Personal Power Struggle.......

[frankmarsi]

4-26-09

I'm just asking here; I think maybe two out of my X-vers (‘caps’ in particular) on my LST's are going?

I'm not sure, maybe it's because the pair in question have my Micro-Statics hooked up to them? Which would be; ‘out-board’ tweeters are rated at 16 ohm and the LST being 4 ohm. The lower pair (out of 4 LSTS in total) are running straight at 4 ohms with no out-board tweeters and do no exhibit any woofer ‘popping’ noise at high volumes.

At high volumes the upper pair 'pop' on heavy bass material, where as the lower pair w/o Micro-Static’s do not 'pop'. All woofers have been recently re-foamed.

Any advice from anyone?

FM

P.S. Presently and newly using two Phase Linear700 Series Two’s- completely re-done with all new power-supply ‘caps’ (up from 19,600uf to 40,000uf per amp),and yes that might be a lower PS cap number by todays standards, but the power transformer on these beasts if insanely huge, almost like something taken off of a huge WW2 battle-ship, all new “On-Semi” transistors in ‘full-complementary’ mode, etc. Rebuilt by the ‘best’ guy in WA. These new and crazy higher volumes are because I now have more power and have no fear of burning out my amps, although I'm certainly risking blowing-up the entire system, speakers, amps, the living room, ears, my face, neck and shoulders, my shoes will probably come off in the accident also. I’m also maybe feeling that the sound of the PL400’s maybe a bit ‘sweeter’ than the PL700’s? Although the more ‘time-on’ and the more the PL700’s ‘cook’, I feel the PL700’s maybe catching up in that department, they certainly do not run out of power at any point. Which brings me to another question. It has been quoted many times from the original test report done by Julian Hirsch (circa’72) that the LST’s could possibly use more power than a PL700 offers? Personally at this early stage of using these higher-powered amps I might disagree, as they seem to never run out of power at any humanly bearable volume level.

Also heard same ‘popping’ problem with lower-powered PL400’s, anyone, anywhere with a notion about this situation? Is it an ‘ohm-age’ problem, or am I running out of ‘wall’ power or something as nutty as that thought? Still AR speaker and power-amp crazy after all these years!

Wish me luck, this new crazy volume level is like watching the latest loud special effects movie at the best theatre one could go to. After all my LST's were originally used in a theater from which I got them from on 42nd. Street, I just keep'em going that way. My cousin was Crazy Eddie.

FM

[ar_pro]

Frank - are you running any air conditioning?...it's insanely hot in the NE, today.

[frankmarsi]

Well AR-Pro, we got you beat, it's 95F degrees here, and I haven't installed my air-conditioners yet, so I'm not running my system until it either cools down, or I break my back to put in the air-conditioners, maybe tomorrow.

In any event the amps do have fans going when they're running.

FM

[Pete B]

Hi Frank,

Have you tried swapping amps and speakers?

Obviously, does it move or stay with the speaker?

Is the popping in both channels, just to confirm, I see you say

the upper pair?

I'd doubt that 16 ohm tweeters would do it, however if the total complex

impedance causes the output protection to trip - that could be the cause.

You might need a high frequency load on the auto-transformer for the

pair without tweeters, in order to minimize inductive effects on the primary.

A 6-8 ohm dummy load in place of the tweeter array should work to test

the theory.

Were the masonite spacers left intact when the woofers were refoamed?

[frankmarsi]

Hi Frank,

Have you tried swapping amps and speakers?

Using the same speakers as LST's are not that easy to move around, only amps were changed and the same results.

Obviously, does it move or stay with the speaker?

Don't understand your question, prob happens in same speakers.

Is the popping in both channels, just to confirm, I see you say

the upper pair?

Yes in both channels.

I'd doubt that 16 ohm tweeters would do it, however if the total complex

impedance causes the output protection to trip - that could be the cause.

You might need a high frequency load on the auto-transformer for the

pair without tweeters, in order to minimize inductive effects on the primary.

A 6-8 ohm dummy load in place of the tweeter array should work to test

the theory.

Were the masonite spacers left intact when the woofers were re-foamed?

Yes I never remove the masonite, it's made to have it.

You wanna know what the problem is? Oh, I'll tell you what Alice, I think it's either the spider, or maybe the foam surround is not stretching far enough, or the speaker's 'caps' as they are original are having a hard time.

Any opinions Alice, I mean members?

FM

[speaker dave]

If they are popping at high volume with a heavy bass line it is possible that the woofers are bottoming. Be careful here or you could damage the woofers. If the woofers bottom the voice coils could be hitting the magnet on big inward excursions and this might do permanent damage to the coils.

Try this: take the grilles off and watch carefully. find a piece of music that has caused the problem and creep up the volume until it just happens. If it is reapeatable (same note of the music every time) and you can see that the woofer has moved a lot (say 1/2 to 3/4 inch inwards from the rest position) then that is the problem and you may just have to live with that limitation. Again, don't overdo it or you may cause permanent woofer damage.

If one pair does it and the other doesn't then suspect air leaks, softer surrounds or perhaps the spyders have been stretched or "broken in" from lots of use.

Are your bass controls at flat, loudness out?

David

[frankmarsi]

If they are popping at high volume with a heavy bass line it is possible that the woofers are bottoming. Be careful here or you could damage the woofers. If the woofers bottom the voice coils could be hitting the magnet on big inward excursions and this might do permanent damage to the coils.

Try this: take the grilles off and watch carefully. find a piece of music that has caused the problem and creep up the volume until it just happens. If it is reapeatable (same note of the music every time) and you can see that the woofer has moved a lot (say 1/2 to 3/4 inch inwards from the rest position) then that is the problem and you may just have to live with that limitation. Again, don't overdo it or you may cause permanent woofer damage.

If one pair does it and the other doesn't then suspect air leaks, softer surrounds or perhaps the spyders have been stretched or "broken in" from lots of use.

Are your bass controls at flat, loudness out?

David

Speaker Dave, you do sound correct in all of your conclusions! I've seen other speakers 'bottom-out' before, but not my babies, these are my AR's mind you!

However, is there also a possibility that the speakers 'caps' are not up to snuff, or am I off-base here?

Actually, I'm siding with you, but I'm open to other possibilities. I suspect that maybe the spiders became 'shan-got-ta', which is Italian slang for stretched-out and droopy. Although they didn't look that way while I was 're-foaming' them. Damn, do I have to re-foam two more? Oh, well this is a problem when you fall in love with older material objects-nothing lasts forever-wait, I'm sobbing here-give me a moment. You realize this is going to deplete my ridiculously large supply of 11 spare woofers. But while I was stocking up on used woofers these past few years, I felt perhaps this day would come. We'll arrange for 'the-services' soon, if it's a dead issue, I just don't have the time right now. I'll simply try to not get so carried away with the volume control until I re-install two more. Damn do I love the AR bass when it's loud, there's nothing like it! That fact I've know this 'phenom' since I used 12 incher's in '74 along with high power amps.

FM

P.S. In the words of Roy Orb- "But wait, what do I see?"

Dave, there's also a chance that the same-old, same-old gaskets that I used over and over again maybe to blame-you did mention that idea. I should have replaced them, but applying the P.E. 3/8" tape roll stuff was hard to adhere into place, and the screw holes are always a problem, so I didn't and hoped the old stuff would do it, maybe it didn't. This might be a job for 'Speaker-Man' *

* "Speaker-Man" will be a new and exciting character I'm working on for this site-stayed tuned. I just know everyone here is already captivated-right? Well actually................

FM

[frankmarsi]

If they are popping at high volume with a heavy bass line it is possible that the woofers are bottoming. Be careful here or you could damage the woofers. If the woofers bottom the voice coils could be hitting the magnet on big inward excursions and this might do permanent damage to the coils.

Try this: take the grilles off and watch carefully. find a piece of music that has caused the problem and creep up the volume until it just happens. If it is reapeatable (same note of the music every time) and you can see that the woofer has moved a lot (say 1/2 to 3/4 inch inwards from the rest position) then that is the problem and you may just have to live with that limitation. Again, don't overdo it or you may cause permanent woofer damage.

If one pair does it and the other doesn't then suspect air leaks, softer surrounds or perhaps the spyders have been stretched or "broken in" from lots of use.

Are your bass controls at flat, loudness out?

David

Speaker Dave, you do sound correct in all of your conclusions! I've seen other speakers 'bottom-out' before, but not my babies, these are my AR's mind you!

However, is there also a possibility that the speakers 'caps' are not up to snuff, or am I off-base here?

Actually, I'm siding with you, but I'm open to other possibilities. I suspect that maybe the spiders became 'shan-got-ta', which is Italian slang for stretched-out and droopy. Although they didn't look that way while I was 're-foaming' them. Damn, do I have to re-foam two more? Oh, well this is a problem when you fall in love with older material objects-nothing lasts forever-wait, I'm sobbing here-give me a moment. You realize this is going to deplete my ridiculously large supply of 11 spare woofers. But while I was stocking up on used woofers these past few years, I felt perhaps this day would come. We'll arrange for 'the-services' soon, if it's a dead issue, I just don't have the time right now. I'll simply try to not get so carried away with the volume control until I re-install two more. Damn do I love the AR bass when it's loud, there's nothing like it! The fact I've know this 'phenom' since I used 12 incher's in '74 along with high power amps.

FM

P.S. In the words of Roy Orb- "But wait, what do I see?"

Dave, there's also a chance that the same-old, same-old gaskets that I used over and over again maybe to blame-you did mention that idea. I should have replaced them, but applying the P.E. 3/8" tape roll stuff was hard to adhere into place, and the screw holes are always a problem, so I didn't and hoped the old stuff would do it, maybe it didn't. This might be a job for 'Speaker-Man' *

* "Speaker-Man" will be a new and exciting character I'm working on for this site-stayed tuned. I just know everyone here is already captivated-right? Well actually................

[speaker dave]

Hey FM,

'shan-got-ta', I like that. I didn't know the Italians had their own terms for woofer ailments. (Or are they referring to something more anatomical???)

I don't think the caps could be a factor here. The low notes go through the woofer inductor and the crossover caps are not a factor for the lowest frequencies.

If you have 11 spare woofers, you should be rotating them every 3000 miles!

David

[Pete B]

You've been at this for a long while Frank so I thought you'd be able to

identify voice coil bottoming. Still, if both channels do it, and the thing in

common is that there are no tweeters, it is very likely an inductive issue

due to no load on the secondary of the autotransformer. Of course check

the woofers for issues that might cause bottoming.

Remember that mod I mentioned to you that eliminates the woofer caps and

autotransformer?