Midrange Internal Volume in a 3-Way

[69stingray]

Hello everyone,

I have a question in regards to the volume of the midrange enclosure in a 3-way system. For discussion, lets say you have a 3-way with a 10" woofer, 5" Midrange and 1" Tweeter and cross-over points of 500 Hz and 4,000 Hz.

What do you use for the internal volume of the midrange enclosure? Playing with WinISD and Dayton Classic 5.25", the required sealed enclosure volume ranges from 1.3 L - 15 L, depending on the alignment. The volume effects how the speaker rolls off the low-end, correct? Since this midrange is operating in the 500-4,000 Hz range, how does volume effect it? I looked at the group delay and that was minimal.

I think I have read somewhere that ported enclosures have less distortion, if this is true, why wouldn't you make the midrange enclosure ported?

Thanks for the help!

[simon5]

If you make the midrange enclosure ported, you get group delay. That's why some keep it sealed. Others think the drop in distortion is worth it. At 500 Hz, the distortion is minimal so IMHO I think it's better to go sealed and get lower group delay.

Since you aren't going lower than 500 Hz, you don't need much volume, probably the 1.3 liter alignment is enough. I don't know how that's looking in WinISD Pro but if there's no peaking, then it's ok.

[janusz]

Hi stingray,

It is the lower midrange frequency which determines the enclosure size. With 500Hz 1.3 to 1.5 L is OK as Simon recommended.

There is however, another important factor when designing a midrange speaker enclosure, namely its internal shape as it strongly affects the output linerity and the quality of sound. As our ears are far more sensitive to midrange frequencies than to any other.

Cube like enclosures are the worst resulting in a few dB amplitude variations. The best are spherical (may be somewhat elongated), and pentagonal or trapezoidal enclosures. It is quite easy to build a spherical enclosure.

One way is to use a rubber ball of required size. The other is to use a few slices of hard foam (used in packaging). It is easy to cut slices first to fit boxy enclosure of the midrange driver and then to cut out something resemblig a sphere in these slices. When these are glued together they have a spherical cavity in them. That spherical cavity should have the right capacity. You can make it somewhat larger if you wish and then reduce its size, if required, by gluing into it some irregular object.


cheers,

[69stingray]

Thanks everyone. It sounds like if you just confirm that your internal volume doesn't create any bumps in the freq. response or group delay problems in the desired frequency range, then you should fine. And of coarse, stick to basic enclosure design principals, non-parallel walls, etc.

Thanks again.

[wintermute]

you might also want to consider your intended crossover order/slope.... if you were to go with a low order crossover, then it may be beneficial to err on the side of a slightly larger volume (optimise the bass response)... this may or may not be desirable, but you can tailor the final slope depending on the rolloff characteristics of the volume you decide on ...... having the freq resp relatively flat for two octaves below your cross over freq (ie down to 125Hz) may simplify your crossover design (could complicate it too depending on the high end rolloff of your woofer

Tony.

[mondaycurse]

Another thing to consider is your driver's EBP(fs x Qes). The dayton has an EBP of ~100. It would be better suited toward a vented box.