Excessive speaker cone movement: Cerwin-Vega AT-8

[Aaron S]

Hey all.

Hope you're all gettin on okay given the times. Got a two (or maybe three) part question here. I just got gifted a pair of Cerwin-Vega AT-8 speakers. I've ordered foam to refoam them from SimplySpeakers, as one of them has a rip in the bottom of it, and they both feel/look pretty deteriorated. I was playing them today, and I noticed that the one with a rip has way more speaker cone movement (back and forth) than the other. Is this because the foam is old and isn't doing what it's supposed to? Or, could caps being out of spec cause this? Any and all input is welcome here.

Second (or third) part of my question is...I have a kenwood KR-6050 and it has a speaker a+b selection. Is it bad to run two sets of speakers at the same time using this or is this what it is for?

I apologize for the newb questions!. I'm new to the game, but good gawd damn do I love the way this vintage equipment sounds! Thanks in advance!

 

[Ds2000]

I’d stop playing them until you foam them with the new kits. For sure, the old foam is allowing for over-excursion. One could damage the coil and former if that old foam lets go.
The receiver can run two sets of speakers of eight ohms or more per set. If one set is the Cerwin-Vega, then just run them alone without running another set. Speaker switches like that are for running an extra speaker set in, say, an adjacent room.

 

[Aaron S]

I’d stop playing them until you foam them with the new kits. For sure, the old foam is allowing for over-excursion. One could damage the coil and former if that old foam lets go.
The receiver can run two sets of speakers of eight ohms or more per set. If one set is the Cerwin-Vega, then just run them alone without running another set. Speaker switches like that are for running an extra speaker set in, say, an adjacent room.

Thanks for the response. I'll let them rest until I get them refoamed. I'd be real bummed if I did irrevocable damage to the speakers. And, good to know what the utility of the a+b switch is.

 

[AudioGMan]

Were you playing a mono signal through the speakers when you noticed one was moving more than the other?

 

[Aaron S]

Were you playing a mono signal through the speakers when you noticed one was moving more than the other?

Not totally sure, but it was an old muddy waters record that was causing the most significant movement. So, maybe? I thought it was strange because it wasn't the bassiest album I had played. It does seem to move a good bit more than the other speaker, regardless of what is played, though.

 

[Ds2000]

Not totally sure, but it was an old muddy waters record that was causing the most significant movement. So, maybe? I thought it was strange because it wasn't the bassiest album I had played. It does seem to move a good bit more than the other speaker, regardless of what is played, though.

LP? Oh that may have just been some record anomaly. Like (here’s an old term) wow. Yes wow can (iirc) in some circumstances cause inaudible cone movement. Pressing the subsonic filter (if there is one) will end that movement.
Still, as mentioned in my first post, wait til you refoam to use.

 

[Aaron S]

LP? Oh that may have just been some record anomaly. Like (here’s an old term) wow. Yes wow can (iirc) in some circumstances cause inaudible cone movement. Pressing the subsonic filter (if there is one) will end that movement.
Still, as mentioned in my first post, wait til you refoam to use.

Huh, it is an LP. And, there is a subsonic filter switch on my KR-6050. I've tried to make sense of what it does...maybe I'll mess with it tomorrow, and see if it makes a difference with this particular recording. Would you be be able to shed more light on what wow is?

 

[Ds2000]

Huh, it is an LP. And, there is a subsonic filter switch on my KR-6050. I've tried to make sense of what it does...maybe I'll mess with it tomorrow, and see if it makes a difference with this particular recording. Would you be be able to shed more light on what wow is?

Like a very low frequency wave. So, sometimes it’s the turntable, but most often it’s a pressing defect in the LP. When I say low frequency, I mean below 15hz. The subsonic filter was designed to remove exactly that in the LP era when your receiver was new.

 

[Pyrrho]

You can read more about wow at:

https://en.wikipedia.org/wiki/Wow_(recording)

You should probably always use your subsonic filter when playing records. According to a brochure I am looking at, it filters out below 18 Hz at 6dB per octave. So, unless you are using a great subwoofer, you could leave it on all of the time, with every source (not just records), as most speakers are not going to reproduce such low frequencies at a usable level anyway. (The reason a manufacturer will have a switch like that is because they can brag about their great bass specifications, but still have this to filter out problematic bass as needed.) It might improve the sound quality you get, because the woofer will not be trying to reproduce frequencies that it is unable to reproduce, which adds distortion to your sound.

But, as has been said above, you should stop using the speakers until the foam surrounds are replaced. When there is a hole in the surround, it allows air to move between the cabinet and outside, resulting in less back pressure on the woofer (even with ported speakers, because the port is of finite size, and you are effectively adding another port with the hole in the surround). So the woofer tends to move back and forth more easily, and that can result in over-excursion, damaging the woofer. Also, of course, if too much of the surround has deteriorated, it will not hold the cone centered, and then you can have voice coil rubbing, which can damage the voice coil and ruin the driver, even without excessive cone movement.


Edited to add:

The reason for A & B speaker sets is to allow you to have two pairs of speakers hooked up at once. The selection for both is fine and should not hurt anything, as long as one follows the guidelines in the manual and on the back of the unit. I have not bothered to download the manual for your particular Kenwood, but many Kenwoods hook the speakers up in series, which increases the impedance that the amplifier "sees" compared with hooking them up in parallel (which decreases the impedance that the amplifier "sees"). The manual probably tells you which it is, but you can figure this out by hooking up one set of speakers and selecting both A & B. If it still plays, it hooks them up in parallel, and if it does not still play, it hooks them up in series. If I were going to guess on your unit, I would guess that it hooks them up in series, but you should look at the manual or do the test I just suggested.

The advantage to hooking the speakers up in series is that as long as each speaker by itself is a fine impedance for the amplifier, then the combination will be fine for the amplifier. However, the impedance curve of each speaker will affect the frequency response of the other speaker, as it reduces some frequencies more than others. So hooking speakers up in parallel tends to sound better. But that way, the impedance is reduced, and so there is more of a risk to damaging the amplifier, if one is using low impedance speakers (low relative to what the amplifier can handle).

 

[Aaron S]

You can read more about wow at:

https://en.wikipedia.org/wiki/Wow_(recording)

You should probably always use your subsonic filter when playing records. According to a brochure I am looking at, it filters out below 18 Hz at 6dB per octave. So, unless you are using a great subwoofer, you could leave it on all of the time, with every source (not just records), as most speakers are not going to reproduce such low frequencies at a usable level anyway. (The reason a manufacturer will have a switch like that is because they can brag about their great bass specifications, but still have this to filter out problematic bass as needed.) It might improve the sound quality you get, because the woofer will not be trying to reproduce frequencies that it is unable to reproduce, which adds distortion to your sound.

But, as has been said above, you should stop using the speakers until the foam surrounds are replaced. When there is a hole in the surround, it allows air to move between the cabinet and outside, resulting in less back pressure on the woofer (even with ported speakers, because the port is of finite size, and you are effectively adding another port with the hole in the surround). So the woofer tends to move back and forth more easily, and that can result in over-excursion, damaging the woofer. Also, of course, if too much of the surround has deteriorated, it will not hold the cone centered, and then you can have voice coil rubbing, which can damage the voice coil and ruin the driver, even without excessive cone movement.


Edited to add:

The reason for A & B speaker sets is to allow you to have two pairs of speakers hooked up at once. The selection for both is fine and should not hurt anything, as long as one follows the guidelines in the manual and on the back of the unit. I have not bothered to download the manual for your particular Kenwood, but many Kenwoods hook the speakers up in series, which increases the impedance that the amplifier "sees" compared with hooking them up in parallel (which decreases the impedance that the amplifier "sees"). The manual probably tells you which it is, but you can figure this out by hooking up one set of speakers and selecting both A & B. If it still plays, it hooks them up in parallel, and if it does not still play, it hooks them up in series. If I were going to guess on your unit, I would guess that it hooks them up in series, but you should look at the manual or do the test I just suggested.

The advantage to hooking the speakers up in series is that as long as each speaker by itself is a fine impedance for the amplifier, then the combination will be fine for the amplifier. However, the impedance curve of each speaker will affect the frequency response of the other speaker, as it reduces some frequencies more than others. So hooking speakers up in parallel tends to sound better. But that way, the impedance is reduced, and so there is more of a risk to damaging the amplifier, if one is using low impedance speakers (low relative to what the amplifier can handle).

Thanks so much Ds2000 and Pyrrho! These responses are super helpful and informative. Fortunately, I just came up on a set of Wharfedale W45's. I guess I'll have to resort to just running those for the time being (sarcasm fully intended).

I was logging in to see if it would be a good idea to leave the subsonic filter on all the time, so it's good to know that I should. And to have an understanding of it's function. Also, I have a manual downloaded for my kenny. I'll dig into and see what the guidelines for running two sets of speakers. I don't think that's something I'll be using in the future though. Ultimately, I'd like to get the Vega's and Wharfedale's both hooked up, and use one set or the other depending on what I'm listening to.

 

[Ds2000]

Thanks so much Ds2000 and Pyrrho! These responses are super helpful and informative. Fortunately, I just came up on a set of Wharfedale W45's. I guess I'll have to resort to just running those for the time being (sarcasm fully intended).

I was logging in to see if it would be a good idea to leave the subsonic filter on all the time, so it's good to know that I should. And to have an understanding of it's function. Also, I have a manual downloaded for my kenny. I'll dig into and see what the guidelines for running two sets of speakers. I don't think that's something I'll be using in the future though. Ultimately, I'd like to get the Vega's and Wharfedale's both hooked up, and use one set or the other depending on what I'm listening to.

You don’t have to use the subsonic filter on sources other than the turntable. That ‘wow’ issue is not something that CD or streaming devices will have, nor will most radio sources.

 

[Aaron S]

You don’t have to use the subsonic filter on sources other than the turntable. That ‘wow’ issue is not something that CD or streaming devices will have, nor will most radio sources.

Okay, good to know! I'll take any excuse to switch the knobs on that kenwood. It's so damned satisfying.

 

[Ds2000]

Okay, good to know! I'll take any excuse to switch the knobs on that kenwood. It's so damned satisfying.

You’ve got the bug! Enjoy it, and that’s a fine one to spin the knobs and flip the switches on.

 

[Pyrrho]

There is no wow from CDs, but your speakers still are not going to reproduce 18 Hz properly, so you can still leave it on all of the time. I suggest that you try it on and off when playing CDs at high volumes, and see if you notice any difference, and see which you prefer.