Likely a quite stupid question but I'd like to know... And, I did do a search prior to asking.
Do the midrange speakers that have 'phase plugs' (as I think the things are called) allow air to go between the outside of the enclosure and the inside of the enclosure?
THEREFORE, defeating the purpose of using them in a scientifically computed/dimensioned sealed and/or ported enclosure?
I have some extra 4ohm midranges that I'd like to use for some bookshelf speakers. They have the bullet phase plug things. The drivers did come with T/S parameters but are those parameters rather pointless?
In other words, would it be worth it to port the enclosure or just go sealed?
BTW, if the air opening caused by the bullet is sealed behind it by the coil and other structures, just say...uhhhhh, yeah, they are actually sealed and you screwed up. 🙂 I will not be offended.
Thanks.
Do the midrange speakers that have 'phase plugs' (as I think the things are called) allow air to go between the outside of the enclosure and the inside of the enclosure?
THEREFORE, defeating the purpose of using them in a scientifically computed/dimensioned sealed and/or ported enclosure?
I have some extra 4ohm midranges that I'd like to use for some bookshelf speakers. They have the bullet phase plug things. The drivers did come with T/S parameters but are those parameters rather pointless?
In other words, would it be worth it to port the enclosure or just go sealed?
BTW, if the air opening caused by the bullet is sealed behind it by the coil and other structures, just say...uhhhhh, yeah, they are actually sealed and you screwed up. 🙂 I will not be offended.
Thanks.
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Yes there is likely some leakage.
But every sealed box should have a small leak to equalize air pressure. And in a BR it is assummed there will be some leakage.
So no big deal in the end
dave
But every sealed box should have a small leak to equalize air pressure. And in a BR it is assummed there will be some leakage.
So no big deal in the end
dave
Unless the gap is vented, the air will have to leak through the spider, so it's not quite an open leak like you'd think.
As someone has said; "The only stupid question is the one you DON'T ask".
You are among friends......
Cheers, Jonathan
You are among friends......
Cheers, Jonathan
Some drivers are vented beneath the spider, more commonly the more expensive drivers with diecast baskets as it is easier to implement (most commonly but not always).
You will get some leakage, but the escaping air has to go past the outside of the voice coil through a gap of 0.5 mm or less, down around the voice coil and back up along the inside edge of the voice coil, where the gap is a similar size.
And at audio frequencies, the resistance provided by the tight clearances would become enough of an acoustic load to prevent any real air leak that might affect the systems characteristics. A lot of dustcaps actually have vent holes in them, and many other dustcaps are made of a light fabric that you can see the magnets pole piece through, and they are also to permit airflow so that while keeping dust out they can breath to provide cooling and reduce unwanted resonance problems due to trapped air.
Hopefully this answers your question, it is a perfectly valid question and more sensible than many others that get asked 🙂
You will get some leakage, but the escaping air has to go past the outside of the voice coil through a gap of 0.5 mm or less, down around the voice coil and back up along the inside edge of the voice coil, where the gap is a similar size.
And at audio frequencies, the resistance provided by the tight clearances would become enough of an acoustic load to prevent any real air leak that might affect the systems characteristics. A lot of dustcaps actually have vent holes in them, and many other dustcaps are made of a light fabric that you can see the magnets pole piece through, and they are also to permit airflow so that while keeping dust out they can breath to provide cooling and reduce unwanted resonance problems due to trapped air.
Hopefully this answers your question, it is a perfectly valid question and more sensible than many others that get asked 🙂
Hi,
Its not very often that you vent a midrange enclosure, usually they
are sealed, and usually for midrange less volume than you would
use if using them as a sealed bass/mid, Qbox around 0.9.
The DC airpath has next to no effect at the frequencies of concern.
rgds, sreten.
Its not very often that you vent a midrange enclosure, usually they
are sealed, and usually for midrange less volume than you would
use if using them as a sealed bass/mid, Qbox around 0.9.
The DC airpath has next to no effect at the frequencies of concern.
rgds, sreten.
There is some air leakage on most phase plug speakers, but the air has to travel down the full length of the thin voice coil gap to the rear motor steel plate.
I have never seen a speaker Application Note that warns the user of a phase plug speaker to use any special enclosure design parameters.
I have never seen a speaker Application Note that warns the user of a phase plug speaker to use any special enclosure design parameters.
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Primarily a Cooling Issue
The resulting turbulence, involving outside air, cools the voice coil whether it is internally vented or not.
The resulting turbulence, involving outside air, cools the voice coil whether it is internally vented or not.
🙂Thank you all on this topic. Excellent assistance and information!
I am going to build some sealed enclosures (very well stuffed) and create an MTM configuration using these extra midranges and supplemented by a small subwoofer and see how that works out.
I'm always for accuracy versus what a driver was not really meant to do, heh.
But with respect to my asked question: I thought that if the phase plug caused a ton of leakage, which apparently is not the case, I'd just go ported and shoot for that low frequency extension. But, as it seems, these are somewhat closed-up so I'll choose the sealed enclosure type first.
I am going to build some sealed enclosures (very well stuffed) and create an MTM configuration using these extra midranges and supplemented by a small subwoofer and see how that works out.
I'm always for accuracy versus what a driver was not really meant to do, heh.
But with respect to my asked question: I thought that if the phase plug caused a ton of leakage, which apparently is not the case, I'd just go ported and shoot for that low frequency extension. But, as it seems, these are somewhat closed-up so I'll choose the sealed enclosure type first.
more info on phase plug but for outdoor large format mids
6" horn - Speakerplans.com Forums - Page 1
more photos
6" horn - Speakerplans.com Forums - Page 1
more photos
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What you will hear (especially when you play at tuning frequency on a ported box) is the air that goes into the gap, down under the top plate, up and around to inside the former, and then in the air gap between the former and the phase plug. This can be audible but isn't a concern.
The most audible of these are the drivers which have a vented former in addition to a phase plug and under spider venting. The Tang Band W4-1337 series is one such driver. That said, this is a full range driver whose box pressures will never be high enough at low frequencies for this to be a problem. The venting in this case is because the tolerance of concentricity is so fine that any turbulence at high excursion caused by what I mentioned in the first paragraph induces distortion. The pressure loss is worth it in this case.
The most audible of these are the drivers which have a vented former in addition to a phase plug and under spider venting. The Tang Band W4-1337 series is one such driver. That said, this is a full range driver whose box pressures will never be high enough at low frequencies for this to be a problem. The venting in this case is because the tolerance of concentricity is so fine that any turbulence at high excursion caused by what I mentioned in the first paragraph induces distortion. The pressure loss is worth it in this case.
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