Building a center channel with SDA SRS styling and crossover questions...

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JayMX
JayMX Posts: 435
in Vintage Speakers
So some of you may remember my endeavor veneering the bezels on a pair of SDA SRS2's earlier this year.
https://forum.polkaudio.com/discussion/182425/has-anyone-veneered-the-face-of-their-srss

The same friend for whom I did that work came into a plethora of Krix (Australian cinema speaker mfg) ported bookshelf-size cabinets loaded with Seas drivers. (1) 6 ohm 1” silk dome & (1) 8 ohm 6.5” woofer. (He has like 30 used cabinets :o in good/rough shape from a 20yr permanent installation). Very Monitor 4-esque, slightly bigger cabinets, better bass... He gave me a pair to fool around with and I quickly found that I really liked them. Not especially sensitive, but good full low end and the tweeters are great. I veneered them and paired them with a Marantz 1060. Makes a nice little rig.

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Krix was not able to provide a Datasheet for the complete cabinets because they were “too old,” but these are the drivers:
http://www.seas.no/images/stories/prestige/pdfdatasheet/h0831_27tff_datasheet.pdf
http://www.seas.no/images/stories/vintage/pdfdataheet/h528.pdf

Since my buddy has so many cabinets he asked if I could use some of them to build a center to match the SRS2's. I’m always up for a challenge, so I dug in this week and cut the tops off two cabinets and married them together so there is one tweeter opening and two woofers, two ports. Internal volume is a little bit less than the aggregate of two cabinets summed. The LF response probably suffers to a certain degree, but it’s a center channel, probably roll it off at 150 or so anyways. Can always fool with fill and damp/plug a port too, if needed. I mocked it up in a rough form and ran frequency sweeps through it. Didn’t find any weird resonances or anything, sounded pretty decent. But since I essentially doubled the cabinet's volume, and doubled the ports up, how messed up is the tuning gonna be? Are there other impacts I should consider? This is just an experiment that I’m probably taking too far. Haha.

Today, I veneered the front with white oak to match the SRS2's and I am building endcaps which I will stain dark. Cloth covered panels will cap the sides and a new grille with rounded corners should make it look very similar esthetically to the SRS2's. Similar depth, similar width. Good way to spend a Saturday! I will post more pics as I get the cabinet all dressed up...

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As I worked I started to wonder, what if instead of building a new, single crossover, I just load it with two stock crossovers wired in parallel, feed a woofer from each. This would keep the crossover point the same, but then what if I wire the tweeter outputs from both crossovers in parallel to the single tweeter...? Bad idea? Would I damage either the crossover(s) or the driver or...? What kind of filtering circuits did the mfg employ in these ol gals? I was able to map it out but I don’t know enough to determine if it’s butterworth or second order or Jedi order...? I know just enough about this stuff to be dangerous.... can’t deternine the inductor values, but the LF has a core, the HF has no core if that matters... Crossover is mapped out below. What’s the best route here? I’m rambling at this point...

All said, if this all works out, I may build another for my HT too. Still plenty of boxes to fool with... Thoughts? Thanks in advance.

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Current Collection: Monitor 4a (Peerless), Monitor 5B (Peerless), Modified Monitor 7b (Peerless), RTA15TL (SL3000), SDA CRS+ (194’s), SDA SRS 2.3TL, R100's, R200’s, R300 🤩
Pairs that have passed through: Monitor 4b (Peerless), Monitor 5a (Peerless), Monitor 5b (SL1000), Monitor 5b (SL2000) (3x pair), Monitor 7b (Peerless), Modified Monitor 7c’s (194’s), Monitor 10a (Peerless), Monitor 10b (5x pair), RTA8, RTA8TL, RTA 11T, RTA12c (194's), SDA CRS, SDA 2 (2x pair), SDA 2a, SDA 2b, SDA 1b, SDA 1c, SDA SRS 2 (2x pair), SDA SRS 3.1TL (198’s) (2x pair)...and more to come, it’s a sickness.
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  • FestYboy
    FestYboy Posts: 3,861
    edited December 2018
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    My thoughts: add poly to the rear baffle, and duplicate the low pass xo for the second woofer. The total load will drop, but it will be more in line with the SRS. Do not parallel or series the woofers off of one xo, that will change the xo point (can't remember which way or by how much right now). It looks like a Butterworth with a zoble from your diagram.
    Post edited by FestYboy on
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  • Schurkey
    Schurkey Posts: 2,100
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    Any consideration for installing a second, rear-facing or upward-firing tweeter? Then one OEM crossover powers a woofer and the front tweeter, the second OEM crossover powers the other woofer and the rear- or upward-firing tweeter. You'd likely need two channels of amplification unless you've got enough amperage drive in your amplifier to handle the lower-impedance load.

    Some sort of volume control on the secondary tweeter may or may not be useful
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  • pitdogg2
    pitdogg2 Posts: 24,554
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    Pretty crazy.......

    I love it :p

    Or schurkey could you up the resistor for the up or rear tweeter? Just a thought
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  • JayMX
    JayMX Posts: 435
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    Schurkey wrote: »
    Any consideration for installing a second, rear-facing or upward-firing tweeter? Then one OEM crossover powers a woofer and the front tweeter, the second OEM crossover powers the other woofer and the rear- or upward-firing tweeter. You'd likely need two channels of amplification unless you've got enough amperage drive in your amplifier to handle the lower-impedance load.

    Some sort of volume control on the secondary tweeter may or may not be useful

    Didn’t think about the loading.... 😬 two stock crossovers @8ohms ea paralleled would be 4ohms with dips lower... I will experiment with a rear firing tweeter, I have a spare...
    Current Collection: Monitor 4a (Peerless), Monitor 5B (Peerless), Modified Monitor 7b (Peerless), RTA15TL (SL3000), SDA CRS+ (194’s), SDA SRS 2.3TL, R100's, R200’s, R300 🤩
    Pairs that have passed through: Monitor 4b (Peerless), Monitor 5a (Peerless), Monitor 5b (SL1000), Monitor 5b (SL2000) (3x pair), Monitor 7b (Peerless), Modified Monitor 7c’s (194’s), Monitor 10a (Peerless), Monitor 10b (5x pair), RTA8, RTA8TL, RTA 11T, RTA12c (194's), SDA CRS, SDA 2 (2x pair), SDA 2a, SDA 2b, SDA 1b, SDA 1c, SDA SRS 2 (2x pair), SDA SRS 3.1TL (198’s) (2x pair)...and more to come, it’s a sickness.
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  • JayMX
    JayMX Posts: 435
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    Just did some testing tonight. I temped up one tweeter fed from both crossovers and the overall intelligibility increased, good for a center channel. 👍🏻
    It sounds half decent :)
    Just need to clean it up, finish the cloth covered side panels, build a new grille and do a little more polishing!
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    Current Collection: Monitor 4a (Peerless), Monitor 5B (Peerless), Modified Monitor 7b (Peerless), RTA15TL (SL3000), SDA CRS+ (194’s), SDA SRS 2.3TL, R100's, R200’s, R300 🤩
    Pairs that have passed through: Monitor 4b (Peerless), Monitor 5a (Peerless), Monitor 5b (SL1000), Monitor 5b (SL2000) (3x pair), Monitor 7b (Peerless), Modified Monitor 7c’s (194’s), Monitor 10a (Peerless), Monitor 10b (5x pair), RTA8, RTA8TL, RTA 11T, RTA12c (194's), SDA CRS, SDA 2 (2x pair), SDA 2a, SDA 2b, SDA 1b, SDA 1c, SDA SRS 2 (2x pair), SDA SRS 3.1TL (198’s) (2x pair)...and more to come, it’s a sickness.
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  • JayMX
    JayMX Posts: 435
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    Finished up and delivered today. Sounds pretty decent. Looks pretty good. Buddy is happy. Fun project!

    Attached top and bottom caps using hangar bolts just like on the SRS2's. Built from 3/4” MDF, veneered with rift cut oak (which I really didn't like much, wanted to bubble up in several spots...)
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    Built cloth covered side caps, glued to the original cabinet:
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    Painted the rear of the cabinet with enamel gloss spray paint. Jumped the two stock crossovers together. Left the tweeter wired to both crossovers. Not sure what the overall impedance is, but it sounds good! :)
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    Built a new grille from 1/2” mdf, sprayed black and covered with grille cloth from Simply Speakers:
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    His theater is coming together slowly!
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    Current Collection: Monitor 4a (Peerless), Monitor 5B (Peerless), Modified Monitor 7b (Peerless), RTA15TL (SL3000), SDA CRS+ (194’s), SDA SRS 2.3TL, R100's, R200’s, R300 🤩
    Pairs that have passed through: Monitor 4b (Peerless), Monitor 5a (Peerless), Monitor 5b (SL1000), Monitor 5b (SL2000) (3x pair), Monitor 7b (Peerless), Modified Monitor 7c’s (194’s), Monitor 10a (Peerless), Monitor 10b (5x pair), RTA8, RTA8TL, RTA 11T, RTA12c (194's), SDA CRS, SDA 2 (2x pair), SDA 2a, SDA 2b, SDA 1b, SDA 1c, SDA SRS 2 (2x pair), SDA SRS 3.1TL (198’s) (2x pair)...and more to come, it’s a sickness.
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  • joecoulson
    joecoulson Posts: 4,943
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    That’s awesome
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