High end sound without the high end price, even for DIY (difficult you say, lets see)
Reasonably high out put, preferably in excess of 105db
Low extension bass output, useable output to 30Hz
Clear detailed midrange
Smooth and clear highs, even at high SPL, no harshness
No complex crossover or filtering networks
Simplistic aesthetic design

Option 1
Firstly the HDS woofer is replaced by a CSX version (850136), this driver is exactly the same but has a stamped basket instead of
the cast, and it has slightly less Xmax and a few different figures, but the primary reason for this change was that the CSX
extends all the way up to 3.5KHz, it also has a recommended crossover of 3Khz.
Secondly I changed the tweeter to a Seas 27TFFC due to recommendations of the seas tweeters and a few recommendations
of this one in particular as being surprisingly clear and detailed, The initial reason for changing away from the peerless
tweeters was that Peerless are well know for their woofers, and I had been told by people that they could be harsh and I
also wanted a slightly more high end sound.

Here is the predicted response curve of the CSX 850136 in 60L cabinet with 34Hz tuning via a 75mm vent 130mm long

This alignment gives greater low bass output that my venom subwoofer *smirk* and there will be 2 of these.
These towers will yield a rather high efficiency in their bottom end so not a great deal of amplifier power will be needed to get them moving.
This efficiency is in the box design, such a large box allows this, but because the box is large it will need to be heavily braced, I am not yet at
the stage of designing the actual box construction but I think I will construct a matrix of bracing.

Update:
Since writing this I have experimented more with alignments and found that 40L would be a more appropriate volume as it allows higher
power handling and hopefully a tighter midbass sound. it also removes the 38-42Hz bump that could potentially be boomy. So by reducing
the volume

Option 2:
This option was established after careful evaluation of existing projects on the net. And LONG forum discussions.
Here we change the 850136 for the highly regarded 6.5" 850122. This woofer whilst having smaller cone area has a lager Xmax, this results in
only a slightly lower swept volume (vd) the vd of the 850136 is 94 cubic cm whilst the 850122 has a vd of 79 cubic cm, this small difference
combined with the better modeling low end response of the 6.5 makes it almost match the 8"ers performance. The 850122 also has a much
smoother fr and also extends slightly higher. The Biggest factor pushing forward the 6.5" is that there are a number of projects that have been
well documented and have crossovers available online, free of charge.

Further developments have led me more towards this option in opposition to the 8", I have discovered that the 8" has slight cone breakup
after about 700Hz making the woofer an inappropriate choice for a 2way of this nature. Hence it is almost certain to not be used in my towers
now.
So with my heart and wallet basically set on the 850122 I will now investigate my alignment options.

Firstly lets start with the most simple, a sealed box. This alignment will yield the most musical alignment, but it has severely limited bass output.
Yielding an F3 of 62Hz this would need to be complimented with a sub to fill in the lower 2 octaves. Also this alignment will yield very similar
results in a 20L cabinet as in a 40L, for this reason this alignment would be best suited as a bookshelf speaker for a sub sat system or as rears.

Secondly I will look at a Vented Alignment, I have chosen a 40L cabinet as it holds a nice compromise between power handling and extension.
Tuned to 34Hz this alignment yields an impressive F3 of 31Hz and an F6 of 28Hz and an F10 of 24Hz after this the response continues to fall
rapidly. this extension is very very good for a single 7" driver. The Maximum SPL is quite good, though does not exceed 100db in its low end.
This makes this speaker unsuitable to heavy bass duties such as those put forth by 5.1 channel material, but the SPL capabilities above 85Hz are
in excess of 105db, from 110Hz up the max SPL hits 108db, these are some very impressive figures considering the size of woofer and enclosure.

Thirdly is a Transmission Line speaker using the tried and tested plans from Bob Brines, this alignment yields a highly musical speaker that will
extend almost as low as the vented alignment but has a more gradual roll off, but TLs have been described as more musical speakers regardless of
of bass response. Also the alignment is very appealing as all the planning has been done and there is also a crossover available.

Option 3:
This option has come about after many different alignments had been "decided", I keep changing my mind so who knows what will actually
get built. Well this option has come about after a want for higher sensitivity than a single woofer can offer, so I began looking at MTM designs,
none seemed to be available for peerless drivers which had documented crossover, though I emailed a person on modifying their 2way design
and they told me that I could use their 2.5way crossover using the CSX 6.5" woofers.
This seems rather appealing to me as it would give me a pre-designed crossover to follow that has been tested.

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