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Need advice on cabinet build, please.

#61
Passinwind said:
The alignment is ideally chosen by the user in the drop-down window when starting a new project. There's no reason at all to accept the default choice if that's not what you want or need, and each available textbook alignment dictates a different set of tuning variable choices. Then you can tweak variables to achieve your own alignments, for better or worse.
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Ah, thanks for clarifying. I admit that I haven't used WinISD since I wrote my own design software. :)
 
#62
fdeck said:
Ah, thanks for clarifying. I admit that I haven't used WinISD since I wrote my own design software. :)
Click to expand...

Personally, I like both Boxsim and the Passive Speaker Designer betas I've tried a lot more than WinISD, but it does come in very handy for quick and dirty graphing for discussions on TB. How come all this software came out just after I stopped building speaker cabinets though? Link Removed
 
#63
Passinwind said:
Personally, I like both Boxsim and the Passive Speaker Designer betas I've tried a lot more than WinISD, but it does come in very handy for quick and dirty graphing for discussions on TB. How come all this software came out just after I stopped building speaker cabinets though? Link Removed
Click to expand...
I've been doing some research into the idea of modifying one of my programs (the web based one) so you can create a web link containing the design parameters. That way, during discussions you could post a model that would be instantly usable by the recipient.
 
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#67
telecopy said:
I am using the beta version from http://www.linearteam.dk
I'm not on Facebook.
Click to expand...

That version is ancient. You don't need to be on Facebook to find the link, just Google the version number I posted and you will be directed to the direct download on Linearteam's site. No worries if you just want to say "enough" at this point though...
 
Last edited:
#69
telecopy said:
I forgot to ask.. Is it best to source "flaired" speaker ports instead of just PVC tubes?
Flaired at both ends make a difference? I've seen both for sale.
Click to expand...

The main advantage of flared ports is, you can get away with a bit smaller diameter because the flared ends will help keep the airflow in and out of the ports from going turbulent (chuffing). Using a smaller diameter means you can use a shorter port length to achieve your target tuning frequency. I'm often trying to shoehorn adequate port length into a compact, busy-on-the-inside box, so I use flared ports all the time. If you can use larger diameter straight ports, that's a more cost-effective route.

If you want to use straight ports to keep cost down but are still cutting it a bit close on port cross-sectional area, cut the inside end of the port on a 45 degree angle (measuring your port length down the centerline). This will help stave off chuffing a little bit. You see, the inside end of the port is where the airflow first goes turbulent, because the outside end of the port has the baffle around it which helps facilitate airflow into it but the inside end doesn't. So we cut the inside end on a 45 degree angle to increase the cross-sectional area of that opening, which is now an oval instead of a circle, and this increased cross-sectional area helps the airflow a bit. Plus it looks cool, though you're the only one who'll know it's there.

Two more thoughts on ports: If you expect the cab to be pushed close to its thermal limits, consider using two ports, one above the woofer magnet and one below. This will facilitate "chimney effect" cooling, as hot air exits the top port, which draws cooler ambient air into the bottom port. Keeping the magnet from getting too hot not only protects the woofer from damage, but also reduces thermal compression, as a hot magnet is a weak magnet. If you've ever noticed that your amp seems to be running out of power on the last song of the set, it's not the amp, it's your woofer magnet heating up and losing power, which means losing efficiency. I'm not saying chimney effect cooling will make a huge difference (if this happens regularly you need another cab, NOT a bigger amp), but it can help.

Also, if you're using a long-voice-coil woofer (especially if it's in a small box), you might want to position your ports so as to provide a fairly symmetrical airload on the back of the cone. A highly asymmetrical airload on a long-voice-coil woofer can cause enough cone-rocking on some notes for the voice coil to "tap" against the sides of the magnetic gap, producing an unwanted clicking sound.
 
#70
Hi, I would like to comment about the cabinet structure.
Nobody have talked about the cabinet construction.
When constructing cabinets, achieving a high degree of rigidity is important. The membranes of the speaker move the air from the interior of the cabinet, compress it and create a high internal pressure.
 
#71
DukeLeJeune said:
The main advantage of flared ports is, you can get away with a bit smaller diameter because the flared ends will help keep the airflow in and out of the ports from going turbulent (chuffing). Using a smaller diameter means you can use a shorter port length to achieve your target tuning frequency. I'm often trying to shoehorn adequate port length into a compact, busy-on-the-inside box, so I use flared ports all the time. If you can use larger diameter straight ports, that's a more cost-effective route.

If you want to use straight ports to keep cost down but are still cutting it a bit close on port cross-sectional area, cut the inside end of the port on a 45 degree angle (measuring your port length down the centerline). This will help stave off chuffing a little bit. You see, the inside end of the port is where the airflow first goes turbulent, because the outside end of the port has the baffle around it which helps facilitate airflow into it but the inside end doesn't. So we cut the inside end on a 45 degree angle to increase the cross-sectional area of that opening, which is now an oval instead of a circle, and this increased cross-sectional area helps the airflow a bit. Plus it looks cool, though you're the only one who'll know it's there.

Two more thoughts on ports: If you expect the cab to be pushed close to its thermal limits, consider using two ports, one above the woofer magnet and one below. This will facilitate "chimney effect" cooling, as hot air exits the top port, which draws cooler ambient air into the bottom port. Keeping the magnet from getting too hot not only protects the woofer from damage, but also reduces thermal compression, as a hot magnet is a weak magnet. If you've ever noticed that your amp seems to be running out of power on the last song of the set, it's not the amp, it's your woofer magnet heating up and losing power, which means losing efficiency. I'm not saying chimney effect cooling will make a huge difference (if this happens regularly you need another cab, NOT a bigger amp), but it can help.

Also, if you're using a long-voice-coil woofer (especially if it's in a small box), you might want to position your ports so as to provide a fairly symmetrical airload on the back of the cone. A highly asymmetrical airload on a long-voice-coil woofer can cause enough cone-rocking on some notes for the voice coil to "tap" against the sides of the magnetic gap, producing an unwanted clicking sound.
Click to expand...
Thank you, thank you Duke.
 

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