Monitor 7B no bass
whitemtntn
Posts: 26
Hi - I just inherited a pair of Monitor 7B's. Hooked them up and there is no bass coming from either speaker. There is sound coming from the woofers but no bass, you can't make out the bass guitar. The bottom passive speaker doesn't seem to be doing anything at all.
Any info appreciated- thank you!
Any info appreciated- thank you!
Comments
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The first thing that I would check is for an air leak. Do so by applying pressure to the passive radiator and look to see if the midwoofer moves in response to the pressure being applied to the radiator. Perhaps you could check that all screws are snug. Visually inspect that there aren't any tears in the rubber surrounds.
Good luck, I hope this helps -
Another possibility is shifted magnets. Not enough to lock up the MW but enough to cause significant drag to slow the cone's response. Either way, testing is done via the passive.
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Don't see any signs of leaks- rubber looks good, screws are tight. I pressed the passive and the midwoofer did not move. Here's a photo of one of the speakers- it looks like it's in very nice condition..
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If the midwoofer did not move with applied pressure to the radiator, then perhaps the midwoofer might have a shifted magnet. Apply even pressure to the midwoofer with your thumb and middle finger in 6 o'clock 12 o'clock position. If you aren't able to move the cone it'll indicate that perhaps the magnet has shifted.
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Open em up and make sure the polyfill is stuffed up behind the mid driver and tweeter. None should be in the passive's chamber. When I forgot to put it back properly I lost almost all my bass.Just a dude doing dude-ly things
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If the midwoofer did not move with applied pressure to the radiator, then perhaps the midwoofer might have a shifted magnet. Apply even pressure to the midwoofer with your thumb and middle finger in 6 o'clock 12 o'clock position. If you aren't able to move the cone it'll indicate that perhaps the magnet has shifted.
When you say the magnet has shifted, is it just a matter of unscrewing the driver and re-aligning the magnet again by hand? -
whitemtntn wrote: »If the midwoofer did not move with applied pressure to the radiator, then perhaps the midwoofer might have a shifted magnet. Apply even pressure to the midwoofer with your thumb and middle finger in 6 o'clock 12 o'clock position. If you aren't able to move the cone it'll indicate that perhaps the magnet has shifted.
When you say the magnet has shifted, is it just a matter of unscrewing the driver and re-aligning the magnet again by hand?
nope not that easy. It would all need to be taken apart realigned and re-glued with the proper anaerobic glue -
To test the MW (mid-bass woofer) driver gently press in on the middle speaker (the MW) in the cabinet with your fingers spread apart just inside the surround so your depressing equally on each point. Press in about a 1/4 inch maybe a little more very slowly and listen for any scratching noise. If you hear it this indicates a shifted magnet, i.e. a bad driver. Be sure the music and power to the speaker is off when you do this. The bottom driver is not a true speaker, it is a non-powered passive radiator used by Polk as an alternative to an acoustic suspension loudspeaker. It's easier to buy a replacement MW driver than to try and fix it yourself. There are some here that will repair them. Also, check for air leaks and make sure the polyfill is not behind the bottom passive-radiator. Your model 7b should have only one fuse on the rear, this is for the tweeter only. Very early models had two fuses one for mid-bass as well.
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So-- I did the 1/4 inch press- no scratching noise. It depressed and sprung back fine. I opened speaker, made sure the poly fill was only behind the MW (it was). Magnets all look like they are lined up appropriately. Put everything back in, still, missing bass in the sound output. I have little Micca speakers that put out more bass than these. Weird. Only thing I can see is the gasket behind the drivers are pretty shot and maybe letting air escape.
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push in and hold the passive in the mid-woofer should come out and slowly return to rest in about 3sec. if it just drops back immediately then yes there is a leak and yes that will affect the bass response. If you push in on the passive and release it will cause the mid to be sucked back in. so push in and hold until the mid goes to rest.
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whitemtntn wrote: »Hi - I just inherited a pair of Monitor 7B's. Hooked them up and there is no bass coming from either speaker. There is sound coming from the woofers but no bass, you can't make out the bass guitar. The bottom passive speaker doesn't seem to be doing anything at all.
Any info appreciated- thank you!
You've gotten really good advice so far on these (IMO) excellent old(er) loudspeakers, and you've done the right things to test they hypotheses presented so far.
EDIT: Because of the passive radiator loading scheme these speakers use, a good seal is mandatory "for best results" -- if the gasket is leaky on any of the drivers of either speaker, that would probably be a problem (although the speaker presumably wouldn't pass the leak test already described).
With the caveat that it may simply be that the speakers are working fine but just don't perform to your expectations for bass (which is absolutely possible, although I would opine improbable
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three questions. maybe four.
1) What are you using for an amplifier?
2) How do you have the speakers located? They'll do best a little off the floor and a bit away from back and side walls if possible. Polk sold stands that positioned them fairly optimally back when they were new.
3) Have you tried listening to just one of the two speakers? It should be unlikely, but perhaps the polarity of one speaker as hooked to your amplifier (or receiver) is reversed relative to the other. In that case, bass would tend to cancel out. This is easily tested for by simply reversing the hookup ("+" and "-", or "red" and "black") of the two conductors of the cable going to one of the two speakers (and not reversing the other one's!).
4) Does your moniker refer to NH's White Mountains? If so, howdy from another New Hampsterite!
earlypolkfamilyportrait by Mark Hardy, on Flickr -
My amp is a Denon DRA-365R. I don't really have the speakers setup anywhere yet. I've moved them around for testing. Had them on a floor, then on a wooden box, not near wall. I did test with just one speaker, same result.
Does it make sense for both speakers to exhibit the same symptoms? Maybe it is just my ears... I don't think it's because of my expectations, the bass just seems to be missing, I can barely even make out the bass guitar. Perhaps it is the gaskets. What about the electronics?
Ha - no, nothing to do with New Hampshire. My last name translated from the German is White Mountain.
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That's a pretty low end receiver, the speakers deserve better.
The gaskets are supposed to be paper thin.
You have to set the speakers up properly, that's Audio 101.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 -
Are the woofers visibly moving?
Have you tried turning up bass control etc?
When you say "no" bass, do you mean literally Nothing at all or just not enough?
Even with mild air leaks there still would "Be" bass, but just reduced.
Any electronic crossovers that would filter bass etc? -
I'll spend a bit more time testing when I get home tonight and get back to you.
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"Some people find it easier to be conceited rather than correct."
"Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip -
here's some photos...
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Were any of the screws loose and not very tight ? Is that mark where you used the screwdriver or something to pry up the MW ? be careful tightening back up you could strip the holes out.
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Ummm...you sure you don't have the left and right channels wired out of phase of each other?
That wouldn't really make that much of an audible effect on anything over, say, 4500 Hz but anything under that, especially bass and sub-bass frequencies, they would cancel each other out at the listening position.Expert Moron Extraordinaire
You're just jealous 'cause the voices don't talk to you! -
the screws were pretty tight - I made them snug when i put them back. That mark might just be gasket debris.
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Oh, also, if you end up stripping the screw holes out, you can do one of two things.
You can rotate the speaker in the mounting spot and make new holes. I would highly recommend pilot holes at that point. Also, fill the old holes with wood glue. It won't affect your surrounds or anything and if you plug the hole with a toothpick after you filled it with glue, that will give the glue something to bond to. It should seal the hole up well enough that speaker gasket material will be effective over it.
The other option is a small dab of wood glue to hold a piece of toothpick in place in the hole. Let it dry, trim any extra toothpick sticking out of the hole with angle cutters or something then mount the speaker again. The toothpick will take up slack in the hole and give some stability to it so the screw has something to bite to so it can hold tension.Expert Moron Extraordinaire
You're just jealous 'cause the voices don't talk to you! -
Ummm...you sure you don't have the left and right channels wired out of phase of each other?
That wouldn't really make that much of an audible effect on anything over, say, 4500 Hz but anything under that, especially bass and sub-bass frequencies, they would cancel each other out at the listening position.
My first thought also, but he mentioned trying them one at a time with the same results.
Really curious what is determined and hopefully can help with his issues. -
In your first post you stated you "inherited" them. Does this mean from a relative/friend rather than garage sale/thrift? By asking this I am just wondering if the previous owner or family could pass along some previous information to you regarding when these were last used, did any one else hear them...
What is your basis of comparison? What did you use for sound reproduction prior to these?
Did you also acquire the Denon receiver with the Polk 7B's? If you had the Denon already what did you have connected to it for speakers?
Do you have another receiver you can try with the Polk's, or do you have another pair of speakers you can try with the Denon receiver?
Do you have the speakers connected to the Denon receiver on either the A or B connections correct and in phase?
We just need some additional information of what you've been using previously and how the Denon and Polk have been connected.
The speakers look fine and as you stated no frozen MW. But possible a air leak- when pushing in on the passive and holding it in, the MW did not extend slightly and return to normal position for 3-5 seconds as desired, in your case there was no movement of the MW, correct? This still would not (like K_M stated) cause virtually no bass, but just less deep bass.
We need to understand your listening habits also, some people are used to and want loud booming bass.
What type of speaker wire (copper/gauge) are you connecting the speakers with?
I have three pair of 7's, two like yours, they are still stock and produce strong bass even with moderately powered receivers like yours with tone controls set to flat with no equalization.
We are gladly trying to help. -
I got these speakers from my father-in-law. He hasn't used them for awhile. He had said they may need new fuses as they didn't sound right when he last used them, awhile back. But it's not the fuses as that only affects the tweeter, correct me if I'm wrong.. The Denon I've had for a long time, never had any issues with it. It usually serves my JBL HLS610's and Micca MB42X's - both of which produce plenty of bass. The JBL's in particular sound great, the Miccas are little speakers but still have much more bass than these Polks at the moment...
I have the JBLs connected in one room to the Denon A Connection and the Miccas connected in another room to the B connection. I unplugged the Miccas and plugged in the Polks for my testing. I tried the test with A connection on and off.
Really I'm not someone who likes booming bass. It's just noticeably missing from the sound.
I do notice tonight when I press in the passive radiator, air hisses out from behind the MW. The seal is not good.
The red plug is on the left (my left when I'm facing the back of the speaker)
I do have a 5.1 Denon AVR-2112CI receiver hooked up to my TV I can try.
What's involved in replacing the cap? What kind of $$?
Thank you for your help, appreciate it. -
If each speaker has only one fuse, yes, it should be for the tweeter.
Otherwise, without hearing them (i.e., how they differ from the other speakers you mention) I don't really have anything else to offer.
The lack of a seal may be all or most of your problem.
I think there are plenty of threads here on rehabbing these fine old(er) loudspeakers.
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No high no lows must be...
