FAQ

Frequently Asked Questions:

 

What is active bi-amping?

Active bi-amping refers to a speaker setup where different frequency ranges of audio signals are split and sent to separate amplifiers and speaker drivers. Active bi-amping involves using an electronic active crossover to split the audio signal frequencies before amplification. This setup allows for very precise control over each frequency range, significantly improving audio fidelity and reducing distortion, as each amplifier and driver handles a specific portion of the audio spectrum. It's commonly used in high-end audio setups and professional sound systems to achieve greater clarity and efficiency in sound reproduction.

 

Why should I switch to active bi-amping?

Simply put, there is nothing like the sound of a high quality analog active bi-amped sound system. Active bi-amping is the single most impactful and low-cost way to massively boost the quality of your sound. It's no exaggeration to say it's the closest thing to magic an audio enthusiast can experience.

Active bi-amping offers several advantages over the typical stereo system where a single amplifier powers a full-range speaker:

1. Improved control: Active bi-amping allows for precise control over each frequency band, as the signal is split before amplification using precision solid-state electronic filters. This can result in better management of audio signals, reduced distortion, and improved clarity, detail, and warmth in sound reproduction.

2. Reduced intermodulation distortion: With separate amplifiers for different frequency ranges, there's less chance of interference or distortion caused by the simultaneous reproduction of various frequencies by a single amplifier.

3. Customization: Active bi-amping enables customization of the amplification and EQ settings for different drivers or frequency ranges, catering to the specific characteristics of each speaker component.

4. Efficiency: By dedicating amplifiers to specific frequency ranges, each amplifier can operate more efficiently within its designated range, leading to better overall performance, power utilization, and speaker damping. The amplifier can control the drivers much more precisely if there are no passive components in the signal path.

5. Flexibility: It allows for easier upgrades or changes in the audio system. You can modify or upgrade individual components (amplifiers, crossovers, etc.) without affecting the entire setup.

 

Is my sound system capable of being active bi-amped?

The system requirements for active bi-amping can vary based on the specific setup and the goals you have for your audio system. Here are some general requirements to consider: 

1. Speakers: To bi-amp speakers actively, you'll need speakers that are designed for bi-amping or can be bi-wired. They should have separate input terminals for the different frequency ranges (typically low-frequency drivers and high-frequency drivers). These sets of terminals are usually connected to each other by large jumpers. For active bi-amping always remember to remove the jumpers to avoid amplifier strain.

2. Amplifiers: You'll need at least two separate amplifiers, one for each frequency range that you're bi-amping. These amplifiers should ideally match the power requirements of the speakers and be capable of handling the specific frequency range efficiently.

3. Active Crossover: Active bi-amping requires an active crossover unit that can split the audio signal into different frequency ranges before sending them to the respective amplifiers. The crossover, like the Sublime Acoustic K231 or K235, is an active electronic device and is wired between the audio source (DAC or pre-amp) and the amplifiers.

4. Cabling and Connections: You'll need appropriate cables to connect the crossover units to the amplifiers and the audio source. Depending on your existing equipment, you can use either balanced signaling via XLR or TRS connectors or unbalanced signaling via RCA type connectors. For unbalanced signaling, high-quality cables are recommended to minimize signal loss and interference.

 

Can speakers be bi-amped with the Passive crossover left in the circuit?

The answer is yes. Though you will get the best sound quality if you entirely remove or bypass the existing passive crossover, you can still achieve a very significant increase in sound clarity even with your passive crossovers left intact. Many of our customers do that since most people don’t want to physically modify or rewire their speakers. The only requirement to do this is you need to closely match the crossover frequency(s) in the active crossover to that of the passive to avoid any humps or dips in the resulting response curve.

The high and low frequency signals will largely just pass through the passive crossovers since the active crossover will have pre-filtered the signal into the high and low channels. This will prevent the passive crossovers from corrupting the signal very much. You'll have much less intermodulation distortion. And the loads on the amplifier channels will be mostly resistive, meaning the load won't vary by frequency, so the amplifier can more accurately reproduce the signal.

 

What if I don't know the XO point(s) of my existing passive crossovers?

You can very easily measure the crossover frequency of your existing speakers using a low-cost spectrum analyzer smart phone app. To do this, remove the jumpers from your speaker terminals and drive the high and low sections independently with a white noise generator (available on YouTube or elsewhere on the web). Then use a spectrum analyzer app to see where the drivers are rolling off. These apps are generally about $10 or $15, and some are available free in the app store. You're looking for the F3 frequency of each of the drivers, which is the point at which the response attenuation reaches 3dB.

You'll want to set the XO point at the center point between those two F3 frequency numbers.

 

Are XO modules the same between the K231 and K235?

The XO modules with 24dB slope are fully interchangeable between K231 and K235. Modules with 12dB slope are not interchangeable.

 

Audio Quality: Analog Active Crossover vs. Digital crossover?

We've had a good number of customers that have switched from various DSP based crossovers to analog. The underlying problem with DSP based crossovers is the unavoidable quantization error inherent in any A/D and D/A conversion. With a DSP based crossover, you have the audio input signal (that is usually from a digital source and has already come from a D/A in the DAC or preamp, etc.) that must be digitized by an A/D converter in the DSP crossover before being processed through some unknown algorithms in the DSP, and then re-converted to analog a 3rd time to be sent to the amplifiers. Most of the signal detail and warmth is lost in these three digital/analog conversions, and the sound quality that reaches the speaker drivers is greatly degraded. On first impression, DSP crossovers may seem to sound decent. But when you listen closely you will find the detail of the sound stage produced by the DSP is not as clear or precisely defined as you'll experience with a high quality analog active crossover. Even the highest quality DSP based crossover will not be able to match the sound quality of an analog active crossover.

 

Why do we use XO modules to set the crossover frequency?

The reason we use the XO modules to select the crossover frequency is to virtually eliminate harmonic distortion in the filters. The crossover frequency of each of the filter stages is controlled by the values of 20 resistors in the filter circuits.  And these resistors must be very precisely matched. Any delta in the values of these resistors will cause significant harmonic distortion in the audio. Using these modules to select XO frequency allows us to match these resistors to within 0.1% tolerance, which allows the filters to perform nearly perfectly with almost zero harmonic distortion. 

Some lower end electronic active crossovers on the market use potentiometers to allow continuous frequency selection by turning a knob. But even the best potentiometers available on the market will have a tolerance of at least 5%, and more often it’s closer to 20%. This level of mismatch between the filter components would lead to massive harmonic distortion.

 

What Crossover Frequencies can be supported?

We can support any of these frequencies from our standard catalog:

 - Any multiple of 5Hz from 30Hz-100Hz (e.g. 30Hz, 35Hz, ... 100Hz)

 - Any multiple of 10Hz from 110Hz-200Hz (e.g. 110Hz, 120Hz, ... 200Hz)

 - 250Hz, 275H, 350Hz, 375Hz, 450Hz

 - Any multiple of 100Hz from 300Hz-4000Hz

 - Any multiple of 500Hz from 4500Hz-16KHz

We can also build custom modules of any frequency you may need for an additional $35 charge.

 

Crossover Filter Slopes:

The slope of an active crossover filter refers to how quickly it attenuates or rolls off frequencies outside its intended range. The slope of an active crossover filter is typically measured in decibels per octave (dB/octave). For instance, a 12 dB/octave slope means that for every doubling (or halving) of frequency outside the crossover point, the signal strength decreases (or increases) by 12 decibels. Our active crossovers can support either 12dB or 24dB filter slope.

We generally recommend 24dB slope, which will narrow the frequency range in which both high and low drivers are simultaneously driving. Each of the drivers will produce a slightly different version of the sound in that over-lapping frequency range, and the summing of the two will cause some amount of distortion. This is why 24dB slope will often give a crisper and cleaner sound.

12dB slope is recommended in cases where you’re trying to coexist with existing passive crossovers. In these cases, it’s best to closely match the frequency and slope of the passive crossovers, which are very often 6dB or 12dB slope.

 

Can the Sublime Acoustic crossover support 230V AC mains voltage?

Yes, all crossovers can support either 110V or 230V mains voltage. There is a selection switch on the back of the unit.

 

Can I leave the active crossover powered on 24/7?

Yes, our active crossovers draw very little power. It’s ok if you want to leave them turned on 24/7.

 

Can I use an integrated amplifier for active bi-amping?

Running an integrated amp is a little problematic for active bi-amping. The crossover needs to be wired inline between the preamp outputs and the amplifier inputs. Integrated amps often have this connection built inside, and do not allow the preamp outputs to be isolated from amplifier inputs. Many integrated amps do however provide the preamp outputs to external jacks. These would go to the crossover inputs. Unfortunately, few integrated amps provide external jacks to the internal amplifier inputs, so in most cases the amplifier stages in the integrated amps would be unusable for bi-amping. If your amp is like that, then you would need to use a separate amplifier to drive your main speakers.

 

Is your balanced signaling truly balanced? And what are the benefits?

Yes our balanced circuitry is fully balanced, differential signaling with precisely matched impedances on the (+) and (-) legs of the cable. Truly balanced signaling virtually eliminates cable induced noise because any electromagnetic radiation that penetrates the cable shielding will couple equally into both the (+) and (-) twisted pair legs of the cable. The receiver reconstructs the audio signal by measuring the difference between the (+) and the (-), and since the induced noise appears equally on both legs, any induced noise is almost entirely nulled out, providing crystal clear noise free audio.

In addition to the SNR benefit, balanced signaling provides three additional very important benefits that improve sound quality:

• Balanced signaling provides 11dB increased dynamic range (the ratio of the largest measurable signal to the smallest measurable signal).
• Balanced signaling doubles the signal slew rate, which helps to more accurately represent the audio signal, providing higher definition audio.
• Balanced signaling reduces channel crosstalk due to elimination of the shared audio ground.

 

What are the differences between the K235 and the K231?

 The K235 offers a small improvement in sound quality over the K231:

• The K235 has slightly improved THD, THD+N, and IMD compared to the K231. 
• The K235 has an 8dB improvement in SNR.
• It has a 5dB improvement in channel crosstalk.
• It has a 4dB reduction in 60Hz hum and related harmonics over the K231.
• The K235's XLR connectors are superior to the K231's TRS jacks from a reliability and noise standpoint.
• The K235 17” or 19” rack-mount form factor is an improvement for many over the non-standard size of the K231.
• The K235 has a couple of new features/enhancements:
  • We added a 15Hz/24dB high-pass sub-sonic filter for LP fans to reduce the impact of needle drops and wow/flutter. 
  • The baffle step compensation mechanism was significantly enhanced by changing the K231's 3 baffle width selections to 16 selections to more precisely set the baffle width and more accurately compensate for the baffle step effect for a wider range of speakers. This offers much higher precision in restoring the bass content lost to the baffle step effect.

 

Are there discounts for buying multiple K231 or K235 units?

Yes, we offer automatic discounts based on quantity of units purchased:

• Purchase 2 units get 5% automatic discount
• 3 units gets 10% discount
• 5 units gets 15% discount
• 10 units 25%
• 20 units 35%