Dirac Live¶

Dirac Live helps your speakers perform better in your room. Using a calibrated microphone, it measures how the speakers and room affect the sound at several positions around your listening area.

From these measurements, Dirac Live sets speaker levels and delays and creates correction filters. These filters adjust the tonal balance (frequency response) toward a target curve you can choose. They can also correct certain timing and phase problems that ordinary equalization cannot address.

Calibration is done with the Dirac Live app on a PC or Mac. The resulting filters are stored in a calibration slot on the HTP-1 and applied during playback when enabled.

Dirac Live can reduce audible problems, particularly in the bass, but it cannot fix everything. Speaker placement, crossover settings, and room acoustics still matter.

Note

Screenshots on this page illustrate the calibration steps. The appearance of the Dirac Live app and the HTP-1 web interface may change with software updates.

Before You Start¶

For a normal calibration, turn PEQ off or use Pre placement. The calibration signal bypasses Pre PEQ but passes through Post PEQ, so active Post filters are included in the measured response. See PEQ placement for advanced uses. Tone control and Loudness are automatically disabled during calibration, and User Delay and User Trim are set to zero.
Use the Speakers page to enable all of your speakers. Don't worry about crossover settings yet, but set any Dolby Atmos Enabled speaker groups to Dolby before calibration. They should then appear in Dirac Live with "Atmos" in the speaker name, and Dirac Live will preserve their specially designed frequency response.
A calibrated USB microphone is required. Using an uncalibrated mic, or a laptop's built-in mic, will skew the frequency response of your system.

Multiple Subwoofers with Dirac Live Bass Management¶

Connect all subwoofers to a single HTP-1 subwoofer output, using a suitable signal splitter, distribution device, or the subwoofers’ supported daisy-chain connections. Enable only that one subwoofer output in the HTP-1 speaker configuration. Dirac Live then measures and corrects the subwoofers together as one system.

With separate subwoofer outputs, regular Room Correction and Bass Management optimize each subwoofer independently. They do not optimize how the subwoofers combine acoustically, so the combined response can differ substantially from the individual responses shown in the Dirac Live app.

This recommendation also applies to Room Correction used with the HTP-1’s own bass manager. Bass Control and ART provide joint optimization and support individually connected subwoofers.

Dirac® calibration requires a PC or Mac laptop running the Dirac Live app with an external mic attached to the laptop.

Note

The HTP-1 requires the desktop version of Dirac Live. The mobile Dirac Live app cannot be used because the HTP-1 does not provide the external microphone support required by the mobile app.

Calibration Steps¶

Complete the basic setup first — be able to play sound through your speaker set.

These steps use Dirac Live Room Correction with Bass Management, included with the HTP-1. Dirac Live handles room correction, speaker delays and levels, and bass management, including crossovers. When this calibration is active, it replaces the HTP-1’s own bass manager.

Bass Control and ART are optional, separately licensed upgrades.

Download and install the Dirac Live app: https://live.dirac.com/download/. Use the latest version for the best results.
Attach a calibrated USB microphone to the computer.
Launch Dirac Live and log in. The HTP-1 includes Dirac Live Room Correction with Bass Management.
Open Dirac Live and connect to the Monolith HTP-1. The Dirac Live app finds the HTP-1 using common networking protocols. The name it shows is the HTP-1's name, set on the Device Settings page.
Choose the microphone you have connected.
The HTP-1 web UI is read-only while a Dirac Live calibration session is connected — a banner tells you this, and the front panel and remote still work for volume. Closing the Dirac Live app restores normal control.

A connected Dirac Live calibration session temporarily puts the HTP-1 web interface into read-only mode.
Set the volumes for calibration. The volume control on the left side of the Dirac Live screen matches the one on the remote control — you can adjust it with the remote. The app sets the volume initially to -34 dB.

Use the Dirac Live Measurement Levels screen to make sure the test signal is well above the room noise floor without clipping. A good target is roughly 20 dB of separation between the ambient noise floor and the test signal, with more being better if the room is quiet.
1. Start with Master output low and adjust Mic gain until the background noise is just below the −50 dB mark, or barely peaking above it. Depending on your microphone and room, you may need to reduce or increase the gain. If the room is noisy, reduce the mic gain and use a louder test signal level; if the room is quiet, you can use more mic gain and a lower test signal level.
2. Move all speaker and subwoofer channel sliders to their maximum, then turn the subwoofer's own gain or level control down as a precaution. If the subwoofer has a low-pass filter, make sure it is switched off or set to the highest value.
3. Click the play button for the left front speaker and slowly raise the master output until that channel plays at a comfortable level. The noise plays for about 30 seconds; press play again if you need to. Then click the play button for each speaker in turn and note which one is the softest. Omit the subwoofer for this step.
4. Click the play button for the softest speaker and raise Master output until its test signal is at least 20 dB above the room’s noise floor. Greater separation is better, provided playback remains comfortable and the input does not clip. In the illustrated example, this results in readings around −20 to −30 dB. Then play each other speaker in turn and reduce its channel level to match the softest speaker. Leave the subwoofer for the next step.
5. Move the subwoofer channel slider roughly to the same value as the loudest speaker, then click the play button for the subwoofer and turn the subwoofer's own gain or level knob up until it also reaches the same target range. Do not use the Dirac Live subwoofer slider for this step; the adjustment should be made on the subwoofer itself.
Proceed to the measure screen and hear the sweeps. When a measurement completes you'll see the frequency response displayed. A single sweep is fine for trying things out, but a good calibration uses more measurements.

If the volume is too low, the calibration may fail with “missing samples” or “poor signal-to-noise ratio.” If it is too high, it may fail with clipping. Return to Measurement Levels and adjust. Dirac Live resets Master output to its initial −34 dB value when you return to this screen, so you may need to restore the level you established earlier.

Also check your speaker configuration: if you configure 7.1.4 but have only 7.1.2, the missing speakers can cause “missing samples” errors.
The Dirac Live app encourages multiple sweep locations. Try a calibration with one location first to become familiar with the process, then do a full set of measurement locations for a better correction.
Proceed to Filter Design, select Bass management, and review the correction Dirac Live suggests. Drag the left and right correction limits to set the frequency range over which Dirac Live applies correction. These limits do not set the speakers’ crossover frequencies. Drag the target-curve points to change the desired response. With Bass Management, you can also adjust the crossover point and recalculate. Dirac Live's default target curve has a slight downward tilt at the low end; most users want more bass than that default:
The groups on the right let you review and adjust speakers together. You can move speakers between groups; the destination group’s target curve and crossover settings then apply to those speakers. Review the target curve and crossover response for each group.
Choose a slot to store this calibration in. The HTP-1 has up to six Dirac Live filter slots (the exact number is shown on the Calibration page heading). You can store calibrations for different room configurations, like curtains open and closed, or for different speaker layouts. Dirac Live suggests the names of physicists and philosophers; this name is visible in the HTP-1 UI, so choose something meaningful to you. The description is not visible in the HTP-1 UI, but you can add your own note to the slot afterward — see Calibration: Notes.
Export the filter. This takes a minute or two. When complete, the resulting filter is installed and enabled on the HTP-1. You can see this on the Calibration page.
Save the session as a Dirac Live "project" on your PC before you exit. Each project contains one calibration session and is tied to your HTP-1's serial number. A project can't be transferred to a different serial number, but you can ignore the warning that results from changing the name.
Close the Dirac Live app. The read-only banner on the HTP-1 should clear. If it doesn't, launch the Dirac Live app again, then close it.
Open the HTP-1 web interface and go to Settings → Calibration. If a calibration does not match your current speaker layout, the page displays a warning. Check your speaker configuration and the calibration you selected.
The calibration delay and trim values shown are what Dirac Live measured, applied whenever that filter is active. Notice that the delay and trim on one channel may read zero — that speaker was farthest from the microphone during calibration.

You can add User Delay and User Trim on top of the calibration values — see Calibration. These are only editable for RC and BM filters; BC and ART filters lock them, since adjusting delay or trim downstream of those calibrations would work against what the filter is doing. Total Delay cannot go below zero. Setting trim to a large value can work, but it sacrifices headroom you may want for other filters.

Dirac Live State: Off / Bypass / On¶

In the web interface, select Off, Bypass, or On directly. The On button also identifies the active calibration type, such as ART On.

The physical remote's Dirac button cycles through Off → On → Bypass → Off.

A slot without a Dirac Live calibration can still be used for manual adjustments. Selecting it switches Dirac Live off while retaining global PEQ and the slot's user delay and trim settings.

Off¶

Dirac Live filtering and its calibration delay and trim are disabled. User Delay and User Trim remain applied. The HTP-1’s own bass manager is used, regardless of the selected filter type. The button reads Off.

Bypass¶

Dirac Live filtering is disabled, but the calibration’s delay and trim remain applied, along with User Delay and User Trim. The button reads Bypass.

RC: The HTP-1’s own bass manager remains in use. Bypass lets you compare room correction on and off while retaining calibration delay, trim, and the same bass-management settings.
BM, BC, or ART: Bass management switches from Dirac Live to the HTP-1’s own bass manager. The audible difference therefore includes changes in bass management, rather than room correction alone.

Note

Before using Bypass with a BM, BC, or ART filter, check the HTP-1’s speaker size and crossover settings. These settings are independent of the Dirac Live calibration and are not automatically synchronized. Matching crossover frequencies does not guarantee identical bass management.

RC On / BM On / BC On / ART On¶

Dirac Live filtering and the calibration’s delay and trim are active. The button identifies the filter type, such as RC On or ART On.

RC: Dirac Live provides room correction; the HTP-1’s own bass manager handles bass management.
BM, BC, or ART: Dirac Live provides room correction and bass management; the HTP-1’s own bass manager is disabled.

User Delay and User Trim can be adjusted with RC and BM filters. These adjustments are locked for BC and ART filters.

If the current speaker layout has no calibration in any slot, the button instead shows a single No Filter state.

With a Dirac Live calibration active, the system may sound noticeably quieter than with Dirac Live off because the calibration can apply substantial negative trim values.

Tip

If you switch between On and Bypass often, consider a macro that does it in one press. See Macros.

Dirac Live Status¶

The status indicator shows whether Dirac Live is working correctly, preparing filters, or needs attention. Its label and color provide more information than a simple on/off indication.

Status	Meaning
Off / Bypass	Dirac Live filtering is intentionally disabled or bypassed.
Ready	Dirac Live is enabled and ready to process audio when playback starts.
Active	The correct filter is loaded and confirmed active for the selected slot and source.
Loading / Applying / Checking	A filter operation is in progress or the processor's state is being verified.
Filter Missing / Wrong Filter	The required filter is missing or the processor has loaded a different filter than expected.
Not Applied / Still Applied	The processor's actual filtering state does not match the selected setting.
Load Failed / Service Down / Setup Failed	A filter operation or service has failed and needs attention.

The Calibration page provides a detailed explanation when something needs attention. The Home page also shows a notice for problems that require action.

When recovery is possible, the interface offers an appropriate button, such as Load 48 kHz filter, Load correct filter, Apply Dirac Live again, or Restart Dirac Live Server.

Follow the action suggested by the interface. Restarting the Dirac Live server is not always necessary and will not resolve every missing-filter problem.

Tips for a Successful Dirac Live Calibration¶

Dirac Live is generally not too sensitive to small differences between calibrations, but a few tips can help it go more easily.

Make an initial measurement (one set of sweeps only) in the center of the sound stage, equidistant from and between the front left and right speakers, even if there is no seat there. After calibrating, check this by comparing the front left and front right Dirac Live Calibration Delay values on the Calibration page — they should be equal or very close.
For the first measurement only, the mic should be at ear height in the main seat. For the UMIK-1, the mic should point straight up, its tip at ear level, using the 90-degree calibration file.
A single measurement is useful for testing, but won't give Dirac Live enough information for a calibration that sounds good — it may sound dry and dull. More data produces better results.
Try to match speaker volumes using amplifier volume controls before relying on the sliders in the Dirac Live app.
- Establish proper levels for all speakers, including the sub channel, at the start of calibration. Dirac Live reduces the gain of speakers that are too loud but does not add gain for speakers that are too quiet — a speaker or group that starts too low will pull every channel's final level down to match it, which can be frustrating and require a much higher master volume to reach normal listening levels afterward. User trims can absorb differences of a few dB; differences of 10 dB should be fixed at the amplifier instead.
Take remaining measurements several inches above and below the first mic position. For example, if your seated ear height is 41 inches: take the first measurement at 41 inches, the next several around 49 inches, and the rest around 33 inches. Precision matters less for these later positions, but a consistent routine helps.
No two mic positions should be closer than about a foot to each other, and don't reuse a position for multiple measurements.
Keep mic positions at least a foot from reflective boundaries where possible. If seat backs sit close to a mic position, fully recline the seat during calibration.
At every mic position, the mic tip should have a clear line of sight to every speaker except subwoofers. Reclining seats can help with rear speakers.

Calibrating for Higher Sample Rates¶

The Dirac Live filter itself does not run above 48 kHz; a sample rate converter drops the rate to 48 kHz range whenever the filter is active. Calibration runs at the sample rate of the active input. 44.1 kHz input is supported for calibration; 48 kHz is recommended.

Tip

You might reserve one filter slot just for a "user only" set of delay and trim values, with no room-correction filter loaded.

Room Correction Methods and PEQ¶

A slot's calibration is one of four types, shown as a small badge after the slot name:

Type	What it is
RC — Dirac Live Room Correction	Standard correction; each speaker and subwoofer is treated individually.
BM — Dirac Live Bass Management	Like RC, but Dirac Live's own bass management replaces the HTP-1 bass manager.
BC — Dirac Live Bass Control	Like BM, with added optimization across multiple subwoofers — delays and filters are tuned to smooth the response over the listening area.
ART — Dirac Live Active Room Treatment	All speakers are optimized together as a matrix rather than one-to-one, using every speaker's measured capability to reproduce the content best at the listening position.

BC and ART both require phase alignment that a later delay or trim change would disturb, so both lock out User Delay and User Trim on the Calibration page. Use Channel Levels for a permanent trim adjustment under either filter type.

Dirac Live Room Correction is included with the HTP-1. Bass Control and Active Room Treatment require separate licenses from Dirac. ART also requires Bass Control when using one or more subwoofers. An existing Bass Control license satisfies that requirement; an ART license is still required.

A more comprehensive overview of Dirac Live ART™ is available at https://www.dirac.com/live/art-technology/.

Filter Storage and Slot Behavior¶

Filter Preparation¶

Each Dirac Live calibration uses separate filter versions for the 44.1 kHz and 48 kHz sample-rate families.

After a firmware update, the HTP-1 checks the filters for the current speaker layout and prepares any missing versions. This can take several minutes during the first startup. Missing versions may also be prepared automatically when the unit is idle.

Missing filters normally load automatically when nothing is playing. If the selected input continuously reports playback, the interface offers Load now. Loading pauses room correction for a few seconds.

When changing speaker layouts, the HTP-1 transfers the required filters to the audio processor. The progress display identifies the filter being loaded and shows an estimated remaining time when available.

When switching calibration slots, the HTP-1 keeps audio muted until the selected setup has loaded and been verified. Some controls are temporarily unavailable during this operation.

Slot Behavior¶

Filters reload on speaker-layout change. Whenever the speaker layout changes, filters for the new layout are loaded into a cache on the DSP. While a filter transfers, a progress overlay shows on screen. Once cached, switching between installed calibrations for the same layout is fast.
Filters are layout-specific. If the current speaker layout has no calibration in any slot, a warning explains this and lists the layouts that do have a calibration:

Dirac Live is disabled; there are no Dirac Live filters available for the current speaker layout.
Mismatched layouts are flagged. If the selected calibration does not match the current speaker configuration, a warning appears on the Calibration page:

The selected Dirac Live calibration does not match the current speaker configuration.

Check the speaker layout and selected calibration. Speakers that are not covered by a calibration pass through without filtering; user delay and trim can still be added to them. - Subwoofer mismatches are not flagged. Using a calibration made with more or fewer subwoofers than your current layout will still produce sound, but not optimally: extra subs get a copy of the first sub's signal, and a layout with fewer subs than the calibration only gets the primary sub signal. - The Dirac Live app can affect HTP-1 slots. Deselecting all filters in the app disables Dirac Live on the HTP-1. Deleting a slot in the app removes that slot's user delay and trim on the HTP-1. Transferring a new filter into a slot resets that slot's user delay and trim to zero. - Speaker-dependent delay is capped at about 35 ms (roughly 35 feet, or 10.7 meters, of distance difference to the listener). If your room would need more, the applied delay may be zero for the affected speaker — worth knowing if you're calibrating a very large room.

Troubleshooting¶

Resolving Dirac Live Problems¶

If Dirac Live reports a problem, open the Calibration page and read the displayed message.

Filter Missing or Wrong Filter: Use the offered filter-loading button.
Not Applied or Still Applied: Apply the selected Dirac Live setting again. If this fails, the interface may recommend restarting the Dirac Live server.
Load Interrupted: Load the filter again when prompted.
Service Down or Setup Failed: Use Restart Dirac Live Server when offered.
Cache Damaged: The stored calibration may need to be transferred again from the Dirac Live app.

Some filter loads may be refused when no audio is playing. If a load cannot be completed, start playback and try the suggested recovery action again.

Dirac Live does not support 32 kHz audio. If the interface reports an unsupported sample rate, switch Dirac Live off while playing that source.

Tip

Loading several calibrations for a large speaker layout can take several minutes. Wait until the filter transfer has finished before changing the configuration again.

Speaker layout after upgrading from a 1.x release

Check that the Speakers page shows your intended layout before running a new calibration. See Upgrading from Version 1.x for the migration procedure.