Another cab build...BP102 in a 110 cab

[Sundogue]

A while ago I made these cabs in an attempt to make something relatively small, yet deep and full sounding. They utilize the Eminence BP102-4ohm speakers.



I typically only use a single 210/6 cab for most gigs and it handles them very well volume-wise. When I really needed more volume I used two cabs.

But I am now starting out with a new blues band and find I will not need anything more than just a single 210/6 cab as the volume requirements are simply not the same as they once were. I can easily get away with a single 210/6 cab. There will be no PA support and we are only going to be playing smaller clubs.

The BP102's are excellent tens with an xmax of 6.2mm and give a lot of low end and when coupled with a dedicated mid range driver give a very full sounding system. But, they aren't neo's and therefore are not lightweight. So what I would like to do is split them up into two 110/6 cabs or use one as only a 110 and the other as a 110/6 (preferable as I only need the single 6" mid driver with the two tens).

I use a Carvin BX1200 and bi-amp so I don't need to consider an internal crossover and I can adjust the output of the BP102 and the mid driver individually. The BX1200 goes down to 2 ohms and doesn't run hot even running it that way for the duration of a gig.

What I am looking to do is build a 110 cab that goes as deep as possible (not looking for tons of volume here, just very deep low end that handles the low B very well) and use the other as a 110/6 cab. So...what do you experts recommend as being the ideal cab volume, porting and tuning frequency to get each single 110 BP102 to maximize the deep lows I want? I'll be building it out of 1/2" ply. Ideally I'd like my 110's to be 30 lbs. each or less and as small as what would be reasonably considered to handle the low end.

I have a pretty good idea what I might do, but as always I'd like to get some input from others who have knowledge on the subject. I realize a single 110 won't do much on it's own so it will be used with another equal 110 when needed. Some gigs and especially rehearsals, I'd only need the little 110/6 cab. I want to utilize the speakers I already have with no expense beyond what little plywood I still need, so let's avoid other speaker recommendations. I'm well aware of the fEarful builds.

To sum it up...BP102- 4ohm in a 110 in a cab as small as what could reasonably be expected to put out deep lows. Compromises to be expected.

Anyone care to chime in?

[bgavin]

Originally Posted by Sundogue

What I am looking to do is build a 110 cab that goes as deep as possible (not looking for tons of volume here, just very deep low end that handles the low B very well) and use the other as a 110/6 cab.

The BP102 will do what you ask, but it requires a large cabinet volume to get there.
It will get all the way down to 30 Hz in the big box.

The alternative is build a pair of BP102 in an isobaric arrangement to cut the internal volume in half.
This doubles the driver weight, which is somewhat offset by the smaller cabinet.

It also results in a 4-ohm load which will play Hobb with passive 8-ohm crossovers.
The net loudness is the same, despite it being two drivers and a 4-ohm load. The intent of isobaric is solely to reduce the box volume.

[Sundogue]

Originally Posted by bgavin

The BP102 will do what you ask, but it requires a large cabinet volume to get there.
It will get all the way down to 30 Hz in the big box.

The alternative is build a pair of BP102 in an isobaric arrangement to cut the internal volume in half.
This doubles the driver weight, which is somewhat offset by the smaller cabinet.

It also results in a 4-ohm load which will play Hobb with passive 8-ohm crossovers.
The net loudness is the same, despite it being two drivers and a 4-ohm load. The intent of isobaric is solely to reduce the box volume.

I'm not concerned with the crossover situation or the resultant ohms as I will be bi-amping with full control over the crossover point to the mids as well as the output to each.

What internal volume are you thinking for the "large" cabinet volume to get down to 30Hz, around 3.5 to 4.0 cu.ft. for a single 110?

[DukeLeJeune]

45 liters or so tuned to the mid-30's will give you very strong output at the first overtone of low B (-0 dB), and mild bumpage above that.

[Sundogue]

Originally Posted by DukeLeJeune

45 liters or so tuned to the mid-30's will give you very strong output at the first overtone of low B (-0 dB), and mild bumpage above that.

Thanks.

That is essentially what I have going on now. It would be my 210/6 cab (about 90 liters) cut in half approximately, although the tuning is a little lower than what mine is at.

Which is kind of what I'm after. I'd like two smaller and lighter 110's delivering what I have now (as these speakers weigh about 10 lbs. per speaker). I thought I could increase the output of the low end a bit by making the 110 cab a bit bigger for a single BP102. But as I expected, it would take using my 210 cab internal volume but with only a single BP102. I wouldn't be saving as much weight/size as I'd like.

I am perfectly happy with the sound and output of my 210/6, so perhaps just splitting it into two 110's would make more sense. Easier to haul for me, yet standing pat on what I already like about my 210/6. Yeah, I know...a 47 lb. cab isn't much to deal with, but I like the idea of cutting the weight into a little more than half that. If I could get each of these BP102's into two 25 lb. cabs I would be happy with that.

[DukeLeJeune]

Sundogue you could certainly tune higher than I mentioned, or go with a larger box, or both. I was just looking at a ballpark tuning that gave good strong low end without a lot of upper bass bumpage. Actually with the BP102, it's pretty much across-the-board bass bumpage; that thing's a little monster.

[Sundogue]

Originally Posted by DukeLeJeune

Sundogue you could certainly tune higher than I mentioned, or go with a larger box, or both. I was just looking at a ballpark tuning that gave good strong low end without a lot of upper bass bumpage. Actually with the BP102, it's pretty much across-the-board bass bumpage; that thing's a little monster.

I modeled your suggestion into WinISD and it looks very much like what I had with my 210/6 (halving my existing cab volume). I've also been playing with tunings and cab volume.

Seems I can still keep it rather small and toy around with the tuning a bit. I don't notice much of a change that makes going bigger worthwhile until I'm at twice the cab volume per driver (like the size of my 210/6, but with only one speaker). It's only at twice my cab volume (roughly 3.0 cu. ft. or about 85-90 liters) per driver that the BP102 goes flat almost down to 40Hz and -6dB at 30Hz .

I probably don't really need to go that low anyway, as you mentioned the harmonic above the low B matters more. It's pretty much flat down to 60Hz with only a 1.5 cu.ft. (or 42 liters) internal volume. And tuning anywhere from 35Hz to 45Hz, I'm not getting that extreme lo-mid/upper bass hump, and I will be adding a 6" mid to the upper 110 cab.

Thoughts?

And yes, for a 10" speaker it is quite a little monster. I really like the BP102 for the lows and I've been able to push them pretty hard and they take it. It isn't a good full range speaker, but any speaker that does lows very well seldom is.

[Sundogue]

My thinking is to build a 110/6 combo with a 110 extension cab. I do believe this will do better for me than most commercially offered 110's given I'm using the BP102 rather than a full range ten.

My Carvin (sans it's own rack case) weighs in at about 18 lbs. A single BP102 weighs about 10 lbs. The 6" mid driver (out of my Bose 201 stereo speakers no less! Which work fabulously by the way for this application. ) weighs only about 2 lbs. So together, without the cab itself, the weight is about 30 lbs. If I build a 20X12X16 cab out of 1/2" ply (with additional height added on for the head compartment) I'm guessing a 110/6 combo will come in at about 40 lbs. or thereabouts. That's only 7 lbs. lighter than my 210/6 cab, but also includes the amphead in that. That, and it will be significantly smaller than my 210/6 cab is alone. So, weight aside, it will not be as cumbersome.

Now if I build a 110 extension cab, I'll have a nice little modular 110/6 combo with a 110 extension cab utilizing BP102's, which IMO are superior to any other ten for low end and I'll have the mids and highs covered with the dedicated 6" mid driver. My head goes down to 2 ohms (to use both 4 ohm BP102's) and it also has a built in crossover and controllable output to the lows and highs (allowing me to adjust the mid output relative to either the single or dual BP102's).

While this certainly isn't a cab/amp configuration that will work for many, it will be great for my new blues band. We don't play very loud, we play small clubs and we rehearse rather quietly so I'd only need the 110/6 combo for rehearsals and even some gigs. Just add the 110 extension as needed.

I plan on angling either the baffle or the cab itself on the 110/6 combo so it sits in tiltback (adjusting the design for the slight loss in internal cab volume) as most gigs I'll be planted right near my rig.

It certainly is nice to be in a relatively "quiet" band after years of cranking out loud rock'n'roll. Opens up a lot of portability options.

[eastcoasteddie]

I am an advocate of the BP-102 speakers as I installed them in an SWR Goliath II and they kill in the low end department

Out of curiosity, for this application, why would you be set on the 4-ohm version for each cab and not the 8-ohm version which have slightly more sensitivity.

[Sundogue]

Originally Posted by eastcoasteddie

I am an advocate of the BP-102 speakers as I installed them in an SWR Goliath II and they kill in the low end department

Out of curiosity, for this application, why would you be set on the 4-ohm version for each cab and not the 8-ohm version which have slightly more sensitivity.

Because I have the 4 ohm version already and my amphead goes down to 2 ohms.

If I were going to buy speakers I'd go the fEarful route and use either a 3012 or 3015 LF.

[eastcoasteddie]

Originally Posted by Sundogue

Because I have the 4 ohm version already and my amphead goes down to 2 ohms.

If I were going to buy speakers I'd go the fEarful route and use either a 3012 or 3015 LF.

OK, sorry, I must have missed that part about using the speakers you already have...my bad.

[Wes Whitmore]

I would like to see that isobaric plans that of Bgavin is talking about...

I agree with the combo for your 2 ohm load abilities though. Not many amps have the 2 amps with crossover built in. That would be a very nice combo.

[Sundogue]

Originally Posted by Wes Whitmore

I would like to see that isobaric plans that of Bgavin is talking about...

I agree with the combo for your 2 ohm load abilities though. Not many amps have the 2 amps with crossover built in. That would be a very nice combo.

The isobaric design shrinks the form factor, but it equals the output of the same 110. So if I used two BP102's in an isobaric design I could get by with a smaller cab, but it would still be the equivalent of a larger 110.

I don't see the gain in using one aside from size alone.

Yeah, the BX1200 (and now the lighter BX1500) is a very versatile amp. I love it.

[Sundogue]

Originally Posted by eastcoasteddie

OK, sorry, I must have missed that part about using the speakers you already have...my bad.

No problem. Anyone else reading this might gain some insight and use the 8 ohm version if they are buying new.

[DukeLeJeune]

One of the issues I ran into when doing DIY isobarics back in the 80's is this: The inner woofer is essentially blaring away into the back of the front woofer, so if you don't roll it off fairly aggressively, it will really mess up the midrange something awful. Isobaric loading is also more likely to drive the outer woofer into over-excursion, and it modifies the effective T/S parameters of the outer woofer. In my opinion the parameters that the BP102 starts out with do not make it a good candidate for isobaric loading.

[greenboy]

I did an isobaric SUBWOOFER with drivers of similar characteristics. You could get lower box tuning in that smaller enclosure, but even so, isobarics are just not worth the trouble.

EDIT: Only if a composite isobaric driver designed specifically for the task was available would I bother to revist isobaric designs. They just don't give a good set of tradeoffs.

[bgavin]

Originally Posted by DukeLeJeune

One of the issues I ran into when doing DIY isobarics back in the 80's is this: The inner woofer is essentially blaring away into the back of the front woofer, so if you don't roll it off fairly aggressively, it will really mess up the midrange something awful. Isobaric loading is also more likely to drive the outer woofer into over-excursion, and it modifies the effective T/S parameters of the outer woofer. In my opinion the parameters that the BP102 starts out with do not make it a good candidate for isobaric loading.

Sorry, but this sounds like more arm chair quarterbacking...

If isobaric loading modifies the outer woofer T/S parameters, please provide Before and After measurement sequences of your observations.
Without measurements (read: proof) your statements are conjecture only, but accepted as Gospel truth due to your leadership position on this board.


The sole purpose of isobaric loading is reducing the box size for subs.
This fits the stated requirement from the OP who wants deep lows in the smallest box.

BP102 is a sub driver.
It has no mid-range, so 'mess up the midrange something awful' does not apply.

The rear driver compressive phase loads into the front driver rarefactive phase for a net pressure change of zero
Blaring does not apply.

Both drivers receive the same voltage, both drivers share a common loading chamber between them.
Neither driver will electrically excurse more than the other.

Isobarics can be good designs, just not popular ones.
Labor costs for the cabinet are prohibitive at commercial price points.
The 4-ohm impedance is a conflict with passive, COTS crossovers.

[Sundogue]

Originally Posted by bgavin

Sorry, but this sounds like more arm chair quarterbacking...

If isobaric loading modifies the outer woofer T/S parameters, please provide Before and After measurement sequences of your observations.
Without measurements (read: proof) your statements are conjecture only, but accepted as Gospel truth due to your leadership position on this board.


The sole purpose of isobaric loading is reducing the box size for subs.
This fits the stated requirement from the OP who wants deep lows in the smallest box.

BP102 is a sub driver.
It has no mid-range, so 'mess up the midrange something awful' does not apply.

The rear driver compressive phase loads into the front driver rarefactive phase for a net pressure change of zero
Blaring does not apply.

Both drivers receive the same voltage, both drivers share a common loading chamber between them.
Neither driver will electrically excurse more than the other.

Isobarics can be good designs, just not popular ones.
Labor costs for the cabinet are prohibitive at commercial price points.
The 4-ohm impedance is a conflict with passive, COTS crossovers.

Points to consider, but in all probability, I doubt I would build an isobaric cab simply because while being able to build a smaller box, I'm still loading two 10lb. speakers into the same box for an output gain of only a single 110, albeit a deeper sounding and smaller one. I can see the merits for the right application. Mine isn't one as my only gain would be size and the weight savings would be nil for what I want.

Really the only way I'm going to get any deeper and save some weight is by building a bigger box about the size of my 210 cab loaded with one BP102 instead of two. I'd lose the weight of one speaker but gain a bit in materials. And then I'm back to the size being the same and still needing one more cab for the other BP102 and mid driver.

I'll probably just go with pretty much what I already have in the 210 but halved to get me two lighter (thus easier to carry) 110 cabs. One 110 loaded with a single BP102 and the other a 110/6 with the other BP102 plus a 6" mid driver.

All I would be accomplishing is gaining some weight savings per cab and nothing more. Although if I make the 110/6 a combo I'm back up to almost the weight of my 210/6 (including the amphead in it). But the weight is offset by a smaller (thus easier to handle) combo cab, one less trip because the head is already in it, and possibly only needing the combo alone for some gigs and certainly rehearsals. The extension 110 cab would only be needed for gigs and possibly not even every gig (although I can't really see not using the extension cab on every gig with it being small enough to not be a pain to haul).

I really love my 210/6 cab. It's the best sounding one I've built and it has handled even some fairly loud gigs with my old classic rock cover band. Of course we had PA support with that band and my blues band will not be using a PA for much of anything but vocals.

Then again, we will not be playing the same venues my old classic rock band did either. Though I did play a couple of gigs with my new blues band using my 210/6 in clubs similar in size to what my cover band did and my rig alone carried the room easily. Many of my friends said we were louder without a PA than my old band was with a PA. But my old cover band unnecessarily hauled a lot of PA around and didn't need to use it much, so the use of a PA and my ability to cover gigs with two 110 cabs should be just fine.

I posted this thread to kind of gauge what I really wanted to do with my rig and what the realistic possibilities were. It seems trying to gain a bit of low end isn't worth it in the long run. I'd rather stand pat with what I have, except split the 210/6 into a 110 and 110/6 combo. I will probably gain just a tad bit in the low end by having each BP102 in it's own cab with a slight increase in internal cab volume rather than sharing the same cab, but certainly not much.

[Sundogue]

In trying to keep the size of my new 110 and 110/6 cabs small, the combo will be compromising some because I can't put the 6" mid driver anywhere on the baffle except along side the single BP102.

The mid will be crossed over so the BP102 and the mid driver will not be sharing the same frequencies. Currently my 6" mid is next to a BP102 in my 210/6 cab and I have not noticed any issues in my sound.

Is there any reason why having the BP102 and the 6" mid side by side would cause problems if they are each independently operating within their own ranges?

[greenboy]

Only in the region where both drivers are reproducing the same frequencies. But that's be an area that carries a lot of detail for bass guitar. I prefer when it's practical not to do that in the mid-midrange. Steeper, tailored crossover sloping can help.