have you modified your speakers?

DaveSen

Hey, forum. Please bear with me - I have some newbie questions and, although you may think they're dumb, I'd really like some knowledgeable answers.Thank you in advance. Last Fall I had to send a burned out tweeter from an RT55 back to Polk for replacement (it was under warranty). While dismantling the speaker it was pretty apparent, even to a non-speaker builder like me, that there is a lack of dampening/insulation material inside this speaker. A couple of rectangles of cheap polyester sheets folded behind each driver isn't much. I DO realize this is a budget speaker, per se, and that production costs have to be kept down. I was just a little surprised because even when my older brother MADE his own speakers in shop class, he did a better job than this! So, my question is this:Have YOU modified YOUR Polk speakers by adding higher-end polyfil (like the kind you can buy from Parts Express) and taking out the stock stuff? If so, HOW did you go about doing it? I just read all about the rear power port and the front acoustic resonance control port and their purposes, and I'm wondering exactly HOW I could add good polyfil without messing up those 2 ports. I looked at a lot of speaker-building projects on Parts Express (the photos are pretty cool) and I saw lots of guys stuffing polyfil to critical mass - but I think that would screw up a Polk with ports (common sense is telling me that). This is a pretty good speaker and you guys helped me find good stands for them. I'm thinking of sending the crossovers out to be rebuilt after the warranty runs out because I've heard that helps a lot. But, right now, I just want advice on this polyfil issue. Somebody must have done it with good results. If not, maybe there's a generic way of doing it. Any help you can give me would be appreciated. My parents will appreciate me getting my speakers off the kitchen table! Thanks, Dave

steveinaz

Be careful of over-stuffing. I would leave the speaker as is. The cabinets are tuned with a pre-determined amount of "damping" and changing this could change tuning.

F1nut

I have to agree with Steve, leave the fill alone. However, your crossover upgrade idea is a good one.

DaveSen

Thanks for the replies, guys. I DO understand that speaker cabinets and subwoofer cubes are "tuned", but have you seen the inside of these RT's? The walls are bare. The polyfil isn't even as good as the stuff that came with my little Infinity bookshelf speakers I had before the Polks. That can't be a good thing. Every speaker kit I see in the Parts Express catalog has better damping/insulating than these Polks. I'm no engineer, but wouldn't any sound coming from the BACK of the woofers (it does come from both front & back, right?) just bounce all around and end up making some "bad" noise? When I put them back together after getting my new tweeter, I put the polyfil back in exactly the same way Polk had built it. I guess it would be best to leave it as you say I should. I was just hoping somebody had luck with a better quality of fill. Thanks again. I'll just wait til the warranty runs out and do the crossover upgrade or start saving for some LSi9's.

DaveSen

Thanks ATCV,
Those are subs, right? If I do end up experimenting with fill down the road - I mean, if I absolutely MUST KNOW - I'll just add it loosely. I won't stuff it like a turkey!!! Somebody's had to have done something to their old Polks after upgrading to a better model. I can't be the only one who's curious around here. For now, I'll just enjoy the speakers as they are on the new stands I just bought. THAT was a cool improvement in itself.

mantis

My feelings are this,
I perfer to use the speakers no matter who made them the way they where designed.If you feel you can do better then build your own.
Binding post changes if they are broken,rewiring if they don't work anymore,changing drivers if they are blown.

There are so many other ways to get your system to sound it's best.

Dan

mantis

If it is not your thing, that is fine, but it is certainly not something to be discarded

Sean,
Others who do is completely fine with me.I feel that maybe those speakers are not the correct speakers for that person.

In cars making it faster or better is done in many ways.I was a 1/4 street racer for many years.

I feel I find upgrading wire,amps,sources and even the speakers yield my personal gains.rebuilding an amp or speaker isn't my cup of tea.I never had the desire to do so.

Just voicing my opnion

Dan

F1nut

As someone who knows the benefits of upgrading such things as wire, it's hard to believe that you couldn't see the benefits of upgrading the crossovers.

jmasterj

Hi DaveSen,

Welcome to the forum, This is a interesting topic. First let me say for the record I'm not in favor of making changes to my equipment. Thats not to say it can't be done, or that doing it might not yeld good results. I research the equipment and try to purchase the best performance for the price. This is in fact why we are here on this forum. Polk is by no means the best speaker on the market, however they do represent an excellent value. If you are not satisfied with your speakers, or just want better sound then I would suggest an upgrade. I don't get to really enjoy my system because I live in a apartment. But every now and then conditions are right and I can let them go. I am just amazed at what these speakers can do. Polk audio builds speakers, It's what they do. They spend many many hours on research and development. If more polyfil would improve the speakers I believe they would already have it. I say spend your time listening to the music, Let Matt spend his time building the speakers. If you still feel the need to improve buy some new ones...
Now thats my 2 cents. Good listening J

jcaut

Hi Dave,


Regarding the fill: Generally speaking, all speakers need SOME sort of fill inside to help absorb/dissipate the back wave from the woofer. Particularly with sealed designs, excess fill can be used to increase the apparent volume of the box. Sealed speakers are often stuffed 100% with polyfill, or the like, for this reason. Beyond that, things get a little more complicated. Vented speakers generally don't benefit from that much stuffing, as it tends to reduce output pretty significantly. Too much can also block airflow to the port(s) and make them not work as intended. (I recently took apart a set of Paradigm Mini Monitors that were 100% stuffed, so sometimes it IS done.) I'll concentrate on vented speakers here, since that's what you're working on, but most applies to sealed designs, as well. When a woofer is put into a box that is smaller than ideal (or, what is generally considered an "ideal" alignment), a peak is produced in the bass response. This, of course, varies a lot depending on the particular woofer you're talking about. The peak generally gets larger in amplitude and frequency, as the box gets smaller. Adding more stuffing tends to dampen this peak. With a vented design, creative port-tuning can sometimes be used to similar effect. Since overstuffing reduces output, most manufacturers only use as much as they NEED to. It's possible to design a vented speaker that NEEDS very little stuffing, so I wouldn't interpret the lack of excess fill in the 55's as being an indication of something WRONG with the speaker. Perhaps it just works better that way.

When I tested that Paradigm woofer I mentioned above, I found that the box it was in was quite a bit smaller than ideal. Perhaps that was the reason for all the Polyfill. The cabinet construction wasn't as good as any of the Polks I've seen, either, as far as I could tell.

Excess reflection of the back wave off the woofer will usually produce an anomaly in the impedance plot. I've run impedance curves on my RT55i's and I can't see anything unusual.

It can't hurt to experiment with it, and it's not hard to do. You might find that they sound better to you with more fill, and that's all that really matters. You could try more polyfill, or maybe some of the convoluted acoustic foam instead. I've used it on DIY speakers I've built. Some say it sounds better than the polyfill, for whatever reason.

Another tweak might be to apply a layer of that vinyl damping sheet material to the inner cabinet walls. That wouldn't affect the tune of the box--- It would just make the walls more inert, which would be a good thing. I think you had mentioned that previously.

Jason

madmax

Make the changes and monitor the results. If you are the type of person who can hear the difference and understand all the side affects and are able to be truthful with yourself as to the resulting sound quality then I say go for it. Be careful to use a large quantity of recorded material when listening for changes though. You can tweak the speaker for any given recording to make it sound better than it did with stock components but other material will suffer. This is a big gotcha that a lot of people never consider. As I've upgraded and tweaked I find that a different playlist sounds better with each change. When it ALL sounds better you've gotten somewhere.
madmax