First OB with vintage Seas

[boris81]

I ran into a similar problem with woofer sensitivity. 4 woofers wired in serial-parallel is not a good idea for OB. Since I am doing a multichannel-amplified project so I added an extra amp channel. 2 amp channels each driving a pair of speakers wired in parallel will give you a good boost in sensitivity. Of course you need to make sure the amps can handle the lower impedance.

[zmyrna]

After giving it a good rethink,
I am moving towards active.
At least for the bass section.
nanoDIGI from miniDSP should work for me.
It is a 1 digital in, 4 digital out DSP.
Ultimately I can use a nuForce or Wadia power DAC for the upper section,
and my Tact digital amp for the bass.
I will see how the 4x10"s behave in that set up first.

[DrBoar]

measurments of those old Seas drivers
Vintagehifi.dk • Vis emne - Seas 25TV-EW TS och frekvensmätning
Vintagehifi.dk • Vis emne - Seas 21TV-EW Thiele-Small och Frekvens

[zmyrna]

Thanks for clarifying series/parallel SPL issue.

@DrBoar
Thank you so much for the measurements. For some reason I was unable to find them on my web searches. 25TVs seem to be less efficient than I have assumed. On the positive side, they have arguably the ideal qts for open baffle. I wonder whether it will be possible to get enough LF dynamics by feeding them enough power. That is what I will try to find out next. Low mms is making me hopeful.

We should start a blackcone fan club.

[zmyrna]

here is another prototype.
3 way active with miniDSP nanodigi.
CO points 250 and 3000, LR4 and EQ.
waveguide experiments on M and T.
MM topology for bass.
moving from 4 way to 3 way was a step backwards.
in an active OB set up like this (similar to SL and JohnK designs) 3 way is not optimum. SL and JohnK think it is because of dispersion problems at the CO point bw M and T.
I suspect there might be another component. narrow M baffle means we need EQ at the lower end of M. and I think EQ at that area might be negatively effecting the upper end of M (1000-3000hz).
in my next prototype I will be crossing the 8" cone to a neo8s around 1k.
another problem area is the resonances in the bass section, even with steep active CO and EQ.
so no wings or h frame in the next project. it will just be 4 10" woofers on a small square baffle. I think those W have enough excursion and the bass will be enough with active and EQ.