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subwoofer with midrange driver...

Sundogue

Sundogue

Apr 26, 2001
8,795
481
65
Wausau, WI
#1
I'm thinking about making a 110 cab and I will be using one of my 4 ohm Eminence BP102's.

The BP102's range is only 40Hz to 2kHz, so I was thinking of adding a midrange driver to the cab.

The thing is, I need to keep my cab a 4 ohm cab. I know with two 4 ohm speakers, I'd end up with a 2 ohm cab, but I thought I read somewhere that wired with a crossover it would still stay at 4 ohms.

Perhaps I read it wrong or misunderstood, but is it possible to wire a 4 ohm subwoofer and a 4 ohm midrange driver with a crossover in the same cab and still have a 4ohm cab?

If it is, anyone know what 4 ohm midrange driver would pair up with the BP102, and what crossover would work best? I've built a lot of straight up bass cabs (115, 215, 210, 410, etc.), but I've never built a full range one using two differing speakers with a crossover.

Any info, or links to info would be appreciated.
 
#2
Use an 8-ohm midrange (I doubt you could even find a 4-ohm midrange driver anyway). In conjunction with a proper passive crossover the cab will act as if it had the load of the WOOFER. Make sure the crossover low-pass component values are predicated on the nominal impedance of the woofer or the crossover point will be shifted an octave.
 
#3
greenboy said:
Use an 8-ohm midrange (I doubt you could even find a 4-ohm midrange driver anyway). In conjunction with a proper passive crossover the cab will act as if it had the load of the WOOFER. Make sure the crossover low-pass component values are predicated on the nominal impedance of the woofer or the crossover point will be shifted an octave.
Click to expand...

OK. I'm not familiar with internal crossovers. What 8 ohm mid range would you recommend? I've been looking at the Eminence Alpha-8MRA 8" Sealed Back Midrange as it doesn't need a separate chamber to be built in the cab.

What kind of crossover would be best and what would be the optimal crossover point? The BP102 goes from 40 to 2000 Hz and the Alpha-8MRA goes from 400 to 4,800 Hz.
 
#5
billfitzmaurice said:
The impedance will that of each driver within its own passband.
Click to expand...

OK. For my purpose, what does that mean? I need my Superfly head to see a 4 ohm cab.

I'm thinking of building an Omni 10.5 with one BP102 (without tweeters) and then a front loaded 110 with the other BP102 plus a mid range driver. I want each to be 4 ohm cabs.

Or possibly two Omni 10.5...still deciding. Either way, I need to utilize my BP102's in two 110 cabs.
 
#6
I hear a big qualitative difference in the sealed-back midranges compared to open back ones in a larger box properly stuffed. They sound peakier and seem to pass reflected sound.

I haven't modeled the Alpha 6-A (but you probably should). I've used the Carvn 6" and it works out real could in about .1 cf. A 6" midrange will have better axial response - doesn't beam at as low a frequency as an 8" driver will. It would seem rather odd to use an 8 with a 10 really.

The Galaxy 5" might work out well, though I normally wouldn't recommend it because it can't keep up with most drivers. It's not as sensitive as Galaxy's specs indicate, but in the case of the BP102 it would probably be an even match. I'd cross it over as low as it can handle - 500 Hz anyway - because the BP102 seems to have a big midrange scoop.
 
#7
It means if you use a 4 ohm woofer and an 8 ohm mid the impedance will be 4 ohms within the woofer passband and 8 ohms within the mid passband. I would not use a BP102 in an O10.5 without tweeters, the BP102 is too weak in the midrange to work well on its own when horn loaded. My Superfly is quite content driving 8 ohm cabs.
 
#8
billfitzmaurice said:
It means if you use a 4 ohm woofer and an 8 ohm mid the impedance will be 4 ohms within the woofer passband and 8 ohms within the mid passband. I would not use a BP102 in an O10.5 without tweeters, the BP102 is too weak in the midrange to work well on its own when horn loaded. My Superfly is quite content driving 8 ohm cabs.
Click to expand...

Yes, but your Superfly is going through your efficient cabs, no? ;) I've tried 8 ohm cabs and the volume isn't where I want it to be...but we are talking commercial cabs.

Maybe I'll just build two Omni 10.5's with tweets. I'm just exploring options to use my BP102's.
 
#10
Low D. said:
Just buy an Acme dude and save your time and even failure (if stuff will go wrong). You can always sell your speakers through ebay or something. ;)
Click to expand...

Ummm...I don't really need the 110 cabs as I already have some kick-ass 115's I use regularly. I've built a lot of my own cabs (successfully). This is just a "fun" project to see what I can do with my BP102's. I'm in no rush, and they won't replace my current rig anyway.
 
#11
The new style Alpha 6 is one to consider. It actually has 3.5mm Xmax, compared to 0.0mm for the old style. The Eminence PXB2:800 is an internal crossover with a 12dB slope for the woofer, and 18dB slope for the mid-range. This will keep the Alpha out of danger, and leave an octave of headroom for smooth transition at the crossover point.

The sealed back is an easier build, but I also prefer the smoother chart of the Alpha 6. You can always build it as a separate mini box that sits on top the 110.

To the best of my knowledge, Eminence has never made a standard BP102 in 4 ohms. Do you have OEM or other custom drivers?
 
#12
bgavin said:
The new style Alpha 6 is one to consider. It actually has 3.5mm Xmax, compared to 0.0mm for the old style.
Click to expand...
What has changed is the method of measurement, not the driver. Traditionally xmax was the difference between voice coil overhang and top plate thickness. Drivers with underhung coils, like the Alpha 6, had no xmax by that definition. Eminence now uses Klippel analysis with xmax defined as the maximum excursion with no more than 10% distortion. This is now the defacto standard, if the AES has not already made it official it probably will soon.

The current retail model BP102 is only available in 8 ohms, but a 4 ohm version will be introduced at the winter NAMM.
 
#13
I saw the changes in the data sheet. They did not have the usual 10% disclaimer that states how they calculated Xmax. I figured the new Polyimide former was using a longer coil.

The JBL E145 and a few others also use under hung coils. They do have zero Xmax by the subtractive definition, but they also have a range of motion where some portion of the coil is no longer contained in the gap. That introduces non-linearity. Angels on pin heads.

I understand the downside to under hung coils is how hot that short coil temp gets, plus some magnetic issues inherent in the design. The Alpha 6 only has a 0.2500" magnetic gap. The under hung coil has to be shorter than this. Not much meat on the bone... but then again, it is a higher frequency driver.

I bought a few Alpha 6 at a firesale, and am looking forward to how they work in modest boxes. They perform well in Wedgehorns.
 
#15
bgavin said:
I saw the changes in the data sheet. They did not have the usual 10% disclaimer that states how they calculated Xmax. I figured the new Polyimide former was using a longer coil..
Click to expand...
Eminence officially made the switch as of the Deltalite II and Kappalite series. But with the coil former changes they had to re-measure all the old stuff too, and that all now has Klippel specs.
 
#16
bgavin said:
The new style Alpha 6 is one to consider. It actually has 3.5mm Xmax, compared to 0.0mm for the old style. The Eminence PXB2:800 is an internal crossover with a 12dB slope for the woofer, and 18dB slope for the mid-range. This will keep the Alpha out of danger, and leave an octave of headroom for smooth transition at the crossover point.

The sealed back is an easier build, but I also prefer the smoother chart of the Alpha 6. You can always build it as a separate mini box that sits on top the 110.

To the best of my knowledge, Eminence has never made a standard BP102 in 4 ohms. Do you have OEM or other custom drivers?
Click to expand...

Nope, I bought the BP102's in 4 ohms from partsexpress a while back. I specifically bought the BP102's because they were one of the few ones I could find in 4 ohms.
 
#17
Thanks for all the info guys.

Looks like a 6", 8 ohm midrange will do the trick, but I need to look into crossovers. I know how they work, but no knowledge on how to hook them up properly. So I need to do a little research.

I'm not opposed to a separate chamber in the 110 for the midrange. Still exploring options.

I'd like to keep this as cheap as possible since I already have the BP102's and plywood. It's just a matter of a crossover and a mid range driver.

Anyone else with info is appreciated.

Thanks again.
 
#19
bgavin said:
Crossovers are impedance sensitive. Running a 4 ohm woofer and 8 ohm mid-bass with a crossover designed for 8 and 8 ohms will throw off the crossover point.
Click to expand...

I've seen a few at partsexpress that were 4 ohm for the woofer. But I don't know what the ideal crossover point would be...1600Hz? 500? Not too sure what would be ideal. The BP102's go to 2000Hz, but I'd probably benefit by crossing it over lower than the BP102's high end.

Ideas?
 
#20
Sundogue said:
I've seen a few at partsexpress that were 4 ohm for the woofer. But I don't know what the ideal crossover point would be...1600Hz? 500? Not too sure what would be ideal. The BP102's go to 2000Hz, but I'd probably benefit by crossing it over lower than the BP102's high end.

Ideas?
Click to expand...

Bruce originally suggested an 800 Hz one, which jibes with what's worked well for me with 15s or 12s crossing to a 6. As he said, just make sure your crossover design factors in the actual impedances of the two drivers you end up using. Those links I sent you allow you to roll your own pretty easily.
 

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