Yes you are right dip is the right word ( notch are a type of eq response giving a dip, the kind of things used in 'feedback destroyers' pa units, or to solve a sibilliance issue with a voice for example).
There is not so much coincidences when it comes to dimensions and wavelengths.
The difference in freq ( 6,9khz) could well be a small change in angle of microphone or an object located nearby. Diffraction is a b.... and why this ( measurements) need to be practised a lot ( can be frustrating but like all in life: no pain: no gain).
One thing you could do to be sure it is from box diffraction is to take measurements under different angle ( we slowly enter 'spinorama' territory) to have a clearer view of effect at works.
That said dips causes less concerns than peaks: we are less sensible to them overall.
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Aaaaand the measurments don't make sence again.
Red: first on-axis
green: 20-ish degrees off axis
blue: second on-axis
There is this enormous dip/descending response to 2,5 kHz which then rises again. I don't understand where this enormous descent comes from in the first place. But then when I add a 2 dB shelf on the midrange from 1.2 kHz up (blue) it doesn't seem to do anything and the dip becomes even larger. I also added a -5 dB at 5 dB bit it is a steep slope and only just starts to roll of at 3 kHz.
Red: first on-axis
green: 20-ish degrees off axis
blue: second on-axis
There is this enormous dip/descending response to 2,5 kHz which then rises again. I don't understand where this enormous descent comes from in the first place. But then when I add a 2 dB shelf on the midrange from 1.2 kHz up (blue) it doesn't seem to do anything and the dip becomes even larger. I also added a -5 dB at 5 dB bit it is a steep slope and only just starts to roll of at 3 kHz.
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I don't think the wool should come alive after being washed properly? I don't think anything in the wool will survive a night long bath in soda and soap. My wool sweaters haven't grown legs either. I'll do a little research on how wool will behave over time. But I think it will be fine if washed properly.
I wasn't planning on carding it. I think it would be fine to use in the shape it is? It is now in fluffy balls. Like it came right from the sheep.
Background: My ex was a fairly serious knitter. I have actually carded and hand spun wool with both a drop spindle and a spinning wheel.
You need to look up instructions for "scouring" wool. You don't want all that lanolin (and dirt) in your enclosure, it will go rancid over time.
Once it's clean, I believe you actually would want to card the wool. Dense clumps of fibers won't be as effective as uniformly fluffy stuff that you can pack in as loosely or densely as desired. Carding is slow, mindless work, but it can be done while you listen to music or watch a movie.
Leftover wool would have to be stored airtight to prevent moth infestation. I have had to try to learn to darn wool to repair many moth holes in my expensive wool cycling jerseys! I'd be tempted to bag it and freeze it overnight to kill any bugs present.
Any boxes I build these days will use recycled cotton insulation as filling. I bought a bale of it that will probably last me for life!
Bill
Oh well, didn't think that process was so critical. Don't think I'm willing to do that.
I've found some cheap alternatives. Real wool strings, similar to what Troels uses. And this mulwohl, recycled fabrics. Both are supposedly very effective. In think I'll use the string for the midrange.
I've found some cheap alternatives. Real wool strings, similar to what Troels uses. And this mulwohl, recycled fabrics. Both are supposedly very effective. In think I'll use the string for the midrange.
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There is a very effective product ( and beneficial as overall: for society, our planet,...) in France called 'Metisse'.
Metisse(R), l'isolant durable > le 1er isolant textile labelise biosource ! | Metisse
It have never stopped gaining notoriety for acoustic treatment since it's introducing.
It is recycled jeans, neutral for your health, fireclassified, and it gives jobs to people which have been excluded of our way of life.
Check if you have access to something like that in Netherlands, it should exist.
This business model has to be encouraged if availlable imho, even more when it is a good product.
Metisse(R), l'isolant durable > le 1er isolant textile labelise biosource ! | Metisse
It have never stopped gaining notoriety for acoustic treatment since it's introducing.
It is recycled jeans, neutral for your health, fireclassified, and it gives jobs to people which have been excluded of our way of life.
Check if you have access to something like that in Netherlands, it should exist.
This business model has to be encouraged if availlable imho, even more when it is a good product.
What I'm listening to: 60% movies and 40% music.
Music: Andrea Bocelli, Adele, Aretha Franklin, but also general pop hits, chill-out/lounge. Lesser often, but I do also enjoy Soul and hiphop. I listen to hiphop mainly with headphones (my DT1990 PRO)
What I don't listen to: heavy metal, rock,
Music: Andrea Bocelli, Adele, Aretha Franklin, but also general pop hits, chill-out/lounge. Lesser often, but I do also enjoy Soul and hiphop. I listen to hiphop mainly with headphones (my DT1990 PRO)
What I don't listen to: heavy metal, rock,
krivium,
Nice material - it looks very much like the "Ultratouch" recycled denim material available in the US and Canada. I have used it in certain designs with good results.
The stuff actually is sold here by the big diy stores. French owners I guess...
This is made from used plastic bottles, made in NL. Have not seen it in person, but it looks great. For a wall, there should be room behind the PET, to make it work down in frq-response. If used in a clever way, I think it could be used like thick felt inside a cabinet. Acoustic Panels Archives | ReFelt
I was actually looking back at the bass enclosure volume and turns out that the ~75 L is actually very big for these woofers. Very low Qtc for an active closed system. So I figured I should make the box smaller for higher Qtc. Which is typical for active systems. Stiffer suspension means better controlled excursion and less effect of room reflections on the cone. And with Qabsorption at 10 which is inbetween "heavy" and "medium" fill in Unibox which I think I will be about applying the low frequency extention is still decent and so is the impuls response. I discussed this with Ulrik (acoustic designer from SB-Acoustics) and he also suggested I would use a volume around this size for a sealed active system.
So I think this will be a very good volume with the right amount of damping. Let me know your opinions anyway.
So I think this will be a very good volume with the right amount of damping. Let me know your opinions anyway.
So I looked back at the bass enclosure volume and the ~75 L of the current design is actually really large for these woofers. Quite low Qtc at around 0.6. I thought I should make this smaller since a higher Qtc is typical for an active sealed system. Stiffer suspension means better controlled excursion and less effect of room reflections back on the cone. With Qabsorption at 10 which is inbetween "heavy" and "medium" in Unibox in 50 L volume low frequency extension is decent and so is impuls response. I discussed this with Ulrik Schmidt (acoustic designer from SB-Acoustics) and he also recommended a volume around this size for a sealed active system.
Your opinions anyway?
Your opinions anyway?
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I think you should listen to Ulrik
Try filling the cabinet with whatever you have and listen to the speaker. You can use, books, sand in 2xplastic bags, empty plastic bottles or so. In return for smaller enclosure, you lower the possible standing waves within the cabinet, hence less need for damping.
One bottleneck in your design is that sidemounting the driver, you need to lower the crossoverpoint, in order to get the drivers to phase properly. Some say max is 150 hz. I think lower is better - below 100 hz.
This puts quite a load on the midrange and will limit max SPL.
All this also need to be tested in practice.
Try filling the cabinet with whatever you have and listen to the speaker. You can use, books, sand in 2xplastic bags, empty plastic bottles or so. In return for smaller enclosure, you lower the possible standing waves within the cabinet, hence less need for damping.
One bottleneck in your design is that sidemounting the driver, you need to lower the crossoverpoint, in order to get the drivers to phase properly. Some say max is 150 hz. I think lower is better - below 100 hz.
This puts quite a load on the midrange and will limit max SPL.
All this also need to be tested in practice.
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