A cab for practice? (reaching for the B1/31 Hz)

[freatles]

How to get the lowest octaves out of a cab? Perhaps one needs to build a custom one? I already have a "fearful cab" on my future research list.

I'm putting together what I'd like to be a "reference standard practice rig" (ie. bass cab + power amp).

Here "reference standard" means it should have high fidelity reproduction of the signal, in musical terms perfect. "Practice rig" means it doesn't have to stand up to physical abuse, minimal budget.

At the least I think it should reproduce the low E accurately, but preferably the low C1-B1 octave (31-62 Hz) - since I play a 5 string BEADG. Of course, the cabs that I personally like have what I would call "easy" and "neutral" tone. The lows come effortlessly and instantly. Far from scientific, but many cabs sound like constipated whales, which I hate (ie. design causes sound compression, limiting, lags and attenuation).

Its been decades since I last reviewed the topic, and its all a big blur to me. But even if I don't exactly remember the reasons, long ago I have memorized this rule:

** For reproducing the lowest audible bass frequencies, the minimum speaker size is 15". **

Is this even true? It might have been about air volume displacement, or the size of the speaker enclosure and the sound waves in it...

 

[DukeLeJeune]

I'm putting together what I'd like to be a "reference standard practice rig" (ie. bass cab + power amp).

Here "reference standard" means it should have high fidelity reproduction of the signal, in musical terms perfect. "Practice rig" means it doesn't have to stand up to physical abuse, minimal budget.

My first question would be, are you sure you need to reproduce the fundamentals? Most bass cabs do the first overtone well but don't really even try to deliver the fundamentals, Acme being the obvious exception.

I once designed (haven't built it yet) a cab that would be -3 dB at the fundamental of C#1, about 34 Hz. It's actually designed for sub-contrabasses tuned to C#0, fundamental = 17 Hz, so 34 Hz would be the first overtone. It's not a "budget" cab, and is designed for gigging (can do 125 dB+ down to 34 Hz within thermal and mechanical limits).

"In musical terms perfect". That's a tall order. I design and build high-end home audio speakers and custom studio monitors, and have yet to do a speaker about which I'd make that claim. But I have ideas about how to come close... imo, such a cab would behave more like a musical instrument than like speakers in a box, in some ways at least.

As you can see I'm intrigued by your goal. Realistically it doesn't make sense for me to put R&D time & resources into something so specialized, but that doesn't stop me from fantasizing about it.

Can you tell me a bit more about how such a cab would be used... at home only, or in a dedicated practice space (how big?); and what sort of group would you be practicing with (in other words, what would you need to "keep up with")?

 

[freatles]

I don't see any point in not trying to reproduce the fundamentals. It should be possible in 2014.

For me "practice" implies solo-practice 90% of the time. Low-volume group playing 5% of the time, "band practice sessions" = actual drum-kit 5% of the time. Something like 200 W RMS @ 8 Ohm should certainly suffice in terms of air pressure.

 

[Bassmec]

I don't see any point in not trying to reproduce the fundamentals. It should be possible in 2014.

For me "practice" implies solo-practice 90% of the time. Low-volume group playing 5% of the time, "band practice sessions" = actual drum-kit 5% of the time. Something like 200 W RMS @ 8 Ohm should certainly suffice in terms of air pressure.

Your need to produce the full fundemental is catered for by this firm:
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but I would think in terms of upping your power requirement for this frequency response by a factor of ten, for use in a Band setting with a live drummer.

 

[AstroSonic]

A Eminence BP102 in a 3 cf cab tuned to 35 Hz (-3 db @33 Hz) will meet your home practice needs for reproducing down to low B. There is some excursion limited power handling in the low mid-bass (120w @54 Hz) that may be a problem for practicing at 'live' levels with drums.

Check out Acme bass cabs for a commercial solution. For gig levels, multiple Acme cabs and a lot of power should get you there.

A critical question posed early on in this thread is still an important one: Are you sure that this is really what you want? Maybe try the BP102 first.

 

[Arjank]

That's a tough one....
I've build a small 12" sub for my homestudio, it's a closed cabinet with an ol' 12"woofer from Philips with a rubber surround. The 12" is driven by a plate amp which has a 3dB boost around 35hz and I've also added a 12dB highpass filter that adds a few dB's extra between 28-50hz. Depending on how I set the crossover point and gain of the plate-amp the sub can reach a -3dB point of 28hz. I have small front monitors that take over at 80hz. When you play a low B through this it sounds very different from a regular bassamp, you instantly hear the fundamental of the note which is almost absent with regular cabs. I must say that your basssound loses clarity because of the fundamental being played louder then you would normaly hear, really something one needs to get used to.

 

[Bmorefoozler]

Acme B1 or B2...

 

[alexclaber]

I must say that your basssound loses clarity because of the fundamental being played louder then you would normaly hear

This can be quite a big problem - especially regarding your string to string pickup balancing and EQ. If you set your bass up to sound right when through a system with flat response to 31Hz (note that even Acme Low-B cabs are -6dB @ 31Hz) then it won't sound right through 99.9% of sound reproduction systems. Once you figure in boundary reinforcement and room gain in a typical small practice it's not uncommon for bass rigs with decent LF response at low SPL to give you more than enough fundamental content on your lowest notes - and a specialist speaker designed to go lower can end up with too much content in the 30-45Hz region due to this.

Then take the specialist (flat to 31Hz) speaker into a louder environment where the room is big enough to not excessively boost the deepest lows and unless that cab is large with lots of volume displacement (cone area x excursion) it won't manage to maintain that super deep response due to exceeding its linear SPL limits. So the cab designed to have 'ideal' response down to 31Hz actually performs worse in a small quiet space (too much bottom) and a larger space (can't go loud enough) than a cab which has been less compromised in sensitivity and output for its size by having a higher low frequency roll-off frequency.

That's probably quite a lot to take in, might need re-reading and thinking about for a while!

P.S. If you want to try something that I feel does low B better than pretty much anything there's at least one of our BB2s in Helsinki.

 

[AstroSonic]

This can be quite a big problem - especially regarding your string to string pickup balancing and EQ. If you set your bass up to sound right when through a system with flat response to 31Hz (note that even Acme Low-B cabs are -6dB @ 31Hz) then it won't sound right through 99.9% of sound reproduction systems. Once you figure in boundary reinforcement and room gain in a typical small practice it's not uncommon for bass rigs with decent LF response at low SPL to give you more than enough fundamental content on your lowest notes - and a specialist speaker designed to go lower can end up with too much content in the 30-45Hz region due to this.

Then take the specialist (flat to 31Hz) speaker into a louder environment where the room is big enough to not excessively boost the deepest lows and unless that cab is large with lots of volume displacement (cone area x excursion) it won't manage to maintain that super deep response due to exceeding its linear SPL limits. So the cab designed to have 'ideal' response down to 31Hz actually performs worse in a small quiet space (too much bottom) and a larger space (can't go loud enough) than a cab which has been less compromised in sensitivity and output for its size by having a higher low frequency roll-off frequency.

That's probably quite a lot to take in, might need re-reading and thinking about for a while!

P.S. If you want to try something that I feel does low B better than pretty much anything there's at least one of our BB2s in Helsinki.

+1 for all of this. Well worth a second read. I wonder if boundary reinforcement and room gain are responsible for the well balanced deep bass from EBS alignments with seemingly over-damped (very low Qts) drivers?

 

[Fuzzbass]

I don't see any point in not trying to reproduce the fundamentals. It should be possible in 2014.

Just because you can, doesn't mean you should. Alex explained well. I have a non-technical response:

I play BEADG five-string, sometimes detuned a half-step (with my hard rock band). In 15 years of steady gigging I've learned that low fundamentals are a double-edged sword: sure, they can sound great in the right environment, but can also cause big problems. They can be especially hard to tame, causing stage rumble that causes your notes to blur. They can also mess with the house mix out front (on their own, or by bleeding into the kick drum mic). You don't need to play 5 string to have these problems (some rooms are awful regardless) but IME the lowest frequencies are the worst offenders.

I've had much better luck with cabs that roll off normally (40Hz and above): in the wide variety of rooms I play, I get consistently better results, and it's much easier to please sound techs (and I regularly work with some excellent sound techs). I don't miss those low fundamentals, not even when playing modern rock that spends a lot of time below low E.

I know some guys who love their Acmes or whatever. I'm not saying you shouldn't try them. My point is simply that there are legitimate reasons to avoid reproducing those frequencies, and you might not miss them as much as you think you do.

 

[DukeLeJeune]

I don't see any point in not trying to reproduce the fundamentals. It should be possible in 2014.

Others have described why reproducing the fundamentals might not be desirable from a gigging standpoint.

From a technical standpoint, extending the low end one octave deeper calls for four times the air-moving capacity to maintain the same SPL. Also if you want to keep the same efficiency, your box size will increase eight-fold. Or if you want to keep the same box size, your efficiency will fall by 9 dB. Or, some combination thereof. The Acmes, for example, mostly trade off efficiency rather than box size. Their woofers also have far more excursion than normal, but not quite four times more.

For me "practice" implies solo-practice 90% of the time. Low-volume group playing 5% of the time, "band practice sessions" = actual drum-kit 5% of the time. Something like 200 W RMS @ 8 Ohm should certainly suffice in terms of air pressure.

Astrosonic's suggestion of the BP-102 in a big box would probably work well, though I think you'd need two to keep up with a drummer. You'd need additional drivers (midrange and/or tweeter) and a good crossover to make serious inroads on the "musically perfect" goal.

The Acmes use a custom long-excursion version of the BP-102, and then add a midrange and tweeter. That midrange and tweeter (along with Andy Lewis's skill in crossover design) make the Acmes good candidates for your other requirement... they're not musically "perfect", but a lot closer than most bass cabs imo.

So my suggestion is Acme, maybe start with a B1 and add a second one for that 5% of the time you need to keep up with a drummer.

As you can see, Bmorefoozler possesses the gift of brevity, and I do not.

 

[Bmorefoozler]

Others have described why reproducing the fundamentals might not be desirable from a gigging standpoint.

From a technical standpoint, extending the low end one octave deeper calls for four times the air-moving capacity to maintain the same SPL. Also if you want to keep the same efficiency, your box size will increase eight-fold. Or if you want to keep the same box size, your efficiency will fall by 9 dB. Or, some combination thereof. The Acmes, for example, mostly trade off efficiency rather than box size. Their woofers also have far more excursion than normal, but not quite four times more.



Astrosonic's suggestion of the BP-102 in a big box would probably work well, though I think you'd need two to keep up with a drummer. You'd need additional drivers (midrange and/or tweeter) and a good crossover to make serious inroads on the "musically perfect" goal.

The Acmes use a custom long-excursion version of the BP-102, and then add a midrange and tweeter. That midrange and tweeter (along with Andy Lewis's skill in crossover design) make the Acmes good candidates for your other requirement... they're not musically "perfect", but a lot closer than most bass cabs imo.

So my suggestion is Acme, maybe start with a B1 and add a second one for that 5% of the time you need to keep up with a drummer.

As you can see, Bmorefoozler possesses the gift of brevity, and I do not.

Brevity is about ALL I have on you in this conversation, so I will take it... thanks. As always, there is few who can offer better advice then you.