I'm dealing with this driver: PRV10MB800FT
The recommended sealed volume is 0.147cf.
Given the driver dimensions, this is physically impossible.
What am I missing here?
Thanks in advance,
Garry
The recommended sealed volume is 0.147cf.
Given the driver dimensions, this is physically impossible.
What am I missing here?
Thanks in advance,
Garry
Put the parameters into WinIsd or similar and see what box size you get
It's probably a mis-calculation when converting litres to cf or something
You can also comment on the Parts Express website and ask them to check
Brian
It's probably a mis-calculation when converting litres to cf or something
You can also comment on the Parts Express website and ask them to check
Brian
Parts Express are quoting wrong values. The sealed box size is about a 1/4 of the Vas for a Qts 0.32 driver. I make that about 0.3 cubic feet.
I know the sealed box formula. It is the inverse of the square of 0.7 divided by the square of 0.32 all minus one as the factor. That's about 4. Thus 1/4 Vas.
You would always use a larger vented box with such a PA 10" driver. A cubic foot or more. Otherwise the bass will be non-existent.
Rule of thumb is you use the Vas as the volume with a 0.38 Qts driver. By the time you add a bass coil with significant resistance to a Qts 0.32 driver, you will be up around 0.38 anyway.
I know the sealed box formula. It is the inverse of the square of 0.7 divided by the square of 0.32 all minus one as the factor. That's about 4. Thus 1/4 Vas.
You would always use a larger vented box with such a PA 10" driver. A cubic foot or more. Otherwise the bass will be non-existent.
Rule of thumb is you use the Vas as the volume with a 0.38 Qts driver. By the time you add a bass coil with significant resistance to a Qts 0.32 driver, you will be up around 0.38 anyway.
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I threw the TS parameters into WinISD for this driver and it appears that PE's recommendation is based on a sealed box Qtc of 1.
That is higher than most people would class has high fidelity.
For a Qtc of 0.7 (maximally flat, before accounting for any bafflestep effects) the required box size is approx 10l, more or less in line with system7's estimate.
FWIW, it would technically be possible to make the 4 litre enclosure for this driver, because we also have to include the volume taken up by the backside of the driver itself, which is probably about 2l, so a 25cm ID pipe cut to just over 12cm length & capped off would do it.
That is higher than most people would class has high fidelity.
For a Qtc of 0.7 (maximally flat, before accounting for any bafflestep effects) the required box size is approx 10l, more or less in line with system7's estimate.
FWIW, it would technically be possible to make the 4 litre enclosure for this driver, because we also have to include the volume taken up by the backside of the driver itself, which is probably about 2l, so a 25cm ID pipe cut to just over 12cm length & capped off would do it.
I like being right! Speakers are terribly simple really. People ask what size cabinet is right for 5", 6", 8" and 10" drivers.
The answer is usually 10L, 15L, 22L and 40L. A cubic foot being 28L last time I looked.
Reflex tubes are usually predictable too. Of course, you must add the driver displacement volume and the tube volume to be accurate.
For a 10" speaker, we thus get 40L and about 3" by 3" reflex tubes. But, TBH, I can never hear much difference whatever you go for. Ends up looking like this WLM Diva for a co-axial Eminence Beta 10CX:
https://eminence.com/products/beta_10cx#specifications
Eminence have been surprisingly slack recently, letting their excellent builder's advice for co-axial PA speakers drift into a broken link. Naturally I have a copy, but don't know how to post a PDF under the new forum software.
Ever helpful, I am willing to email the PDF to interested parties.
The answer is usually 10L, 15L, 22L and 40L. A cubic foot being 28L last time I looked.
Reflex tubes are usually predictable too. Of course, you must add the driver displacement volume and the tube volume to be accurate.
For a 10" speaker, we thus get 40L and about 3" by 3" reflex tubes. But, TBH, I can never hear much difference whatever you go for. Ends up looking like this WLM Diva for a co-axial Eminence Beta 10CX:
https://eminence.com/products/beta_10cx#specifications
Eminence have been surprisingly slack recently, letting their excellent builder's advice for co-axial PA speakers drift into a broken link. Naturally I have a copy, but don't know how to post a PDF under the new forum software.
Ever helpful, I am willing to email the PDF to interested parties.
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Thank you, this is starting to make more sense. I've been building speakers for my own use for a long time (50+ years), but my knowledge is basically that old too. I would generally use a VTVM, audio oscillator and my ears for tuning, but these modern drivers seem to be in a different class so I thought I'd bring myself up to date.
The volume taken by the driver itself was never a real issue back then, but with parameters like these it seems to be now. Do programs such as WinISD and Unibox take this into account, or should I add the estimated driver volume to the results they give?
The volume taken by the driver itself was never a real issue back then, but with parameters like these it seems to be now. Do programs such as WinISD and Unibox take this into account, or should I add the estimated driver volume to the results they give?
Add it.
Yes, since the likes of the acoustic suspension enclosure it has become the norm to make the air suspension more significant than the driver mechanical suspension.
Yes, since the likes of the acoustic suspension enclosure it has become the norm to make the air suspension more significant than the driver mechanical suspension.
You should add the drivers' volume. in Winisd there is a dimension" tab for all drivers where that info and litre/volume it takes up can be input etc.
And parameters like this are very common in pro drivers these days, low Vas, low Qts and highish FS.
Maximum spl and power handling, in as small and light package as possible, which makes sense for the application.
Just downloaded WinISD, I'm impressed! The results line up well with my "seat-of-the-pants" expectations for the drivers I plan to use, maybe there is something to this modern method lol.
After years of doing 2 ways, I'm planning a 3 way design with 15" low, this 10" mid, and compression horn on top. Had planned a cross to mid around 100-120Hz, my goal was to keep male vocal fundamentals on the 10". This may not be possible, still playing with options.
Here's what I've got so far, if there's any glaring errors I'd appreciate someone pointing them out! Btw, this is for hifi with a 2x7w tube amp, not PA.
After years of doing 2 ways, I'm planning a 3 way design with 15" low, this 10" mid, and compression horn on top. Had planned a cross to mid around 100-120Hz, my goal was to keep male vocal fundamentals on the 10". This may not be possible, still playing with options.
Here's what I've got so far, if there's any glaring errors I'd appreciate someone pointing them out! Btw, this is for hifi with a 2x7w tube amp, not PA.
It's debatable how much it matters when you get them into a room and things start to happen... but while you're on the sim you could have a quick look at group delay.
Hi Prof,
Just noticed a couple of issues with your data entry for these drivers - they're not affecting what you see yet but would if you were to model higher power where we need to pay attention to excursion.
1: You've entered Sd in m^2, whereas the stated numbers (990 for the 15" and 380 for the 10") are in cm^2. Likewise Xmax should be in mm, not m. When entering your driver data you can double click on the units to change them from one type to another - always make sure that you choose what matches the drivers actual spec's.
2: I think you've entered the chassis diameter for each driver, whereas it should be the effective radiating diameter of the cone (typically plus half the surround) for the purposes of modelling. It's been a while since I used that older version of WinISD (there's a newer one available, 0.7.0.950) so I can't remember if it works the same but you don't typically need to enter both diameter and Sd - if you enter one, the program should calculate the other for you - see the helpfile for more info on that.
HTH,
D.
Just noticed a couple of issues with your data entry for these drivers - they're not affecting what you see yet but would if you were to model higher power where we need to pay attention to excursion.
1: You've entered Sd in m^2, whereas the stated numbers (990 for the 15" and 380 for the 10") are in cm^2. Likewise Xmax should be in mm, not m. When entering your driver data you can double click on the units to change them from one type to another - always make sure that you choose what matches the drivers actual spec's.
2: I think you've entered the chassis diameter for each driver, whereas it should be the effective radiating diameter of the cone (typically plus half the surround) for the purposes of modelling. It's been a while since I used that older version of WinISD (there's a newer one available, 0.7.0.950) so I can't remember if it works the same but you don't typically need to enter both diameter and Sd - if you enter one, the program should calculate the other for you - see the helpfile for more info on that.
HTH,
D.
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Note too that the male fundamental goes down to ~80-180 Hz with ~100 Hz the most common per this interactive chart with 'fullness' at the ~120 Hz mean and 'boominess' at ~240 Hz, so normally best to let the woofer do it or limit the sub to ~80 Hz and use an appropriate sized (mid) bass for the app.
@David Morison Thank you very much for the feedback, I did not realize you could change units in WinISD!
It appears the 10" I'm using will give the best performance in the smallest possible box, basically 9" x 9" x 5" and crossed at 200Hz or above.
Kinda goes against everything I know as an oldtimer, but is this correct?
Kinda goes against everything I know as an oldtimer, but is this correct?
The efficiency/bandwidth product of this woofer is quite high. It may seem out of place but it's unusual that it would be chosen for use in a closed box although there's certainly no reason you shouldn't. It's EBP suggest it's more of a horn driver.
Math wise it is and since designed for up to 3 way they apparently used octave spreads in 3rds = 20-200 Hz, 200 - 2 kHz, 2 k -20 kHz.