Put in the Delta dB so I can fiberglass the cabinet and see if the tuning works out. Should be 26Hz last one came in about a 1/2 Hz off. Can't wait to see what a pair sounds like for LFE.
Rob
Put in the Delta dB so I can fiberglass the cabinet and see if the tuning works out. Should be 26Hz last one came in about a 1/2 Hz off. Can't wait to see what a pair sounds like for LFE.
Rob
"I could be arguing in my spare time"
Just curious. What's the purpose of laying fiberglass in the cabinet?
Hello Lee
It does a couple of things, it helps absorb any high frequecy output from the back of the cone and also adds virtual volume to the box. When I calculated the internal volume I didn't acount for the volume taken up by the woofer, bracing and the port. The fiberglass adds volume and effectively cancels out the space of the woofer bracing and port. Works very well. I will know if I got it right as soon as I run an impedence curve on the box. The minimum should be at 26Hz which is the target box tuning Fb.
Rob
"I could be arguing in my spare time"
Good thread!Originally Posted by Robh3606
Put in the Delta dB so I can fiberglass the cabinet and see if the tuning works out. Should be 26Hz last one came in about a 1/2 Hz off. Can't wait to see what a pair sounds like for LFE.
Rob
Can you tell me where you purchase the Delta dB? I looked on the net and didn't find a source.
Rob, my question about fiberglassing the enclosure may have sounded pretty, pretty stupid and now I realize it. I thought the black stuff in the picture was some sort of "fiberglass/epoxy", hence my question. Now I realize it is " Delta-db coating" for which I just made a search...
http://www.coatingsolution.com/produ...p/delta_db.php
So, it all makes sense now. Damping the interior of a cabinet with fiberglass or foam panels (my prefered method) does "enlarge" the volume and decreases reflections. But that I already knew. I just got confused...
Funny. There was a brief moment where I thought the fiberglass ref was re a fiberglass/gel coat too
Now that rang a bell but onset dementia prevents me from remembering. Please remind me GrumpsFunny. There was a brief moment where I thought the fiberglass ref was re a fiberglass/gel coat too
LOL Yeah you had me wondering why you would ask thatI just got confused...
So I put in the fiberglass closed them up dropped the woofer in and did a low power sweep to see what the Fb was. I just love this box design software came in at 26.1Hz. In any case I might get to fire it up tonight.
I am going to try driving a pair of amps off a single BX-63A. Just going to use a Y connector and try flipping the Imp switch to the mid setting. Let you know how it works out.
25.1189 7.6715 -5.3027
25.5859 7.6410 -3.3327
26.0616 7.6267 -1.3665
26.5461 7.6299 0.7583
27.0396 7.6580 2.7827
Rob
"I could be arguing in my spare time"
Hi Rob,
After talking with Dr. Toole and the rest of the Harman gang during my recent visit, they really drove home to importance of multiple subs in small rooms,(Small rooms means a residential space as opposed to a large commercial venue.)I have to say I am now a believer... seeing and hearing is believing. I am sure adding this sub will make your room sound much better.
What box program is it that you are using?
Widget
Interesting that multiple subs are now coming to the fore. I thought it was a normal thing to do so I incorporated 4 2235's into my room when I built it. That was a few years ago now and I can honestly say that I have not found any issues with them.
Allan.
I have to disagree here: a cabinet loading the driver has 2 effects- it shifts the Fc upwards (From Fs), and the Qtc is shifted upwards (From Qts) in the same manner. Damping does not lower Fc back down, as it would be in a larger cabinet, but it DOES lower Qtc. In overstuffed cases, it can actually RAISE Fc. So stuffing should not be overused, as it can throw alignments off. None of that is a concern in this case, where the main function is to prevent leakage of higher frequency components through the vent, and the stuffing is just a modest lining of the walls.So, it all makes sense now. Damping the interior of a cabinet with fiberglass or foam panels (my prefered method) does "enlarge" the volume and decreases reflections. But that I already knew. I just got confused...
For the most part, you can follow the rules of thumb (medium stuffing of a sealed cab, and lining the walls of vented) without having the enclosure effects make too much difference, it's heavily stuffed cabs where you start seeing the issue. The lowering of Qts is not entirely a bad thing- you get more deep bass output at the cost of output near Fc due to the slower rolloff. This is particularly useful in undersized cabs.
At least, that's my understanding. I'm a stickler for some things like this. One could build properly sized sealed cabs then stuff the hell out of them and lose a goodly chunk of their bass. They'd have been better with light-medium stuffing to kill internal standing waves.
Hello WidgetWhat box program is it that you are using?
I am using Bass Box Pro and the data sheet for the 4" Precission Port. The data sheet has a formula for port lenght and when all is said and done the port should be 1" longer than the calculated length. When you do it in Bass Box using a double flared port it comes in exactly 1" short. So the two back each other up. Using just Bass Box in the past on my 4344 cabinets the measured numbers came up right on target.
Well one things for sure with a pair of B 380's a pair of Le-14 subs and E-145's the amount of air being moved is incredible. Talk about room lock! You put on the opening credits scene in Serenity or any part of Cloverfield and you can actually feel the air movement against your skin. I have to readjust the levels with the added sub which I didn't do last night just for kicks and it was Wow!I am sure adding this sub will make your room sound much better.
Well I can move the 4rth sub around a bit. The other 3 are basically locked in their positions. The BX-63A has no issues driving both sub amps. I think I am going to stick with the Imp switch in the center position. I also want to drag out my Synthesis Sub EQ and see what it can do.
Rob
"I could be arguing in my spare time"
Nice Rob!
Simply revisited. Way back when the L212 first hit the market it was immediately discovered that more than one B212 could dramatically improve system performance and JBL made it available separately.Interesting that multiple subs are now coming to the fore. I thought it was a normal thing to do so I incorporated 4 2235's into my room when I built it. That was a few years ago now and I can honestly say that I have not found any issues with them.
Since that time it has been common practice to use multiple subs, be they B212's, B380's, B460's or the myriad models that have followed.
Revisited and expanded- traditional explanation was "More output GOOD!" AFAIK, whereas in more recent years we've seen the use of distributed subs for modal management.
I say both are true- true 4 or 5 location sub setups are awful hard for real-world rooms, so sometimes people can only get the multisub modal benefit in a very limited way by using "stereo" subs, but also gain extra output. I currently use 4 subs, but they're stacked in pairs so it's more like my "stereo" example. Even that gets a raised eyebrow from my VERY beautiful VERY understanding wife. Hell, it's at the threshold of my own tolerance.
Modal management was always the goal. We did have a grasp on the situation even way back then. Some people have merely put a multi-million dollar spin on it. Good for them!
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