Apparently the first set went into service about 5 minutes after they got home (it's a screenshot of the video, not an actual video).
Pictures of the guts of the Sphere-ish design, and the measurements from the other two (edit: the ones with two plots are with and without the BSC that I ended up not using).
The bottom ports right on the foot isn't ideal, but I wanted the "spokes" on the one with the foot and didn't want to make that too spindly (I thought about trying to put a 1/4-20 insert like a tripod mount, but then that's another expense and I am not sure how it would work out on a shelf or something anyway).
That's two guts, but only one set of bowls. I know the interior round-overs might be counter-productive, I was using a trim router to even up the ports (not circles, I needed all the volume I could get) and I think I went on auto-pilot.
I forgot I measured the foam boxes, I should go back and look at comparing to those (while consistency was favored over strict accuracy, I think I am only off by ~2mm in any interior dimension).
Thanks!
Darrell
Pictures of the guts of the Sphere-ish design, and the measurements from the other two (edit: the ones with two plots are with and without the BSC that I ended up not using).
The bottom ports right on the foot isn't ideal, but I wanted the "spokes" on the one with the foot and didn't want to make that too spindly (I thought about trying to put a 1/4-20 insert like a tripod mount, but then that's another expense and I am not sure how it would work out on a shelf or something anyway).
That's two guts, but only one set of bowls. I know the interior round-overs might be counter-productive, I was using a trim router to even up the ports (not circles, I needed all the volume I could get) and I think I went on auto-pilot.
I forgot I measured the foam boxes, I should go back and look at comparing to those (while consistency was favored over strict accuracy, I think I am only off by ~2mm in any interior dimension).
Thanks!
Darrell
Attachments
Lovely woodwork. Lucky nieces and nephews!
Did you use a BSC circuit to get a nice bass/treble balance?
Usually on 8ohm compact speakers I add 0.68mH to 1mH air core paralleled with 10w 6.8ohm or 5ohm resistor and find that makes the speaker a lot less forward and warmer sounding, albeit at the expense of overall sensitivity.
Did you use a BSC circuit to get a nice bass/treble balance?
Usually on 8ohm compact speakers I add 0.68mH to 1mH air core paralleled with 10w 6.8ohm or 5ohm resistor and find that makes the speaker a lot less forward and warmer sounding, albeit at the expense of overall sensitivity.
Thank you!
I did try a 0.5 mH air core inductor and a 3.7 Ω resistor on the larger 1-Port (the drivers are 4 Ω), and the wife decided she preferred it without. I kind-of think that decision might be based on [more is better], because she said "I can't tell when it [the increased treble] goes away, I can only hear it when it comes back."
Since the kits had 15W/30W amps I was already worried about them turning it up to 11 and power/clipping - and I don't know enough to know if the BSC would appreciably hurt or just be a drop in the bucket, or say if a Zobel is helpful. I tried a Zobel (12 µF and ~4 Ω) with the BSC as well just to see what it would do on the DATS machine but I didn't save it (as I recall it flattened the peaks significantly and dropped the impedance graph significantly - but that might have been the auto-axis adjustments).
I had put everything away when I assembled the 4-Port, but now I wish I had tried it.
Comparing the two, think I want to like the 4-Port more. I don't know if I am biased to the 4-Port because I know it "should" sound flatter, since I like the increased bass from the 1-Port, but that bass does come with a sound that is less appealing.
I did try a 0.5 mH air core inductor and a 3.7 Ω resistor on the larger 1-Port (the drivers are 4 Ω), and the wife decided she preferred it without. I kind-of think that decision might be based on [more is better], because she said "I can't tell when it [the increased treble] goes away, I can only hear it when it comes back."
Since the kits had 15W/30W amps I was already worried about them turning it up to 11 and power/clipping - and I don't know enough to know if the BSC would appreciably hurt or just be a drop in the bucket, or say if a Zobel is helpful. I tried a Zobel (12 µF and ~4 Ω) with the BSC as well just to see what it would do on the DATS machine but I didn't save it (as I recall it flattened the peaks significantly and dropped the impedance graph significantly - but that might have been the auto-axis adjustments).
I had put everything away when I assembled the 4-Port, but now I wish I had tried it.
Comparing the two, think I want to like the 4-Port more. I don't know if I am biased to the 4-Port because I know it "should" sound flatter, since I like the increased bass from the 1-Port, but that bass does come with a sound that is less appealing.
I couldn't get the ML-Voigt past design approval*, so I went with a sphere-ish design based on the Ikea Blanda designs @planet10 described (mostly because I thought gluing two bowls together would be quicker - ha! ... ha!). Still debating the shape of the stands.
I understand the wall lining is much more important in the hemispheres (no golden or room ratio to avoid resonances). Although nothing is consistent in the rest of the build, starting with the bowls available at Target two days before Christmas.
-- Is Renewliner or [Magic Eraser] appropriate, or good enough?
-- The round hemisphere baffle should greatly reduce any need for a BSC, correct?
* But a lady that uses part of our land to teach Tinkergarten, liked the purple foam prototype, and I have some extra drivers (because a certain 3-yo dented the dust caps on two drivers), so I might continue down that lane.
-- Is this PC68-4 a design appropriate to cut the dustcap off and use a phase plug, or is the cap an integral part of the sound-making?
https://www.daytonaudio.com/product/1538/pc68-4-2-1-2-full-range-poly-cone-driver
Attachments
No experience with M.E. as a damping material, but IIRC if you Google it for audio, pretty sure you're going to get some links at least on these forums.
Well, based on the driver's Qt specs it likely won't need any or very little at most, though the needs of the app could in theory require the max amount depending on how much lower mids/mid-bass she prefers, if any, since their hearing is fundamentally tuned to children's ~400 Hz identifying 'cry'.
No clue per se other than its specs, polar response indicates it contributes to its extended HF, so if true, then IME assume it will depend on the dimensions/shape of the plug, i.e. not a simple cone or even some folk's socket wrench sockets as phase plug tweak.
Well, based on the driver's Qt specs it likely won't need any or very little at most, though the needs of the app could in theory require the max amount depending on how much lower mids/mid-bass she prefers, if any, since their hearing is fundamentally tuned to children's ~400 Hz identifying 'cry'.
No clue per se other than its specs, polar response indicates it contributes to its extended HF, so if true, then IME assume it will depend on the dimensions/shape of the plug, i.e. not a simple cone or even some folk's socket wrench sockets as phase plug tweak.
Thanks!
Bonus, you reminded me that now these aren't ~secret presents, I can have the Niblings come over and try some things out. I need to wait on the walnut hulls to soak a bit more for stain (assuming they don't want the great contrast), so it likely won't get done this weekend anyway.
I tried to read up on the melamine foam here, but got lost in the usual "you need special audio density - no, it's the same thing" then totally derailed by "insulation is bad for your lungs - no, it's only not-good for your lungs".
I assembled and tried them (with clamps) without any damping, -- I don't have the others to compare with, the convenient dining room speakers are Q Acoustics BT3 two-way bookshelves with a Emotiva BasX 8" sub -- so with the sub off, they seem to be missing something in middle - although I don't know I could identify which bands.
I got a usb microphone for Christmas, would that help - or would it be more of a distraction than a help? I loaded REW on an old Chromebook running Ubuntu, but I haven't taken the microphone out of the box (I now know how my dad must have felt when we gave him tools for presents).
Am I supposed to "Like" posts here? Is it offensive to fail to "Like" posts? I don't have Facebook and barely know how to use the work iPhone, so that's just not something that I thought of before seeing folks do it here.
-Darrell
Bonus, you reminded me that now these aren't ~secret presents, I can have the Niblings come over and try some things out. I need to wait on the walnut hulls to soak a bit more for stain (assuming they don't want the great contrast), so it likely won't get done this weekend anyway.
I tried to read up on the melamine foam here, but got lost in the usual "you need special audio density - no, it's the same thing" then totally derailed by "insulation is bad for your lungs - no, it's only not-good for your lungs".
I assembled and tried them (with clamps) without any damping, -- I don't have the others to compare with, the convenient dining room speakers are Q Acoustics BT3 two-way bookshelves with a Emotiva BasX 8" sub -- so with the sub off, they seem to be missing something in middle - although I don't know I could identify which bands.
I got a usb microphone for Christmas, would that help - or would it be more of a distraction than a help? I loaded REW on an old Chromebook running Ubuntu, but I haven't taken the microphone out of the box (I now know how my dad must have felt when we gave him tools for presents).
Am I supposed to "Like" posts here? Is it offensive to fail to "Like" posts? I don't have Facebook and barely know how to use the work iPhone, so that's just not something that I thought of before seeing folks do it here.
-Darrell
Well, I tried measuring one of them (in the dining room - with clamps). Here's what I got, not sure I did this right, especially the impulse window thing, I set it really short since it was .75m to the side wall while I was measuring 1m to the microphone for the far distance. The near distances were done on the table mostly because I was just seeing if everything worked.
I only measured one of the six ports (the 3 o'clock one) and the instructions I found said to eyeball the offset in the deep bass section to align and make the combination.
Edit: Should I have done something to account for the other 5 ports before the summing thing? This is also without any dampening in the echo chambers.
Does this tell anyone anything?
I only measured one of the six ports (the 3 o'clock one) and the instructions I found said to eyeball the offset in the deep bass section to align and make the combination.
Edit: Should I have done something to account for the other 5 ports before the summing thing? This is also without any dampening in the echo chambers.
Does this tell anyone anything?
Attachments
You're welcome!
Well, there was a time when most building materials were dangerous; my 1952 house is shingled with asbestos siding, attic full of blown in fiberglass insulation, though long since covered the outside with fiberboard and the attic is so full of dust, long since dead bugs it's much more a issue if one were to live in it and while I've had lifelong sinus issues from minor birth defects, no cancer/whatever, yet, at 76 from all this, so unless you snort it for 'kicks'/whatever, all you need is your Covid mask and cheap throwaway gloves, long sleeves, pants and you're good to go.
The melamine foam is open cell, so be more worried about what it collects, i.e. use fresh pieces with no soap/whatever additive. Most folks use polyfil pillow stuffing or ground up bluejeans if needing more density, both as benign as it gets and there's always the classics, cotton T-shirts, socks. 😉
Could only find one review listing as have a 'mellow tone/easygoing' = rolled off low end for the ladies, so short on (mid) bass, lower mids, but your sub goes to 150 Hz, so get the somewhat necessary 'fill' missing from the mains. All things considered, a good match up for a small system.
Can't comment about measurements, though FWIW, all I ever had was a signal generator, O'scope and a SPL meter plus my ears for overall and female ears for fine tuning/HF response, which was a lot more than most speaker DIYers I knew. The electronics guys OTOH had benefit of military dumping for next best thing to free for most stuff, so they filled back bedrooms, closets or built an 8x8x8 ft shed out back filled to barely having room to sit.
My hotrodding buddy's dad had one and on a hot June night in '56 we stood outside listening to Radio Free Europe broadcast the Polish rebellion against its Soviet Gov't. and later the Berlin Wall fiasco before moving away.
'Likes'
Well, it tells us it's tuned in the low 70s with excellent bass 'fill', so apparently it's summing in room (note that to mike just a driver, vent in a room typically requires it be < ~ 1/4" of the dustcap and ~ a 1/4" inside a horn, vent); a typical falling response with increasing frequency as a basic form of baffle step compensation, though apparently not enough to compensate for your 'missing something' unless backed up against a wall and that it 'rings' way too much for my 'heart attack fast' transients 'taste' (impulse response).
Thanks!
I did take the driver and vent measurements with the mic right up against the speaker, for the driver I aimed for right inside the profile of the surround, but the vent is smaller than the the mic, so that was probably 1/8-1/4". However, the high end of the summed response line is still these near-field measurements. I don't know how to cut that off and splice in the far-field measurement. The red line at the top is the far field 1m measurement, gated for reflections - and I don't know if I put the gate at the right place: i.e. if that bump was a "ring" or a reflection.
I tried with and without the BSC I calculated for the 4-Port box - both meant to be ~2.2L and theoretically tuned the same*, and I only have certain values of components on hand, so it was 3.7Ohm and 0.50mH. We could only actually hear a change on specific songs. Then I got lost listening to music (... again ... once to a point of making sound, all these to include the foam prototypes probably spent more time playing music with the clamps on - than I spent working on them...).
But ... I just read half of the How to build a spherical speaker ? thread, so I take from this that I still need a BSC, I just don't know how to calculate it from baffle size alone. I think I will try modeling a circular baffle of that size, I think that's what the thread is saying - the BSC 6dB drop is the same and the sphere is about the higher ripples.
I hope the "ringing" is something that I can fix with the damping material. I will try some of that and set up a more proper measurement outside when I get a chance and it's pretty - since I am not tied to the wife's computer (REW can run on an old chromebook+Linux). Not sure if I need to put a pole or a ball in the center to break up the reflections/waves. It kind of seems odd that a sphere in the center wouldn't make things worse though (being then equidistant from all the surfaces again).
I have a big bag of those melamine blocks I bought a while ago, so I think I can make a geo-dome from the melamine that I might not have to glue to the insides for testing (Maybe I can talk my wife into building "igloos" with the kids for a project one day this week).
On the electronics lots - I am kicking myself now, because my father was an instrumentation specialist and he bought those kinds of lots from Dupont and one time a school electronics lab, so he had a whole pile of older oscilloscopes, tube testers, you name a late 80's device for vocational education. But when he downsized seven years ago, I bought a 20' CONNEX/MILVAN to put some things I wanted from his shop, I didn't save any. I don't know that I still have the two old black analog meters with the roll-up front that I grew up with.
I've been stationed in SE Asia, SW Asia, and Central/South America, but never Europe.
* Although the volume is set more from making the spokes and rings have ~square cross-sections to balance strength/grain (bowls were only 1.75L), and I freehanded the vent slots on the tablesaw - so don't tell but they aren't precise or uniform.
My sister talked me into trying to 3-D print something at the library yesterday, so I didn't get to measure anything outside, but I did try two different styles of damping using the melamine stuff this morning. So I have new measures (both speakers) vs the previous one.
The one labeled A-B has a 30mm (full pad thickness) [circular disc / curtain] right behind the driver in front of the spokes, plus an [igloo] of 10-15mm rectangles lining the back bowl (not perfect, I was free-handing them).
The one labeled C-D only has the [curtain].
It looks like the damping isn't remarkably different, it might have done something to the dip right before 2K in the previous measurement. As shown below, it doesn't seem to helped any ringing.
Should I just keep the [curtain] and skip the igloo, or should I try something else?
Both have a 3.7 Ohm resistor and .50 mH air coil inductor, it kind-of looks like that caused a hump in the upper bass but didn't seem to do much for the upper treble, am I reading that correctly? It could be me eyeballing the combination of the vent/driver measurements. Or some other type of operator error.
Should I adjust those values or even remove the BSC at all?
New vs previous.
The one with both [curtain] and [igloo]:
The one with just the [curtain].
So, if I am reading these right, I don't think either scheme seemed to help the ringing (below I re-scaled the previous measurement charts to compare).
v/r,
-Darrell
The one labeled A-B has a 30mm (full pad thickness) [circular disc / curtain] right behind the driver in front of the spokes, plus an [igloo] of 10-15mm rectangles lining the back bowl (not perfect, I was free-handing them).
The one labeled C-D only has the [curtain].
It looks like the damping isn't remarkably different, it might have done something to the dip right before 2K in the previous measurement. As shown below, it doesn't seem to helped any ringing.
Should I just keep the [curtain] and skip the igloo, or should I try something else?
Both have a 3.7 Ohm resistor and .50 mH air coil inductor, it kind-of looks like that caused a hump in the upper bass but didn't seem to do much for the upper treble, am I reading that correctly? It could be me eyeballing the combination of the vent/driver measurements. Or some other type of operator error.
Should I adjust those values or even remove the BSC at all?
New vs previous.
The one with both [curtain] and [igloo]:
The one with just the [curtain].
So, if I am reading these right, I don't think either scheme seemed to help the ringing (below I re-scaled the previous measurement charts to compare).
v/r,
-Darrell
Attachments
Thanks!
Is the way I address the impulse that "critical damping" of the port you were talking about? (Instead of all the other stuff I was doing per below?) Since I have kept her waiting long enough (stain is drying now), if you only had one shot, would you put a layer (1/16") or two of cotton batting over the inside of the (6) ports or would that more likely compromise something else?
I am hoping that the bass dip/hump I now see is a result of the non-standard stuff I used for damping mostly just taking up volume (changing the tuning), and that taking it out and only using a layer of cotton batting on the inside of the bowls is better.
I also see I should use the BSC.
Longer description below:
Adjusted REW plots (per below).
One speaker is labeled AB and the other speaker is CD
This compares each one with (BSC + Foam) vs (no BSC and some Renewliner insulation stuffing)
Since those traces use an adjustment to the measurement that is supposed to adjust the nearfield measurements for the Baffle Step as calculated by an excel file by someone (here I think), these have the original measurement compared to the adjustment. The bottom is the combined near and far (1m) and the top two are the original measurement in grey under the calculated adjustment for baffle step effect.
What I was noodling through:
I was having trouble figuring out damping materiel, since the stuff I had didn't seem to be working the way I thought it was going to. And I couldn't find that Ultratouch denim, tried to get OC 703, but Amazon (ATS Acoustics) wanted around $200 (1/3 shipping), Lowes was going to add another two weeks to get here, and other rockwool stuff wasn't much easier. I couldn't figure out what felt to get/use either, anyone with 15mm+ of felt were very proud of it.
Then I got to thinking about what you said about critical damping, I should try that. But the wife and kids vetoed enough time to set all that stuff up outside and fiddling with the clamps for every change (if I do it again, I will take the time to use dowel locators, if not bulk-heading it so it just screws together front to to back).
Also remembering I have kept the poor girl waiting long enough messing about with what to do, I said just get on with it.
Once I committed to getting on with it, I was just going to leave it bare as the foam and BSC seemed to measure worse. Then it hit me that I probably had it wrong and the melamine erasers I was using weren't doing anything for the impulse and seemed to just add the bass hump by effectively cutting the volume down (the original measurement didn't have that big hump). And that meant the BSC was probably not causing the mid to hump up either (which was confusing me since the Basta! model didn't behave that way - explicitly, the things needed to behave like that with the resistor and inductor values seemed to be well outside measurement or operator head-space and timing error).
Seeing some designs specify "no foam, felt lining", and not having felt, I went and got some cotton quilting batting (~1/16"), glued it to the back bowl and a ring around the front bowl, added the BSC (3.7R, .5 mH) and glued it up. (Thought I got pictures, but didn't).
I did read some more on how to work REW, so I think maybe I got it right this time, most measurements were with more consistent volume settings on the amp, I saw that the nearfield measurements should be adjusted for the baffle step when adding to the far, and I combined the near and far measurements (roughly at 192Hz on three traces but 177 on the fourth).
OK, I'm slow.
I saw another post you made on this that seemed to answer this question, and it looks like that's the thing to do.
I had some energetic 3yo help (one of the BSC came loose inside) so I have to figure out how to do through-hole surgery anyway.
So I will try to use that opportunity to test port damping using the impulse graph - the last time I tried it, it was just my wife's ears and I didn't have the right words to describe what she should be listening for (my wife is very literal).
Speaking of 'slow', been having some 'episodes' to the point where not sure I'm following all that you've recently posted, though yes, damping the port will 'tighten up' the impulse response's long 'tail', though not to the point where it's like an ideally sealed alignment.
Hmm, women are sensitive to 'ringing', though if low tuned it may not go high enough for them to notice, so another way to 'listen' for it is either at higher SPL and/or at what point does the response begin rolling off, i.e. become over-damped, but since you can measure it............
Hmm, women are sensitive to 'ringing', though if low tuned it may not go high enough for them to notice, so another way to 'listen' for it is either at higher SPL and/or at what point does the response begin rolling off, i.e. become over-damped, but since you can measure it............
Re FG for damping; while OC 703 is nice to have for tacking to box panels, otherwise pealing the paper backing off of thick wall/attic insulation and encasing it in cheesecloth or similar porous bag(s) and tacked to walls or just 'floated' or suspended loose in the cab is the 'hot ticket' 😉 or my fave, Bozak's acoustic curtain/blanket.
Sorry to hear that.
My convoluted way of talking probably doesn't help either.
If a recap is useful:
-- I tried the click test with my wife on the first two sets of box speakers
-- While I am sure she can hear it, I just cannot describe what she is to listen for in terms she understands. She tends to the literal and accepts most things as they are - so if it squeaked the first time she used it, well then I guess it's supposed to squeak. Therefore, without a way to provide an example of [good] vs [poor], she could only report "it's different".
-- My tests with the baffle step compensation circuit went about the same way - "It's different, I can't hear it go away (adding in BSC), I can only hear it come back. I guess I like the one with [more sound] (i.e. no BSC).
-- As I shifted to the Spheres, I ran out of time.
-- But I got a microphone for Christmas, and posted the measurements of the Spheres.
-- Your feedback on those measurements indicated they had more than desired ringing.
-- I thought the ringing was from the inner hemisphere shape, so damping would reduce/stop it. I had some melamine foam, so I tried it.
-- I also remembered you mentioning the blanket idea before, so I thought a layer of melamine foam behind the driver in front of the spokes might be similar. I didn't think about if having three sides free was an operational aspect of the blanket.
-- In one of the speakers I also lined the back bowl (making an igloo).
-- So one set of measurements included Foam and the baffle step compensation circuit.
-- Then I took all the foam out, and removed the BSC circuit. I replaced the "curtain" with one layer of ~1" (Renewliner) plastic insulating batting (comes in refrigerated shipments we get) that I thought might work like the pillow batting. And I folded up an about 18"x18" square of that 1" batting and stuffed it into the back bowl.
-- Those are the other measurements.
-- Initially, I thought all this seemed to make things worse compared to the first measurement, and the BSC seemed to be wrong - I thought it was making the high bass / low mid bump up.
-- But I was holding up the Niece from getting her speakers, I knew I needed some damping, and it looked like the BSC was working on the top end, so I said --- just do it already --- settled on a layer of ~1/16" cotton batting over the insides of the bowls, reattached the BSC circuits, and glued them up.
-- Then it hit me --- the big hump that appeared in the bass looked more like a reduction in volume (i.e. without adjusting the port tuning) than something weird with the BSC.
-- Then another thing hit me - the thing to address impulse/ringing was that critical damping of the port (not the wall damping).
-- Since I was still trying to deliver them, I was asking if there was a rule of thumb / good guess about port damping.
-- But ... then right as we were getting ready, there was an oops ... so the BSC is now loose in one of the speakers.
-- Now that I have to figure out how to fix that this weekend, if the weather cooperates, I might be able to test and measure the responses rather than guessing.
So I am wondering if I have to construct the whole outside set-up to measure the impulse? Or can I just use the near field driver measurement, ignore the reflection/gating etc. stuff (and do it on the dining room table)?
My convoluted way of talking probably doesn't help either.
If a recap is useful:
-- I tried the click test with my wife on the first two sets of box speakers
-- While I am sure she can hear it, I just cannot describe what she is to listen for in terms she understands. She tends to the literal and accepts most things as they are - so if it squeaked the first time she used it, well then I guess it's supposed to squeak. Therefore, without a way to provide an example of [good] vs [poor], she could only report "it's different".
-- My tests with the baffle step compensation circuit went about the same way - "It's different, I can't hear it go away (adding in BSC), I can only hear it come back. I guess I like the one with [more sound] (i.e. no BSC).
-- As I shifted to the Spheres, I ran out of time.
-- But I got a microphone for Christmas, and posted the measurements of the Spheres.
-- Your feedback on those measurements indicated they had more than desired ringing.
-- I thought the ringing was from the inner hemisphere shape, so damping would reduce/stop it. I had some melamine foam, so I tried it.
-- I also remembered you mentioning the blanket idea before, so I thought a layer of melamine foam behind the driver in front of the spokes might be similar. I didn't think about if having three sides free was an operational aspect of the blanket.
-- In one of the speakers I also lined the back bowl (making an igloo).
-- So one set of measurements included Foam and the baffle step compensation circuit.
-- Then I took all the foam out, and removed the BSC circuit. I replaced the "curtain" with one layer of ~1" (Renewliner) plastic insulating batting (comes in refrigerated shipments we get) that I thought might work like the pillow batting. And I folded up an about 18"x18" square of that 1" batting and stuffed it into the back bowl.
-- Those are the other measurements.
-- Initially, I thought all this seemed to make things worse compared to the first measurement, and the BSC seemed to be wrong - I thought it was making the high bass / low mid bump up.
-- But I was holding up the Niece from getting her speakers, I knew I needed some damping, and it looked like the BSC was working on the top end, so I said --- just do it already --- settled on a layer of ~1/16" cotton batting over the insides of the bowls, reattached the BSC circuits, and glued them up.
-- Then it hit me --- the big hump that appeared in the bass looked more like a reduction in volume (i.e. without adjusting the port tuning) than something weird with the BSC.
-- Then another thing hit me - the thing to address impulse/ringing was that critical damping of the port (not the wall damping).
-- Since I was still trying to deliver them, I was asking if there was a rule of thumb / good guess about port damping.
-- But ... then right as we were getting ready, there was an oops ... so the BSC is now loose in one of the speakers.
-- Now that I have to figure out how to fix that this weekend, if the weather cooperates, I might be able to test and measure the responses rather than guessing.
So I am wondering if I have to construct the whole outside set-up to measure the impulse? Or can I just use the near field driver measurement, ignore the reflection/gating etc. stuff (and do it on the dining room table)?
Well, that lightbulb I had about the foam changing volume wasn't that bright I guess (or maybe it was a train...).
Still trying to avoid cutting into this thing, so while I am waiting (need 3mm more thread on binding post to reach where I can get the socket wrench) I tried to figure things out in a sim and realized that it wasn't dropping volume, but more than intended volume causing that.
I probably dorked it up with the spokes. I was worried about getting enough volume in there and I apparently went too far.
I was targeting a 2.2L volume with 6 ports ~7mm x 7mm at 50mm length for an 85Hz tuning (85Hz was the target and 50mm length fit the hole saw I had handy). The Basta! sim uses round ports (so I simmed ~.50mm2 or 8mm diameter - not sure how off that will be).
Playing around in PPT and some geometry (I never really got into the CAD thing) I think I changed the volume to closer to 2.8L. Updating that in Basta! and adjusting the tuning to the previous port length - so now if I sim a 2.8L enclosure tuned to 75Hz, it shows that funky dip and peak.
And that better matches your first response that it seemed to be tuned to 70Hz. I couldn't figure it out before, but I was probably trying to be too precise, it looks like the driver dips at ~74 and the port humps at ~73, so that's probably it.
Other regrets...
I actually bought a wooden egg, I just didn't try to suspend it off center in there, it might have made a nicer sound (by taking up volume) but it would have completely eliminated any way to fix the BSC coming loose without cutting it open.
I am also staring at the hide glue I bought to try out. I chickened out based on the complexity of trying to clamp this together to do the tests. But in practice, the actual glue up was dead simple (without the drivers installed, there are flats on both bowls so it was just plopping, centering, weighting) and I could have done it in the short working time.
Still trying to avoid cutting into this thing, so while I am waiting (need 3mm more thread on binding post to reach where I can get the socket wrench) I tried to figure things out in a sim and realized that it wasn't dropping volume, but more than intended volume causing that.
I probably dorked it up with the spokes. I was worried about getting enough volume in there and I apparently went too far.
I was targeting a 2.2L volume with 6 ports ~7mm x 7mm at 50mm length for an 85Hz tuning (85Hz was the target and 50mm length fit the hole saw I had handy). The Basta! sim uses round ports (so I simmed ~.50mm2 or 8mm diameter - not sure how off that will be).
Playing around in PPT and some geometry (I never really got into the CAD thing) I think I changed the volume to closer to 2.8L. Updating that in Basta! and adjusting the tuning to the previous port length - so now if I sim a 2.8L enclosure tuned to 75Hz, it shows that funky dip and peak.
And that better matches your first response that it seemed to be tuned to 70Hz. I couldn't figure it out before, but I was probably trying to be too precise, it looks like the driver dips at ~74 and the port humps at ~73, so that's probably it.
Other regrets...
I actually bought a wooden egg, I just didn't try to suspend it off center in there, it might have made a nicer sound (by taking up volume) but it would have completely eliminated any way to fix the BSC coming loose without cutting it open.
I am also staring at the hide glue I bought to try out. I chickened out based on the complexity of trying to clamp this together to do the tests. But in practice, the actual glue up was dead simple (without the drivers installed, there are flats on both bowls so it was just plopping, centering, weighting) and I could have done it in the short working time.
Yeah, with many folks, best one can get is 'which do you prefer' and if ambivalent, then I choose easiest/cheapest 😉.
Interesting in that BSC normally shifts the bass balance enough to 'trigger' a strong preference, but haven't done a globe so wondering if it instead needs a higher dB offset to sound 'flat' and/or tune it higher.
Hmm, critically damping the vent only damps the BW around tuning, usually requiring just relatively light/tightly stretched damping whereas 'ringing' from a globe's excessive eigenmodes requires considerable damping (density) to the point where it rolls off too much of its gain BW, so better IME to tightly stretch the damping over the back of the driver(s) before doing any vent damping, which you may find isn't necessary with the globe potentially 'killing two birds with one stone' 😉.
Reducing net Vb tunes the cab higher for a given vent alignment whereas sufficient damping/stuffing can increase effective net Vb lowers tuning. https://www.ranger5g.com/forum/attachments/box-builder-fill-er-up-pdf.35156/
My experience with measurements is limited to (crude by today's standards) outdoor ground plane and for narrow BW (extreme nearfield) or just general in room SPLs.
Interesting in that BSC normally shifts the bass balance enough to 'trigger' a strong preference, but haven't done a globe so wondering if it instead needs a higher dB offset to sound 'flat' and/or tune it higher.
Hmm, critically damping the vent only damps the BW around tuning, usually requiring just relatively light/tightly stretched damping whereas 'ringing' from a globe's excessive eigenmodes requires considerable damping (density) to the point where it rolls off too much of its gain BW, so better IME to tightly stretch the damping over the back of the driver(s) before doing any vent damping, which you may find isn't necessary with the globe potentially 'killing two birds with one stone' 😉.
Reducing net Vb tunes the cab higher for a given vent alignment whereas sufficient damping/stuffing can increase effective net Vb lowers tuning. https://www.ranger5g.com/forum/attachments/box-builder-fill-er-up-pdf.35156/
My experience with measurements is limited to (crude by today's standards) outdoor ground plane and for narrow BW (extreme nearfield) or just general in room SPLs.
Thanks!
While I was waiting on the parts, I put a layer of cotton batting over the vents of the other one just to test.
As you said, it did nothing I can see to the impulse, but it did put a damper on the bass extension. So I took it out.
Drivers + Ports (I didn't measure the 1m upper range here)
Drivers only - lost the dip...
But you predicted all that.
I am now tempted to go put something behind the driver ... but Grace has been waiting long enough, and it took WAY more time than I wanted to fish around and get the guts fixed through the driver hole.
So I'll probably just call it a wrap.
Seriously, thanks for all the help! I really appreciate it.
-Darrell
While I was waiting on the parts, I put a layer of cotton batting over the vents of the other one just to test.
As you said, it did nothing I can see to the impulse, but it did put a damper on the bass extension. So I took it out.
Drivers + Ports (I didn't measure the 1m upper range here)
Drivers only - lost the dip...
But you predicted all that.
I am now tempted to go put something behind the driver ... but Grace has been waiting long enough, and it took WAY more time than I wanted to fish around and get the guts fixed through the driver hole.
So I'll probably just call it a wrap.
Seriously, thanks for all the help! I really appreciate it.
-Darrell