Replacing sound proofing in cabniets

Are these speakers vented or sealed? At what frequency does the woofer cross over to the mid? Sean
>

NO fiberglass in a speaker with open vents.

Acoustic foam can work very well, especially since you can easily adhere it within the cabinet and vary the density through-out it. I would suggest covering the entire inside of the cabinet with a layer of low density foam and then stuffing the open chamber in the top end of the cabinet using the same material. That is, if the port is located in the bottom section.

From there, you can vary the amount and density of stuffing within the open area between the woofer and the port. Don't go crazy here as all you want is just enough to very loosely fill the open space.

Not only will this provide what is probably a far more natural sound, you may actually experience a slight increase in bass extension. If you find the presentation to be lacking mid-bass ( warmth ), reduce the amount of foam between the woofer and ports. Most people will tell you not to block the area between the ports and the woofer at all, but that is because they don't know what good sound is and are used to high levels of sonic colouration. By placing a small volume of low density foam between the woofer and the port, you minimize the contribution of the port above its' tuned frequency. In effect, the port works as a port and not as a "leaky hole" radiating sound above the frequency it was designed to work at.

As a side note, carpet pad can work, but there are quite a few different types and densities available. This can be really hit or miss, depending on the materials and densities used. Dacron, polyester fiberfill, "acousta-stuff", etc... can all be used, but low density foam is by far the easiest to work with. Sean
>

Richard: I agree that Fiberglass is typically a GREAT insulator inside of sealed speakers, but due to all of the health hazards and variables involved, i'm hesitant to recommend it unless i know exactly what's going on. After getting "bit" a few times, i've learned to ask questions before responding with answers. Not all dogs ( or questions ) are as friendly as they seem : ) Sean
>

As Barry aka "Bright Star Audio" mentioned, i typically do not advocate stuffing the port in any way, shape or form. That is, unless one is "experimenting" and does so in a fashion that is easily reversed.

Having said that, most mass produced and even many "audiophle approved" and "hand built" vented designs will benefit from what i've mentioned. As mentioned in another thread, i just got done doing this to a pair of speakers that currently retail for over $3K. The results were quite obvious and highly beneficial. For the record, these speakers were HIGHLY under-designed to begin with in almost every aspect. Even though they were poorly designed, lacked proper implimentation of the design, which resulted in them sounding like crap, they get rave reviews all the time. Sean
>

Trelja: Yes Joe, these were the Legacy's we were working on. We just got them finished tonight and are pretty happy with them. That is, considering what we started off with. They are like a completely different speaker now i.e. MUCH better sounding. They still have a "ported" sound to them, but you can't get rid of that without sealing them or using a more advanced bass alignment. This type of problem is especially hard to conceal when the designer crams TWO woofers into a box that is too small for just one of the woofers!!! All of these designs use a box that is just too darn small for the drivers being used, hence the bloated bass that lacks definition. Believe me, this is only a very small part of the problem too. I took pictures of the crossover network before and after. If i can figure out how to transfer these pics from my camera to my puter, i'll forward them over. As i mentioned in what was probably another thread, we were able to go from a total of 122 connections in the pair of crossovers down to 46 connections total!!! All of this by paying attention to how the crossover was laid out on the board. There were NO circuit changes made, so it's not like we changed the parts count in order to reduce the number of connections. Then again, i'm "preachin' to the choir" on this one, so i'll save it for a more appropriate time : )

Steveallen: Most vented designs can be drastically improved by adding damping materials internally. Very few vented designs make use of optimally sized boxes, so adding internal volume via damping material typically helps to reduce the output peak at resonance and smooth the overall response. This is because internal reflections are damped and the box appears to become "bigger", bringing the alignment closer to what the driver would optimally like to see. To top it off, this approach will typically produce increased clarity and definition due to the reduction of the aforementioned internal standing waves being reproduce and less leakage from the ports.

While i do agree with your suggestion to read this book, many people have read hundreds of books and even graduated from schools with a degree. Reading textbooks and passing tests vs knowing how to properly interpret and apply that information are two very different things. This is why we have so many speakers that sound like crap but look so good on paper. Even those that know how to talk the talk end up not knowing how to walk the walk due to a lack of understanding and experience. If this were not true, Trelja and i wouldn't have initially been impressed with what we read and saw about Legacy's, but we were. Wanting to believe and being able to believe are two different things, especially if you are honest with yourself. Sean
>

Barry: Neither Joe or myself are encouraging anyone to "stuff" their ports so much as we are encouraging additional damping material inside the cabinet.

Having said that, most vented boxes are pieces of junk and closing the ports completely could quite possibly produce better quality, albeit less quantity of sound. As such, yes, most people would be better off with different speakers than what they have, especially given the majority of under-designed, poorly executed, over-priced products that are currently available. Like most changes in society that have taken place over the years, the public seems to desire greater quantity, even if it is at the expense of quality. As such, the designers / engineers / manufacturers have responded to those desires and given the consumers higher sensitivity and greater extension at the expense of linearity and over-all quality. There are exceptions to this generalization, but that is why they ARE exceptions and are far and few between. Sean
>

You can't replicate the response of a transmission line with anything other than a transmission line and even then there are variables involved. Other than that, i try to avoid vents of any type as much as possible. If i had to choose out of what is commercially available, i typically prefer sealed low Q designs. Second would be an IB ( Infinite Baffle ) and third would be a stuffed or partially stuffed T-Line. Bringing up the rear in a very distant fourth place would be an aperiodic ( vario-vent ) design. Anything else would be WAY down the list. Sean
>

I have used it in a few cabinets. In the grander scheme of things, it is just about useless on a well designed cabinet. Other than to help seal any seams / cracks and help keep the cabinet "air-tight" if sealed, the benefits / results are far out-weighed via other simpler and less messy methods. Sean
>