One head, 2 cabs = One cab MUCH louder than the other, why?

[Michael Pearce]

I believe the word "sensitivity" as applied to loudspeakers is inherited from its meaning as applied to microphones (speakers and dynamic microphones are essentially the same thing used in opposite directions). A word that might make more sense for the concept is "efficiency". A speaker can be said to convert electrical energy into sound energy. Given the same electrical energy, a more sensitive speaker will produce more sound energy, and hence seem louder.

I'm really bad at dB math, but a 3:1 ratio ("25/75") would be 9 dB of difference? Offhand, I'm not finding sensitivity listed among the specs of these cabinets, but looking at specs for other kinds of speakers, a 9 dB variation seems plausible.

 

[agedhorse]

I believe the word "sensitivity" as applied to loudspeakers is inherited from its meaning as applied to microphones (speakers and dynamic microphones are essentially the same thing used in opposite directions). A word that might make more sense for the concept is "efficiency". A speaker can be said to convert electrical energy into sound energy. Given the same electrical energy, a more sensitive speaker will produce more sound energy, and hence seem louder.

I'm really bad at dB math, but a 3:1 ratio ("25/75") would be 9 dB of difference? Offhand, I'm not finding sensitivity listed among the specs of these cabinets, but looking at specs for other kinds of speakers, a 9 dB variation seems plausible.

Sensitivity generally incorporates directivity data as well. One way to increase sensitivity is to increase directivity. This is exactly what happens as you go from full space to 1/2-space to 1/4-space measurements.

Efficiency generally does not include directivity data, it's the ratio of total electrical energy in total acoustic energy out. Total acoustic energy is SPL divided by directivity factors, which normalize as directivity goes up SPL goes up thus the ratio remains relatively constant.

Where directivity is the same, sensitivity and efficiency tend to be used interchangeably.

A 9dB difference in sensitivity would be HUGE, not at all plausible.

 

[Robb Fesig]

* I read every post in this thread, and I think these are the real questions:

Are you really going to be taking the 6x10 and 4x12 to shows when you play?
Do you think your soundman is going to give you TWO microphones for your bass rig?
Do you think you'll be able to drag both cabs (back and forth) to the studio for recording?

Typically, a sound guy will want you to run direct when playing live. And often (since we're second class citizens) the studio will want you to use whatever bass amp they happen to have laying around.

You're putting a lot of effort into getting these things sounding good together, and there's a good chance you'll be the only person that ever gets to hear them that way. In any event, I wish you luck with your endeavor.

 

[packhowitzer]

This will let you use one bass into two amps with zero loss of signal. but it is kind of pricey for what amounts to an AB/Y.

 

[Tim Skaggs]

They are both 4 ohm cabs

He was explaining why the two cabs are wildly different, and that what you observed is normal. You're comparing a 612 with a 410... no surprise the 612 is louder, unless you had some ultra efficient super 410.
You need to aim for two similar sensitivity cabs. Best chance to get a good result: use two identical cabs.

612? I want to see and hear that, but I'd rather not move it.

 

[juancaminos]

I would love to try that 4X12 cabinet, yes sir!

 

[DukeLeJeune]

We know bass waves interfere with one another, so why not manipulate this fact to our advantage? Using multiple subwoofers, and placing them in precise, specific ways can have the effect of canceling out modal resonances, thereby dramatically flattening the bass response.

Speaker Placement 201, Part Two: Using Subwoofers -

Imo a distributed multiple subwoofer system is a good solution for home audio.

Ironically the smaller the room, the greater the qualitative benefit from adding more subwoofers and distributing them deliberately. And likewise the larger the room, the smaller the qualitative benefit from adding more subwoofers and distributing them deliberately. The reason is, in a large room, the bass wavelengths are small relative to the room dimensions (in the horizontal plane anyway), so we have greater modal density. Greater modal density is desirable because it keeps any particular modes from sticking out like sore thumbs. Indeed, that is the primary benefit of a distributed multisub system - it makes a small room behave like a much larger one by increasing the modal density. The effectiveness of targeting specific modes is questionable, as the effective acoustic dimensions of a room at low frequencies are almost always different from the actual physical dimensions because of such features as doors, windows, closets, air vents, and any other "soft spot" on a room boundary.

I designed a four-piece distributed multisub system that The Absolute Sound magazine named 2015 Product of the Year in its category, so I'm definitely an advocate of the concept for home audio, but it is not something I'd do for a sound reinforcement system.

 

[Jack]

There is a big difference between a cab .97% efficient and 103% efficient with regard to the amount of decibels they will produce.

Indeed, a 102.03% different is huge.

 

[David Sutkin]

* I read every post in this thread, and I think these are the real questions:

Are you really going to be taking the 6x10 and 4x12 to shows when you play?
Do you think your soundman is going to give you TWO microphones for your bass rig?
Do you think you'll be able to drag both cabs (back and forth) to the studio for recording?

Typically, a sound guy will want you to run direct when playing live. And often (since we're second class citizens) the studio will want you to use whatever bass amp they happen to have laying around.

You're putting a lot of effort into getting these things sounding good together, and there's a good chance you'll be the only person that ever gets to hear them that way. In any event, I wish you luck with your endeavor.

Thank you for your input but ....

This has ZERO to do with playing live, I gig quite often and either just bring the Mesa 6x10 if I choose to use my own back line or if the stage is small, I just go DI into the club's PA.

I've mentioned quite a few times in this thread already that my desire to try both cabinets with the one head had NOTHING to do with wanting extra volume either. I simply liked the 2 very different tonal colors of each cabinet and wanted to hear what playing out of both cabs together would sound like in my band's rehearsal spot. A self indulgent experiment at best.

And I'm really not putting a lot of effort into this other than posting a question on TB

 

[David Sutkin]

This will let you use one bass into two amps with zero loss of signal. but it is kind of pricey for what amounts to an AB/Y.
View attachment 3102586

Thank you for the suggestion but I bought this yesterday ... It was highly recommended by other TB'ers and had great reviews.

 

[BadExample]

I think I'd listen to the Mesa Engineer about that Mesa cab and have it checked out.

 

[David Sutkin]

I think I'd listen to the Mesa Engineer about that Mesa cab and have it checked out.

I'm planning too.

Although there "appears" to be nothing wrong with it when I use it solo with the D800+ head ... it's got PLENTY of volume and appears to be working fine.

It's just got a darker, warmer tone than I'd prefer when using it solo'd, in hindsite, I should have purchased the powerhouse cab instead of the traditional when I first bought it.

The GK 412 cab has a brighter, punchier tone .... That's why I experimented with hooking up BOTH cabs, simply to hear what the two together would produce tonally.

My mistake, was hooking them up together incorrectly ... I've decided to just experiment with running 2 separate rigs moving forward.

This isn't about more volume, or live show rigs, or "why would I need more than a 610 or 412?" or ANYTHING ELSE except tonal experimentation ...

I'm sure there will be a post coming up shortly asking me why I need more volume? Lol

 

[agedhorse]

Have you verified that both cabinets are wired in phase? Its possible that if both cabinets alone sound fine but when combined do not, one is wired with reversed polarity.

I encourage you to troubleshoot and find the real cause before damaging something from continued experimentation.

I also encourage you to read the manuals of all of the equipment that you are using in order to rule out user error.

 

[BadExample]

Battery test.

 

[Rick James]

I believe the word "sensitivity" as applied to loudspeakers is inherited from its meaning as applied to microphones (speakers and dynamic microphones are essentially the same thing used in opposite directions). A word that might make more sense for the concept is "efficiency".

Efficiency, which is a T/S spec that's very rarely used, is the ratio of acoustical watts output versus electrical watts input, expressed as a percentage. The average pro-sound driver efficiency is about 5%. Sensitivity is measured in decibels, measured at a specified distance, power input, frequency and room boundary conditions. It's completely different from the sensitivity ratings of microphones.

 

[Old Garage-Bander]

Battery test.

Frog test.

 

[dbsfgyd1]

Indeed, a 102.03% different is huge.

Seems as though that pesky decimal point got away from me again.... with skills like that makes me glad I'm a security trader..lol!!. Good catch!

 

[Jack]

Seems as though that pesky decimal point got away from me again.... with skills like that makes me glad I'm a security trader..lol!!. Good catch!

0.97% is closer, most pro sound drivers are around 3% efficient or so.

 

[fatNfunky]

Imo a distributed multiple subwoofer system is a good solution for home audio.

Ironically the smaller the room, the greater the qualitative benefit from adding more subwoofers and distributing them deliberately. And likewise the larger the room, the smaller the qualitative benefit from adding more subwoofers and distributing them deliberately. The reason is, in a large room, the bass wavelengths are small relative to the room dimensions (in the horizontal plane anyway), so we have greater modal density. Greater modal density is desirable because it keeps any particular modes from sticking out like sore thumbs. Indeed, that is the primary benefit of a distributed multisub system - it makes a small room behave like a much larger one by increasing the modal density. The effectiveness of targeting specific modes is questionable, as the effective acoustic dimensions of a room at low frequencies are almost always different from the actual physical dimensions because of such features as doors, windows, closets, air vents, and any other "soft spot" on a room boundary.

I designed a four-piece distributed multisub system that The Absolute Sound magazine named 2015 Product of the Year in its category, so I'm definitely an advocate of the concept for home audio, but it is not something I'd do for a sound reinforcement system.

Im sure in an ideal situation you are right. But when your 'average joe' has more then 1 subwoofer/cab to play with, and they know little to nothing of nodes and cancellation, and they 'plonk their boxes down willy nilly' -

I fear bass quality would suffer (over a single subwoofer instal)

 

[DukeLeJeune]

I'm sure in an ideal situation you are right. But when your 'average joe' has more then 1 subwoofer/cab to play with, and they know little to nothing of nodes and cancellation, and they 'plonk their boxes down willy nilly' -

I fear bass quality would suffer (over a single subwoofer instal)

Assuming we're talking about home audio here, in general the in-room smoothness improves with each additional sub as long as they are spaced fairly far apart. The reason is, each sub is producing a unique peak-and-dip pattern, and the ONLY way the sum of these two dissimilar peak-and-dip patterns could be as bad as just one sub's pattern would be, if they were identical. And if they are not in the same location, their peak-and-dip patterns will not be identical.

The spatial variation also improves, so there is less difference in the bass response from one location to another within the room. This makes EQ more effective, because fixing a problem in one microphone location is less likely to make things worse somewhere else.

So in my opinion no knowledge of nodes and cancellation is needed for the average joe to get a significant qualitative improvement from a distributed multisub system. All he has to do is follow a few simple guidelines and spend some time dialing in the control settings (which applies to any subwoofer system).

Here's a bit of anecdotal evidence that two subs are better than one: There are many Magnepan owners who have tried subwoofers. If you read enough of their posts, a trend emerges: Those who tried a single sub usually went back to not using any subs, while those who tried two subs usually kept them. You see, dipoles have smoother in-room bass than monopoles, and two dipoles are smoother than one dipole. The discrepancy between a single monopole sub and two dipole main speakers is just too much to ignore. Two monopole subs comes significantly closer. I went with four for my system because four monopole subs intelligently distributed will have similar in-room bass smoothness to two dipole main speakers, which helps them to blend well. But unlike dipole subwoofers, multiple small monopole subs can pressurize the room at low frequencies, generating satisfying chest-thump.