I'm working on a FLH subwoofer design. All along I've been planning on not porting the chamber. But I've been a bit concerned about thermal buildup in the chamber, as well as protecting the driver below the sub's lower cutoff frequency. So I've started to consider porting it, as this adds some way for hot air to get out (at least something better than nothing, right?), and it limits cone excursion at the bottom end of the frequency range. All good things.
However, this is requiring the chamber to get a bit bigger -- not ideal. And the port required is quite long too (because the chamber is still relatively small compared to a typical bass reflex cabinet). Trying to balance port length and particle velocity appears doomed. Even with the port area larger than I'd like, and the length longer than I'd like, particle velocities are still around 45 m/s. This is quite a bit higher than the general consensus amongst the community thinks is OK (9m/s seems to be a number people are comfortable with). Though perhaps this is just for a bass reflex design, and not a horn?
I'm looking at other commercial designs and their ports are not huge. Fulcrum SS18 is one. Looks like there is a nice rounded exit to reduce turbulence. But the port area still looks quite small.
Helps? 😕
However, this is requiring the chamber to get a bit bigger -- not ideal. And the port required is quite long too (because the chamber is still relatively small compared to a typical bass reflex cabinet). Trying to balance port length and particle velocity appears doomed. Even with the port area larger than I'd like, and the length longer than I'd like, particle velocities are still around 45 m/s. This is quite a bit higher than the general consensus amongst the community thinks is OK (9m/s seems to be a number people are comfortable with). Though perhaps this is just for a bass reflex design, and not a horn?
I'm looking at other commercial designs and their ports are not huge. Fulcrum SS18 is one. Looks like there is a nice rounded exit to reduce turbulence. But the port area still looks quite small.
Helps? 😕
If you're sure it's not a mechanically noisy driver you can put driver reversed so that magnet is on horn side, and about venting the port to gain low end but protecting from over-excursion, since it will output just low frequencies content, you should consider using a passive radiator. It will help limiting excursion mechanical (even if it cannot be shown in sims), and filter some noise content. It won't have port resonnance if port were needed too long. And about flared port vent air velocity (compression and chuffing wize), here is some experimental interesting stuff www.subwoofer-builder.com you want depend of frequency, and port flare.
Typical FLH has tight compression chamber, so its not sensible putting driver/magnet in a horn..
Ported FLH's sounds somewhat slower.
There are many well known commercial plans avaliable for good FL horns.
Startech super bass horn, 186/1850 horns, Martin WSX, Labhorn..
Another topology is so called bandpass horn. ES18bph as example (mostly for midbass applications tho).
Back to ported flh, you know Martin WLX?
Plan WLX Martin
I have heard them, not much difference to a standard reflex. As I said, they are slower than typical FLH.
Ported FLH's sounds somewhat slower.
There are many well known commercial plans avaliable for good FL horns.
Startech super bass horn, 186/1850 horns, Martin WSX, Labhorn..
Another topology is so called bandpass horn. ES18bph as example (mostly for midbass applications tho).
Back to ported flh, you know Martin WLX?
Plan WLX Martin
I have heard them, not much difference to a standard reflex. As I said, they are slower than typical FLH.
Last edited:
- Status
- Not open for further replies.