MW6511 Issues/Questions

jayu969

I recently sold a pair of SRS 3.1TL's and the new owner is telling me that the MW6511 drivers are "bad" as their excursion is too large and they bottom out. These have 1 month old "new style" MW6511 drivers that I bought (on eBay from moparnut) as one of the original MW6511's was bad (buzz) so replaced them both.

Is the excursion of the MW6511 supposed to be SAME as the MW6503 stereo drivers?

Is this a common issue with these? I did not notice this when I had them.

Any feedback would be appreciated.

F1nut

What is he using for power and at what volume level is he having the issue?

codycatalist

I will say I have not bottomed out my SDA2B with 6511s and 6503s and I have cranked em.

jayu969

He has a couple of TFM Carver amps and think he is bi-amping them.

jayu969

He was having the issue at "medium" volume.

Schurkey

Since I have trouble keeping track of which drivers go where, I looked at the schematic.

The 6511s are the single-driver-per-channel SDA driver in the 3.1. They reproduce the SDA signal, plus whatever bass comes through the sub-bass whirlygig inductor circuit.

They're also going to react in passive-radiator style to the pressure difference between the cabinet interior and exterior.

I'd be wondering if there's a fault in the inductor circuit, or air leak(s) in the cabinets. The general consensus has been that the SDA circuit is run at approximately half-volume of the midrange/bass Stereo circuit. OTOH, there's one SDA driver and multiple stereo drivers, so I could believe that the excursion is greater on the SDA driver. Note that I have zero experience with the SDA 2, SRS 3.1 or the SRS 2.3, each of which have a non-equal number of stereo-to-SDA drivers.

I suspect we'll need either Polk Company expertise, or a current/former owner of 3.1s to provide a "real" answer.

jayu969

Thanks for the feedback...any current/former owners of 3.1TL's out there to chime in?

codycatalist

@lawdogg

F1nut

jayu969 wrote: »

He was having the issue at "medium" volume.

What model amps?

He may think he's bi-amping, but he's not really. At best, passive bi-amping, but that's a waste of power.

Ask him exactly where the volume knob is, such as 10 o'clock....1 o'clock, etc.

lawdogg

jayu969 wrote: »

Thanks for the feedback...any current/former owners of 3.1TL's out there to chime in?

I have not noticed any difference in excursion in my SDA drivers, but have been listening grilles on for a while. I'll take em off and report back.

F1nut

lawdogg wrote: »

jayu969 wrote: »

Thanks for the feedback...any current/former owners of 3.1TL's out there to chime in?

I have not noticed any difference in excursion in my SDA drivers, but have been listening grilles on for a while. I'll take em off and report back.

The guy is claiming the SDA drivers are bottoming out. Yours aren't because you'd hear it if they were.

pkquat

What is the source material? For HT duty, even at reasonable volumes, I found I can bottom my 1C's when running the mains full range with no sub or having the .1 mixed into the mains. It was usually only one driver from 1 channel (as I was finding the limits). I forget if it was the main or SDA speaker. It did have slightly more movement than the rest. IMO tolerances very.
With ported and IMO more so with PR systems there is a natural system frequency where the drivers get very excited, and the risk of bottoming is greatest. For most music this is a low enough frequency and levels are of low enough that this is not an issue. For HT, the "rumbles" can be at high levels at these frequencies.

xschop

Very intriguing anomoly with my 6511's also.
Installed alongside the 6510's in my CRS+ they also looked as if they were moving alot more in relation to the 6510's. After removing the passive radiator and installing a Power Port, their movement diminished. Same volume same tracks played.

F1nut

pkquat wrote: »

What is the source material? For HT duty, even at reasonable volumes, I found I can bottom my 1C's when running the mains full range with no sub or having the .1 mixed into the mains. It was usually only one driver from 1 channel (as I was finding the limits). I forget if it was the main or SDA speaker. It did have slightly more movement than the rest. IMO tolerances very.
With ported and IMO more so with PR systems there is a natural system frequency where the drivers get very excited, and the risk of bottoming is greatest. For most music this is a low enough frequency and levels are of low enough that this is not an issue. For HT, the "rumbles" can be at high levels at these frequencies.

That means you have a bad driver.

lawdogg

F1nut wrote: »

lawdogg wrote: »

jayu969 wrote: »

Thanks for the feedback...any current/former owners of 3.1TL's out there to chime in?

I have not noticed any difference in excursion in my SDA drivers, but have been listening grilles on for a while. I'll take em off and report back.

The guy is claiming the SDA drivers are bottoming out. Yours aren't because you'd hear it if they were.

Was responding to @Schurkey asking about SDA driver excursion.

"I could believe that the excursion is greater on the SDA driver ... I suspect we'll need either Polk Company expertise, or a current/former owner of 3.1s to provide a "real" answer."

But I think the more important question for @jayu969 is whether they were ever bottoming out for him, and if not, what changes if any the new owner made beyond the creative new amp arrangement.

For example maybe if the SDA drivers somehow became out of phase with the stereo drivers, they'd have more of a reason to bottom out? Something logical is happening, we just haven't confirmed what that is yet.

decato

Yes, the single dimensional driver will exhibit greater excursions than the four dimensional drivers. I have the 3.1TLs and observed this behavior. Even on the 1.2TL, the four MW 6511s move more than the four MW 6503s when playing very low frequencies (approximately 20 Hz and lower). The inductor in series with the dimensional drivers offers little resistance at such low frequencies, not to mention that the MW 6511s have a DCR of around 3 ohms.

However, to say that the driver is "bottoming out" seems to indicate abuse. Reaching the excursion limit should not pose a problem with normal, even loud, listening.

Hope this helps...

Nightfall

Is this person using tone controls with the bass cranked up and the loudness control (or equivalent) turned on?

jayu969

OK....thankyou for all of the feedback. Through a lot of time by the new owner the issue has been figured out.. My stupidity mostly. When I replaced the bad MW6511's with the newer ones I reversed the polarity when hooking them up. There was also an air leak from when the feet were added.

lawdogg

Nice - glad you got it figured out!

lawdogg wrote: »

For example maybe if the SDA drivers somehow became out of phase with the stereo drivers, they'd have more of a reason to bottom out?

jayu969 wrote: »

When I replaced the bad MW6511's with the newer ones I reversed the polarity when hooking them up.

Yay! What do I win?

F1nut

Good on ya, lawdogg.

How about a cookie?

lawdogg

F1nut wrote: »

Good on ya, lawdogg.

How about a cookie?

Jesse, a cookie from you would be an honor!

F1nut

lawdogg

[Deleted User]

Tell the guy to run his pre-amp or what ever receiver he's usingc totally flat. No loudness buttons, bass/treble knobs turned up, or internal EQ, / sound processor. Or he may need to send it to Polk to get the magnet(s) recharged

[Deleted User]

If he's running the two amps mono left, mono right, is he using the correct IC cable? If he's using the two amps to bi-amp, he may have the amp that's going to the low-pass inputs gained up too much to try to get more bottom end. Or maybe he's not familiar with a passive radiator type speaker system that's not going to control cone motion like a sealed or vented design does. I read the post saying a driver was wired out of phase but a user that's used to dumping a lot of signal into sealed/vented designs in the past can definitely over-drive a PR speaker design if he doesn't understand the difference.

westmassguy

Reversed polarity will cause this, but also, unlike most other SDA/SRSs, I never recommend replacing the Sub-Bass Drive Inductors on the 3.1s for that reason.

Schurkey

Slapaho wrote: »

Or he may need to send it to Polk to get the magnet(s) recharged

I didn't know that was an option. If Polk does this, I think it would be a good idea for any of the SDAs--aren't they all old enough that the magnets would be getting weak?

[Deleted User]

Schurkey wrote: »

Slapaho wrote: »

Or he may need to send it to Polk to get the magnet(s) recharged

I didn't know that was an option. If Polk does this, I think it would be a good idea for any of the SDAs--aren't they all old enough that the magnets would be getting weak?

More than a few times I've taken woofers in for warranty exchange that sounded like crap that ended up being fine after they were recharged.

pitdogg2

Slapaho wrote: »

Schurkey wrote: »

Slapaho wrote: »

Or he may need to send it to Polk to get the magnet(s) recharged

I didn't know that was an option. If Polk does this, I think it would be a good idea for any of the SDAs--aren't they all old enough that the magnets would be getting weak?

More than a few times I've taken woofers in for warranty exchange that sounded like crap that ended up being fine after they were recharged.

I call bs

K_M

decato wrote: »

Yes, the single dimensional driver will exhibit greater excursions than the four dimensional drivers. I have the 3.1TLs and observed this behavior. Even on the 1.2TL, the four MW 6511s move more than the four MW 6503s when playing very low frequencies (approximately 20 Hz and lower). The inductor in series with the dimensional drivers offers little resistance at such low frequencies, not to mention that the MW 6511s have a DCR of around 3 ohms.

However, to say that the driver is "bottoming out" seems to indicate abuse. Reaching the excursion limit should not pose a problem with normal, even loud, listening.

Hope this helps...

It is easy to reach the excursion limit with any vented speaker. Just have to have some loud deep bass and have it turned up a bit.

They have very good deep bass extension, but at the cost of a larger sized speaker box, and somewhat limited excursion ability.

I think its simply a nice trade-off, deep bass and somewhat limited excursion.
You can not have it both ways.

Other brands go for hardly any deep bass, but more power handling.

leftwinger57

Pretty interesting as I just had a #6511 go bad on me but in my 2Bs. No raw speakers for replacement on the WTB site or E-Bay so I'm getting a new one from Polk. Now when they were working it looked like they were pumping in tandem w/ the #6503 next to it. ( cabinets sealed w/ Liquid Nails, new gaskets and Larry's Rings)
I do have a question. The beat driver had 2 dates on it. One in black I think saying Jan '88 and then in red stamped Dec '87. Is one date the speaker born on date and the later date the mating of speaker to cabinet. ???