3 way design help

[Tex Houston]

Hi All - I'm building a 3 way active speaker setup using chipamps. I'm using vifa 8" woofer, Vifa 5" mids and morel tweeters. I have an existing speaker box I want to use which is about 35litres - a little less than the required 37litres for the woofer - I am also putting a 5 litre housing around the mid which then takes me to about 30 litres. I guess this is less than ideal but how would I go about getting the best out of this set - up? Should I use light fill or heavy and what port length and diameter should i use - maybe two ports? I'm crossing over the bass/mid at 300 and the tweeter at 3k. Any help greatly appreciated.

[sdclc126]

Is the "required" 37 liters for the woofer measured for a port? If not the volume will be too small - vented enclosures need to be larger than sealed.

Either way, if you want to get the best out of your design with an existing enclosure I would recommend removing the rear panel and extending the depth of the cabinet to achieve the required volume. This will also make it easier to install bracing (if needed - they usually do), the crossover, and stuffing.

[Tex Houston]

The 37 litres is for a ported enclosure. The amp and crossovers are located in a compartment under the main enclosure. It would be too big a task to extend the back - just want to optimise the cabinet as it stands. Thanks for the reply.

[tinitus]

Impossible to say with out woofer specs ... who says 37liter are optimal

[Tex Houston]

The woofer is a Vifa PL22WR09 8 inch -

Vas - 56 litres
Qts - 0.34
Qes - 0.37
Qms- 5.65
Fs - 27 Hz
Lower freq= 25
Upper freq = 500

Thanks again

[tinitus]

You are right, calculation says 38liter BR

With 30 liter Q is raised from 7 to 10, and it will peak with around 1db in midbass ... and port will need to be slightly longer (ø50x120mm)

F3 will be raised from 32hz to 37hz, which probably is ok considering its an 8" with limited Xmax ... but you may want to tune a bit lower with a longer port (ø50x150-200mm ?)


But what are the dimensions ... with 35liter it sounds like you will need a base and make what I think you call a "stand-mount" speaker

You should be able to use the base for additional volume

[Tex Houston]

Thanks Tinnitus

The cabinets are floor standers about 280mm W x 290mm D x 750 H. The photo shows where I'm gonna put the amps and crossover, so I'm runnin out of room - I just want to see if this is gonna be a winner - then maybe do a made to measure cabinet if it goes well. Is there any other tips for helping with midbass peak? Would two ports help?
Thanks again.

[sreten]

Hi,

You need to detune the port to around 28Hz, 25 litres will be fine
with this. Extending the rear of the cabinet does not seem a good
idea because it is simply not necessary.

/sreten.

[tinitus]

1db midbass peak is nothing to worry about, and the higher Q of 10 may only give the feel of a little more bass and could be wellcome with an 8" woofer
No need fore twin ports
As said, tune a little lower with a port of ø50x 150-200mm ... Sreten seem to agree

[sreten]

Originally posted by tinitus

As said, tune a little lower with a port of ø50x 150-200mm ... Sreten seem to agree ...

Hi,

50mm diameter and 28Hz = 200mm / 30L, 250mm / 25L.

/sreten.