Speaker Cabinet Fill?

msg

I have a pair of BIC DV62sib bookshelf speakers I was playing with and am going to gift. I was working on them a while back and think I pitched the polyfill. There wasn't much in there.

Generally speaking, for speaker "upgrades"...
What type of fill material should I use in the cabinets?
How much material should I put in?

It's a rear ported speaker. Do I stuff it full, or do I have to leave a path of some sort between the main driver and port?

History: I read a long time ago about a mod for these speakers, and sent the little crossovers to a guy to "upgrade". As part of his process, he recommends lining all the sides with fiberglass insulation, and a small flap for the back of the tweeter inside the cabinet. I hate working with fiberglass, so I never got around to it. I'm clearing out some stuff and planning to send these to my brother and he has a small child, so I don't really like the idea of fiberglass in a ported speaker, but I don't know anything about this, so...

Let me know what you guys think, thanks.

pitdogg2

no fiberglass it can chuff out the port. go to wally world and get a bag of polyfill or if you have a local upholstery business see if they will sell you some dacron roll it up and stuff behind the tweeter but keep away from the port and woofer

Face

No need to get itchy: http://www.homedepot.com/p/UltraTouch-16-in-x-48-in-Denim-Insulation-Multi-Purpose-Roll-60301-16482/202709974

Since your speakers are ported, I wouldn't recommend filling them with polyfill.

msg

Thanks guys. After reading PD's post and talking to WMG, I ended up finding some 10oz Dacron at a local fabric shop. They had all kinds of neat stuff - foams and such.

Regarding the speakers, I wasn't really sure where to place the insulation, but found a few threads out there. Face - I think I saw you in one of the threads over on PE? Do you do a lot of speaker building? I'll check out the denim stuff maybe for the next project.

I ended up lining the entire interior with the exception of the baffle.

Should I be concerned for proximity of the insulation to the crossover, and fire risk? Doesn't seem likely, but I don't know nothin' from nothin' here.

msg

As far as sound goes, I think I'm probably just a bit spoiled, but I can't really call these a favorite speaker. They're okay, but just okay. I'm finding them a bit muddy. I started this a year and a half ago, and just never got around to finishing, mostly because I didn't want to mess with the fiberglass. I hate working with that stuff, and just couldn't be bothered with it. Point is, I don't really remember how they sounded before the crossover upgrade.

I did run them for a while the other day with just the oe insulation loosely suspended inside, but I can't say whether they're profoundly different now with the the insulation. They do seem tighter. Almost too tight, actually. Restrained comes to mind. They're smooth up top, and once settled in with the sound, they're not bad, and I could see kicking back with them for relaxed background listening. It's just that they don't compare to speakers in a different class.

I thought last night about removing the insulation from the lower half of the cabinet to see if that loosens things up a bit, but then found all this community contribution saying how hifi use ported speakers should be insulated on all five sides internally?

msg

I just found my old correspondence regarding the crossover upgrade. It seemed more like a redesign mod than an upgrade. I should have followed through on all of this long ago to more properly compare. Looking back, I think I would have preferred to just go with keeping the existing component values and just upgrading with better quality components. At the time, I didn't know how to solder at all, and decided I was willing to give it a shot as an experiment to satisfy curiosity about this variation of another mod I kept reading about for these speakers, accepting that I may be writing them off as total loss if it didn't work out. Nothing against the guy who did this mod for me. He's had lots of great feedback on this design, and he wouldn't accept any money for his time/design; I only bought parts and paid shipping both ways.

1. Remove the tweeter coil which changes the tweeter circuit into a 1st order filter.
2. Increase the tweeter series cap from 2.7 to 3.4 uf (3.3 + 0.1).
3. Replace the 1.5 ohm tweeter series resistor with a 12 ohm.
4. Top off by replacing the 3.3 uf woofer bypass cap to a 0.1 uf.
5. Clarity caps and Mundorf resistors on the tweeter series
6. Solen caps on the woofer bypass

When done it sounds like a completely different speaker. It has a warm, rich sound. It increases the bass especially the upper mid bass. There is a smooth transition from woofer to tweeter. This makes the speaker sound more like 3 ways. The mids especially the upper mids are much more prominent.

This is the original crossover


This is the modified crossover

westmassguy

Glad you got your feet wet

msg

I'll do the grunt work, but will leave the big stuff to the experts

msg

Just had to post back that I have these running for further testing in the spare room, and with a little room placement assistance, they don't sound so restrained and aren't too bad for what they are. Granted, they're running in a "real" system now, as well, but they do okay. I have no idea what difference those mods made. Thanks to all you folks tolerating my neuroses.

I think I'm channeling @afterburnt this eve...
Bruce! whey you at?!?

pitdogg2

For what it's worth egg crate foam also works well just something to keep in mind. My cerwin Vega D7's came from the factory nude inside stapled some egg crate foam in them and it made a big difference. But they also went bye bye a long time ago.

westmassguy

pitdogg2 wrote: »

For what it's worth egg crate foam also works well just something to keep in mind. My cerwin Vega D7's came from the factory nude inside stapled some egg crate foam in them and it made a big difference. But they also went bye bye a long time ago.

I'm offended. I'm going to my safe place.

pitdogg2

Good thing I didn't use a strap on

Lol

msg

lol ah jeez... I get the best education here from you guys.

I'm reporting back with once again a contradictory observation.
After listening my regular system most of the morning, I just walked into the spare room with the modded DV62si's running to get something. gyah, no. they're just... I don't know. I can settle into the sound after a while if that's all I'm listening to, but coming from another system to the one running these speakers, no. They just sound... I don't know... really dirtied up is about the best I can describe it. It's like they're running on a system with an EQ set to a broad and fat midrange bump.

If I still had the oe components I'd revert them to spec, but I don't. This is why I always keep oe parts whenever I mod something, and why I am really particularly about letting people work on my stuff. Generally speaking, not just audio.

westmassguy

Sorry to hear Scott. I don't know the designers qualifications, but he made significant changes to the crossover, and I don't get the " This makes the speaker sound more like 3 ways" comment either.
All the vintage Polks are 2 way designs, but they're well engineered.
Compare his modifications to CP Member @decato 's modifications to the RTA-15tls.
A lot of work went into them.
I've done about a half dozen of them, and get very positive feedback on them.

msg

Thanks David. Luckily we're just talking about a pair of cheap speakers here, but I'd prefer to not trash them. Trying to see if I can find the oe spec/design somewhere, or whether the designer still has any stock of the oe components laying around. He's done a bunch of these mods for people on other boards and they all seem to like them okay [ shrug ] I can solder well enough now to hack these back together if I can get my hands on the parts and layout. I remember them sounding okay when I first got them.

I just found decato's thread on the 15TLs - that looks chock full of info. I'll give that a read, thank you. I'm curious to see what the goal was with that mod. Seems like with the other crossover work, we're just upgrading, but not necessarily making significant modifications to the design.

westmassguy

Read the thread thoroughly. He raised the crossover frequency, changed the slopes, and inverted the tweeter phase. The 198 gets a little ragged at the low end of its frequency response, and inverting the tweeter phase helps mitigate lobing.

msg

I will.
Jeez David, that sounds pretty advanced. I like to think I have a better ear than an average every day listener, but I don't have an accurate sense of what frequency ranges I'm hearing for the respective sound. How does one learn this? Charts and practice?

westmassguy

These should help:

msg

wow, thanks David

pitdogg2

Any way you can Google up the speaker and see if there is a schematic out there some where? Seems like a logical first step to finding original cap values.