Help,
Just finished building a set of bookshelf boxes and I'm having second thoughts on the chamfer cut I did on the back side of the driver hole.
The baffle is 36mm thick, the driver hole is 150mm in diameter and the 45 degree chamfer goes down about 15mm, so there's about 20mm inside the hole that is not chamfered. Do you think this is enough for the driver to breath or should I remove more wood?
The 2 options that I am thinking about are 1) Use a Dremel tool and remove more wood, 2) lining the inside of the hole wall with weather strip or felt, I've read that this might do the trick and reduce reflections.
BTW, driver is fullrange, if that makes a difference.
Thanks
Just finished building a set of bookshelf boxes and I'm having second thoughts on the chamfer cut I did on the back side of the driver hole.
The baffle is 36mm thick, the driver hole is 150mm in diameter and the 45 degree chamfer goes down about 15mm, so there's about 20mm inside the hole that is not chamfered. Do you think this is enough for the driver to breath or should I remove more wood?
The 2 options that I am thinking about are 1) Use a Dremel tool and remove more wood, 2) lining the inside of the hole wall with weather strip or felt, I've read that this might do the trick and reduce reflections.
BTW, driver is fullrange, if that makes a difference.
Thanks
I think you are good to go. If you want to measure what is happening get Arta or REW and do a close mic measurement and look at the impulse response. You can calculate the time of flight for a wave to go from that cone and then reflect off the wood and come out of the speaker. .150 meters / 2 / 343 meters/second = 0.2 milliseconds. So a blip in the impulse response at 0.2 ms after the main peak would be hard to spot. That is a full wave at 4,500 Hz. So possibly some small dip in the response would appear at half wave frequency 2,250 Hz in the response.
FYI/FWIW, the goal is a very rough taper like one gets with a curved coarse wood rasp file perpendicular to the baffle, so can quickly finish what you started and not having a router during my DIY years is how I quickly tapered driver mounting holes. 😉
GM, I wasn't asking how to chamfer the hole but rather if it were necessary to make the chamfer deeper and wider than how I did it. Will the driver breath enough with the opening I did or must it be bigger?
Understood; implying it's possible 😉, so with little effort can guarantee it's not an issue, though really depends on the frame's design (which 'we' don't know), hole depth.
From my experience hotrodding cylinder heads I knew there were gains to be made, ditto with the coarseness, but not that much with audio!
I read that article which goes into great details explaining the effects of difference chamfers. Troels suggests to cut the chamfer down about 15mm in the driver hole, but that is for, I'm assuming, a 18mm thick baffle. My question is how deep should I cut the chamfer down a 36mm baffle? Is 15mm enough? Should I go lower?
Looking at the 5 scenarios, A, B, C, D, E, he seems to suggest in scenario E, which is what my baffle looks like, to cut the chamfer all the way down the driver hole. But unfortunately he hasn't tested and measured that option so I'm questioning whether it will make a difference compared to going down only 15mm.
If cutting the chamfer all the way down the driver hole is the way to go, I will remove more wood from the opening but I'm trying to avoid this since my boxes are now closed and can only access the driver hole from the front of the baffle.
Possibly. Even probably, but the only way to know for certain in any particular case is to try it -there's no single answer unfortunately, as (to a point) it depends on the cone profile, and much more importantly the basket & motor structure of the drive unit. Potentially (potentially) you can also add proximity of side-walls & what damping is applied to those also. Short version though is 'providing structural integrity is maintained, within reason the more relief you can give to the cut-out, the less the chances of problematic reflections, resonances & the like.
Look at it this way, a simmed response assumes a zero thickness baffle, so seems we can't go wrong flaring it all the way. That said, once we get down to the magnet we don't care if there's reflections since they're absorbed in the cab's presumed uniform particle density air mass 'plug', so 'D' seems OK to me.
+1, unless (possibly) you get to ~Avalon type 4in - 5in thicknesses, when my antennae start twitching about possible lateral standing waves or echoes from the tunnel the driver is lurking in. I doubt it'd be an issue if the initial relief is good enough; I'd probably just flare it for the sake of not letting the old brain start going round 'in the wee small hours'. 😉
Yes, definitely have to consider its organ pipe modes once completely shrouded, hence the need to damp drivers in pipe tubes regardless of whether tuned or not 😉, though flaring the back end based on its flanged pipe end correction should suffice same as back cutting a valve seat, i.e. flare depth (k) = 0.732d
Yeah, my nearly from birth vehicle (street/road) racing addiction and all that implies predated my audio one, so has been helpful in audio and vice versa 😉.
Has anyone tried damping the inside wall of the driver with either felt or weather strip? Result?
I use a simple method. I place the driver face down on the edge of a table beside a piece of baffle material. I then make a note of how much and what angle can be removed from the baffle without compromising the holding power of the driver fasteners yet allowing the necessary breathing.
Like GM, I found a hand rasp was a good friend after either saw or router work. Sometimes the chamfer was rather oddly shaped because of leaving extra meat around the mounting holes.
Like GM, I found a hand rasp was a good friend after either saw or router work. Sometimes the chamfer was rather oddly shaped because of leaving extra meat around the mounting holes.
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Wouldn't lining the inside of the hole just further reduce the available rear wave exit path?
I evaluate such things by visual inspection... if you can look at the back of the mounted driver and easily see the cone, you're probably good. If it's obscured by magnet and speaker frame and baffle material, then you'd want to do something about that.
It sounds like you've already got the box together. If you didn't have a look before assembly and you really wanna know, maybe cut a scrap piece to mimic your baffle driver cutout.
I evaluate such things by visual inspection... if you can look at the back of the mounted driver and easily see the cone, you're probably good. If it's obscured by magnet and speaker frame and baffle material, then you'd want to do something about that.
It sounds like you've already got the box together. If you didn't have a look before assembly and you really wanna know, maybe cut a scrap piece to mimic your baffle driver cutout.
I'd break out the rasp and between the driver mounting holes take it down to 10- 15mm or so and call it good.
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A bigger one of these 🙂
https://www.amazon.co.uk/ORXPLUS-TO...ee-a8eb-3f4130bebb1a&pd_rd_i=B0BP2VXKNH&psc=1
https://www.amazon.co.uk/ORXPLUS-TO...ee-a8eb-3f4130bebb1a&pd_rd_i=B0BP2VXKNH&psc=1
If you mean the frame, then yes, me, Dave P10 and others have done it to 'FR' drivers with good results and also bracing/mass loading the frame/motor joint and I've reinforced/mass loaded flimsy frames with brass rod wire, though don't recall others doing it, but really, all you need to do is mass load/brace it with an adjustable tensioner or as part of the cab's bracing as Dave, Scott among others do nowadays.
