Polk L800 speakers - SPL below 100 Hz dropped about 6db.
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So far no any response from Polk NZ or Polk US.
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They're stumped too. Resistance measurements?George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Gardenstater wrote: »They're stumped too. Resistance measurements?
Thanks. I don't know how to do a proper Resistance measurements.
And I bought L800 to enjoy music, however now I learned a lot about testing speakers, I guess next step is learning how to repair speakers, Lol. -
Is what I found a hidden quality issue of L800 woofer?
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Is what I found a hidden quality issue of L800 woofer?
I think you may have a discrepancy somewhere other than the speakers. Perhaps the amplifier...
The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD
“When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson -
So far no any response from Polk NZ or Polk US.SeleniumFalcon wrote: »Polk's head speaker designer, Scott Orth, is aware of what's going on and is making suggestions on how to troubleshoot the speaker with the folks in New Zealand.
This is a response from Polk US....working on it
2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
erat interfectorem cesar et **** dictatorem dicere a -
txcoastal1 wrote: »So far no any response from Polk NZ or Polk US.SeleniumFalcon wrote: »Polk's head speaker designer, Scott Orth, is aware of what's going on and is making suggestions on how to troubleshoot the speaker with the folks in New Zealand.
This is a response from Polk US....working on it
Thanks , just saw that post. -
Hi Everyone, here is more information for troubleshooting.
After the first testing this morning, I left the room and came back and test on 1 hour and 5 hours later.
All conditions are same for each test, before every test, the Yamaha A-S2200 will be warm up for 1 minute.
Here is the test result:
You can see the bass performance of my L800 is slowly recovering, I guess the issue is temperature related.
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txcoastal1 wrote: »So far no any response from Polk NZ or Polk US.SeleniumFalcon wrote: »Polk's head speaker designer, Scott Orth, is aware of what's going on and is making suggestions on how to troubleshoot the speaker with the folks in New Zealand.
This is a response from Polk US....working on it
Thanks , just saw that post.SeleniumFalcon wrote: »Polk's head speaker designer, Scott Orth, is aware of what's going on and is making suggestions on how to troubleshoot the speaker with the folks in New Zealand.
Thank you very much, I just posted more information for troubleshooting. -
Specs on the Yamaha A-S2100 are barely adequate to drive the L800 IMHO… you really need to hit them with more power and current in order to get the best out of them. I like the Yamaha with a nice set of bookshelf speakers, but big power-hungry Legends are too much for it to properly handle.The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD
“When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson -
Is it possible a driver became disconnected? I don't know how the woofers are wired but that would definitely change the response...
But again for that to happen in both speakers simultaneously would be wild- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit. -
It seems the speakers were working as they should then something happened while listening that resulted in a loss of bass response. We have then seen the bass response change in relation to the amount of time they have been playing. IMO, this points to an issue with the crossovers. I can only suggest removing one to visually inspect as a starting point.
Another thought crossed my mind...what are you using for speaker cables? How long are they? How are they terminated?Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
nooshinjohn wrote: »Specs on the Yamaha A-S2100 are barely adequate to drive the L800 IMHO… you really need to hit them with more power and current in order to get the best out of them. I like the Yamaha with a nice set of bookshelf speakers, but big power-hungry Legends are too much for it to properly handle.
Thanks. I also have Rotel RA-1592 MK2, which is 350w at 4Ohm.
Rotel drives the L800 usually.
In this test I use Yamaha because I neend to make sure the amplifier running at same temperature in every test.
If I use Rotel, in the first test Rotel is hot, in the one hour later test the Rotel will be cold. -
It seems the speakers were working as they should then something happened while listening that resulted in a loss of bass response. We have then seen the bass response change in relation to the amount of time they have been playing. IMO, this points to an issue with the crossovers. I can only suggest removing one to visually inspect as a starting point.
Another thought crossed my mind...what are you using for speaker cables? How long are they? How are they terminated?
Thanks for the reply.
Cables are new and only 2 meters long. Terminated with banana plug. I don't think the problem is caused by cables because a test only take 10 seconds.
I guess it's more about the temperature of the crossovers inside the speakers. -
Just tossing this out there... if the Rotel has a differential amplifier, it could have damaged the crossovers... I am unsure of the topology of the Rotel and the amplifier design they use in the integrated, but differential amps and the SDA tech in the L800 do not play well together and damage will result. Rotel has been known to use that topology in the past, and a brief search on the web seems to indicate that some of their offerings still do.The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD
“When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson -
nooshinjohn wrote: »Just tossing this out there... if the Rotel has a differential amplifier, it could have damaged the crossovers... I am unsure of the topology of the Rotel and the amplifier design they use in the integrated, but differential amps and the SDA tech in the L800 do not plat well together and damage will result.
Rotel RA-1592 MK2 is a single-end amplifier. I bought this amplifier for L800. Thanks.
By the way, differential amplifier will not damange L800, if you use differentail amp with L800, L800 got less power from the amp, so it's impossible to damage L800 by using a differential amplifier.
And L800 can work just like normal speakers when SDA calble disconnected. -
Who told you a dual differential amplifier will not harm the speakers?Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Who told you a dual differential amplifier will not harm the speakers?
Please read the Polk L800 manual. If a differential amplifier would harm the speakers, Polk Audio would have clearly stated that in the manual. Thanks.
By the way, here in New Zealand, the Polk Audio distributor doesn't even know L800 don't work with differential amplifier. Lol. -
It is well known here in the states that Polk messed up the manual, BADLY!
The speakers can be damaged with differential amps, just like the original SDA and non-common ground amps also had problems.The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD
“When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson -
nooshinjohn wrote: »It is well known here in the states that Polk messed up the manual, BADLY!
The speakers can be damaged with differential amps, just like the original SDA and non-common ground amps also had problems.
Thanks for letting me know.
Anyway it's not relevant to my case. Please note that the bass drop issue happened while using Rotel RA-1592 MK2 amplifier which is a single-end amplifier. -
Somebody should run this by Raife. 👍
Tell him he has 3 days for a fix.Sal Palooza -
This is from Scott Orth:
"If he wants to get a good measurement free of room effects, he could try doing a nearfield measurement of one of the woofers. Place the mic about 1-2cm from the enter of the cone. Make sure the mic can handle the SPL or maybe turn the volume down until it can. Measure before and after the change in output. That will remove the room and the mid/tweet from the measurement."
1. There’s a rather large notch in the response at 100Hz. I’m going to assume that this is due to the room, possibility the reflection off of the front wall.
2. The stereo and dimensional arrays don’t appear to be affected by the issue. Is the stimulus being applied to both L&R simultaneous or just the left?
3. A drop of 9-10dB would tell me it’s not a single woofer cutting out as that would cause 6dB of drop and then the broken driver would act as a passive radiation and screw up the bass response. The drop in bass appears to be rather even across the bass range.
4. Is it happening to both speakers or just the left?
5. There could be a bad internal connection, poor solder joint or crack in the inductor of the woofer crossover and when the unit heats up that issue rears its head. Then the woofer doesn’t get the proper amount of current.
6. It could also be a problem in the woofers, but I doubt it because both would have to go wrong at the same time and that’s unlikely.
7. Amplifier type should have no bearing on the woofer performance like they would for the dimensional array.
8. Break in would not cause this amount of change.
So, for trouble shooting purposes, I would first make sure all of the connections between the input and the woofer crossover and woofers are good. Next I would try replacing the woofer crossover. Failing all of that I would try replacing woofers. -
Number 5 sounds plausible for Polk NZ to follow up on.
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The temperature of the amp will have zero effect on what is happening with the speakers. If the troubles began WITH the Rotel, chances are that your troubles are with the Rotel, and the possible damage done to the L800's resulting from that pairing. Pull the bass drivers and measure them for their resistance values and inspect the crossovers. Until then you are chasing your own tail and we are lacking any useful information that will help solve the problem.nooshinjohn wrote: »Specs on the Yamaha A-S2100 are barely adequate to drive the L800 IMHO… you really need to hit them with more power and current in order to get the best out of them. I like the Yamaha with a nice set of bookshelf speakers, but big power-hungry Legends are too much for it to properly handle.
Thanks. I also have Rotel RA-1592 MK2, which is 350w at 4Ohm.
Rotel drives the L800 usually.
In this test I use Yamaha because I neend to make sure the amplifier running at same temperature in every test.
If I use Rotel, in the first test Rotel is hot, in the one hour later test the Rotel will be cold.
The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD
“When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson -
nooshinjohn wrote: »The temperature of the amp will have zero effect on what is happening with the speakers. If the troubles began WITH the Rotel, chances are that your troubles are with the Rotel, and the possible damage done to the L800's resulting from that pairing. Pull the bass drivers and measure them for their resistance values and inspect the crossovers. Until then you are chasing your own tail and we are lacking any useful information that will help solve the problem.
Thanks for the advice, I also tested with Rotel RA-1592 MK2, same result. My job is software tester, I guess I know how to do a test under controlled conditions.
The Rotel is brand new and it also been tested with my Focal Aria 936, I'm sure the Rotel works properly.
My L800 carries 10 years full warranty so I can't pull the bass drivers out and measure them by myself, that should be done by Polk NZ.
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SeleniumFalcon wrote: »This is from Scott Orth:
"If he wants to get a good measurement free of room effects, he could try doing a nearfield measurement of one of the woofers. Place the mic about 1-2cm from the enter of the cone. Make sure the mic can handle the SPL or maybe turn the volume down until it can. Measure before and after the change in output. That will remove the room and the mid/tweet from the measurement."
1. There’s a rather large notch in the response at 100Hz. I’m going to assume that this is due to the room, possibility the reflection off of the front wall.
2. The stereo and dimensional arrays don’t appear to be affected by the issue. Is the stimulus being applied to both L&R simultaneous or just the left?
3. A drop of 9-10dB would tell me it’s not a single woofer cutting out as that would cause 6dB of drop and then the broken driver would act as a passive radiation and screw up the bass response. The drop in bass appears to be rather even across the bass range.
4. Is it happening to both speakers or just the left?
5. There could be a bad internal connection, poor solder joint or crack in the inductor of the woofer crossover and when the unit heats up that issue rears its head. Then the woofer doesn’t get the proper amount of current.
6. It could also be a problem in the woofers, but I doubt it because both would have to go wrong at the same time and that’s unlikely.
7. Amplifier type should have no bearing on the woofer performance like they would for the dimensional array.
8. Break in would not cause this amount of change.
So, for trouble shooting purposes, I would first make sure all of the connections between the input and the woofer crossover and woofers are good. Next I would try replacing the woofer crossover. Failing all of that I would try replacing woofers.
Thank you very much for the help! -
My L800 carries 10 years full warranty so I can't pull the bass drivers out and measure them by myself, that should be done by Polk NZ.
Do you expect them to send a tech to the house? Or do you want to pay the freight to a Warranty center? Polk does not want the two-way freight bill, and there is no field support. Therefore they have no problem whatsoever having their customers swap drivers and other parts on their own. Pull the drivers and put an Ohm meter on them and record the readings. Inspect the crossovers and report back.Thanks for the advice, I also tested with Rotel RA-1592 MK2, same result. My job is software tester, I guess I know how to do a test under controlled conditions.
I am not saying at all that your problem is with the Rotel. What I am saying is there is a bilateral internal problem with your speakers and that problem is either a pre-existing condition from their time as demos or caused by some mis-match between the Rotel and the speakers. Further, the problem is now confined to the speakers themselves and no amount of further testing is going to solve that. The time has come to open them up and start inspecting the individual crossover components for damage and test the drivers for resistance to a load. That is the only way to learn what is truly going on here.
I do not mean to come across as an asshat, but the time has come to stop testing and getting the same results and start investigating for the cause.
The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD
“When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson -
I think it would help if Polk technical support would tell you what the resistance measurement should be across the binding posts; positive to negative. Easy measurement to do when they are cold and then when they are "hot" after playing bass heavy material for a while.
Just pick up an inexpensive DVOM, assuming you don't want a real fancy one, and read the instructions on resistance measurement.
If you detect an anomalous reading, perhaps Polk could give you a shipping label to the nearest authorized repair center, or authorize you to remove the crossovers and drivers and test further, or ship the crossover to them. Various possibilities but you will be making progress towards a solution.
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
nooshinjohn wrote: »My L800 carries 10 years full warranty so I can't pull the bass drivers out and measure them by myself, that should be done by Polk NZ.
Do you expect them to send a tech to the house? Or do you want to pay the freight to a Warranty center? Polk does not want the two-way freight bill, and there is no field support. Therefore they have no problem whatsoever having their customers swap drivers and other parts on their own. Pull the drivers and put an Ohm meter on them and record the readings. Inspect the crossovers and report back.Thanks for the advice, I also tested with Rotel RA-1592 MK2, same result. My job is software tester, I guess I know how to do a test under controlled conditions.
I am not saying at all that your problem is with the Rotel. What I am saying is there is a bilateral internal problem with your speakers and that problem is either a pre-existing condition from their time as demos or caused by some mis-match between the Rotel and the speakers. Further, the problem is now confined to the speakers themselves and no amount of further testing is going to solve that. The time has come to open them up and start inspecting the individual crossover components for damage and test the drivers for resistance to a load. That is the only way to learn what is truly going on here.
I do not mean to come across as an asshat, but the time has come to stop testing and getting the same results and start investigating for the cause.
Thank you, I understood.
To be honest I don't know what Polk will do, no any responese from Polk NZ so far. I post everything here for Polk NZ's referrence.
Polk NZ distributor's head office is only 10 minutes drive from my home, so in the worst case I will drop off the speakers to their office. -
SeleniumFalcon wrote: »This is from Scott Orth:
"If he wants to get a good measurement free of room effects, he could try doing a nearfield measurement of one of the woofers. Place the mic about 1-2cm from the enter of the cone. Make sure the mic can handle the SPL or maybe turn the volume down until it can. Measure before and after the change in output. That will remove the room and the mid/tweet from the measurement."
1. There’s a rather large notch in the response at 100Hz. I’m going to assume that this is due to the room, possibility the reflection off of the front wall.
2. The stereo and dimensional arrays don’t appear to be affected by the issue. Is the stimulus being applied to both L&R simultaneous or just the left?
3. A drop of 9-10dB would tell me it’s not a single woofer cutting out as that would cause 6dB of drop and then the broken driver would act as a passive radiation and screw up the bass response. The drop in bass appears to be rather even across the bass range.
4. Is it happening to both speakers or just the left?
5. There could be a bad internal connection, poor solder joint or crack in the inductor of the woofer crossover and when the unit heats up that issue rears its head. Then the woofer doesn’t get the proper amount of current.
6. It could also be a problem in the woofers, but I doubt it because both would have to go wrong at the same time and that’s unlikely.
7. Amplifier type should have no bearing on the woofer performance like they would for the dimensional array.
8. Break in would not cause this amount of change.
So, for trouble shooting purposes, I would first make sure all of the connections between the input and the woofer crossover and woofers are good. Next I would try replacing the woofer crossover. Failing all of that I would try replacing woofers.
More information for troubleshooting:
Today after warm up the speakers, I tested again from 30cm (Right speaker), the bass is weaker than yesterday.
Below is nearfield measurement of four woofers:
Photos of testing:
