I saw that the correct size for PR is twice the sub size, but as I want a minimum box size, I wonder if I can increase the total surface of the PRs, in order to reduce the box size, bellow the recommended size for the speaker characteristics.
I plan to build a sub with a Dayton Epique E180HE-44 with it’s associated PR HE180HE-PR.
could I put 4 PR (One on each side of the box)?
I plan to build a sub with a Dayton Epique E180HE-44 with it’s associated PR HE180HE-PR.
could I put 4 PR (One on each side of the box)?
No, you can't reduce cabinet volume by increasing passive radiators area size.
Twice the driver's volume displacement is typically the suggestion for passive radiators. The driver and passive radiator often have different Xmaxs, so the size alone isn't always enough to know.
Multiple radiators on different sides of the box are fine. There are a few commercial subwoofers done that way.
Thanks for your answers. the xMax & size of the PRs are the same as the sub, so, 2 should be fine. Now, would 4 of those PRs make better bass?
PRs
PRs
A blanket statement about more passive radiators being better is hard to make.
The passive radiator(s) and the driver have their own sets of parameters that interact with the box volume to produce the final response shape. Modeling each configuration and comparing the results is the typical way to find out without building them.
More passive radiators tend to need more mass added to each to tune to the same frequency as a single passive radiator. You may exceed the maximum suggested mass for the passive radiator.
The passive radiator(s) and the driver have their own sets of parameters that interact with the box volume to produce the final response shape. Modeling each configuration and comparing the results is the typical way to find out without building them.
More passive radiators tend to need more mass added to each to tune to the same frequency as a single passive radiator. You may exceed the maximum suggested mass for the passive radiator.
I did some research with WinISD tool to simulate the frequency response with different combinations. It confirms that increrasing the surface of the passive radiators above the x2 vs the sub surface has some impact on performances. The sub is a Dayton Audio Epique E180HE-44. Passive radiators are E180HE-PR.
See the graph:
See the graph:
- Bass Reflex (Green): best curve - But requires a very long vent
- Closed box (Black): worse curve (but cleaner bass for Hifi)
- 2 Passive PRs - x2 sub surface (Red): Intermediate
- 4 passive PRs - x4 sub surface (Blue): Better than 2 PRs above 35Hz (+2.5db at 50 Hz). But: is it worth the extra investment? Or is it cheaper to push the equalisation at low frequencies?
adding more passive radiators has a similar effect like adding bass reflex ports or increasing port cross section.
it increases the bass output capability before excursion limit kicks in but also results in higher box tuning.
using radiators will not save box volume, except, of course, the volume of the port, which is not needed with PRs.
in your example above the box with red curve seems to be tuned too low for even bass response.
either you added to much weigth to the PRs or you should use different ones e.g. with lighter diaphragm (or even equalize output).
blue curve is tuned slightly too high for even response thus the ripple.
you could try simulation with three PRs or adding weight to all four radiators.
it increases the bass output capability before excursion limit kicks in but also results in higher box tuning.
using radiators will not save box volume, except, of course, the volume of the port, which is not needed with PRs.
in your example above the box with red curve seems to be tuned too low for even bass response.
either you added to much weigth to the PRs or you should use different ones e.g. with lighter diaphragm (or even equalize output).
blue curve is tuned slightly too high for even response thus the ripple.
you could try simulation with three PRs or adding weight to all four radiators.
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tank you Mattstat and Stv for your very valuable advises 🙂 In fact, looking at the extra costs for PRs and the complex tuning (around 50 Euros for each PR), I start wondering if a closed box + equalization/dsp for bass couldn’t be a solution to keep the minimum sub size (around 12 liters). Indeed, the speaker I plan to use supports 200 Watt RMS / 400max, with 14 mm XMax. So, with class D amplifier, I can send a lot of power to move it at rather low cost.
Your desired output at low frequencies will have a big influence on whether a small equalized sealed enclosure is good enough. There's typically an excursion graph in most software. With your given driver/box combination, see how much power you can put into the speaker before Xmax is exceeded, and/or how much output it has at your desired lower frequency limit with the intended power. I haven't modeled your woofer, so I don't have a feel for where you are.
Ha indeed, thanks Mattstat! there is an option for cone excursion. I reach xMax at 30Hz for 150 W. Already quite a lot of power a 7"sub. Knowing that I plan to cut frequencies with high pass filter bellow 30-35Hz. I will also certainly configure my DSP as limiter for frequencies bellow 50 Hz, to avoid exploding the sub.
