What do think of Es180 in an open baffle

[bvbellomo]

Could a Dayton Esoteric Es180 work in an open baffle design with a passive crossover? I remember reading a high Qts is recommended, but am not sure why. This is a medium low qts driver. The high xmax might work well, obviously you'd have a trade off between bottom extension and baffle size.

[5th element]

With box loudspeakers a drivers natural Qts (and other parameters) are augmented with the correct box volume (etc) to arrive at a preferred and 'optimal' system Q or Qtc.

For example you may have a driver with a Qts of 0.4 and you decide that the correct target for the system should be 0.7. As a result you place it in a box of suitable volume to arrive at that target. This gives you your desired roll off and transient performance.

With an open baffle loudspeaker you cannot do this. The driver effectively runs in free air and it's roll off and transient performance are entirely dictated by it's natural T/S parameters.

Of course when you place a driver on an open baffle you are also going to see the 6dB/octave roll off due to rear wave cancellation at some point (plus the dipole peak).

Technically speaking, when placing a driver on an open baffle, you are confronted with two issues (at least when concerning its low end roll off).

The first is the 6dB/octave, open baffle, roll off. This is easily corrected for with a shelving filter (when going active at least).

The second is the roll off that the driver will add on top of this due to it's T/S parameters. The easy way to measure this is to perform a near field measurement (like 1cm away from the cone) of the driver when mounted on the open baffle. The way the driver modifies the response is by essentially what it's frequency response would be like in an infinitely large sealed box. For approximation purposes this can be used, but it's always best to measure because usually it ends up more like you've placed the driver in a less than infinitely large box, still a very big box, but it raises the fs and Qts of the naked driver a tad.

If you go active you can use a driver with any Qts that you want. As running the driver open baffle is essentially like having it in a very large sealed box you can simply use a Linkwitz transform to set the target Q to anything you desire.

The above is what Linkwitz did in the original Orion. The XLS drivers have a natural Qts of around 0.2, which is terrible low, but the rest of their parameters are well suited for OB use - large xmax and low fs.

Linkwitz used a Linkwitz trasform to first rise the open baffle Q of the XLS drivers up to 0.5 with a target fs of what I believe was 40Hz. He then applied a shelving filter to correct for the open baffle roll off of the original H baffle.

If you only have a passive solution available then the options to correct for the above issues are very limited, but they still need to be addressed.

[Face]

I hope it's for a very small listening area(computer desk, etc..) or a midrange, otherwise you will find yourself running out of excursion quickly. For example, I use a pair of high excursion 15s in OB configuration in my living room, anything smaller either lacks bottom end or runs out of headroom quickly.

[bvbellomo]

Wow, thanks. I might measure this, but it is for a fairly large room. I love the sound of open baffle, but my wife would never let me get away with this size.