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Discussion Starter · #1 ·
My bookshelf speakers allow you to plug up ports with a spongy foam to compensate for near-wall placement.


I have Sony sub with a rear port as well. 2 questions: is plugging its rear port going to control any excess boominess/peaks, and is this a safe thing to do for a subwoofer?
 

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Discussion Starter · #3 ·
Thanks bluesky - I don't recall the full details of the manual that came with this subwoofer 10 years ago, so I still am not sure if it's overall a safe practice to cover the port hole will soft foam or cotton material to tighten things up. In experimenting it certainly did tighten up the bass, but I just don't know how safe it potentially is over long term.
 

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Not harmful in the least bit. All you're doing is turning it into a sealed enclosure (as long as it is plugged tight with something that does not let air through). If you like the sound of it better then go for it.
 

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Quote:
Originally Posted by XanderMoser /forum/post/18262777


Not harmful in the least bit. All you're doing is turning it into a sealed enclosure (as long as it is plugged tight with something that does not let air through). If you like the sound of it better then go for it.

Sorry, but I have to disagree with you. Plugging the port of a subwoofer that is designed as a ported system will change the entire response characteristics of the sub. It will change the frequency response of the sub and may change how loud the sub is able to be played.


There are many subs that are designed to be used either way. My Hsu VTF-2 Mk 3 is one. I have the choice of leaving both ports open or blocking one port with a supplied plug. With both ports open, the sub will not go as low in its frequency response, but it gains 3 - 4 dB of headroom to allow it to play louder with the same input power. Plugging one port (and flipping a switch to change the electrical charateristics of the amp) allows it to go lower in frequency but not play as loud.


Plugging the port on a sub that is not designed to operate in this way may or may not change the frequency response of the sub and may require more power to play as loud which could result in overdriving the sub amp, causing distortion and breakup. If the OP cannot locate an owner's manual for the sub (either at hoem or on-line), I would not recommend doing this.
 

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Discussion Starter · #6 ·
2 differing opinions here.


Well I did locate the manual online for the Sony SA-WM40. It doesn't say anything about port or plugging.


bluesky - I have the same receiver as you do which means I'm running Audyssey Multi-EQ. I was hoping that plugging the port frankly would tighten the bass. Then when I ran Audyssey, it would have an easier job of flattening the curve.
 

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Go ahead and plug the port. If it sounds good to you, no worries. If it doesn't, take the plug out. Personally I think you will end up taking the plug back out. You should be able to tell right away if it is a bad idea or not. I don't think the power requirement are going to change so drastically that you will have immediate failure of either your sub amp or driver.


bluesky is just playing it safe and he was just reinforcing the point that your sub wasn't designed for sealed operation. However as he attempted to allude to, if you find yourself needing to crank up the sub level a great deal to obtain the same volume it may not be such a good idea.
 

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Discussion Starter · #10 ·
Thanks, Ratman! That was a great find. I read something about this earlier today in researching this, but there wasn't as much info as there is on this link. I think this might be the way to go. I will try it out and let you all know how it works.


Thanks!
 

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When designing a subwoofer, there's interplay between the mechanical properties of the woofer being used and the size and type of enclosure (ported or sealed). The magic is mating the proper woofer to the proper enclosure to get the desired performance from the combination. Often the main trade-off is power vs low-end extension (meaning the ability to reproduce low low bass, such as the LFE effects in movies.) If you plug up the port of a pre-designed subwoofer enclosure, you are changing properties of the enclosure. This means you just changed the design. It may be for the better, it may be for the worse. The best way to tell objectively is to measure the subwoofer's performance before and after the change, and make your decision based on that. Of course you could just go by ear, but be aware that that is more about "pleasing" sound than "accurate" sound.
 

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I have this same sub and I've filled it with polyfill - worked great and improved the sound considerably. The trick is how much polyfill to use. At first, I put too much inside the cavity and it sounded funny. I took it apart again and only used 1/2 bag so it wasn't so dense and kept the polyfill away from the port and the driver. Try it and I think you'll be surprised how good it works.
 

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Discussion Starter · #13 ·
Kurolicious - did you also apply the modge podge to the cone? I've been told to try that in addition to the polyfill.


How big a polyfill bag did you use, was it the 20 oz. bag?


I've always noticed this sub to be boomy, but I assumed all subs were like this sans treatment. I've also noticed that phase must be set on "reverse" for every setup I've had with this sub in order to evenly fill in everything up to 80Hz.
 

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Quote:
Originally Posted by Napoleon D /forum/post/18272568


Kurolicious - did you also apply the modge podge to the cone? I've been told to try that in addition to the polyfill.


How big a polyfill bag did you use, was it the 20 oz. bag?


I've always noticed this sub to be boomy, but I assumed all subs were like this sans treatment. I've also noticed that phase must be set on "reverse" for every setup I've had with this sub in order to evenly fill in everything up to 80Hz.

No, I only used polyfill, nothing else. Honestly, I don't recall the size of the bag but 20 oz sounds about right. I have tried the reverse phase but didn't care for it so I keep it on normal. The only time I noticed a boomy sound was when it was up too loud. Ever since I got an SPL meter and calibrated all the channels to 75 db, the sub blends beautifully with my other speakers. Also, the placement of the sub makes a big difference. The farther away from the walls or corners I have it, the tighter the bass is.
 

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Discussion Starter · #15 ·

Quote:
No, I only used polyfill, nothing else. Honestly, I don't recall the size of the bag but 20 oz sounds about right. I have tried the reverse phase but didn't care for it so I keep it on normal. The only time I noticed a boomy sound was when it was up too loud. Ever since I got an SPL meter and calibrated all the channels to 75 db, the sub blends beautifully with my other speakers. Also, the placement of the sub makes a big difference. The farther away from the walls or corners I have it, the tighter the bass is.

I have a 20 oz bag so I'll use about half of it. That sounds about right with placement. For phase, I noticed a large dip on phase "normal" in the 50-80Hz range. The bass was deeper, but it dropped off fast the higher it went and did not blend well with speakers crossed over even at 80Hz. "Reverse" was not quite as deep a bass, but it filled in that middle and seemed to blend much better with everything. It could be a placement issue, but it's been like this each time.
 

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Quote:
Originally Posted by Napoleon D /forum/post/18273175


I have a 20 oz bag so I'll use about half of it. That sounds about right with placement. For phase, I noticed a large dip on phase "normal" in the 50-80Hz range. The bass was deeper, but it dropped off fast the higher it went and did not blend well with speakers crossed over even at 80Hz. "Reverse" was not quite as deep a bass, but it filled in that middle and seemed to blend much better with everything. It could be a placement issue, but it's been like this each time.

That's exactly what the switch is for. Each setup will be different. How the sub blends with the mains all depends on the distance between each speaker and the sub, the room acoustics, the frequency response of both the mains and the sub, and the phase response of both the mains and the sub. Among other things which I am sure I am overlooking at the moment.
 

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Discussion Starter · #17 ·
Well, I'm not sure how any of you got the screws out of this subwoofer. I literally just destroyed a screwdriver trying to get one of them off, and am starting to strip the screws themselves. These things are screwed in tighter than the bolts in a dam. I will probably buy another screwdriver but it may be a lost cause. I even have a batting glove on doing this. If I can't get these off, I may just look into another sub as it has been 10 years. I'll get something that doesn't have the same natural boominess to it, that is a little more smooth.


**UPDATE: Got a far more sturdy phillips-head and everything came off. Got just about half of that 20 oz bag in there as instructed. Kept it reasonably thick but not dense on all walls leaving room for driver and porthole. Results: on first notice there seems to be a bit more of a sharper, chest-thumping, bass. It sounds as if it's reaching a bit deeper than it did before. I would say I like it better. It seems to be about the exact same volume as before, as I measured bass peaks in a couple of movie scenes - comparing the before and after adding polyfill. One of the peaks I measured was a decibel or 2 louder after than it was before. I'm measuring the first explosion of the MI-3 bridge scene. I wonder if this is because there is a bit more bass extension than before.


Overall though, bass seems to be somewhat tighter which was my number one goal, but it still can get better I think. I'll have to give it some time to take it all in. It is a definite improvement though.
 

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Discussion Starter · #18 ·
Another update: I not only lined the subwoofer enclosure with polyfil, but also applied a couple coats of modge podge to both sides of just the cone - a modification which is recommended for this model across the internet. I then plugged ports of all 5 of my Energy C-100 and C-C100 speakers - which are recommended to be plugged if bass is too boomy, and my room isn't very large. I then re-ran Audyssey after all mods and adjustments. Audyssey/Onkyo crossed the plugged speakers at 50-80Hz so bass was ample.


I now know why people comment on the lack of bass in Audyssey, and this is why I think I like what I've done. To me, bass in a movie sountrack is not supposed to overwhelm the soundtrack as it should balanced with the rest of the tones, and only call attention to itself in the loudest of effects. From what I'm hearing now, the bass in my system now is so tight that it is barely audible. To be honest, I think plugging the speakers did as much for me as the work on the subwoofer. The lowest peaks seem much more tamed, if not quieter. And those mid-bass peaks that came in loud waves aren't assaulting my ears now.
 
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