, I'm thinking of a more serious, ear level surround system in the kitchen. That would require a new set of 4 Gallo A'Diva SE speakers, in Stainless, which will depend on my cash situation later this year. The current surrounds would then become "ceiling" surrounds...which would require a processor, as would the intended front width and height speakers...which should probably be SE's as well. My ultimate planned LX55box + special 5" woofer + Infinity Walsh tweeter system will be the ultimate side height surrounds.
For now, the improvement in my surround system (with fixed right surround--the new one) is comparable in magnitude to the discovery of how to enable true 7.1 from discs, which was just two months ago--that was when I spun the wheel and did the the final Oppo update on my BDP-95, which seems not to have adversely affected anything, including my later ability to use "the ISO" disc to make it region free, and the update made the rear surround outputs work for the first time in 10 years. It hadn't been an issue until this year anyway, after I added the permanent rear speakers, so I finally decided to take the risk of update.
Updates Friday May 3
Actually, John Atkinson recommended having the speakers on low rather than high stands, because below the tweeter axis a suckout quickly develops at 3kHz... I was measuring on the woofer axis, but at least consistently on all speakers.
I couldn't resist the desire to see what would happen if I did the full AudioGeorge crossover modification, eliminating the choke on the woofer as well as reversing the tweeter phase.
And the result is, yes, the combination of both of these changes does boost the highs to be pretty amazingly close to an unmodified unit that "works" (but not the amazing new NOS unit). Also, not quite as far as my two actual AudioGeorge modified units. So it looks like those units are intrinsically among the "better, but not best" category of LX55 drivers, and Unit #1 is intrinsically a bummer of some kind, suggesting there are at least 3 cateogries of LX55 drivers, #1 being the worst, and all but #6 being he middling kind.
While #1 with the double crossover mod is similar to #5, there are telltale differences, such as the apparent bulge right around 2kHz, where #5 is stock. That seems to be a telltale sign of removing the choke, it adds a lot more output just below the crossover frequency.
Carefully studying the #1 before and after the second modification graph, it appears that unchoking the woofer adds output all the way up to about 7kHz.
Now I haven't listened to #1, but I have listened to the fully modified units #2 and #3, and generally I find the bump at 2kHz adds a somewhat honky quality, whatever the benefits of greater extension provide. But for unit #1, it was so rolled off and dark sounding that now at least it should have credible highs.
In both cases, however, notice that unit #1 actually has response extending to 20kHz at the same level as 10kHz. On the actual tweeter itself, it's pretty level from 5kHz to 20kHz. This suggests to me that the tweeter is at a too-low level compared with the woofer, in effect a "low output" lineaum, but one that turns out to have more extended response than the others, at the lower output that it does have.
An additional test on unit 1 showed that bypassing the light bulb "fuse" did not make a significant difference.
I adjusted an Athena speaker stand I haven't used in years to the maximum height. That turned out to be what was needed to align the bottom of the speaker with the UMIK-1 measurement microphone in my microphone stand. Fortunately I had previously obtained the correct adapter to attach the UMIK-1 microphone coupler to the stand (along with a few others). This was a bit over 3 feet from the floor.
I actually adjusted the microphone to be at the height of the center of the woofer, believing that to be a pretty good spot for these speakers. Actually, in my near ceiling surround positions, I'm way below that axis, which I'm pretty sure is suboptimal for these speakers. But I think they are supposed to be on fairly high stands so you are not too far ABOVE the tweeters.
The microphone and speaker were adjusted to be 1M (39 inches) appart, plus or minus an inch or two. This is far better than the 10 inches yesterday.
I put the microphone toward the back corner to be out of the soundpath of the refrigerator, and the speaker in the middle of the room facing towards it.
I've never done a series of speaker measurements with such a serious set up. And now, including a calibrated microphone and the industry standard program REW.
One big surprise was that the improvements I made to the right surround speaker, called previously and still unit number 1, still didn't seem to have made it a very flat speaker. It's too much work now to go back and restore the factory out-of-phase tweeter, but previous measurements showed that to be horrifically cut off above 5kHz. But it's still pretty much shelved down, starting at 3kHz, making this speaker fairly useless without further modification:
I had to go back and double check that it was this speaker I had actually modified.
Meanwhile, I hadn't for a long time measured the two speakers with the complete AudioGeorge (tm) modification, which I bought directly from George himself. This modification consists of correcting the tweeter polarity (as I just did for unit #1), and also bypassing the choke which normally rolls off the woofer, as well as damping materials on the tweeter and straws on the port. (I have sealed the ports on all my surround speakers, which is a more drastic measure, to help compensate for near ceiling corner locations.) I had previously disliked the choke bypassing, feeling it produced some hump in the upper midrange around 2kHz. In fact, it does, but it also seems to contribute to a generally flatter or at least more extended upper frequency range from 1kHz to 10kHz. Though we can't tell exactly yet how much of this may be due to drivers with better response than in unit #1. Here is LX55 number 2, which has these modifications.
This looks greatly preferable to the partly modified #1.
Meanwhile, #3, another AudioGeorge unit, looks pretty similar to #2, which is a good thing, maybe even more extended and better in the highs, before the seemingly inevitable 10kHz roll off.
Unit #4, which is a stock unit whose woofer I damaged in January (the woofer surround was so flaky a mere touch of a screwdriver caused it to break into pieces). This still looks far better than unit #1 even after having done the phase correction on #1. Which begs the question, has unit #4 had the phase reversal mod? Not as far as i know.
Unit #5, had been in storage, climate controlled storage, until I damaged the woofer in unit #4. Then I brought #5 out of storage to replace #4 as the left side surround. This is another stock unit, I think, but measures the best of all the stock units I've had for over a decade.
Now, I recently acquired a sixth unit, with a mind to ultimately expanding to a "9.1" system, and also doing lots of tests, experiments, and modifications. This new unit #6 is clearly the best measuring unit of all, the most extended high frequency response anyway, with only about 5dB of decline at 10kHz, and only 12dB at 20kHz (at which point, it might pick up, according to the wider bandwidth LX5 measurements by John Atkinson).
Well, except for that hump in the bass, which I had not dealt with until today. After stuffing the port with the same polyurethane foam backing rods I used for the other speakers, I got flatter bass:
Now for unit #6, I don't imagine the phase reversal to have a positive effect. The response 200Hz to 5kHz is virtually flat! Changing the tweeter polarity and especially bypassing the woofer coil is going to cause elevation in the 3-5kHz response.
So if something ain't broke, don't fix it, I decided. I decided to use Unit #6 as s drop in replacement for the funky unit #1, which can't seem to achieve extended flat response regardless of tweeter phase, as the right side surround. Meanwhile, the here-to-fore hardly used unit #5 is the best of the remaining unmodified units, on the left side surround. And with the existing AudioGeorge units in back, I have a full set of pretty good LX55's.
That solves the immediate problem, and right away the surround setup no longer has a dark sound like it did before (just one dark sounding speaker can do that). I had to readjust the level for the right side surrond a little, and it is very reassuring the speaker now sounds pretty much like the others.
As to what is going on here, one thing seems to be pretty obvious. There is high variability in the drivers is these inexpensive speakers, just as John Atkinson noted, which can cause excessive rolloff in the highs above 3kHz. In some cases, but not all, it might improve matters greatly to provide the AudioGeorge modifications, which tend to boost the highs. But not always, and that's all I can say now (though I suspect speaker aging, and the woofer dustcap resonances, are critical factors).
It may be, that the now useless unit #1 could be salvaged with the AudioGeorge modifications. It's worth pursuing, but now that I have a great set of 4 for my "7.1" system that are all pretty good, I feel that the important work is done here for now.
It may be more interesting to see what the modification does for unit #4, since #4 has virtually identical response to the now-in-use #5. It's a decent way of doing the experiment without messing up my now better-than-ever (as of Friday morning, all channels leveled within 1dB, something I'd never been decently able to do before) surround sound system. #4 is currently more rolled off than the new #6, could the AudioGeorge modification bring them both to the same level? I'm currently disinclined to mess with #6 for many reasons, including how much of a pain it is to get back on the wall again, and also it just seems to work best of all right out of the box. But if I get favorable results with two other speakers first, that could be the third. If.
The long term plan for #4 and #1 is woofer and even tweeter replacement experiments. At least #4 has a messed up woofer that needs replacing anyway. It could be the tweeter on #1 is defective somehow.
But meanwhile, also, I'm thinking of a more serious, ear level surround system in the kitchen. That would require a new set of 4 Gallo A'Diva SE speakers, in Stainless, which will depend on my cash situation later this year. The current surrounds would then become "ceiling" surrounds...which would require a processor, as would the intended front width and height speakers...which should probably be SE's as well. My ultimate planned LX55box + special 5" woofer + Infinity Walsh tweeter system will be the ultimate side height surrounds.
For now, the improvement in my surround system (with fixed right surround--the new one) is comparable in magnitude to the discovery of how to enable true 7.1 from discs, which was just two months ago--that was when I spun the wheel and did the the final Oppo update on my BDP-95, which seems not to have adversely affected anything, including my later ability to use "the ISO" disc to make it region free, and the update made the rear surround outputs work for the first time in 10 years. It hadn't been an issue until this year anyway, after I added the permanent rear speakers, so I finally decided to take the risk of update.
Updates Friday May 3
Actually, John Atkinson recommended having the speakers on low rather than high stands, because below the tweeter axis a suckout quickly develops at 3kHz... I was measuring on the woofer axis, but at least consistently on all speakers.
I couldn't resist the desire to see what would happen if I did the full AudioGeorge crossover modification, eliminating the choke on the woofer as well as reversing the tweeter phase.
And the result is, yes, the combination of both of these changes does boost the highs to be pretty amazingly close to an unmodified unit that "works" (but not the amazing new NOS unit). Also, not quite as far as my two actual AudioGeorge modified units. So it looks like those units are intrinsically among the "better, but not best" category of LX55 drivers, and Unit #1 is intrinsically a bummer of some kind, suggesting there are at least 3 cateogries of LX55 drivers, #1 being the worst, and all but #6 being he middling kind.
 |
| Unit #1 with both crossover mods |
 |
| Unit #5, Stock |
Carefully studying the #1 before and after the second modification graph, it appears that unchoking the woofer adds output all the way up to about 7kHz.
 |
| Unit 1 with both mods |
 |
| Unit 1 wih only tweeter polarity change |
In both cases, however, notice that unit #1 actually has response extending to 20kHz at the same level as 10kHz. On the actual tweeter itself, it's pretty level from 5kHz to 20kHz. This suggests to me that the tweeter is at a too-low level compared with the woofer, in effect a "low output" lineaum, but one that turns out to have more extended response than the others, at the lower output that it does have.
An additional test on unit 1 showed that bypassing the light bulb "fuse" did not make a significant difference.
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