[versus rider]

Hi all just popped over from the open baffle section, some of you will know me from there, if not don't tell them I have slipped over here At present my own playback consists of open baffle 15" woofers and 6.5" drivers up to 1500Hz and then tractrix horns all active and digital, tri-amped. My latest project will require a box speaker for the bass and up to 1500Hz again with a horn from there up. I have decided on audax PR170MO from 150Hz -1500Hz and have used winisd to calculate the box, this box will be incorporated into a larger box containing one Eminence Kappa pro LF driver or maybe something you guys may wish to suggest. Winisd seems to always come up with a tall box thats wider than the depth of the box. Is it possible to make a suitable box thats deeper but not so tall. Ideally the box height at the baffle would be no more than 800mm - 900mm including the audax enclosure at 407mm high. This would give me a baffle height for the Kappa of 400mm - 500mm but could be up to 900mm deep. Any thoughts appreciated

[richidoo]

The box shape itself is not critical for WinISD which is only considering the volume in its simulation. But in reality, box shape affects mechanical box resonance, internal pressure distribution, internal acoustic resonance, baffle step response, edge diffraction, which all affect tone quality.  No reason not to make it any shape you want, it will simulate the same, but consider the other factors in your shape choice.

It sounds like a nice project you're starting. Is the bass sealed or ported?  If sealed, you might want to boost the bass which would require a driver than can handle the additional power, and more box reinforcement against the higher pressures.

The Audax looks like a nice sounding driver. The only caution is in using it down to 150Hz as you plan to. Its flat surround limits the excursion, which makes it roll off at higher freq, -10 at 150.

[versus rider]

vented seems the way to go, in winisd the plot for a vented box shows the response flat to 100Hz then falls quite sharply, does this make sense when the free air resonance is 117Hz?  I will try making a box for the Kappa Pro LF of the right volume but a different shape and see how that works. If I just screw the box together with seals on the joints I will then be able make alterations or use the wood for other projects if not successful. After searching for drivers with fs around 30Hz or less I have found they all seem to be low spl i.e. 80 -93 db when the audax PR170MO is 100db. I may end up with a plate amp for the low end of things. The project is very exciting and involves a mate who is a very talented artist who will be enclosing the tractrix horn, lets just say it will be something your avatar when finished.

[richidoo]

WinISD is not as smart  as you think. You can change many values and the chart will not change. It does not use the excursion spec so it doesn't factor in the unique surround of the Audax. Audax' FR chart shows the rolloff. WinISD assumes flat response down to speaker resonance.

A reflex port can make the speaker play lower than resonance. But you want good blending between your bass and mid drivers, so you may not want the phase and EQ issues that using the resonance band will give you.

[versus rider]

WinISD is not as smart  as you think. You can change many values and the chart will not change. It does not use the excursion spec so it doesn't factor in the unique surround of the Audax. Audax' FR chart shows the rolloff. WinISD assumes flat response down to speaker resonance.

A reflex port can make the speaker play lower than resonance. But you want good blending between your bass and mid drivers, so you may not want the phase and EQ issues that using the resonance band will give you.

yes I noticed that the response remains flat in almost every case. Maybe I'l just use the box volume as a guide and experiment

[JLM]

With my preference for pipes (TQWP, transmission lines) I prefer seeing the baffle directly behind the driver to be slanted (not parallel to the front baffle) to reflect back waves away from coming back out through the semi-transparent driver cone material.

Also I'd recommend using the "golden ratio" in cabinet building (similar to what a room should be).  After all, the highest spl's are inside the cabinet not the room.  Those ratios would be 8:13:22.

OTOH with the very large sound waves of bass note maybe none of this matters??