"Statement" type mid tunnel

[Squidspeak]

I was wondering about the theory and possibility of using the hybrid TL
mid section of the Statement family of designs. I have a 3-way diy speaker
with a ESS AMT on top running dipole,below I have a 5" Morel in a too small
sealed cab covering 120hz.-1200hz. with 12" Titanic Mk1 for bass duties.
Active X-over DCX2496. Anyway never been happy with the mid,want to
change woofer and either increase box volume or open back of mid chamber
or do the TL tunnel like the Statements.The two woofers I am considering are
SS Revelator 15W/8530K or Seas Excel W15CY, I know both are capable of
being used in an open baffle design,so my question is how do I determine my
best option and can I copy the mid design from the Statements,because I
would like to have the mid and AMT both as Dipole. Being a newbie and
recovering lurker I need good advice because it is a big investment and I
think it sounds good now but can be much better.

[Face]

I don't believe either would do well down to 120hz in an open baffle.

[Squidspeak]

I don't believe either would do well down to 120hz in an open baffle.

Do you think I would be better off increasing the volume of the sealed
mid enclosure? Or is the TL tunnel an option?

[Curt C]

This issue as I see it is the excursion issues running a 5" driver down to 120 Hz without box compliance. I'd suggest an fc of 250 Hz and a 6.5" mid/woofer. The higher fc would reduce the excrusion requirements by a factor of 4. Since you are crossing at 1.2K to the AMT the larger midwoofer should not compromise the design.

C

[Squidspeak]

This issue as I see it is the excursion issues running a 5" driver down to 120 Hz without box compliance. I'd suggest an fc of 250 Hz and a 6.5" mid/woofer. The higher fc would reduce the excrusion requirements by a factor of 4. Since you are crossing at 1.2K to the AMT the larger midwoofer should not compromise the design.

C

Curt thanks for replying (I was hoping), anyway it is an existing cabinet and
I would actually be making a bigger hole to fit those woofers. I can increase
the volume of the mid chamber (sealed) by building onto the back of enclosure. Or can I run the 12" titanic up to 250hz. and do the tunnel for
the mid? I know those drivers should not have a problem going to 120hz.
sealed. What do you feel is my best option?

[Curt C]

I did a little off the cuff modeling tonight assuming you have the MW143 for a mid. Even at 120 Hz a 2nd order BW HP filter will limit excursion sufficiently to not reach Xmax until about 106 dB. A smaller then optimal enclosure actually exhibited slightly more excursion as fc was pushed higher.

If you add onto the sealed mid enclosure, can you get at least 7 liters of volume back there? That's my personal rule of thumb for sealed mid volumes to ameliorate the standing waves.

Or: How about 20" of 6" PVC pipe? That's the minimum length you would need to support a 120 Hz crossover. Line the pipe with 1" foam but leave the first few inches closest to the driver free, and adjust the foam from there. -And of course leave the back of the pipe open. -Although you can cap it as well, and it will make an excellent sealed enclosure of slightly over 9 liters.

C

[Squidspeak]

I did a little off the cuff modeling tonight assuming you have the MW143 for a mid. Even at 120 Hz a 2nd order BW HP filter will limit excursion sufficiently to not reach Xmax until about 106 dB. A smaller then optimal enclosure actually exhibited slightly more excursion as fc was pushed higher.

If you add onto the sealed mid enclosure, can you get at least 7 liters of volume back there? That's my personal rule of thumb for sealed mid volumes to ameliorate the standing waves.

Or: How about 20" of 6" PVC pipe? That's the minimum length you would need to support a 120 Hz crossover. Line the pipe with 1" foam but leave the first few inches closest to the driver free, and adjust the foam from there. -And of course leave the back of the pipe open. -Although you can cap it as well, and it will make an excellent sealed enclosure of slightly over 9 liters.

C

Yes Curt, that is the Morel woofer in question. On your first suggestion, are
you saying to add that passive components to the woofer after the active
X-over?

I can definately add that much volume to the mid enclosure.

I like the idea with the PVC, do I have much to gain by going with the
slightly larger SS or Seas woofers in this configuration?

[Curt C]

I was thinking you could add the HP filter using your 2496... Passive would work, but it would take a very large value cap and doing it line level or via DSP would be a better choice.

I'd suggest you try the enclosure change with the Morel first. -That's the frugal Scot in me talking...

C