thanks gm.
I was going to ask what types of bracing and which spots would be most beneficial. Based on the box itself I'm wary that I'll actually be able to get braces where I need them. I'm sort of leaning towards just doing a new box Ala the osmc linked above, I may even go the waveguide route as I find the current tweeter to be a bit lacking in imaging vs the waveguided speakers I have. I don't see the midrange on that as obtainable for me so I might use one of my many woofers such as rs180 with xt25/dx25 waveguide.
The fun never ends with diy speakers lol.
I was going to ask what types of bracing and which spots would be most beneficial. Based on the box itself I'm wary that I'll actually be able to get braces where I need them. I'm sort of leaning towards just doing a new box Ala the osmc linked above, I may even go the waveguide route as I find the current tweeter to be a bit lacking in imaging vs the waveguided speakers I have. I don't see the midrange on that as obtainable for me so I might use one of my many woofers such as rs180 with xt25/dx25 waveguide.
The fun never ends with diy speakers lol.
Going back to the start problem, a 200Hz 'resonance' does not show-up in your impedance graph.
Box tuning of your size would surely not be the cause of a 200 Hz anomaly.
So, to my mind, there only 3 likely causes (or a combination).
1. Box resonances & bracing. Which you seem to be 'on top of'. (the boxes look good)
2. You have unintentionally chosen the wrong bass driver for what you want to hear.
3. (what I think is most likely) Room characteristics & placement. (some rooms are just nasty)
GOOD LUCK🙂
Box tuning of your size would surely not be the cause of a 200 Hz anomaly.
So, to my mind, there only 3 likely causes (or a combination).
1. Box resonances & bracing. Which you seem to be 'on top of'. (the boxes look good)
2. You have unintentionally chosen the wrong bass driver for what you want to hear.
3. (what I think is most likely) Room characteristics & placement. (some rooms are just nasty)
GOOD LUCK🙂
From here, looks like you can easily add quite a bit of bracing if you want to investigate that. It'll be easier if you do it in smaller pieces, but that's OK as long as everything is glued together and fits reasonably well. You may also have to get a little creative here and there with how it's done, but bracing doesn't have to be perfect to make an improvement.
Personally, I'd spend more time trying to figure out what's going on with the current box. I often prototype very fast and loose, and unless my method is total garbage it tends not to have a disconcerting affect on the sound.
If you're picky, crossovers tend to be fussy in my experience, and almost always need some adjustment based on how the speaker sounds in the room.
Alrighty mr. mattstat. (any reason I can't quote you?)
I've got some top braces cut, and I should be able to fit one between the woofer and port. I'm thinking I can fit a piece in the middle of the cabinet that connects to the back, which does seem to vibrate a lot even though it's two layers of 3/4".
I have noticed that the "resonance" or build up around the problem area seems to be potentially specific to areas in the room, sadly one of those areas is right down the middle of the room. This is speculation but do you think my little entertainment center of mostly empty shelves is creating some little resonant chambers that shoot some nastiness out in the middle of the room?
I very much appreciate anyone using their time to help me out with this one.
I've got some top braces cut, and I should be able to fit one between the woofer and port. I'm thinking I can fit a piece in the middle of the cabinet that connects to the back, which does seem to vibrate a lot even though it's two layers of 3/4".
I have noticed that the "resonance" or build up around the problem area seems to be potentially specific to areas in the room, sadly one of those areas is right down the middle of the room. This is speculation but do you think my little entertainment center of mostly empty shelves is creating some little resonant chambers that shoot some nastiness out in the middle of the room?
I very much appreciate anyone using their time to help me out with this one.
The forum frowns on quoting a full post immediately before a reply (which is why that button is missing for the final post in a thread). They do give you a workaround though: highlight text and it'll pop up a dialog to quote. If it's just a small snip or helps make a point, it's usually OK.
I doubt it's your entertainment center in particular. You're likely describing your room modes. Part of good system setup is trying to smooth them out at the listening position by moving it and the speakers. Basic positions are often started at mathematically, but in the end it's usually a matter of running pink noise and a 1/3 octave RTA to do fine tuning. Furniture sliders and hearing protection are handy. You're also ultimately trying to optimize positioning for imaging and soundstaging, which have their own needs. Balancing all this comes down to personal preference on multiple fronts.
You can do a long-windowed impulse-based measurement of room response too, but they're slower and the additional resolution can make things harder to judge when it comes to frequency balance. Adding smoothing helps.
How have you set your listening and speaker positions? Are they fixed or flexible? If you have the ability to move them both by a couple feet, you can likely make larger differences in frequency balance than you may appreciate if you've never done that kind of thing.
Another thing that's helpful is having a reference speaker that you know has pretty flat frequency response. If you get that one set up properly, setting up a new speaker in the same spot can help you come to a reasonable balance in a new design. Of course if you're intentionally designing something that goes against a wall or some other non-traditional speaker location, your design will need to deal with that differently.
I doubt it's your entertainment center in particular. You're likely describing your room modes. Part of good system setup is trying to smooth them out at the listening position by moving it and the speakers. Basic positions are often started at mathematically, but in the end it's usually a matter of running pink noise and a 1/3 octave RTA to do fine tuning. Furniture sliders and hearing protection are handy. You're also ultimately trying to optimize positioning for imaging and soundstaging, which have their own needs. Balancing all this comes down to personal preference on multiple fronts.
You can do a long-windowed impulse-based measurement of room response too, but they're slower and the additional resolution can make things harder to judge when it comes to frequency balance. Adding smoothing helps.
How have you set your listening and speaker positions? Are they fixed or flexible? If you have the ability to move them both by a couple feet, you can likely make larger differences in frequency balance than you may appreciate if you've never done that kind of thing.
Another thing that's helpful is having a reference speaker that you know has pretty flat frequency response. If you get that one set up properly, setting up a new speaker in the same spot can help you come to a reasonable balance in a new design. Of course if you're intentionally designing something that goes against a wall or some other non-traditional speaker location, your design will need to deal with that differently.
I have some genelec 8030c and amiga by Paul C that I tested and neither gave me this problem in the same room and placement.
Have you measured outside? I saw this post on ASR as well and I feel for you. They're really excellent cabinets. It could need more bracing, but consider it may need different bracing than it has. These braces can conduct resonance to side panels as much as they can tie them to the rest of the cabinet to reduce resonance. You also had difficulty with stuffing, right? I highly recommend checking out @augerpro's threads, as they include rigorous testing of many construction techniques, including CLD braces.
I have not measured them active outside yet, only passive with the pit viper xover which I ended up just taking a loss on as it was not good. I might toss then up for sale for any prospective builders.
as far as dampening materials go, I'm not entirely sure what the cabinet actually needs so ive been trying different things, but with more braces it'll have to come out anyway and be redone.
as far as dampening materials go, I'm not entirely sure what the cabinet actually needs so ive been trying different things, but with more braces it'll have to come out anyway and be redone.
You're welcome!
Not for me, though have only built a few 'FR' driver pairs in the last ~41 yrs and now lost track of how many have been done by others or at least significantly influenced other's designs.
Maybe not, but not the 'end of the world' if not in ideal positions, just means maybe needing a bit more, such as a lone, slightly angled ~ 4" wide strip of hardwood or plywood ~ 71% the length of the rear open height glued on edge opposite the mids/HF and another to ~triangulate the area below the left side of the woofer and of course something vertical pieced together to tie to the six sides and apply a little pressure to the backside of the motor. Use another strip to tie the vent to it and pretty sure the box won't 'color' the sound from a resonance POV.
Ditto doing the on edge strips on any mids/HF boxes if not otherwise heavily mass loaded. Also, as a general rule, adhere to these ratios for offsetting drivers if not designing for any specific polar response.
For sure each has its own eigenmode, resonant output structure and also summing with each other to create a larger one, so goes lower and assuming these are ~sealed in the rear, then it's a closed cylinder resonator acting as a band-stop filter of sorts, which definitely is modifying the room's resonances to some extent.
Typical rooms have both even and odd harmonics with a huge null at the acoustic center of each set of parallel walls, so any resonances will be even order.
I would use WinISD's or REW's tone generator to find the offensive frequencies.
I would then feel lightly with my fingers, which panels are resonating badly. you can then use an F clamp or similar with pieces of wood to temporarily clamp from the outside to see where damping that panel resonance has any or most effect.
You are then better informed to whether bracing will help and specifically which vibration points to target.
PS: I am assuming this is all woofer and box vibration generated. Can you play the above youtube video without midrange and tweeter connected and hear these annoying resonances?
Edit: you may be able to mass load the panels - adding bitumen / rubber to lower the resonance frequency. however this may simply shift the problem down the spectrum, but could be less offensive (as our ears become less sensitive)
I would then feel lightly with my fingers, which panels are resonating badly. you can then use an F clamp or similar with pieces of wood to temporarily clamp from the outside to see where damping that panel resonance has any or most effect.
You are then better informed to whether bracing will help and specifically which vibration points to target.
PS: I am assuming this is all woofer and box vibration generated. Can you play the above youtube video without midrange and tweeter connected and hear these annoying resonances?
Edit: you may be able to mass load the panels - adding bitumen / rubber to lower the resonance frequency. however this may simply shift the problem down the spectrum, but could be less offensive (as our ears become less sensitive)
After thinking a bit more overnight,
I realized a very likely cause of a '200Hz sound' and that is >
Because you have a large diameter port, internal damping material will be very important.
EG. If you had no damping material, 200Hz ish boxy-sound would definitely come out of your port.
I realized a very likely cause of a '200Hz sound' and that is >
Because you have a large diameter port, internal damping material will be very important.
EG. If you had no damping material, 200Hz ish boxy-sound would definitely come out of your port.
I have tried several different dampening approaches with little success from 2 inch auralex stuff, memory foam, oc703 2inch, polyfill. I didn't notice much of a reduction in the issues stated, but the memory foam did sound noticeably worse.
Just one final thought ...
I had read many years ago that a port can be just too close to the woofer,
and your port being large diameter may be a case of this.
I read that you are considering starting a new enclosure, and this could be the solution (?)
CHEERS🙂
I had read many years ago that a port can be just too close to the woofer,
and your port being large diameter may be a case of this.
I read that you are considering starting a new enclosure, and this could be the solution (?)
CHEERS🙂
Hmm, considering the pioneers actually put drivers in the vent per the original patent and I've used up to 12" tube vents below vintage wide range 12-15" woofers with no noticeable acoustic problems, just lots of port gain, having a hard time figuring why it could be an issue.
Assuming it's actually your problem, absorption coefficients get pretty bad at lower frequencies, so 2 inches of Auralex or Owens Corning may not have been enough. See below.
But the recent review of the TAD CE1TX in Stereophile is also interesting to compare to your filtered port response. While the TAD's bump in port roll-off is a bit more gradual, it's also higher in level and wider than yours, and they didn't seem bothered. Narrow frequency response disturbances tend not to be glaring unless the magnitude is large. But I also understand wishing it wasn't there in principle.
https://www.stereophile.com/content/tad-ce1tx-loudspeaker-measurements
https://www.prosoundweb.com/18-para...-the-parametric-method-of-acoustic-treatment/
https://www.atsacoustics.com/page--Selecting-the-Right-Acoustic-Material--ac.html
I wasn't sure if the oc703 behaves differently in cabinet vs. used in room. I see a lot of dampening materials used out there, bitumen pads and what not, but haven't run into any tests on what actually works in different situations so I'm just kinda trying whatever.
I'll get around to sharing some info on what I've tried soon, but I'm a little burnt out on thinking about this problem at the moment. It also feels easy to get lost in some suggestions so I'm going to try and weed out what I think will work. For instance I don't really think the port is too close to the woofer, tons of speakers have locations like this without issue.
I'll get around to sharing some info on what I've tried soon, but I'm a little burnt out on thinking about this problem at the moment. It also feels easy to get lost in some suggestions so I'm going to try and weed out what I think will work. For instance I don't really think the port is too close to the woofer, tons of speakers have locations like this without issue.
I had experience with the vent too close to the woofer once. However, the lower impedance peak was largely deformed (and things didn't sound "right").
The small wiggles in the impedance shown in original post may be more due to some kind of vibration at those frequencies. I have seen small leaks or a bit of looseness around the port causing this. I also had a similar problem with a removable front baffle. Added thickness helped, as well as adequate fastening and gasket sealing. Also check that the woofer itself is secured and not leaking at mounting flange/cutout interface.
Incidentally, I found that (for most of my projects) the distance between the edge of the woofer cutout and the edge of the port cutout should be at least one (1) port diameter. Also, it's a good idea to keep the sides of the port (and the open end) away from interior wall surfaces and other fixed boundaries.