Do Tweeters Get Tired? (Peerless on Monitor 5 / 5a)

tommch

OK, kind of a weird question here... I have original Monitor 5s - bought them new in 79 or 80-ish as I recall. They seem to be between 5 and 5a as they have some mismatches to both (fuse, Polk logo on mesh cover not wood, Peerless, fuses, paper ring on the mid driver, etc etc). I guess in those days Polk was kinda notorious for "gradual" shift from one model to the next :-)

Anyway, I rebuilt the crossovers recently with new capacitors and resistors (original specs) and they work fine except...

The high end sounds like it's coming from a padded room. (It sounded equally bad before the crossover upgrade too). Overall midrange and bass sound just peachy. So these speakers are kind of like me. They work, but everything hurts in the morning.

A 5Mhz test signal seems to work fine through the tweeters and I disconnected them from the crossovers and measured resistance right at 8 Ohms with a Fluke. And no visible damage at all.

For kicks, I substituted one of the Midwest Speaker Repair Peerless copies (https://www.midwestspeakerrepair.com/shop/home-audio/tweeters/dome/mw-audio-mt-4115-1-inch-dome-tweeter/) and, wow, brightness again on the high end. Night and day difference. I have the system on mono switching back and forth to one speaker with original Peerless and the other with the new Peerless copy so I can hear the difference.

I don't know enough about the internals of a tweeter to know what the cause might be and if it's even worth attempting to fix. Hate to replace the original Peerless, but at this point, they sound terrible bordering on non-existent.

Any thoughts? Might this be an example of partially blown if there is such a thing?

Thanks in advance for any opinions...

VR3

Did the original tweeters use ferro fluid?

tommch

Well, here my lack of speaker guts knowledge is exposed - I have no idea. But I'm Googling ferrofluid as we speak :-)

tommch

Hmmm - found an interesting thread here. At this point, I don't have much to lose, so I'll carefully crack one open and take a look...

https://forum.polkaudio.com/discussion/170787/lets-talk-about-ferrofluid

ChrisD06

Ferrofluid if applicable is my guess. I had obtained ferrofluid for my RT800 tweets and the difference was pretty night and day.

The shady Kijiji guy is no longer selling so now I can't reobtain it for my RT5000 setup... if you're in Canada you'll face a similar issue.

pitdogg2

Before you kill any tweeters know this, the fuse holders and wire leading to and from it has been known to corrode. If your wire and the fuse holder have some corrosion it can affect on the signal getting to the tweeter.

F1nut Posts: 49,101
February 2017
Since this thread has been resurrected and since the original question was primarily in regards to the original Peerless tweeter I asked Ken, who asked Stu and the answer is no ferrofuild in the original Peerless.

tommch

pitdogg2 wrote: »

Before you kill any tweeters know this, the fuse holders and wire leading to and from it has been known to corrode. If your wire and the fuse holder have some corrosion it can affect on the signal getting to the tweeter.

I popped the cover off and it is bone dry in there and perfectly clean (no sludge), so it appears there never was fluid in these. Thanks for the heads up on that.

Re: the fuse possibility, I would think that would also impact the replacement clone tweeter, but that seems to work just fine?

xschop

Both original Peerless exhibit this phenomenon, yet their replacements do not? Strange, unless there was galvanic corrosion of the coil lead wires where they attach at the pressed-in terminal mount/s. Got pics?

Gardenstater

Peerless KO10DT tweeters don't use ferrofluid.

Mine are about the same vintage as yours and are working fine (1979), not that that helps you much. I have verified their smooth response using a sweep sine tone of 5s duration which I downloaded from an online site and played from my hard drive while graphing the freq. response using Advanced Spectrum Analyzer Pro for Android. Actually they have a bit of a small rise around 15k or so which is appreciated with my aging hearing.

Since you are the original owner, how did they used to sound? Was it a gradual change so that you can't put your finger on when it happened?

tommch

@xschop you may be onto something with the corrosion theory. They're definitely corroded on the exterior surfaces, so maybe that's worked into the coil leads...

tommch

Gardenstater wrote: »

Since you are the original owner, how did they used to sound? Was it a gradual change so that you can't put your finger on when it happened?

Hard to say, they were in storage for a while when I moved and out of use as I was using a different setup. Perhaps its just corrosion. The pics look worse than they are, but there is definitely some mess there.

Gardenstater

The voice coil looks a "little" crinkled or out of round in the upper left quadrant area of your photo.

My Peerless have that same aluminum oxide deposits but since it is only on the bezel plate I don't think it matters and the plate is "supposed" to be fully insulated from the terminals. That's something you could check with a meter.

tommch

Gardenstater wrote: »

The voice coil looks a "little" crinkled or out of round in the upper left quadrant area of your photo.

My Peerless have that same aluminum oxide deposits but since it is only on the bezel plate I don't think it matters and the plate is "supposed" to be fully insulated from the terminals. That's something you could check with a meter.

Thanks, will check it out and report back...

F1nut

That corrosion is common/normal on those vintage Peerless tweeters.

F1nut

The Midwest tweeters are a one size fits all that fits none. They also come in 8 or 4 ohm versions. Which did you buy?

VR3

Going to have to agree with the tight tolerances of the tweeter I think that voice coil is to out of round to function properly

tommch

F1nut wrote: »

The Midwest tweeters are a one size fits all that fits none. They also come in 8 or 4 ohm versions. Which did you buy?

The 8 Ohm. Just had one and figured I’d test it out.

xschop

tommch wrote: »

@xschop you may be onto something with the corrosion theory. They're definitely corroded on the exterior surfaces, so maybe that's worked into the coil leads...

Also as pointed out, the coil itself could be out-of-round and rubbing the pole-piece. (FYI...You can carefully massage the perimeter back into roundness.) However, from experience there is alot of play between the face plate thru-holes and the magnet set screws where they become misaligned over time/vibrations, binding the coil also. (So you can re-set the magnet/coils also since they ohm out good)

tommch

xschop wrote: »

Also as pointed out, the coil itself could be out-of-round and rubbing the pole-piece. (FYI...You can carefully massage the perimeter back into roundness.) However, from experience there is alot of play between the face plate thru-holes and the magnet set screws where they become misaligned over time/vibrations, binding the coil also. (So you can re-set the magnet/coils also since they ohm out good)

Interesting. While I certainly could have stressed the coil separating the parts, the symptoms pre-existed ever disassembling the tweeter, so whatever went wrong did so before I started messing with it. Makes sense.

xschop

Indeed the galvanic corrosion between the pot-metal faceplate and steel set-screws can also allow slippage/coil binding also. Clean them up and re-set the coils by ear, playing music while they are hooked up to their respective cross-overs.

tommch

xschop wrote: »

Indeed the galvanic corrosion between the pot-metal faceplate and steel set-screws can also allow slippage/coil binding also. Clean them up and re-set the coils by ear, playing music while they are hooked up to their respective cross-overs.

Holy High Frequency Batman! You get the fresh-baked chocolate chip cookie! I just did this on the speaker I hadn't touched yet, and the high end is out of the padded box and restored to like new with the original Peerless. Wow, what a difference. Will put the original tweeter back in the other speaker post haste and repeat the process. So to sum up for those just tuning in, the coils had shifted ever so slightly in position over the years, and some loosening of the screws and careful adjustment by ear fixed it right up!

Thanks SO MUCH for your tips on this; saved my sentimental 1979 setup I bought with hard-earned lawnmowing money :-)

Now I'm on the hunt for some original Monitor 10s. Just because...

xschop

Good deal. Refreshing the crossovers and internal wiring will result in much better imaging/clarity too.

Gardenstater

I thought I read in one of their tech sheets that Peerless made the bezels out of aluminum (diecast?) but don't quote me on it. Needs verification/brain refresh.

I remember reading in one of Polk's informational advertisements that they were famous for, that they had a precision fixture for aligning the voice coils on their tweeters. Don't know if they ever checked or adjusted the ones they purchased from Peerless.

It seems that the adhesives used in the tweeter magnet assemblies didn't ever have problems with losing their grip. It would be awesome to have a ring of billet aluminum that clamps or screws onto the bezels and allows alignment of voice coils by way of 4 fine threaded set screws.

This is what I measured (yellow line) with a sine sweep tone with Android phone mic 1 in. from the tweeter dome (orig. 1979 Peerless) and with the wool felt and my dispersion control modification (chunk of foam basically):



This is a makeshift/sorta hokey thing I came up with to adjust a tweeter once using shims and test tones, that got shifted in shipping (Fried Peerless repaired with Chinese voice coil courtesy of xschop):

tommch

@Gardenstater That is awesome, quite handy I bet when doing a bunch of these over time...

xschop

"I remember reading in one of Polk's informational advertisements that they were famous for, that they had a precision fixture for aligning the voice coils on their tweeters. Don't know if they ever checked or adjusted the ones they purchased from Peerless."

We need pics