[Ironman]

I have a Yamaha 6.5" 6 ohm 25 watt subwoofer.  It has an enclosure with an amp.  It is model YST SW012  120 watt powered sub.   
My issue is the voice coil is incorrectly installed.  One side is about 1/8 of an inch from the voice coil, and the other side is about 1/4 inch of a gap.  I know simple glue of sorts would fix it.  What would be the best way to get it apart?  It sounds terrible with low tones and when there is some power behind it.  Obviously because it is so crooked on the voice coil.  Thanks in advance!

[UpperCut]

Before going all out why not look first at the non existing relation Amp / Speaker - to each other! I assume you are talking about Watts not RMS Watts, but even so 25 Watts for a 6.5 speaker which you like to call a Subwoofer to a 120 Watt amp is well say it this way not working simple because it can’t. rgs UpperCut

[Letitroll98]

Did it sound good at one time and now it's misbehaving, or did it come out of the box this way?  In either case, would you be willing to move on to a larger sub?  I think what UC was saying above is that it may not be worth it to try and repair, it's never going to sound like an even slightly larger, more powerful unit would.  Valid point, but I'd like to hear more about your side of the story.  Things like are you looking to have some fun and learn a few things about speakers, or are you really just throwing good money after bad?  How do you look at it?

[srb]

I assume you are talking about Watts not RMS Watts, but even so 25 Watts for a 6.5 speaker which you like to call a Subwoofer ..... to a 120 Watt amp is well say it this way not working simple because it can’t.

Actually, it's the manufacturer that calls it a "Subwoofer System".  If it is in fact a Yamaha YST-SW012, it  contains an 8" driver and a 50W (100W Dynamic Power) amplifier.

Edit:  It has now been revealed that it is not the YST-SW012, but is actually the Yamaha model YST-SW015, which does have a 6.5" driver.

Yes it's an inexpensive $100 subwoofer, but should be able to add some bass reinforcement within the obvious limitations of its output.

I'm also a little unclear as to how the voice coil came to be uncentered and is the "terrible sound" due to the voice coil actually rubbing or is it distorting when being driven beyond its capability?

Steve

[UpperCut]

Actually, it's the manufacturer that calls it a "Subwoofer System".  If it is in fact a Yamaha YST-SW012, it  contains an 8" driver and a 50W (100W Dynamic Power) amplifier.  Yes it's an inexpensive $100 subwoofer, but should be able to add some bass reinforcement within the obvious limitations of its output.

I'm also a little unclear as to how the voice coil came to be uncentered and is the "terrible sound" due to the voice coil actually rubbing or is it distorting when being driven beyond its capability?

Steve

I do understand that! and if it would be the other way around (like speaker 100 Watt & amp 25 or even 50 Watt maybe not to bad yet not ideal, but 25 Watt that is the problem!!!) that would ask it simple to jump out of its socket!!!

And well, you said it yourself it is for sure driven beyond its capabilities. rgs UpperCut

[Ironman]

The sub initially and at lower output levels sounded good.  Filled the room well.  I was quite amazed it being a 120 watt 6.5 inch woofer or sub woofer that it produced such rich lows.  I have a much larger sub in the living room and it sounds pretty good side by side.  With that said, I bought it used.  So I was taken a bit on the deal.   I got it, 6 speakers, and a receiver for the sum of $100.  So I am not that torn up about it.  Just would like to fix it.  The voice coil is causing a distorted sound when to much power is applied.  When I looked it over I noticed that the cone and voice coils well mis- aligned.   

[Ironman]

As far as the ratings of the speaker/amp.  It is bizarre.  The speaker says 25 watts on the back.  I am assuming that cannot be peak.  It goes way beyond that level.   The 120 watt amp, is what the manufacturer claims, and it might be so.  Being it is a 6 ohm system,  I may be hard pressed to find a 6 ohm replacement speaker for it.   

[mresseguie]

Ironman,

By any chance are the 6 speakers and a receiver from a "Home Theater in a box" 5.1 system? Can you post pictures of the subwoofer and the other speakers?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Separate from what you might answer to the above question, I would encourage you to determine how much you can afford in order to seriously consider buying a better subwoofer.

Michael

[Ironman]

Probably was, I bought it used.  Good speakers.  You can buy the speakers individually.  The sub is no loner made.  Its not a screamer of a sub.  But I am turning it up all the way outside here and its not acting up.  Pretty loud.  But not as good as in the house with the stereo.
  Yamaha 5740 85w per channel nice receiver.  I think it was a wire making a lot of the noise.  The one inside the sub enclosure. 

[Ironman]

Now I am getting another sound like something is else is loose now that I can turn it up more.     I will take it a part and see if I can shut this wire up more, and see if I can find a cause.   My 10 inch sub walks all over this one.  So yeah, I know it is not the biggest of beast.

[mresseguie]

Oops!

[mresseguie]

Advanced YST II (Yamaha Active Servo Technology II)
Front-firing active subwoofer
Linear Port for minimizing extraneous noise
8” cone driver with magnetic shielding
High 100W dynamic power
28–200Hz low frequency response

http://usa.yamaha.com/products/audio-visual/speaker-systems/subwoofers/yst-sw012_black__u/

[Ironman]

No, it is the Yst SW 015  120 Watt 6.5 inch sub.  Sounds actually pretty good for what it is.  The cab helps it a lot.  Out side of the cab, you can barely hear the thing.  The good part about it, is that it is small and  pretty effective.  I highly recommend these at just $100 if you can find them at that price.  The same model in 270 watts has got to be amazing.   I put links down below.   I would definitely want the bigger more powerful version of this subwoofer.   It reflects the bass really evenly through the room.  Despite its size, it has a heck of a kick.  Also, the mains that came with the 6.1 system can give my 15 inch MCS towers a run for their money.  They have a lot of depth in those little cabs.  I would love a couple more of those speakers for sure.  Great sound quality.   

[Ironman]

http://usa.yamaha.com/products/audio-visual/speaker-systems/subwoofers/yst-sw015/   This is the sub. 
This is the complete set.   I guess it is saying 100 W per channel http://www.amazon.com/dp/B0001XAJDO/  It has quite a punch to it though.

[srb]

Just a note on the variation of Yamaha power specs:

Although the YST-SW015 product page says "QD-Bass 120W Powered Subwoofer", the manual states that the amplifier output is 70W @ 5ohms.  As the maximum power consumption is also listed as 70W, it's doubtful that the 70W output is RMS.

And the HTR-5740 receiver, although referred to as "100W X 6", is specified in the manual as 85W RMS per channel at 8ohms, but with a maximum power consumption of 350W, that is somewhat questionable also.

Steve

[Ironman]

You are saying it says 5 ohms?   I measured the actual speaker to be like 6.4 ohms.   I do not have a copy of the manual on the speakers, let alone the subwoofer.   I would love one on each of them.   In the actual manual on the stereo it states  85 Watts RMS x6  20hz- 28khz  I want to run towers on it.  I have two MCS towers that can handle anything that amp can toss at them.  Just having a heck of a time figuring how to get that much bass into the Yamaha mains, which I know can handle the bass, I tested them on another receiver.  Which I would love how to put more bass to the mains.  They can hack it.   It has a section that allows you to apply bass to the sub, mains or both.  Then a section to change the crossover which I do not understand.   My speakers (Yamaha towers) are rated at 55hz-27khz I believe it is.  With bass being applied to the main only.  I am lucky to hear 120hz maybe.   Outside, they were getting down into the 55 hz range easy.  So I know there is some setting I am missing.   I want to bypass that part of the set up, send bass to the mains, and the sub or subs.   Also, if my sub amp is producing at 5 ohms, wouldn't a 4 ohm speaker be safe for the system?  Its pretty close. 

[srb]

You are saying it says 5 ohms?   I measured the actual speaker to be like 6.4 ohms.

Although the subwoofer amp is specified to output 70W @ 5ohms, the actual impedance of the driver could be different.  If your ohmmeter is accurate, then the amplifier would likely produce less than 70W into a higher impedance load than 5 ohms.

Because the Yamaha sub is a servo system, you probably would not want to replace the driver with anything other than the exact replacement driver.  I don't know if the servo circuit uses a secondary coil in the driver or just a sensor glued to the cone or other part of the driver.

I do not have a copy of the manual on the speakers, let alone the subwoofer.  I would love one on each of them.

Not sure which speakers you are referring to but most Yamaha manuals are available from the Yamaha website by clicking the Support tab on the relevant product page.

Yamaha YST-SW015
http://download.yamaha.com/api/asset/file/?language=en&site=usa.yamaha.com&asset_id=35257

If you want to run your front main speakers full range, then you will have to set the front speakers (FRONT) to Large in the Sound Menu (page 46 in the HTR-5740 manual).  You may want to set your Center and Surround speakers to Small.

Regular bass (other than the .1 LFE effects channel) is normally not sent to the subwoofer for speaker channels that are set to Large, but if you want additional bass sent to the subwoofer, you can set the Subwoofer (BASS OUT) to BOTH.

You might also want to experiment with the crossover (CossOver) setting in the receiver.  The default is 80Hz, but you could try a setting one lower or one higher.  Using the crossover setting in the receiver is probably more accurate than setting the crossover frequency on the subwoofer.  There is no crossover defeat switch on the subwoofer, so set the High Cut knob on the subwoofer to maximum (150Hz) to "get it out of the way".

Read through all the speaker settings in the manual a few times and you will probably be able to tune them to your liking.

Steve

[Ironman]

What is the LFE and all that?   Also, it has an eq section that really does not effect the sound too much.   I have a manual but they are pretty vague on things.    I want the 20hz and up on my mains.  I went from a late 90s receiver to this thing.  Wow, what a difference.  I know this thing has nothing compared to the latest greatest stuff out there.   If I am running a Large speaker, and a small speaker for my mains, will the system notice the difference?  It is also switchable from 6-8 ohms, which I would run 8 on the towers.   Thanks for the link by the way. 

[srb]

What is the LFE and all that?

LFE stands for Low Frequency Effects and is a separate discrete channel in video sound formats (Dolby Digital and DTS) and is the ".1" in formats such as "5.1" or "6.1".

It's up to the TV or Movie producer to determine what is regular bass and what is specific LFE effects bass.  Setting a speaker to "Large" means it will not have any low-pass crossover applied to it and will receive a full-range signal.  If your main speaker can produce 20Hz (not too likely) and 20Hz exists in the program material (also not too likely), then you will hear it.

LFE low frequency sound effects (thunder, explosions, dinosaur stomping, etc.) are best reproduced by a dedicated subwoofer (usually larger than 6.5"!) rather than a main speaker and are usually conveyed on the .1 LFE channel.

If you set a receiver to NO subwoofer, then the LFE channel might be mixed into the front speaker channels.

Steve

[Ironman]

We have wires crossed.    The 20 hz is the receiver portion, not the speaker.  The speakers with this unit are rated 55hz and up.  20hz mains, that would be a pretty interesting speaker.
  Til you owned this little Yamaha 6.5, you don't know what it is capable of. It is well worth a $100 bill.  Quite impressive for a tiny speaker.   As I said I have much larger subs laying around.  I know what much larger speakers sound like and what they can do.