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

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Hi everyone

I love the Harbeth P3ESR midrange and highs, but obviously, they suck at bass.

Id like to turn my small P3ESR into a 3 way. Id use my Eminence pro omega 15 woofers in a 100l ported cab.

I was thinking going with a Pass b4 electronic XO to highpass the P3ESR and integrate the Woofers, but a passive solution would probably be much cheaper... Maybe I should go with the Pass b4. My pre amp is the pass b1...

can anyone help me design a passive xo? is it even feasible? I really dont know anything about passive crossovers so I have no idea how to design it.
 
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There's huge efficiency difference between the Harbeth and the Eminence so you'd have to pad the woofer way down which would waste power. Jeff Bagby designed a universal crossover for this application but the woofer needs to match the monitor's efficiency fairly closely. As usual - I'd go with Dave's advice.
 
A modern man would solve this with a minidsp 2x4HD and a pair of reasonable quality active subwoofers. Put minidspbetween pre-and power amplifiers and set xo, eq, levels and delays with it. If present amplifier is integrated without looping possibility, you will need new amps too.




A clever man would just go and buy a pair of good 3-way speakers and sell Harbeths or save them for another room.
 
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As Jimbro says, there is a big mis-match in sensitivity. Your Harbeth are low sensitivity at 83.5 dB and the Omega pro 15 would be around 97dB. Even figuring losses in the woofer crossover and other factors, your P3ESR would need 10x-15x more power for the same level as your sub. Or somewhere around 7x-10x more voltage.

And Dave is right about the cost of parts. In a passive crossover that low, the inductors are going to be large and $$$. Active, like with a plate amp, is probably the way to go here. Or choose a much less efficient woofer and still spend a lot on your passive filter.
 
Did you determine what frequency at which you'd like to XO? Unless the room is huge, I'd think that anything below 100Hz should be OK, in which case a simple "plate" or stand alone sub amp would make life a lot easier. A great example of a fairly flexible and decent enough sounding unit is the Dayton APA150 - 2x75W stereo or bridgeable to ~150W. I'd used a pair of them in mono in my own HT rig until very recently. The only reason they were retired is that with the full bass management DSP in contemporary surround receivers, the XO is redundant, and an old NAD power amp worked just fine.

Having experimented with 3 different methods for a low XO 2 way within the past year - DSP/Active via Onkyo receiver, passive LLXO , and passive high level ( 2nd order), I can attest that the cost for the latter with a low frequency XO can easily run into the hundreds of dollars to do "right" - and there's rather more to it than cookbook / online spreadsheets. Fortunately, I had access to someone with a lot of experience in the field, a complete LMS/LEAP system, and a large enough interior space that gated ground plane measurements of drivers in the actual enclosures were easily attainable.
 
I have a mini dsp 2x4 but I dont like the sound. I would have sold my P3ESR but sadly, ive dropped one on the floor and its pretty damaged. so damaged that its not worth it to sell them at a huge lost, so decided to try to find a way to make them work cause the mid and highs are very good.

thanks everyone for your help, I understand I cannot go with my eminence due to sensitivity mismatch.

I have included a 1st order line level highpass for the P3esr in my pass b1 that I can adjust the FREQ cut off. I think ill try this first as Pano and others have suggested.
the Dayton APA150 seems really perfect for my needs.

I have no idea how low I want to cross my P3esr. maybe 160hz?
 
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You might also look at an Eminence subwoofer, like the Lab 12C. It's much closer in sensitivity to your Harbeth and should play nice and low in a 2 foot ported box. Should you decide to go passive the 4 ohm impedance will make the low pass inductor smaller and less expensive than an 8 ohm woofer. Same cost as the Omega, I think.
 
You might also look at an Eminence subwoofer, like the Lab 12C. It's much closer in sensitivity to your Harbeth and should play nice and low in a 2 foot ported box. Should you decide to go passive the 4 ohm impedance will make the low pass inductor smaller and less expensive than an 8 ohm woofer. Same cost as the Omega, I think.
what would you do? would it be easier to integrate a woofer + highpass to the p3esr actively or passively?

im looking at the dayton audio APA to power my eminence and could highpass my P3ESR via my pass b1 but the Lab 12c + simplicity of a all passive system is very attractive to me
 
Note that the APA's variable LP crossover goes from 50-150, and crossing over that high, I think you'd need to go with stereo woofers. While HP to the amp driving the Harbeths (PLLXO) might seem like an extra complexity, you could expect improvements in their midrange performance, and overall attainable SPL - well worth the effort to my mind.
 
Note that the APA's variable LP crossover goes from 50-150, and crossing over that high, I think you'd need to go with stereo woofers. While HP to the amp driving the Harbeths (PLLXO) might seem like an extra complexity, you could expect improvements in their midrange performance, and overall attainable SPL - well worth the effort to my mind.

yes, I want to go with stereo woofers. the cabs will be directly under the P3ESR.

I think this is the best solution. HP the P3ESR via line level in my pass b1 and use the Dayton amp to Low pass and power the woofer.
 
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It looks to me that if you 1st order high pass your Harbeth circa 165Hz and low pass the LAB 12 2nd order @ 60Hz you'd do well. The sub would be little louder, but I imagine that would sound rather nice, depending on placement.

The low pass on the LAB12 could be something like 15mH and 470uF, but that would need some refinement. The coil is going to be pricey, like $35 each coil. I don't see how you can do the cap as anything but a non-polarized electrolytic. That won't be expensive. Active for the woofers is not a bad idea.
 
Experimenting passively

I second Pano's thinking. We have not turned to the soft side yet. Ha ha ha.
I'd have to study the sattelites more seriously to come up with a HP suggestion. This is a sim of the optima 15 in 100 litres vented, tuned to 40 Hz. Second IMP peak is flattened through RLC. The last graph is how it would have looked without one. Large inductance low pass coil is effectively reducing SPL so we'd not need to turn the woofer further down to meet the rest of the gear.
 

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It looks to me that if you 1st order high pass your Harbeth circa 165Hz and low pass the LAB 12 2nd order @ 60Hz you'd do well. The sub would be little louder, but I imagine that would sound rather nice, depending on placement.

The low pass on the LAB12 could be something like 15mH and 470uF, but that would need some refinement. The coil is going to be pricey, like $35 each coil. I don't see how you can do the cap as anything but a non-polarized electrolytic. That won't be expensive. Active for the woofers is not a bad idea.

im confused a bit.

if I go with the LAB12, id like to go all passive in that the P3esr are not HP via my pass b1 but in the passive xo crossover and the Low Pass for the LAB12 also would be in the passive XO. would that be easy to do?
after looking at the parasound xo ( Parasound CX 1002 120Hz Passive Crossover-Audio Advisor) , that would be ideal for me to build something similar with R+L input then Low and Highs output. I think I prefer this solution as I can let go of my pre amp and simplify the system.

Is the LAB12 the best option for me? is there any 15 inch woofers that would work sensitivity wise with the P3ESR?

thanks everyone with your help, very cool!
 
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15s will likely be more sensitive, but have a look around Parts Express in the subwoofer section to see what you can find.

If you want to stay all passive, you'll need a mighty big cap in series with the Harbeth to high pass it. Maybe 147uF. If you let the Harbeth run all the way down, as you now do, you might get away with just adding a sub down around 60Hz. Most "bass" in music is really in the 60-120 Hz octave, just FWIW.
 
I'd simply add a .5 woofer, of suitable sensitivity (10" Peerless?), that way you're only spending for one crossover inductor / side, (although it will be large & somewhat expensive). You need to decide whether you need baffle step correction or not, & your crossover freq. (I'm using a 10" peerless with 3.3mH ferrite inductors, works well, but sensitivity is a bit low for my mids & highs, in the process of building a 'centre" sub)
 
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It's not a bad idea to go with a single subwoofer, probably active. It may be all you need to give you the bass the Harbeth lacks.

As for the big subs that I know, the LAB 12 is the best choice as it's close to the same sensitivity as your speakers and it will play low in a 2 foot box. I don't know a 15 that will be as well matched, but maybe it's out there. Someone here will have a suggestion, like the Peerless 10". I use the Peerless 12" and it's a well built driver, but maybe won't play as low as the LAB-12 in a reasonable size box. Cheaper, tho. :)
 
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