Reality Check SDA 1B crossover rebuild

gilberca

In the process of gathering the proper (recommended) components to update/rebuild HF and LF crossovers in my SDA1Bs. I've previously upgraded the SL2000 tweeters to the RDO194 units back in 2016. After much reading on this forum, I'm ordering Sonicaps and Vishay Mills resistors for the HF and Solens caps for the LF unit.
So far items include:
For the HF Xovers:
2x .0.50 Ohm Vishay Mills MRA-5 to replace the RDE090 Safety bypasses
6x 2.7 Ohm Vishay Mills MRA-5
2x 2.0 Ohm Vishay Mills MRA-5
2x Gen I Sonicap 4.4 uF 200VDC with Precision Matching
2x Gen I Sonicap 12 uF 200VDC with Precision Matching
I'm planning on deleting the 750pf bypass caps based on reading previous posts about them.

For the LF Xovers, I'm ordering the following:
2x Solen Capacitor 180.0uF 400Vdc PB Series
4x Solen Capacitor 33.0uF 400Vdc PB Series
Hopefully these cap values are "close" enough to the original schematics that are using 34uf and a combo of 130 and 55uf electrolytics.
Let me know if I'm way off here please.

Thanks in advance

westmassguy

Looks good, you're within 3% of the specified value on the Solen caps. I'd consider 10 or 12 watt on the Mills/Vishay-Mills resistors. Solen Fast Caps don't get a lot of love here, but you should be fine.
You'll need to remote mount the 180uf Solens. Also consider replacing the sub-bass drive inductors with some nice Erse Super-Qs

Schurkey

gilberca wrote: »

For the HF Xovers:
2x .0.50 Ohm Vishay Mills MRA-5 to replace the RDE090 Safety bypasses
6x 2.7 Ohm Vishay Mills MRA-5
2x 2.0 Ohm Vishay Mills MRA-5
2x Gen I Sonicap 4.4 uF 200VDC with Precision Matching
2x Gen I Sonicap 12 uF 200VDC with Precision Matching
I'm planning on deleting the 750pf bypass caps based on reading previous posts about them.

Are you satisfied with the VOLUME of the tweeters? I am not on my 1Bs. From the day I got them, (1986 or '87) and even now, I thought the treble was too soft. I deleted the poly-switches and DID NOT install a half-ohm resistor to compensate. The treble is still not loud enough for me. I've been threatening to remove the 2.0 ohm resistors and replace them with 1.8 ohm units.

If the treble IS loud enough for you, you might save some money by ordering a pair of 2.5 ohm resistors instead of separate .5 ohm and 2.0 ohm resistors, and just slap a jumper wire across the solder-points where the polyswitch went.

gilberca wrote: »

For the LF Xovers, I'm ordering the following:
2x Solen Capacitor 180.0uF 400Vdc PB Series
4x Solen Capacitor 33.0uF 400Vdc PB Series

"I" would not use 400 volt caps in this application. Too large, needlessly expensive. I used two, 91uF, 250 volt caps soldered together to achieve 182uF.



It fits fine behind the bassive radiator.


Some time AFTER the photos were taken, I electrically disconnected the bigass inductor in favor of a 10mH iron-core inductor sourced from ERSE just as Westmassguy stated. Each inductor was un-wound to match the OEM spec, I think it's either 9.6 or 9.8mH.

gilberca

Thank you for the insights on this. The RDO194 Tweeters are plenty bright enough for me. I did find that the original grill cloth damped the highs noticeably and normally ran the speakers without the front grills. Last week I replaced the grill cloths with fabric sourced from Parts Express. Now I can hardly tell any difference with grills on or off the speakers.
Regarding the sub base inductors: I am assuming you are referring to the 9.6 as well as the pair of 1.2mh units?

Cal

Schurkey

gilberca wrote: »

Regarding the sub base inductors: I am assuming you are referring to the 9.6 as well as the pair of 1.2mh units?

Only the 9.6s.

gilberca

Ok. So this one? ESQ55-16-10000 10.0mH 16ga ESQ - Super Q Coil
Thanks in advance

westmassguy

They make a #14 gauge also, but your amp must be able to handle less than 4 ohm loads.
http://www.erseaudio.com/Products/SuperQCoils14Gauge/ESQ55-14-10000

Schurkey

gilberca wrote: »

Ok. So this one? ESQ55-16-10000 10.0mH 16ga ESQ - Super Q Coil

westmassguy wrote: »

They make a #14 gauge also... ...
http://www.erseaudio.com/Products/SuperQCoils14Gauge/ESQ55-14-10000

I think when I bought mine, the 14-gauge was on perpetual back-order. Therefore, I think I bought the 16-gauge. ERSE doesn't have a record of my purchase--too long ago, I guess.

I bought an LCR meter so I could unwind the coils, but ERSE will do that for you if you ask. About $15/each last time I heard them advertise this service. Contact them to confirm.

westmassguy wrote: »

but your amp must be able to handle less than 4 ohm loads.

Good point. All the film caps we install that shunt current will have lower resistance than the electrolytics they replace, AND the big inductor will have less DC resistance, so the impedance of the speaker will drop somewhat--and they were a 4-ohm nominal load to begin with.

gilberca

Thanks for the clarification. The 14 ga inductors are on backorder from ERSE.
I'll check to see if they offer the customization service since I don't have an LCR meter.
Guess I'll find out whether the amp will drive them after the mods. Its an old SAE TWO P10. Its driven the SDAs without issue so far....

westmassguy

FYI, Erse Inductors are always on back order, at least the ones we use most. Translation: they make them to order. I've never waited longer than two weeks for supposedly back ordered SuperQs.

gilberca

Good deal. I emailed Erse and they will dewind the inductors to meet my requirements. Cost is $10.00 each. I requested they go ahead with the custom order.

pitdogg2

money well spent. Hopefully it will be closer than +/- 10% IIRC that they list their inductors as.

westmassguy

pitdogg2 wrote: »

money well spent. Hopefully it will be closer than +/- 10% IIRC that they list their inductors as.

More like +20%/-30%. They're all over the place. Polk's spools are even worse.

gilberca

I was finally able to collect all the components to do the Xover upgrade and performed the operation this weekend.
Thanks for all the help from those who responded to my original query.

For the HF xover, I went with Sonic Caps and Vishay Mills resistors. I checked the original components upon removal and none were far out spec; at least when measured with an LCR meter (I broke down bought one).
For the LF xover, I used the 400V Solen caps and boy are they HUGE! The 180uf looks like a stick of dynamite. Also got ERSE to dewind the 10mh coils to 9.6mh.
Both the 180uf cap and coil presented a challenge mounting in the cabinet due to their size. I wound up using solid 14 ga copper wires soldered to the LF xover board to allow the cap and coil to be remote mounted.

See attached pic for mounting details.

All spade connects were cleaned with Caig Deoxit then coated with Caig ProGold.

When I first fired them up, highs were very muted, but after running them for just few hours, they are sounding fantastic. I have to say that the upgrade very worthwhile.
The speaker measured resistance decreased from 3.8ohms to 3.0ohms and my amp is driving them without issue so far.

Thanks again for all the help.

pkquat

Great to hear. Welcome to the family rabbit hole