[kinku]

Wow!!. Speaking of God and God presented himself.Thanks MJK. Much appreciated.
Will you be kind enough to explain the pros and cons( if any) of these two designs.

[MJK]

Both designs have a nice flat SPL response with a slight downward slope. I think the trade-offs are as follows.

FR - W - W : The Lowther is close to ear level for a sitting listener but the vertical radiation pattern is biased down towards the floor. You will probably get significant low frequency reinforcement, and also a few dips, from the floor bounce. I had a similar design on my room many years ago and it performed quite well.

W - FR - W : the vertical radiation pattern is much more uniform. But the Lowther is well below a sitting ear level hence the slanting back of the OB in the simulation.

In both designs the L-Pad can be tweaked to adjust the SPL output from the Lowther to produce the best results in a given room. If I was picking between one or the other I would probably use the second option and build an adjustable base for the OB so I could vary the angle of tilt. I would make sure I was sitting on axis for the Lowther and then adjust the toe in a little so I was slightly to the side of this axis.

[kinku]

MJK please help me here "building adjustable  bass for the OB so I could vary the angle of tilt."is it like an adjustable stand for the unit to tilt the entire baffle back and forth in vertical plane?

[MJK]

Yes.

Some kind of hinged base or a rear leg with an adjustable length.

Anything that you can tilt the baffle back to find the optimum position for your setup.

[kinku]

A thank you is not enough. Really appreciate your input Martin.

[MJK]

You are welcome.

It was an interesting design and only took a few hours to come up with the two options. If you build one of them please let me know your impressions.

[kinku]

One of them is my next build.Do you think the low extension can be tweaked to low 40s with an active system?

[MJK]

I would not recommend adding EQ to try and get more low end. If you plan on using an active crossover the frequencies and slopes may change from those I used for the passive version. You will need to tweak it by ear.

If you want deeper bass, put the Alpha 15A woofers in H frames and set the Lowther in a separate open baffle sitting on top. It will work great. There are advantages to this set up, you can adjust the position of the OB on top of the H frames to dial in the vertical radiation pattern. This set up would require a new crossover design and probably a more aggressive L-Pad (or more boost if active).

[kinku]

Martin wondering the reason behind the change when I switch from active to passive crossover ?
Will it be better to tweak with a measurement microphone?

[MJK]

A passive crossover interacts with the driver's impedance. An active crossover does not. So the final crossover frequencies and transitions can be different, it is probably small but you need to determine if it is important. It is not always easy to have an active and passive crossover act exactly the same.

Getting good measurement results is the hardest part of speaker building. Have you performed measurements and tweaked the settings of an active crossover before? It may not be so straight forward.

[kinku]

Thanks for explaining the science.
I have not done measurements using a cross over, but curious to learn. Is there any references / guides that you  recommend?

[Retsel]

Dick Olsher created an open baffle speaker that uses Lowther drivers and some woofers crossed over using passive components.  He used the DX4 drivers.  I purchased his plans and mounted my 15 ohm DX4 Lowther drivers on open baffles using a couple of other woofers for bass.  The 15 ohm Lowthers have an advantage of not having the 2.5khz peak, and also having 3 mm of x-max - the 8 ohm drivers only have 1 mm of x-max.  Dick Olsher developed his design for the 8 ohm variety and had a trap for the 2.5khz peak. 

Lowthers sound spectacular on open baffle.  You might want to consider treating your Lowther drivers with enABLe.

Retsel   

[holdent]

Hi Petzel:
I didn't know DX4s are/were available as 15 ohm versions.  The DX4s measured by MJK were 7.1 ohms and had some pretty nasty peaks on axis (see here http://www.quarter-wave.com/Project04/Measurements.html) - worse than measured for DX2s and DX3s.  (However he liked the DX4 much more in the MLTL he designed than the cheaper DX models).  Lowther lists the xmax for all of their drivers  as +/- 1mm. Are you referring to the PM series which are available as 15 ohm versions?  Or are these modified? Thanks.

[holdent]

Sorry - should've been "Hi Retzel"