Why 2.67-Ohms?

Ever since Class D amps have become the mainstay of today’s amplifier technology and designs, one of their limiting factors has always been their ability to drive speaker loads down to 2-Ohms. As a new generation of Class D amps become available, even though they are not necessarily specified down to 2-Ohms, there are ways designers can allow these amps to operate safely down to 2-Ohms with certain caveats in mind.

The biggest concern running a power amp rated at 4-Ohms down to 2-Ohms is the extra power demand in terms of current the amplifier will try to deliver to these lower impedance loads. When a manufacturer designs an amp’s power supply and output stage, they design it to operate safely at a specified rated output power. In other words, why go through the trouble and expense of designing a power supply and output stage that can handle 1000 watts when you’re only going to deliver 500 watts? They would have to charge based on the added cost of the 1000 watt design, but without delivering the full 1000 watts. Not a very wise design choice from a pure economical and business perspective. Another thing to realize and understand is that getting an amplifier to handle a lower impedance load doesn’t necessarily mean it can or will deliver more power than its designers intended it to. It just means it can deliver and distribute its maximum, available output power into a lower impedance load safely.

So what does this all mean?

Let’s first consider the following equations (you didn’t think you would need to remember your basic high school algebra to read this article, did you?)

Ohms Law:

1.) V = I x Z where V = voltage, I = current, and Z = impedance

This equation can also be written as:

2.) I = V/Z

Amplifier Power output is calculated as follows:

3.) P = V x I where P = power, V = voltage, and I = current

Substituting for I with equation 2, Power can also be calculated as:

4.) P = V²/Z

or:

5.) V² = P x Z ;   ⇒  V = sqrt(P x Z) ; sqrt   ⇒   square root

Now that we got that over with: (there may be a pop quiz on Monday, btw!)

Let’s take an example of a typical amplifier rated at 500 Watts @ 4-Ohms

Using equation 5 we can calculate the amp’s maximum output voltage before clipping:

V² = P x Z

V² = 500 x 4

V² = 2000

V = sqrt 2000

V = 44.72 Volts. This is the maximum voltage the amp is capable of producing.

And just to check what this amp will deliver into an 8-Ohm load given the same output voltage we can use equation 4 as follows:

P = V²/Z

P = 44.72²/8

P = 2000/8

P = 250 watts

This is typical of an amplifier’s power spec such that it will deliver half as much power into 8-Ohms as it does at 4-Ohms, given the maximum output voltage is the same for both impedances.

Notice from the above example and equation 4 that as the impedance goes up, the power output goes down proportionately. In other words, Power Output (P) is inversely proportional to Impedance (Z).

So, what if we hook up a 2-Ohm load to this amplifier without taking any precautions?

Using equation 4 and solving for Power, using Z = 2-Ohms we get:

P= 44.72²/2

P= 2000/2

P = 1000 watts!

This is clearly much more power than the amp was designed to deliver. Hopefully the amp’s protection features will kick in long before it tries to deliver anything close to 1000 watts, as the amp’s power supply and output devices were not designed to handle this extra current and power demand. So what does this translate to in the real world if you were to hook up a 2-Ohm load to this amp as is? Chances are, during your bass solo when you’re digging in having a grand ole’ time for yourself, the amp will enter protect mode from either over current, over temperature, or both and shut itself down. So much for your bass solo!

So what can a designer do to allow two 4-Ohm cabs in parallel (2-Ohm load) to be connected safely to this amp? They can limit the output voltage swing such that the power output can never exceed 500 watts, even at 2-Ohms. And how do we determine this voltage level?

Using equation 5, we can calculate the maximum output voltage we want in order for the amp to only deliver 500 watts @ 2-Ohms as follows:

V² = P x Z

V² = 500 x 2

V²=1000

V = sqrt 1000 = 31.62 Volts

If we can limit the amp’s output voltage to 31.62 Volts instead of 44.72 volts when the amp is driving a 2-Ohm load, we can make sure the amp still doesn’t deliver more than 500 watts, which is in line with what the amp was designed to do (assuming it can safely handle the required current of 15.8 amps @ 2 ohms vs. 11.18 amps @ 4-Ohms see equation 4).

How is this done? There are various ways to accomplish this which is beyond the intended scope of this paper.

But…. you knew there was going to be a “but”! What about a 2.67-Ohm load, which is becoming more and more common these days, with players adding an 8-Ohm 112 cabinet to their 4-Ohm 212 cabinet, or combining an 8-Ohm 210 cabinet with their 4-Ohm 410 cabinet?

Let’s find out:

Using equation 4 and V = 44.72 volts (amp’s max. output voltage) and Z = 2.67-Ohms, solving for Power we get:

P = V²/Z

P = 44.72²/2.67

P = 2000/2.67

P = 750 watts

Again, like in the case of the 2 ohm load at the amp’s maximum output voltage of 44.72 Volts, the amp is still being placed in a potentially compromising position, by being called upon to deliver more current and power than it was safely designed to do. At higher volumes, this could cause it to enter protect mode and shut itself down, not something a player would want to risk have happen in the middle of a gig.

Re-calculating using the 2-Ohm Voltage output of V=31.62 Volts, and again using equation 4

P = 31.62²/2.67

P = 1000/2.67

P = 375 watts

This is much safer and well within the amps power ratings, but, we just lost 125 watts or ¼ (25%) of the amps total available output power at 2.67-Ohms! Just like above in the 4-Ohm vs. 8-Ohm scenario, when you hold the output voltage constant and raise the impedance, you get proportionately less power to the load (speaker). However, unlike the 8-Ohm example above, where its power output was limited by the available output voltage, this is not the case here. It would be great if this amp could offer a 3rd selection for 2.67-Ohm operation and allow the amp’s output voltage to reach 36.54 Volts when being used with a 2.67-Ohm load. It certainly has this output voltage available to it. This would give us the amp’s full output capability of 500 watt at 2.67-Ohms as shown below using equation 4 and V= 36.54 Volts:

P = 36.54²/2.67

P = 1335/2.67

P = 500 watts!

So “Why 2.67-Ohms?” Being able to safely extract the maximum available output power of an amplifier at various impedances gives players using various combination of cabinets much better access to the amplifiers full output capabilities without leaving any “Watts on the table”.

And with the B|AMP’s software based architecture, along with its computer controlled, DSP processor, it was just a few extra lines of code to allow the B|AMP to deliver its full output power of 800 watts, not only into 2-Ohms, but into 2.67-Ohms as well. Without a 2.67-Ohm option, the B|AMP, and any other 800 watt amp for that matter, would only be able to deliver 600 watts, or 25% less, safely into 2.67-Ohms. Pretty cool, huh? And speaking of “cool”, even though the amp’s output power may be the same at 2-Ohms as it is at 2.67-Ohms, its current is not. Higher operating current, and the associated heat that goes with it, is still a concern that needs to be addressed when designing an amp capable of 2-Ohm operation. That is why with the B|AMP, when 2-Ohm operation is selected, the fan is automatically engaged, keeping its heatsinks running cooler, ensuring a safe operating condition for the amplifier under these more demanding conditions. We know of no other commercially available Bass Amp on the market that does all this!

 

AdobeIcon50Click HERE to download a copy of the “Why 2.67-Ohms” article.

New Bergantino Dealer in Giebenach, Switzerland!

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We want to welcome our new dealer in Switzerland – MusiX AG!! They are waiting on arrival of their first shipment soon. Call them, visit them, play some Bergantino Audio. They have a great crew, so please support them!

MusiX AG
Sägeweg 15
CH-4304 Giebenach
Tel 41 61 813 11 77
www.musix.ch

Why B|AMP?

Before any engineer worth his or her weight puts pen to paper to start any design, he or she needs to ask themselves one very simple question: “Why?” In fact, that’s exactly the first question a venture capitalist would ask a would-be entrepreneur looking for investment money… “Why X?”

For years I’ve been asked by dealers to produce a Bass Amplifier. My response was always “the industry doesn’t need another ‘Me Too’ product with another off-the-shelf power module with another voiced preamp”. The multitude of preamp voicings reminds me of my old hi-fi days when department stores had shelves lined with speaker cabinets. The most successful manufacturers of those ‘lo-fi’ speakers knew that they had at most 5-10 seconds to impress a potential customer before they moved on to the next speaker system. So what did they do? They voiced their speakers to have the boomiest bass and most sizzly treble. Why? Because they knew, given a very short audition time, this approach would put their speaker’s sound out in front of their competitors. What the unaware customer did not know was once they got these speakers home, what they initially thought was the most exciting speaker in the store would soon turn out to be the most un-enjoyable and fatiguing speaker to listen to at home! Anyone who has listened to a very well designed and engineered hi-fi system knows that a balanced, low distortion system, always wins out in the end for a long term and enjoyable, musical listening experience.

As I’ve watched and observed many bass amplifier designs evolve over the years, I can’t help but wonder if any of these manufacturers truly understand the relationship between the amp and speaker system they are attempting to power. This explains why most of them are just using their existing or slightly modified preamps, some from as far back as the ‘60s and ‘70s, and just adding a lightweight, class D power module to it. Kind of reminds me of Einstein’s definition of insanity (“doing the same thing over and over again and expecting different results”). So how can the same tone controls, with fixed frequencies and q’s, EQ different speakers with different frequency responses, to sound balanced, if the electrical response of the EQ is constant, but each speaker’s acoustic response is different? The simple answer is they can’t! It’s like trying to fit a square peg in a round hole! How many times have you read on the news groups and blogs that this amp works great with that speaker but no so much with this one and vice versa? That’s because one amp’s EQ points may better match one speaker’s response than another’s, but it’s still not very close, just “better”. To think of all the time these manufacturers spend trying to voice their preamps, choosing EQ filter type, q’s, and frequencies that either offer the best compromise between all their different speaker models, or worse, basing their EQ choices on specific players with specific basses and speakers!

But wait a minute… I thought these were tone controls, not speaker EQs. Exactly! And herein lies the problem. Most players don’t even realize they’re actually using their tone controls to try and EQ their speakers long before they are even EQ’ing their tone. And unfortunately, we believe most manufacturers don’t understand this either. Tone controls, with their typically wide q’s, or broad shelving filters, are no more useful to EQ’ing a speaker than are mudguards on a tortoise! You may be thinking right about now of all the time and money you’ve spent over the years, chasing your tail, searching for that tone in your head, not even realizing that you were trying to solve this very problem. And unfortunately, not even knowing there wasn’t a solution to this problem…until now!

So “Why B|AMP?” Very simple. As an engineering company we’ve identified a real world problem, and are offering a real world solution to it. That’s what the Profile concept and system is all about. We’re EQ’ing the response of your speaker for you, with very precise filters, unique to each model, based on actual, real world acoustical measurements. So now you can focus on EQ’ing your tone, and not your speaker. And the only way to implement this concept is with a 21st century amplifier architecture, utilizing the latest in DSP technology along with an embedded system to control the process. No other bass amplifier on the market has the power and control over the entire system’s response and user experience than the B|AMP. And we believe that few, if any, other bass amplifier manufacturer understands the very nature of this problem like we do nor possesses the technology to solve it.

Bergantino Announces ‘Advanced Design’ Series of Electric Guitar Speakers

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Hear your guitar again for the very first time! Introducing the new AD Series (‘Advanced Design’) of guitar cabinets from Bergantino. These speaker cabinets are engineered from the ground up for performance, musicality, and definition of tone. They are not your grandfather’s guitar cabinet using an “off the shelf” speaker, stuffed into a generic box like everyone else’s. The AD112 and AD212 use our proprietary, custom drivers mated to a highly engineered cabinet which delivers articulate, accurate, and very musical tone. Notice the metal grille? This feature was deliberately chosen to ensure that the tonal transparency and accuracy of our custom engineered drivers are delivered to you, the artist, and to keep these qualities from being muffled and compromised by a cloth grille. In fact, did you know that’s exactly why grill cloth became the de facto standard for guitar cabs? To alleviate the harsh, ice-pick highs on many of the most sought after guitar speakers! We also use Baltic birch cabinetry, cut to close tolerances, to ensure our custom drivers perform to their exact intended specifications and carry forth all your musical creativity as you intended and wanted to hear!

The internal components used are extremely high quality and they are of Bergantino design. Our custom designed AD series drivers have ceramic magnets and the low-end on this series of cabinets is full and round – they can handle high power output from your amplifier. The AD series have a tight-creamy low end with an extremely balanced tone, while staying very open and articulate. Each of the AD series cabinets are covered in durable black tolex, have mounted rubber feet and include a high-impact metal grill for durability and acoustical transparency.

AD112 ‘Advanced-Design’ 1-12″ Electric Guitar Speaker Cabinet
Woofer: 1-12” AD12G-16 woofer
Cabinet Design: Sealed
Cabinet Material: Baltic Birch w/ Metal Grill
Cabinet Covering: Tolex
Impedance: 16-Ohms
Power Handling: 75W RMS
Frequency Response: 70hZ – 5.5KhZ
Sensitivity: 100db @ 1-watt / 1-meter
Dimensions: 18.5″ x 19.25”W x 12”D
Weight: 35 Lbs.
ProNet Price: $599.00

AD212 ‘Advanced-Design’ 2-12″ Electric Guitar Speaker Cabinet
Woofer: 2-12” AD12G-16
Cabinet Design: Sealed
Cabinet Material: Baltic Birch w/ Metal grill
Cabinet Covering: Tolex
Impedance: 8-Ohms
Power Handling: 150W RMS
Frequency Response: 70hZ – 5.5KhZ
Sensitivity: 103db @ 1-watt / 1-meter
Dimensions: 24”H x 26”W x 13”D
Weight: 62 Lbs.
ProNet Price: $999.00

Platinum Dealer – South Shore Music

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If anyone in the Boston, Massachusetts area wants to hear every Bergantino Audio speaker currently available we recommend you go by South Shore Music. They’ve got ’em all and will be happy to help you out.

South Shore Music
13 Washington Street
Weymouth, MA 02188
781-331-3333
www.southshoremusic.com

Platinum Dealer – Bass Club Chicago

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If anyone in the Chicago, Illinois area wants to hear every Bergantino Audio speaker currently available we recommend you go by Bass Club Chicago. They’ve got ’em all and will be happy to help you out.

Bass Club Chicago
5055 N. Western Avenue
Chicago, Illinois 60625
773-561-3521 & 877-385-3521
www.bassclubchicago.com