Lambda driver-based sub build.

[dumptruck]

I was wondering what to do with/make of the hole in the center of the magnet. I did vent the second one. But the first one is still covered. How much of a priority should I make of opening it up and drilling it out? Is it something that can wait? a week? a month? a year?

Picture here:
http://www.audiokarma.org/forums/attachment.php?attachmentid=420102&d=1364487318

Please advise.

Well, the air under the dust cap is at the end of there, so you can imagine quite a bit of air gets moving through the vent at high excursion. The effect of plugging or obstructing it, I don't know (depends on a whole bunch of aspects of the motor and I'm really not too knowledgeable about that stuff), but it'll do something. It's not going to hurt the driver, though. Well, except if there's no gap venting (and I think there is), and you've got it really sealed, it might pop the dustcap off if you give it enough juice .

 

[Brett a]

Well, the air under the dust cap is at the end of there, so you can imagine quite a bit of air gets moving through the vent at high excursion. (...)

Sounds like reason enough to open it back up. Thanks.

 

[dnewma04]

That hole provides a lot of the ventilation to move heat away from the voice coil. Definitely open the hole up.

 

[RayW]

Well, except if there's no gap venting (and I think there is), and you've got it really sealed, it might pop the dustcap off if you give it enough juice .

That's really cool when it happens...provided you're power testing them for the company and you didn't pay for them.

 

[Brett a]

That hole provides a lot of the ventilation to move heat away from the voice coil. Definitely open the hole up.

Done.

I was happy to see that I could do it in place. None of the braces were obstructing the drill. All I had to do was remove some stuffing. I was not looking forward to the possibility of having to remove the driver to do this.

 

[Brett a]

OK, a few more days passed and I have gotten to tweak and twist and listen and here is where I'm at today.

One sub sounds better than two subs.

I don't know why; perhaps it's the quality of the subs/cabinets themselves; maybe it's the limited placement options, but I can't get any improvements by adding a second sub on the right side of the room (or down with the rest of the gear).

Near the couch doesn't work b/c then it has a definite "presence" in the immediate area that just doesn't make sense to the ears/skin spatially.

Down by the system, near the main speakers, it just adds mud. And the two spots along the side wall where it will fit only serve to muddle things up a bit as well.

So I'm going to just go with one for now.

Here's a shot of where the right one has spent most of its time. The main speakers are out of the frame on the left, and the couch/listening position to the right. You can see that the driver is essentially blind to the listening seat, but I'm not sure how much that matters.

In this position, it is pretty much directly across from the one on the left wall.

I'll move this out/pack it up. It'll be good to have full access to my CD collection again.

 

[dumptruck]

One sub sounds better than two subs.

Well that's a new one to me. Even when they are about the same distance from listening position? Or was that never an option? I guess it's possible you need two amps with variable phase controls to make it work to your satisfaction .

You can see that the driver is essentially blind to the listening seat, but I'm not sure how much that matters.

Not at all.

edit: Oh hey, just for kicks, what happens when you put the second one at the same location a single one is working for you? If that sounds worse, suddenly the amp becomes suspect.

 

[Brett a]

edit: Oh hey, just for kicks, what happens when you put the second one at the same location a single one is working for you? If that sounds worse, suddenly the amp becomes suspect.

I had this thought this morning. I'll try them side-by-side and maybe even stacked tonight when i get home.

 

[Brett a]

One of the guys at my local shop was kind enough to modify my amp so it has a second set of preamp out puts for the sub. (I say he was kind enough b/c this kind of work isn't something they really offer).

I asked him to re-purpose one set of RCA inputs (the ones marked SACD) which he was able to do using some Siltech hookup wire. This just makes it neater and eliminates all the extra connections involved in using external splitters.

Before:

After:

 

[240sx4u]

I'd have had him jumper those preamp in/outs while he was in there

 

[dnewma04]

Well that's a new one to me. Even when they are about the same distance from listening position? Or was that never an option? I guess it's possible you need two amps with variable phase controls to make it work to your satisfaction .


Not at all.

edit: Oh hey, just for kicks, what happens when you put the second one at the same location a single one is working for you? If that sounds worse, suddenly the amp becomes suspect.

Considering that they are both being fed the same power, with the same adjustments in different locations, I'm not really surprised that it didn't integrate well. Each sub in a multi-sub setup typically needs individual controls to integrate well.

 

[dumptruck]

I've set up dual subs on single amps in several rooms without much trouble, but I guess I've always had symmetry (each sub the same distance from the mains, and each the same distance from the listening area).

 

[dnewma04]

Right, you just don't get the full benefit of multiple subs like you do with individual controls and in some cases, you can get worse results.

 

[Brett a]

I'd have had him jumper those preamp in/outs while he was in there

I didn't want to do that, as it's handy to have the flexibility of external connections. Plus, if I did that, I'd be left with a pair of stupid-expensive jumpers I had no use for.

 

[Brett a]

Considering that they are both being fed the same power, with the same adjustments in different locations, I'm not really surprised that it didn't integrate well. Each sub in a multi-sub setup typically needs individual controls to integrate well.

So this is where I have them now. The left one really has found a home next to the chair about halfway up the left wall.

The right one, after not really working out by the CD rack (pic a few posts back), I decided just to stick it behind the right main and live with it there for a while.

After several days with both running in these positions (I ran the right one out-of-phase for a day just for yuks), I'm back to just running the left one. I have not been able to get the addition of the right cab to improve the presentation; only muddle it up.

I'll continue to futz with them, but may just end up putting the second one in storage until I feel like buying a second plate amp.

All this said; my system sounds better than it ever has! Standmounts and a sub really is the way for me to go. :thmbsp:

 

[dumptruck]

Connecting the near one in reverse polarity would probably be more likely to work out than vice versa, by my guesstimate.

 

[Brett a]

Connecting the near one in reverse polarity would probably be more likely to work out than vice versa, by my guesstimate.

The problem with running that right-hand sub in phase is that it really has a presence that is undesirable; it draws attention to its self. I think I may just put it in storage until I feel like getting another amp.

 

[davidro]

All this said; my system sounds better than it ever has! Standmounts and a sub really is the way for me to go. :thmbsp:

You're running 2 subs right?

Man this all looks daunting. I'm glad I just hunted for good deals for the 2 subs of mine... I don't think I could ever handle this much of DIY. Well-done!