jimjimbo Posted February 10, 2016 Share Posted February 10, 2016 2x4's on the back panel? http://www.ebay.com/itm/Klipsch-Heresy-pair-/151975603022?hash=item236273ab4e:g:lX0AAOSwvUlWtiki Quote Link to comment Share on other sites More sharing options...
jason str Posted February 10, 2016 Share Posted February 10, 2016 This is how you properly brace a Heresy back panel. Quote Link to comment Share on other sites More sharing options...
Max2 Posted February 10, 2016 Share Posted February 10, 2016 I like how there are 35-40 screws holding the 2X4's secure, yet only 8 holding the rear panels. They may have increased the resonance doing that 1 Quote Link to comment Share on other sites More sharing options...
mustang guy Posted February 11, 2016 Share Posted February 11, 2016 That little 2" by 4" long port added 10MHz to the bottom end. I just threw WinISD at it. Has anybody here tried this port mod??? Quote Link to comment Share on other sites More sharing options...
wvu80 Posted February 11, 2016 Share Posted February 11, 2016 That little 2" by 4" long port added 10MHz to the bottom end. I just threw WinISD at it. Has anybody here tried this port mod??? I don't know the numbers, but I bet you lose efficiency doing that. That 2x4 trick is ugly but I bet it adds plenty of mass to the enclosure. +++ Minor thread drift: Can any of you guys actually HEAR the difference between a braced and un-braced cabinet? I can't. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted February 11, 2016 Share Posted February 11, 2016 That little 2" by 4" long port added 10MHz to the bottom end. I just threw WinISD at it. Has anybody here tried this port mod??? I don't know the numbers, but I bet you lose efficiency doing that. That 2x4 trick is ugly but I bet it adds plenty of mass to the enclosure. +++ Minor thread drift: Can any of you guys actually HEAR the difference between a braced and un-braced cabinet? I can't. Nope, the efficiency is actually slightly better... Quote Link to comment Share on other sites More sharing options...
wvu80 Posted February 11, 2016 Share Posted February 11, 2016 (edited) Nope, the efficiency is actually slightly better... Is that to be expected? I was always under the impression that you don't get something for nothing. More bass (takes more power), less efficiency, that sort of thing. Edited February 11, 2016 by wvu80 Quote Link to comment Share on other sites More sharing options...
mustang guy Posted February 11, 2016 Share Posted February 11, 2016 (edited) Check it out. Same size box, same driver, one sealed, one with 2" diam 4" port no flares. Blue is ported Heresy: Here's the 1 watt spl: Edited February 11, 2016 by mustang guy 2 Quote Link to comment Share on other sites More sharing options...
minermark Posted February 11, 2016 Share Posted February 11, 2016 Well when you have rear porting it is a good thing to space it out from the surface, 2X4s work, who cares? nobody sees them. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted February 11, 2016 Share Posted February 11, 2016 The trade off is that you need a HP filter to keep from turning the woofer inside out with low frequencies. A 35Hz Butterworth would work. The Klipsch HIP recomends a 55Hz 12db slope HPF. When I plug that in, the response drops to almost what the regular Heresy is. Checking cone excursion, the 35Hz BW will keep away from over excursion without sacrificing the low end gained with a port. 2 Quote Link to comment Share on other sites More sharing options...
jason str Posted February 11, 2016 Share Posted February 11, 2016 Well when you have rear porting it is a good thing to space it out from the surface, 2X4s work, who cares? nobody sees them. I highly doubt those 2x4's are doing much of anything besides uglying up the back panel. 2x4's could work i guess but not arranged like that. Looks as if the port does add a bit of bass but like Mustang guy says would be best with a high pass filter in conjunction so not to cause over excursion. Quote Link to comment Share on other sites More sharing options...
moray james Posted February 11, 2016 Share Posted February 11, 2016 This is how you properly brace a Heresy back panel. SAM_0164.JPG when you design a brace you will find that you will achieve near optimum stiffness will be with when the width is about 2.5 time the thickness. It is clear that the build shown is wasting both a lot of material and cabinet volume to achieve no better performance. Quote Link to comment Share on other sites More sharing options...
jason str Posted February 11, 2016 Share Posted February 11, 2016 (edited) This is how you properly brace a Heresy back panel. SAM_0164.JPG when you design a brace you will find that you will achieve near optimum stiffness will be with when the width is about 2.5 time the thickness. It is clear that the build shown is wasting both a lot of material and cabinet volume to achieve no better performance. That scrap 1/2" material i used reduces the cabinet volume less than if i were to just glue a 1/2" sheet to the inside of the back and is far superior to other methods, try it for yourself if there is any doubt in your mind. Edited February 11, 2016 by jason str Quote Link to comment Share on other sites More sharing options...
moray james Posted February 11, 2016 Share Posted February 11, 2016 That scrap 1/2" plywood only needs to be cut 1.25 inches wide to achieve best results. Making your braces wider than 2.5 times the material thickness is not a good compromise. You could glue a second half inch of ply onto the outside of the back of the cabinet with no detriment and that would be worth while so long as you don't mind how it looks. Baffles don't always come off as in the H3 and CW3 so you are working through the woofer openings. I did all sorts of experimenting decades ago. Attached is a photo of what the inside of my two sets of H3 look like this is a hardwood matrix made with 3/4"x3/4" white oak which is the stiffest material that costs the least. Every panel has has braces and is tied to every other panel the cabinet cannot flex inward or out. The front baffle has two hardwood cross braces which significantly improves stiffness. Every single cabinet seam has a strip of 3/4" oak strapping where the panels join each other full cabinet width. These cabinet are extremely rigid yet minimal cabinet volume was given up to achieve this and cabinet damping (high density fiberglass) more than compensates for the volume loss. There are no wood screws fixing the drives all machine screw inserts and machine screws are used epoxy fitted. Using less material would result in a loss of stiffness more would provide no benefit what so ever. The goal was not just a much more rigid cabinet but also improved bass and all of the original cabinet modification goals were very nicely achieved. Quote Link to comment Share on other sites More sharing options...
jason str Posted February 11, 2016 Share Posted February 11, 2016 (edited) That scrap 1/2" plywood only needs to be cut 1.25 inches wide to achieve best results. Making your braces wider than 2.5 times the material thickness is not a good compromise. You could glue a second half inch of ply onto the outside of the back of the cabinet with no detriment and that would be worth while so long as you don't mind how it looks. Baffles don't always come off as in the H3 and CW3 so you are working through the woofer openings. I did all sorts of experimenting decades ago. Attached is a photo of what the inside of my two sets of H3 look like this is a hardwood matrix made with 3/4"x3/4" white oak which is the stiffest material that costs the least. Every panel has has braces and is tied to every other panel the cabinet cannot flex inward or out. The front baffle has two hardwood cross braces which significantly improves stiffness. Every single cabinet seam has a strip of 3/4" oak strapping where the panels join each other full cabinet width. These cabinet are extremely rigid yet minimal cabinet volume was given up to achieve this and cabinet damping (high density fiberglass) more than compensates for the volume loss. There are no wood screws fixing the drives all machine screw inserts and machine screws are used epoxy fitted. Using less material would result in a loss of stiffness more would provide no benefit what so ever. The goal was not just a much more rigid cabinet but also improved bass and all of the original cabinet modification goals were very nicely achieved. Lets stay on subject for arguments sake and concentrate on the rear panel we started with. There is nothing wrong with a wider (height in this case) brace and everything depends on the span of the brace like basic carpentry 101. Your 2 1/2 x material theory is flawed because it does not take panel length into consideration, it may be fine for a very small panel but very weak if it were longer and the length in this case with a 2 1/2 x material thickness is not enough and no way would i personally intentionally ugly up a perfectly nice cabinet back even if it does face a wall. For instance say you were constructing a floor, a 2x12 would be less resistant to flexing than a 2x8 over the same span correct ? If there is room witch there is in this case i see nothing wrong with added strength and displacement is minimal overall as stated before. Edited February 11, 2016 by jason str Quote Link to comment Share on other sites More sharing options...
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