Could I turn my small Harbeth into a big 3 way with passive crossover?

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My two cents: Dayton SA 25 plate amp $44.50 at PE.

I'm not sure that ykyk actually indicated what amp / power level was being used to drive the Harbeths, and I suspect the little SA-25 might not be sufficient?
If your thinking was to incorporate the amp(s) in the sub woofer enclosures - certainly a valid approach- I'd be more inclined towards the SA-100. Granted it's twice the cost, and it sounds like two would be required, but regardless of driver sensitivity I think the bottom end is definitely one place where you can't have too much power on tap.
 
So, what amp are you using on the Harbeths? You mentioned B1 buffer, but I can't recall power amp. And while I'm at it, do you have a preference of location for woofers' amp(s)?

Also worth noting is that while many plate amps have a rudimentary HP filter on the mains out when the speaker level inputs are used, their quality is crap, while the RCA line "daisy-chain" output jacks are about as transparent as you can get.
 
Ah ha. So you are thinking bring the new woofer up pretty high, then? Like maybe 200-250?
yes, at least up to 120hz but I was thinking up to around 160hz...

I have a feeling the higher I try to cross the woofer, the harder it would be to integrate perfectly with the P3esr, but maybe im wrong and it would actually be easier?

Id like a 1st order for the P3esr and 2nd order for the woofer....
 
So, what amp are you using on the Harbeths? You mentioned B1 buffer, but I can't recall power amp. And while I'm at it, do you have a preference of location for woofers' amp(s)?

Also worth noting is that while many plate amps have a rudimentary HP filter on the mains out when the speaker level inputs are used, their quality is crap, while the RCA line "daisy-chain" output jacks are about as transparent as you can get.
im using a LM3875 gainclone or a sony ta707es for the harbeth. yes I dont want to use built in HP filter in plate amps!
 
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OK, here's my somewhat scientific guess based on published measurements. All 2nd order.
  • High Pass P3ESR. 75uf Series, 5.6mH Paralell
  • Low Pass LAB-12 9mH Series, 140 uF Paralell. Reverse polarity (probably)
That should sum very nicely and puts the acoustic crossover point at about 200Hz. Both sections will contribute above and below that, of course.
I would buy some nice motor run caps near the needed value and add film caps to fine tune for the high pass - Motor start for for the low pass. The inductors should be Erse iron core or equivalent. $28 for the low pass coil, $25 for the high pass. You could put a 5.6mH aircore there, for about $17 and it won't affect the response much.
 
I've always found the integration easier at the lower end of the range you nominated. Note that the slope of LP filter on the APA150 is 18dB/Octave, while the two models cited above from the SA are 4th order.

There's of course more than one way to skin a cat, and Pano's advice for the HP is as good as any, and if using a plate or sub-amp, the LP is already covered. Some of the lower priced models don't have a direct LFE / LP filter bypass, so even when dialed as low as they'll go the filter is still in circuit, and I personally like to avoid concatenating them.
 
Anything I suggest will be the cheapest route I can imagine that will work at all. So if the OP has two 8 ohm 97 db 15" woofers that are going to combine with 83.5 db sensitive monitors, then a baby plate amp will suffice. Used to be such amps had 100 uf caps incorporated in the high level in/outputs, which would need a bit of tinkering, but there you go. Low rent advice, worth two cents.
 
Anything I suggest will be the cheapest route I can imagine that will work at all. So if the OP has two 8 ohm 97 db 15" woofers that are going to combine with 83.5 db sensitive monitors, then a baby plate amp will suffice. Used to be such amps had 100 uf caps incorporated in the high level in/outputs, which would need a bit of tinkering, but there you go. Low rent advice, worth two cents.

oh yeah, 25 WPC for the eminence would be plenty for my room but I think ill go with a all passive xo with the LAB12. will be a exciting winter project

as for the eminence omega 15, I have another interesting project that will make good use of it so if I would have used it with the Harbeth project, I would have had to buy another pair.

thanks a lot everyone, will bump this thread once I get a hold of the drivers and cabs
 
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Yes, that is very likely. You want a B4, or one of the diy B1 buffered PLLXOs. If you want to keep it simple you can start with just a 1st order PLLXO. You need at least one amp with a gain control (often the bass amp), and XO high enuff that both the woofwe & the Harbeths have smooth response out of band.

Alternatively one of the DSP XOs, but that often means an extra ADC/DAC stage. Best kept all digital.
dave
 
You're more likely to mess up the sound. You need to select proper bass material to match the midrange. Not knowing what Harbeth driver is made of, it's kind of hard. Of course the big if is if you know how to design a proper xover. You need to completely rework the mid, tweeter, and of course the bass. (Not to mention having to purchase measurement equipment).
 
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