Spica TC-50 woofer

This is one speaker that I have not seen cloned (or facsimiled)

Spica TC-50 (woofers 8 ohm data)
Spica TC-50 Product Information, The Spica Speaker Enthustiast


Crossover
Spica TC-50 Crossover, The Spica Speaker Enthustiast

Speaker Replacements: Madisound Speaker Components

"Spica Speaker Replacements
Spica TC50

The Audax tweeters used in this speaker are available again! The new tweeter is the Audax TW025A2 tweeter, replacing the old part number of HD100D25. The woofer is the Hif 17JVX 4 ohm and we don't know of any similar speaker to replace this driver. There is no fix for the woofer that we are aware of. Bad woofer = junk speaker."



I think this is close to the Audax.

Visaton W170s (vas? difference)

Visaton W170S-8 6.5" Woofer with Treated Paper Cone 8 Ohm

Visaton W170S-4 6.5" Woofer with Treated Paper Cone 4 Ohm


Aside from an exact replacement woofer, what are the important parameters for a substitute?

TIA
-Chris
 

ScottG

Member
2003-02-04 12:23 am
US
-just the crossover itself is nearly useless (unless you want to repair a TC-50), it's the net result that's important.


Look to the TC-60 instead.

You don't have to make it a Bass Reflex.

Here you can actually see the net result (both high and low pass filter):

Spica TC-60 loudspeaker Measurements | Stereophile.com

..it's also a better design, even if you want to put an active high-pass with it for integration with a subwoofer. (..part of the reason it is better is because it's a bass-reflex design with a larger volume enclosure: that low port tunning freq. puts a load right on the lossy in-box resonance of the driver and keeps the result in the bass/upper-bass better damped.)
 
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This is your project, not mine, so I expect you to do the work:

Download Boxsim:
Software | Visaton

To make it easy, start with a similar Visaton CT 142 project, which you put in the projekte folder:
CT 142 mod – Boxsim Projektdatenbank

Now I would use the Spica TC50 filter and see what happens. It's a single 10uF cap and LCR Fs impedance correction on the tweeter. A single 1mH coil and 3.3uF shunt with another LCR which takes out some breakup around 4kHz.

This will need different values with different drivers, but all doable. 6" bass always has awkward time-alignment and phase problems, and a stepped or sloped baffle can help with a near LR2 slope:
Studio-101-mkII

Lastly I see a polycone bass, and what better than the Classic Vifa P17WJ-00-08 ?

Tweeter might be a Scanspeak D2606/9220.

6" polycone bass must still have some mileage in it. Still made and rather BBC, IMO:
Chartwell LS6.
 

boswald

Member
Paid Member
2014-06-27 3:32 pm
I'd second the P17WJ, and offer the 830874HDS for a little more bass in the same box.
The LCR may become redundant, but will do no harm, maybe just RC for a full or partial zobel if you are parts-averse.


As always, it's worth spending for an easy to work with driver, rather than have to squeeze a square peg into a round hole
 
I was yakking with Michael Chua recently about the 6" Polycone Peerless 830874. Lots of people here like it. Lojzek is one. Joe Rasmussen is another. :cool:

Cardinal-TA (Peerless 830874 with Seas 27TDFC) – AmpsLab

I am sure you will have a good time with this midbass. The SEAS 27TDFC is the sort of tweeter that won't let you down either. Cheap too!

We have had a recent burst of interest in the Morel CAT 378 waveguide tweeter too.

Way I see it is you build a box for the drivers, then fiddle about with crossovers to get it working. The Spica sloped baffle speakers get close to transient perfect. Which is OK if you don't mind a bit of distortion when loud.

Jeff Bagby did something similar with The Tributes using a 6" SB polycone and SB soft-dome. Jeff is very good on series crossovers. I have used some of his precisely calculated values in modelling.

But really, you don't know till you build it. But I think these are good drivers to play with. You won't go far wrong. :)
 
But honestly, ScottG, these sort of adjustments are not rocket-science! :D

Suppose you use a SEAS U18RNX/P polycone:

H1571-08 U18RNX/P

I see a 4kHz LCR bass notch there. Especially off-axis. Maybe 6.8uF and 0.2mH and 2.2R.

Suppose you use a Visaton Paper cone W170S:

W 170 S - 8 Ohm | Visaton

That looks like a LCR 6kHz notch. Maybe 3.9uF and 0.2mH and 2.2R.

Tweeters are similarly adaptable. The Fs notch is done like this:

Notch filter design calculator - for speakers | Audio Judgement

This is a well-established way of doing things. The rest, as they say, is just technique. :)
 
Oh, it looks like we did a Spica clone a while back! Nvr2manybikes built these sloped-baffle beauties. He said they sounded good.

387529d1386991100-series-system-7-steve-based-series-crossover-speakers-seas4-jpg


This was slightly (2.4cm) time-aligned and based around a Visaton W170S-8 6" paper cone and a G20SC 3/4" tweeter.

341543d1365537933-resistor-parallel-inductor-low-pass-crossover-1-timealignment_twoway_fr-png


341544d1365537933-resistor-parallel-inductor-low-pass-crossover-1-timealignment_twoway_phase-png


344652d1366826723-resistor-parallel-inductor-low-pass-crossover-system7_time_aligned-_filter-png


Slightly iffy impedance, but everything else falls into place. Series filters can come with built-in notches in just the right places if you get lucky. All about good driver selection.
 

I have learned quite a lot since that project. Mainly how to get impedance better. You really need those online calculators for 6 ohms and get Butterworth values for the filter.

2-Way Crossover Calculator / Designer

Series filters work best like this, a near 3:2:1 ratio with time-alignment

591258d1484013729-flat-impedance-flat-power-response-design-flat-impedance-series-filter-circuit-png


591257d1484013729-flat-impedance-flat-power-response-design-flat-impedance-series-filter-fr-png


Flat Impedance and Flat Power response design.

But I expect the original Spica filter does much the same things.
 
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Fossil

Member
2001-09-30 5:18 pm
SG
So surprised to see this being mentioned in 2020.
I came across this when I was a poor student back in the late 80s and it was already quite a classic coz there were so many notable bookshelf, big and small during that time.
My remaining impression of this tc50 is that it's mids was so effortless and mesmerising. Correct me if I'm wrong.
Oh... Not sure why I always thought it has an 8" midbass... Perhaps coz I always see it as a bookshelf version of the vandersteen 1