Hi all,
I'm planning to embark on a DIY speaker build project and need help in calculating the size of the box I need based on the woofers I'd like to use:
2 x Peerless 6-1/2" Nomex Cone HDS Woofer
1 x tweeter
1 x super tweeter
Peerless woofer specs are as follows:
Qts: 0.37
V(as): 24.76 L
According to this chart, i'm getting a volume of 18.57 L or 0.65 cu/ft.
Multiplying 0.65 cu/ft x 2 Woofers = 1.3 cu / ft box.
If my calculations are correct, then I'm thinking on a 1.3 box, with a 2" x 6.5" long port, I should be getting low 30Hz?
Anyhow, please feel free to correct me on anything here, I'm doing this for the very first time.
Cheers all,
Rado
I'm planning to embark on a DIY speaker build project and need help in calculating the size of the box I need based on the woofers I'd like to use:
2 x Peerless 6-1/2" Nomex Cone HDS Woofer
1 x tweeter
1 x super tweeter
Peerless woofer specs are as follows:
Qts: 0.37
V(as): 24.76 L
According to this chart, i'm getting a volume of 18.57 L or 0.65 cu/ft.
Multiplying 0.65 cu/ft x 2 Woofers = 1.3 cu / ft box.
If my calculations are correct, then I'm thinking on a 1.3 box, with a 2" x 6.5" long port, I should be getting low 30Hz?
Anyhow, please feel free to correct me on anything here, I'm doing this for the very first time.
Cheers all,
Rado
Last edited:
Love the attitude Galu
Thank you for asking this question bcos it made me realize I used wrong data for my initial calculation. So, here we go again:
Qts: 0.36
V(as): 42 L
Fs: 28 Hz
According to the chart, i'm getting a volume of 31 L or 1.1 cu/ft per woofer, for a total of 2.2 cu/ft.
This recommendation came from the manufacturer of the driver.
What do you think @Galu?
No, you don't get to 30 Hz or how it goes on the lower end. Because what you are using to calculate is a late 70s rule of thumb and does not in any way care for the Vas, which would show how much the Qb would shift to. Back then it could be used since computers weren't that common and the most drivers back then had parameters in a much narrower range. If you want to make a statement/calculation with any significance, you'll need to calculate the Qt first, for which you need the Vas (for wich you need the cone surface, not driver diameter) and the Mms (moving mass) and the suspension stiffness.
For the love of god (if you believe in it anyway..), do yourself a huge favour and use a simulation program.
Sorry @Galu, it wasn't a Peerless driver in the end, it was SB Acoustic. I had too many tabs open and have been doing too much research. Here is the link to the PDF spec sheet.
No, not real loud, but too loud for an apt.,etc., especially if corner loaded, though on the upside, HR predicts only needing a cheap 5 W to drive them to Xmax down low. Just as well since at anywhere near rated power the vent needs to be an Av = Sd area pipe/TL length long to tune a 58.34 L [min] cab to a 28 Hz Fs, requiring either a TQWT alignment or use PRs [preferably two].
GM
GM
If you really want to fly by the seat of your pants, here are some rough calculations for the 6" SB17CAC35-8 driver in a reflex enclosure (the initial figures relate to a single driver):
Volume of box = 1.1 cu ft
Tuning frequency = 30Hz
Bass cut-off frequency = 35Hz
Length of 2" diameter port = 6" approximately (exact length to be determined by experiment)
If mounting two drivers you will need:
Weak bass - shorter port
Boomy bass - longer port
At this point, the loudspeaker designers are holding their heads in their hands, but I like your attitude!
Volume of box = 1.1 cu ft
Tuning frequency = 30Hz
Bass cut-off frequency = 35Hz
Length of 2" diameter port = 6" approximately (exact length to be determined by experiment)
If mounting two drivers you will need:
- twice the enclosure volume (2.2 cu ft)
- two 2" x 6" ports
Weak bass - shorter port
Boomy bass - longer port
At this point, the loudspeaker designers are holding their heads in their hands, but I like your attitude!
To use the potential in bass, your midrange will suffer greatly in your concept because of the intermodulation/the excursion. The needed changes would involve either a low crossed over midrange driver or a subwoofer. The former would avoid the influence of the bass to the midrange , the latter would avoid the excursion by moving it from the bass-mid driver to the sub driver.
The two tweeter setup isn't very favorable either, the high x-over f would bring interferences between the tweeter and supertweeter. It's much cheaper and sounds a lot better if you just scrap the supertweeter plus the crossover parts and get instead a really good tweeter.
The two tweeter setup isn't very favorable either, the high x-over f would bring interferences between the tweeter and supertweeter. It's much cheaper and sounds a lot better if you just scrap the supertweeter plus the crossover parts and get instead a really good tweeter.
My goodness me, people do spend a lot of time reinventing the wheel!
Why not ask Peerless for the 830875 details?
Peerless 830875 HDS 164 NOM MidWoofer Speaker
Though really the 830874 polycone bass has a more illustrious history for the splendid 6" plus 1.5" or 1" plus 3/4" idea:
Peerless 830874 HDS 164 PPB MidWoofer Speaker
Anyhoo, here's the answer straight from the Peerless application note.
Why not ask Peerless for the 830875 details?
Peerless 830875 HDS 164 NOM MidWoofer Speaker
Though really the 830874 polycone bass has a more illustrious history for the splendid 6" plus 1.5" or 1" plus 3/4" idea:
Peerless 830874 HDS 164 PPB MidWoofer Speaker
Anyhoo, here's the answer straight from the Peerless application note.
Attachments
You're a little late to the party , it's actually a SB Acoustics: Help Calculating the speaker box size
GM
, it's actually a SB Acoustics: Help Calculating the speaker box sizeGM
My goodness me, people do spend a lot of time reinventing the wheel!
Because it's a SB Acoustic, not a Peerless, like GM already said? If you would have read the thread, you surely wouldn't have missed it, would you?
A. Because it isn't a Peerless and
B. Because someone probably want to make something different? On a ported speaker you have a lot of freedom with the most drivers. You have to live with the consequences as a result though.
Anyhoo, here's the answer straight from the Peerless application note.
That's just one of a lot of different possibilities. And - as you surely already realized - they did not include any serial resistances (especally the coils), which increases the Q factor and therefore the response, enclosure size and port dimensions. Some of that is negligible, others is not, some are wanted, some are not. These datasheets just give you a rough estimate what is a possible use.
If you really want to fly by the seat of your pants, here are some rough calculations for the 6" SB17CAC35-8 driver in a reflex enclosure (the initial figures relate to a single driver):
Volume of box = 1.1 cu ft
Tuning frequency = 30Hz
Bass cut-off frequency = 35Hz
Length of 2" diameter port = 6" approximately (exact length to be determined by experiment)
If mounting two drivers you will need:
You can make the final port adjustments by ear.
- twice the enclosure volume (2.2 cu ft)
- two 2" x 6" ports
Weak bass - shorter port
Boomy bass - longer port
At this point, the loudspeaker designers are holding their heads in their hands, but I like your attitude!
Thank you @Galu. Some friends over at Steve Hoffmann forum did a WinISD calculation for 2 SBA drivers, with the following results:
2.078 cu/ft box
30.06 tuning frequency
F3 = 31 Hz
With 3.0" vent, 7.91" long
With 2.0" vent, 3.03" long
SPL at 3 ft, with 120 watt input = 109 dB
I am glad to observe that those simulation calculations are in reasonably good agreement with my rough paper calculations.
(I also could have suggested a single 3" diameter pipe in the region of 8" long.)
Now get building.
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