If this is being done actively, which is where things seem to be, efficiency of the woofer is immaterial, you just need an appropriate amp.
While it is indeed true that a text book XO is unlikely to be perfect, with the bass/sat XO so far away from the midTop that is moot, and the new XO is into the room dominated region so for perfect you need to deal with the room.
dave
If you cross the mid with a high pass, the amp on the woofer will be different than the amp of the mid+tweeter. There is still a lot of overlap between the bass and the mid and possibly with the tweeter as well. You end up with listening to two separate speakers. It will only work if you use the bass purely as a subwoofer. But of course the best solution is to rework the entire xover.
Anything can be done. The question is the sound you're after will be completely different from the original Harbeth. If that is the case then just buy a 3way and you might actually end up with a better sound.
do you mean it will only work if i lowpass the the woofers very low?
I was thinking around 120hz 4th order
BTW' the woofer cabinets will act as stand for the P3ESR...
Well it depends on how you cross the mid. If you cross the mid around 200hz, I think there is still a lot of overlapping between the bass and the mid. The bass will be run a separate and probably a different amp than the mid, the overall sound may not be coherent.
That is a potential problem. I listened to some Martin Logan electrostatic panels with a separate woofer, and you could tell the mid and the bass were playing at different speed. From what I can tell, they get better nowaday but it's been awhile since I listened to them.
As I said, you can do anything, but I was saying the original sound of the Harbeth will be lost if you're solution is not optimal.
Different driver material, different amplifiers, different speed,Have I entered the twilight zone?
Your post is a twilight zone.
I see at the bottom of your posts under "mine" that you have listed the Harbeth SHL5 but not the P3. Am I correct in assuming that your desire is to make the P3's sound like the HL5's?
I mentioned in my other post that 20 years ago Harbeth made a bass unit for the P3's. They were sized like what your OP states that you are looking for. The were rectangular enclosures about 36 inches high and the P3 sat on the top of them. They had the same driver as in the P3. I don't remember what it was but it was an off the shelf unit from one of the driver manufacturers. In essence it was a 2 1/2 way with the P3's unchanged and the bass unit rolled off above somewhere to not interfere with the P3's.
You could probably make something similar if you could purchase a pair of drivers from Harbeth. The do keep records and they do sell spares. If you explained what you want to do they might even help you out a little, rather than just tell you to buy a bigger Harbeth.
This would fill in the 60 -160hz area you wish filled in. And if you kept the REL you'd still have the low low bass.
If you are on the Harbeth User Group forum you could probably post your desires there and see what happens. Harbeth User Group - Harbeth: For 40 years - the world's most natural sounding loudspeakers
Crossovers can make or break a speaker - no doubt about. And driver tonality matching is something not a lot of people consider, it can even be crossover point specific. These are important issues.
But YKYK wants some more mid bass, and would like to do it passively if possible. I researched the speakers and drivers in questions, took the most reliable FR and impedance measurements - did box simulations I could, and came up with a passive crossover that will be a very good starting point.
I pointed that out to you Andy, but you didn't comment.
The LAB -12 woofer will play low in a reasonably sized box and will be slightly louder than the Harbeth, but not by much. Room placement would change that anyway. To go with a passive setup, the crossover I posted is easy to build and not overly expensive.
If the system is done with active crossovers and EQ, there is much more flexibility and opportunity for tuning.
I'll repeat my post #50 - I can't see why leaving the little Harbeths intact - particularly advantageous if there's any likelihood of them ever being sold / passed on - and using any of several described methods of both high-passing them in the under 150Hz or so range to increase SPL/reduce excursion related distortion, and adding powered woofers with their own XO wouldn't be a simple approach.
And as ScottJoplin notes, exactly why would different cone material for those woofers and that used in the Harbeths make them not "play nice" together? I have a pair of large MTMs with dual Alpair A12PW (paper), and A7.3 (metals) - they work just fine.
And as ScottJoplin notes, exactly why would different cone material for those woofers and that used in the Harbeths make them not "play nice" together? I have a pair of large MTMs with dual Alpair A12PW (paper), and A7.3 (metals) - they work just fine.
If you cross them low enough and using filter steep enough then different material may not matter, but either way you have to rework the whole xover. I don't see how you can get away with just "high pass at 200Hz".
To try one more time to make it clear - my suggestion is to leave the Harbeths alone, and conduct any additional HP XO filtering outboard, - ie. either a PLLXO ahead of the amp driving them, or a more expensive passive speaker level after same - as described by Pano - and sub /plate amp(s) driving the woofers between them and the existing REL sub .
If the OP actually wants to gut the little guys, and redesign the entire system as a 3-way in single enclosure, then it's a completely different story - in which case you're definitely right about back to square one.
If the OP actually wants to gut the little guys, and redesign the entire system as a 3-way in single enclosure, then it's a completely different story - in which case you're definitely right about back to square one.
It sounds great in theory but in reality it's difficult to be done. You'll end up with integration problem - either it will sound too lean, or too warm, or too dry and sterile. There is no other worst feeling than a pair of 3way speakers having integration problem.
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