Help With winisd

[BOOURNS]

I need to put new speakers into an old Traynor 2x15 cab. Im looking at Eminence Legend CB15's. I looked at the thiele small parameters and everything seems like it would be ok. Plugged the info into winisd and im lost.
The cab has internal volume of 6.63 cubic ft. There is a shelf in between the two speakers that divides the cab in half. So it really like each speaker has its own enclosure of 3.3cf. They also have a port in the plywood that is 2x10x3/4in.
im running a 400w head at 4 ohms.
I dont know anything about this stuff! I thought it looked ok but i really dont know what im looking at.
If someone could tell me if this looks good or not that would be awesome! thanks

[dhomer]

I modeled your setup, and if it was my project I might reconsider... A 3.3 cu.ft enclosure with that port is tuned to about 60Hz. A bit too high for the CB15. The response curve tells me the bottom end's gonna be weak, and its gonna boom like a bomb.. +3dB@80Hz isn't real desirable.

If there is a way to extend the length of the ports to 4 inches, the response smooths out pretty nicely, and the tuning frequency is a more reasonable 46Hz. One caution I would mention is the fact those vents might be a bit small, and you could experience what I call "portnoy's complaint"..

[will33]

+1

You need to get the box tuning down to at least 50hz. If the cab size is a bit small, maybe something in the mid 40's. Those legends are good speakers and they will perform well for you if you get the box tweaked to better suit them.

[BOOURNS]

Thanks for doing that for me! I could probably do something to extend the port, I'll have to put some thought into that.
Is there a better suited speaker? I'm not hell bent on the Legends.
This is really all new to me so I appreciate the help.

[billfitzmaurice]

Originally Posted by will33

+1

You need to get the box tuning down to at least 50hz.

45 Hz is about perfect.

[BOOURNS]

Does the port extension have to be the same 3/4 ply as the box or can i use something else?
I read about using PVC pipe in another thread, which I couldnt use in this application but it got me thinking about using other materials.
What have others used I could use some ideas.

[dhomer]

Glad I could help. You can use any rigid material you want for ports. The only considerations are the need to keep internal dimensions true to design, and there is a secure method of mounting. In your case I'd make it out of 1/2" ply. Just be certain the internal opening matches the baffle opening, and subtract the length of the baffle. Should be easy to glue/screw into place.

The CB15 looks like a pretty good match for your cab IF you lengthen the port. Of course you could model every 15" speaker in existence... WinISD will allow you to "set" the cab size and port openings, then you can play w/the line to optimize response and calculate a new port.

A quick and dirty on how to read the line. 0dB is very important. An optimum design will show its response line at or near that 0dB line. More than a dB or so over the line, the cab will tend to "boom". Appreciably under the line, especially starting at 100Hz or so, bass will be weak. Also pay close attention to where the response curve intersects the "-3db" line. Ideally this should be in the mid-high 40's. In addition, the response line should be relatively flat between 60 and 100Hz or so. This will help insure a pretty good balance w/B strings.. If you play 4 and/or don't detune, 80Hz is an acceptable target. Hope this helps, and good luck!

[BOOURNS]

Yes!!! that answered all the questions I had thanks! I'll either be getting the legends or kappa pro 15s. I'm so excited to get this thing going.
Thanks for all your help guys!