My former speakers: B&W 805s came with a foam plug to modify the output of the port. I tended to use them without the foam plug. And without the grills too.
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my room has an open wall which leads to the kitchen and the opposite side is closed in. after running some test tones with a decibel meter i noticed i had a 13db boost between 40-50hz. i stuffed the port on the speaker near the closed in area and reduced it by 9db. i am now within 5db from 38hz to 80hz.
I had B&W P6s with foam port plug that I used to good effect.
I loosely obstruct the ports of my Dynaudio Contour 1.3mkiis and OHM 100S3 Super Walsh 2s in my wife's sunroom, which is 12X12 with cathedral ceilings in that the speakers are relatively close to the rear walls and the bass can be too much otherwise in there.
My smaller less bass heavy Triangle Titus XS monitors run with ports unobstructed when in that room.
I do not obstruct the ports with the same speakers in my 12X12 office with conventional ceilings directly below the sunroom.
My point being that obstructing ports to various degrees can be an effective tool to help tune a speaker to room better if needed.
If your bass is booming you can improve the sound by blocking the ports on bass reflex speakers. The only speakers I've needed to block the ports on had raw cotton fiber in them (PSB Stratus). I tried the foam from an equipment box I had but it did not give the result I wanted. I looked around but could not find any raw cotton fiber so I went to a fabric store and bought some pillow stuffing fiber which worked very well. Hope this helps. Happy listening.
Using plastic straws on my Mirage M3's changed nothing until there was a sustained bass note like a pipe organ, for example. The straws then prevented the woofer from oscillating. The improvement in such cases is dramatic. The Reference Recording "Star of Wonder" has such a sustained bass at the beginning of the "Nativity Carol".
I think ports are used strictly to achieve lower freqs. instead of increasing the size of the box. That said, assuming correct, does stuffing the ports change any other characteristics of the sound other than just low freq. output? For example, if the drivers being ported are also intended for mid freqs., would mid freq sound be affected as well in any way?
"f a speaker was designed to operate with a port, how can it be correct to plug the port, thereby making it a virtually sealed box? "
Plugging the port is an extreme case.
The effective approach is to restrict the air flow through the port to various degrees in order to reduce the energy level at the low frequencies the port is designed to enhance to various degrees as well, more or less like a specialized type of bass tone control.
Good speakers are designed to perform well in a variety of rooms however the room acoustics largely determine the results regarding the bass region to which ports are directed. Obstructing the port to some degree (as opposed to blocking it which is the extreme case) can be looked at as a way to fine tune the design of the speaker to best match the room. This does not defeat the design in any way if done right, it merely adapts it better to the room and teh listeners location within it. Its another (easy and practical) thing that can be done to better match the speaker to the listener's environment, along with tweaking speaker location and toe-in, room treatments, etc.
I would say it is ill advised for anybody to be spending money on upgrading equipment until they have done everything they can first to optimize the sound of what they have in the listener's environment. That is the key to good sound in most cases. Obstructing the port to various degrees is just one weapon in your arsenal if your speakers are ported.
Rather than follow some dogma about what is the right and wrong way to approach audiophile sound, try tweaks like this that are easy and cheap to implement and painlessly reversible as well if needed and let your own ears be the judge, which is all that matters.
The benefit of the bundled straw approach is that you can adjust its affect by adjusting which straws extend in or out in comparison to the other straws. I would bundle the straws and then tape or secure them together as a single bunch (around the perimiter), leaving all the straws (except the outer layer) free to be adjusted. I would start with them all the same length, but then you can adjust a certain percentage either in or out farther to adjust the results of their use. I would definately recommend trying this approach, it is virtually free (as is port stuffing in general). The speakers I own (Gemme Katana's) come with a port insert (that reduces the overall size of the port) and when installed delivers tighter bass vs. a more boomy bass without them installed (in my room at least). Using the straw bundle approach should produce two affects; 1 - reducing the overall size of the port and 2 - providing for some tuning of the port.
Just checking out your system, and on 11/14 you were really excited. So what happened? Sometimes, a change that initially sounds better will sound inferior after a period of time. Sometimes one change begets another. You could try re-positioning the speakers or try some different interconnects, or go back to your old tubes.
I don't think stuffing the ports of a speaker designed as a ported speaker with whatever material comes to hand or has received someones personal rave will accomplish anything musically satisfying.
Response to the "leave it as designed" argument. Simply make a list of the designer's problems:
1. Which shape, size and furnishings in the room?
2. Used with what equipment?
3. How close will actual production be to my specs?
4. What safety factors must I provide so that abusive idiots will not return the item and reduce profits thereby putting me out of a job??
5. What will the reviewers say?
Compare these with my problem of simply how to make it sound best to me in my room with my stuff.
My experience has been that the best sound is achieved either when a good dealer does the whole setup, or when the consumer tries every suggestion that does not result in personal injury.
Rhljazz - Overall I am very satisfied with the improvements the NOS tubes have provided - they are NOT coming out. However, they do seem to provide deeper and bigger bass so am wondering if this is causing any issues with my drivers (only 6.5" poly) as I think mid bass is sounding slightly distorted now - not exactly positive as have not had enough time lately to properly evaluate. Since I have a pair of powered subs, which never break a sweat as they are rolled in very low freq., am curious what it might sound like if they were given a more prominent role in the mix. Which I intend on trying just for fun and thought one way to do this would be to stuff the ports and raise the x-over. But I certainly do not want to mess up the mid freqs. the mains supply, or the speaker's ability to image well. Thought I'd get some input prior to trying (I am not a tinkerer so prefer to have only a few options to try rather than running the gamut myself.)
My HSU subwoofer, operating on the same principles as all other ported bass enclosures comes with a SINGLE dense foam plug for one of TWO ports.
The sub is provided with a switch for 1port / 2port operation. I don't know what the internal circuit changes entail.
The manual says the switch is for 'Maximum extension mode' and 'Maximum output mode'
Not that it matters, but I run maximum extension mode, since I rarely go to nose-bleed levels.
Any blockage of a port will roll off the bottom of your speaker sooner, Your speaker will not go as low in frequency! If your speaker is truly "Boomy", you might try removing the port and replacing it with a longer one. The longer the port, the lower the tuned frequency which will lower the frequency hump. If your port is too long, you will change your hump to a dip. If at at all possible, I really recommend moving the speaker, trying to remove room boundry reinforcement and not mess with the design of the speaker.
But if you must block the port, Material matters on each application, just because a pair of pajamas was ok on one speaker in one room in Australia, doesn't mean the same application will work on a different speaker in a different room in Ohio. The amount of air escaping will change the tuning frequency, so a sponge will sound different than cardboard or pajamas. Good Listening, Tim
"Changing a ported design to a sealed without understanding design or knowing specs on driver etc shows a miss understanding of loudspeaker design. "
It's redundant to say not understanding design shows a misunderstanding of design. Not much insight there....
My very limited understanding of speaker design will only get me so far. Plus, good design alone is not guaranteed to float my boat, so I have to trust my ears.
Sorry about the delayed response to the follow up question. By having a bundle of straws with the bundle sized to fit the port, they when pushed in, the outside diameter of the port holds them securely in place. The bundle is round, with tape only around the outer perimeter. This is really a two person job, one holds the bundle in the round position and the other tapes around them.
Once the tape is applied, you can push the straws that aren't taped, ie. those toward the center versus the outer layer either in or out (so to speak). Since the bundle of straws are only held in due to the tight fit, you can easily pull the whole bunch out from the port at any time and may find it easier then adjusting how many straws are pulled out or pushed in.
Imagine holding a bunch of straws clamped in your hand. Your hand only comes into contact with the outer layer. The inner layers can be slid in/out while still holding onto the outer layer.
I hope this is clear. You may find that standard straws are longer than you want, but you can always cut them down to different lengths. There is actually a speaker manufacturer that provides such a device for tuning their port - I don't remember the brand and I am sure they use something that at least looks nicer than drinking straws.
This approach does not "close" the port making a sealed design. It does reduce the total opening and the way the air interacts to some degree. There are lots of speaker mfgs. that offer partial port inserts for tuning (my Gemme's and Wilson speakers are two examples of companies that do this). The straws have a similar affect, but actually provide for more variability than just a simple insert that reduces the diameter of the outlet.
One of the funniest things I ever saw... This was about 25 years ago. Started off being silly, rigged up a "recycled", cast iron, claw foot tub, a 2' thick pine table top, C-clamps, and a 18" "subwoofer" for this theater. Hey, that was the budget we had to work with. Anyways, my partner and myself were listening and snickering, trying to get this monstrosity to work. We talked about plugging the tub drain when my partner had an idea. This tub sat under the screen and I went to work behind the screen. When I came back and we cranked it up, he had put the drain pipe back on and duct-taped a condom onto it. Took a while to stop laughing but it actually did sound better. Covered it back up and left it there.
Went back years later to watch this action flick, (Rambo, Terminator, I forget) but I was the only one laughing as the bombs blew up.
I have a total of 5 B&W 805S speakers in my bedroom 5.1 system. I use the supplied foam port plugs on all five. I did this to better integrate the 805S's with my dual B&W ASW800 subwoofers.
I have tried this system both with and without the plugs. Here is my take. If you are using the speakers without the B&W subs then they are best without the plugs. This set up gives deeper bass (such as it is). However, with subs, the plugs allow a smoother integration with the subs.
BTW, this is an incredible little system. The 805S's are excellent within the limitations imposed by their small size.
You are talking about a very different animal with your B&W's. They are designed for the plug to properly roll off the bass to integrate the subwoofer... B&W knew the outcome of your plug before you ever thought about plugging them... The principle is the same for stuffing the port on any speaker, it will roll off the bottom....period.
What it comes down to really, is, you won't cause any damage stuffing ports, if you like the results, sit in front of them and enjoy. Good Listening, Tim
Yes you are right. B&W is pretty smart. The result is the 805S's and the subs integrate seamlessly. When Stereophile's John Atkinson reviewed my speakers he ran curves with the ports both unstuffed and stuffed. While neither he or B&W gave any guidence concerning when or why to use the port plugs, it was semi-obvious what was intended. Note that not only is the low frequency response decreased somewhat with the plugs (to close to a acoustic suspension alignment), the response is also smoothed with the typical port hump reduced to almost zero. This is the desired result to integrate the subwoofers.