Thanks for info on the ports. I'm going to take a much needed break and come back to the speakers with some bracing.
I don't know much bracing will help, I sat on the cabinets on the top and sides (240lbs) and measured and there was 0 change in FR and impedance.
Wanted to take a break but listening to music and hearing that nasty honk put me to work again.
Found a piece of 3" inch pvc and cut the length, wrapped it in gasket tape to make a snug air tight fit inside the 4" inch port. Resonances measure louder while port output went down.
I cut some braces from leftover red oak, put in two, one just above the woofer magnet and in the middle of the cabinet, and one between the port and woofer, no measureable changes.
So yeah, not sure what else to try ¯\(ツ)/¯
Found a piece of 3" inch pvc and cut the length, wrapped it in gasket tape to make a snug air tight fit inside the 4" inch port. Resonances measure louder while port output went down.
I cut some braces from leftover red oak, put in two, one just above the woofer magnet and in the middle of the cabinet, and one between the port and woofer, no measureable changes.
So yeah, not sure what else to try ¯\(ツ)/¯
However tempting the path of least resistance is, it's leading nowhere. It's not the braces, nor the port tube itself, it's a column of air resonating. Make a tube 10-15 cm in diameter, (your cab inner height)/4 in length, close one end, place it inside the cab so open end is near the top corner. That's your tuned absorber. Or plug the front port and make a new one in the back at H/2. Or both.
orange is with 7 inch tube.
with tube impedance, I lost my test resistor and my multimeter is giving me overload with no leads connected, its a very old fluke, so the imp is reporting lower than it really is. I had to guess on the 100ohm.
with tube impedance, I lost my test resistor and my multimeter is giving me overload with no leads connected, its a very old fluke, so the imp is reporting lower than it really is. I had to guess on the 100ohm.
I don't think this a solvable issue. No suggestions are working and some don't even make sense to me, the resonant tube really did nothing and peoples confidence in things that don't seem to work is a little exhausting. I do mix work and I cannot work on anything with this resonance, I simply do not trust what is happening in the 150-200hz region. Some songs, the resonance just absolutely screams at you. The only thing I have to try is to cut the ports and try some other rear mounted ones. I'm open to suggestions on port sizes, quantity, and location. Then again if the issue is dimension related this could also be a waste of time.
The OSMC style speaker looks great, I even have a WG of the size and tweeter ready to go ( don't really like the sound of this non-waveguided stuff anyway, image is not nearly as stable) , and the dc130 seems like a totally competent mid driver to my ears. But this cabinet is not much different dimension wise than mine and the paper specifies vertical length resonances as well.
What general cabinet dimensions should I be considering to avoid such a problem? Simply make shorter cabinets?
The OSMC style speaker looks great, I even have a WG of the size and tweeter ready to go ( don't really like the sound of this non-waveguided stuff anyway, image is not nearly as stable) , and the dc130 seems like a totally competent mid driver to my ears. But this cabinet is not much different dimension wise than mine and the paper specifies vertical length resonances as well.
What general cabinet dimensions should I be considering to avoid such a problem? Simply make shorter cabinets?
Honestly I think we’re grasping at straws because no theory explains it. None of the typical resonance calculations appear below 300hz for either the box’s volume or port shape. There has to be something unexpectedly fundamental to cause this issue. I’m on team gaskets and seals, maybe team box shape, but to be fair, you’ve already done everything reasonable. I can only see the remaining problems being related to room resonance or edge diffraction, both barely problems with the speaker. They’re more room issues. But it’s really tough to tell without hearing it ourselves and inspecting with our own eyes and hands. Our early warning equations don’t account for this, which is definitely frustrating and confusing everyone here.
Please take a photo: where exactly and what kind of tube did you place? It should be like this:
Approximately 25 cm long tube with one end closed, fixed to a front or back baffle, open end looks into corner.
Approximately 25 cm long tube with one end closed, fixed to a front or back baffle, open end looks into corner.
It shouldn't be in or near the port.
The tube is at the top and it's upright on the opposite side of the cabinet. Honestly I'm going to pass on that one, it just seem dumb and the tube being where it is now made no difference. I'm not interested in tooling some sort of mount for it and there isn't any room to place it like the brace behind the mid range gets in the way.
"It shouldn't be in or near the port."
It's not, that post was referring to something completely different, which was reducing the port inner diameter. I think you might have gotten my posts mixed up.
"It shouldn't be in or near the port."
It's not, that post was referring to something completely different, which was reducing the port inner diameter. I think you might have gotten my posts mixed up.
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Feel free to look at this mdat. Just some quick measurements. Left mid and tweeter are louder to help with hearing imbalance. Hopefully ou know what REW is because last time I shared an mdat someone here actually got mad at me because they didn't know what REW was. That was a strange interaction to say the least.
You ain't makin it easy.
Hot glue them in, staple with leftover fabric, duct tape them. It's a test-of-concept, not a reference golden sample for mass production.
Place them down at the bottom of the cabinet so open end is 3-5 cm from side wall, no mount required.
For my design (80 l inner volume) 2 absorbers with total volume of 4 l were required, so about 5% of cabinet volume. May depend on resonator Q.
Holes at 67 and 142 Hz are your room modes. Nothing to do with speaker itself. Any speaker at that position would excite them.
Not worried about the holes, yeah that's the room and placement.
I really think it's that ~178hz peak on the port graph, because a parametric EQ filter levels it out, it is audibly "fixed". Of course I'd rather not have that at all. I did try removing the port but there's no way it's coming out.
I really think it's that ~178hz peak on the port graph, because a parametric EQ filter levels it out, it is audibly "fixed". Of course I'd rather not have that at all. I did try removing the port but there's no way it's coming out.
You were right about needing to update/reinstall.
These are two REW measurements I'm hoping will help you understand the room mode theory and why EQ is your best solution. If these problems don't exist in free air, they are the room. Taking it outside and getting some 4pi measurements is all about eliminating reflections from the measurements. Here are three speakers that do not have box resonances demonstrating serious resonance in-room. The first two are my friend's B&W 807 S2's in green and the red is Sonus Faber Lumina II's. Each speaker is corner loaded to some extent and the result is an impossible to remove suckout. The next picture is my own set of three-ways demonstrating a number of rippling resonances. Green is left, blue is right, red is L+R. You can also see a cross cancellation between 4-5khz when the beamwidths overlap. All of these speakers have hard edges which diffract sideways. By smoothing them, you can reduce the resonance of the room. Hope this helps.
These are two REW measurements I'm hoping will help you understand the room mode theory and why EQ is your best solution. If these problems don't exist in free air, they are the room. Taking it outside and getting some 4pi measurements is all about eliminating reflections from the measurements. Here are three speakers that do not have box resonances demonstrating serious resonance in-room. The first two are my friend's B&W 807 S2's in green and the red is Sonus Faber Lumina II's. Each speaker is corner loaded to some extent and the result is an impossible to remove suckout. The next picture is my own set of three-ways demonstrating a number of rippling resonances. Green is left, blue is right, red is L+R. You can also see a cross cancellation between 4-5khz when the beamwidths overlap. All of these speakers have hard edges which diffract sideways. By smoothing them, you can reduce the resonance of the room. Hope this helps.
Attachments
I'll have to try to measure them outside again and get better low end results but that's really hard here.
If this were a room problem, why do I not hear it with other speakers in the same spot? Also the issue is at like 178hz which I can't see the baffle edge having much effect over.
If this were a room problem, why do I not hear it with other speakers in the same spot? Also the issue is at like 178hz which I can't see the baffle edge having much effect over.
It could be that previous speakers didn’t excite room modes because of their dispersion pattern having better control. Here are two examples, one of baffle diffraction affecting bass and another explaining why in detail:
https://www.diyaudio.com/community/threads/what-do-roundovers-do.303155/page-5
https://audiojudgement.com/speaker-baffle-design-and-diffraction/
There’s a lot of detail in the first link’s thread, but Patrick Bateman’s measurements do the most revealing.
I took a good look at your REW measurements and they look really good for an in-room response. The room modes may be powered through with EQ and the tweeters and mids could remain as-is for a bi-amp setup. If you can stand it, it’s more or less the dream for big box systems. Distortion looks like the room is lively and responsive. Maybe you’d prefer a tighter beam width? Waveguides do wonders for that depending on the application.
https://www.diyaudio.com/community/threads/what-do-roundovers-do.303155/page-5
https://audiojudgement.com/speaker-baffle-design-and-diffraction/
There’s a lot of detail in the first link’s thread, but Patrick Bateman’s measurements do the most revealing.
I took a good look at your REW measurements and they look really good for an in-room response. The room modes may be powered through with EQ and the tweeters and mids could remain as-is for a bi-amp setup. If you can stand it, it’s more or less the dream for big box systems. Distortion looks like the room is lively and responsive. Maybe you’d prefer a tighter beam width? Waveguides do wonders for that depending on the application.