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SUNN Beta Lead IR Pack

Cabinet impulse pack
Shift Line SUNN Beta Lead IR Pack is a pack of impulses (IR) that can be used with our A+ CabZone LE cabsim or with any other cabinet simulator, either hardware or software.

The impulses were recorded and edited by the Shift Line team in St. Petersburg, Russia. This is the second instalment in the series of exclusive impulses recorded from lesser-known and somewhat rare cabinets. The previous pack was comprised of impulses recorded from the Shift Line SUNN 200s IR Pack.
This pack is distributed on the Pay-What-You-Want basis: this means you name your own price. No matter how much you pay (if anything), the files are always available for you to download.


The Sunn Beta Lead is a legendary combo amp with a peculiar design and distinct sound. Given the abundance of tube amps on the market, why would anyone even think of solid-state ones? The reason is simple: with some amps, you're too busy enjoying the sound to care whether they are tube or solid-state. The Beta Lead is one of those.

Sure, it doesn't give you a universally applicable guitar sound. Sure, it doesn't make your eyes water with its singing. What it does is bark and bite — and it does that well. This impulse pack isn't the first time we've addressed this amp: a limited run of our preamps was based on the Sunn Beta Lead. Now, you can try out the impulses of this amp's unique cab and hear for yourself why it's so special.

Two 12-inch speakers angled towards each other inside an open-back cab make for a rare design solution — one that ensures a unique sound but also brings about an array of problems for the sound engineer trying to record the cab with a traditional mic setup. The angled speaker cones create a rather complex frequency/phase curve, and mic placement has a drastic influence on the resulting sound. With the Beta Lead, getting consistent results while recording is tricky — but on the flipside, there's a huge sound palette available from that single cabinet.

Two mics were used for recording: a Sennheiser e906 and a Lomo 19A19. The Sunn Beta Lead power amp was also used. Each of the 10 impulses in the pack has different mic positioning, mic combinations and balance between them (see details below).


CabZone LE: Unpack the archive into the root directory of a blank MicroSD card. An AFX folder should appear on the card along with text description files.

Twin MkIIIS: Copy the needed impulses into the appropriate folders on the SD card. Remember to delete any old files in the folders beforehand.

All impulses in the pack have a 24bit 48kHZ WAVE PCM1 non-compressed format and are adapted to working with our devices (A+ CabZone LE cabsim and Shift Line Twin MkIIIS tube preamp). Of course, you can also use them in any device or software that supports that format.

Mic positioning schematics

SUNN Beta Lead

Details on each impulse

The impulses in the pack have the necessary minimum frequency correction. Each impulse is a snapshot of a particular "cab/mic/preamp" combination. The design of the cabinet implies inevitable frequence/phase clashing when using a microphone to record the speakers facing each other. Thus, most impulses in this pack have a deep scoop (notch filtering) happening at particular frequencies. This impulse pack will feel at home in genres like sludge, doom, desert and stoner rock, although you are surely welcome to use it in traditional rock or pop music.

For easier navigation, the name of each impulse reflects the position and type of the mic used.
• 01 BetaLead center e906 is an impulse recorded from the center of the speaker with a Sennheiser e906 mic placed perpendicular to the speaker cone. The characteristic frequency scoop caused by the second speaker's interference is at 5170Hz here. The impulse highlights the areas of 350Hz (which is typical of the cab in general) and 2200Hz, thus giving the sound a lot of punch and bite despite the relatively tame lows on the frequency spectrum.

• 02 BetaLead cone e906 was also recorded with the Sennheiser e906 mic — this time, placed at the center of the speaker cone. Unlike the first impulse, this one doesn't have any prominent notch filtering. The spike at 350Hz, however, is more noticeable; the 1000Hz area also has a bit of a boost. Without the deep scoop, the overall sound is more balanced and lends itself very well to distortion.

• 03 BetaLead cab25 e906 was recorded with the Sennheiser e906 placed 25cm from the protective mesh and pointed right in the middle of the cab. This impulse might be the best reproduction of how the cab feels when used at a close distance in real life. The characteristic notch is at 1030Hz which makes the mids sound a bit scooped but results in a rather "neutral" sound to an extent.

• 04 BetaLead cab25 L19 employs the same mic positioning as the previous impulse; however, this time the Lomo 19A19 is used, which results in a completely different image. The notch around 1000Hz is still present — but now the mids sound way more scooped, while the highs and lows are more open. This one will work great if you want an "open" sound without the nasal mids.

• 05 BetaLead dome edge e906 was recorded with the Sennheiser e906 placed 10cm from the speaker and pointed at the edge of the protective dome. The impulse boasts focused mids with no prominent boosts or scoops except for a slight low-frequency rolloff.

• 06 BetaLead dome edge L19 was recorded with the Lomo 19A19 in the same position as the mic in the previous impulse. The noticeable upper bass boost around 280Hz coupled with a wider frequency response will ensure that your distorted guitar sounds like a bulldozer — or just add a little body to your clean signal.

• 07 BetaLead cab75 e906 will work well if you're aiming for a wall of sound but also don't want to take up all the mids in the mix. This impulse has not one but two sharp notches (at 1100Hz and 1800Hz) which make the sound a little "boxy" but help it to fill in the guitar range. The impulse was recorded with the Sennheiser e906 placed 75cm from the cab, slightly offset from the center.

• 08 BetaLead cab75 L19 uses the same mic distance as #7 but switches the Sennheiser e906 for the Lomo 19A19. This impulse has a prominent upper bass boost and a noticeable mids scoop resulting from the mic being exactly aligned with the center of the cab. The boosted highs give the sound some extra bite; however, the impulse works very well for clean guitar, too.

• 09 BetaLead cab15 L19 was recorded with the Lomo 19A19 mic placed 15cm from the protective mesh and aligned with the center of the cab. This is probably the most bass-heavy impulse in the pack, and there are no prominent scoops. The peaks at 2500Hz and 6100Hz add some clarity, while the mild rolloff at the low mids suggests using this impulse in heavy genres.

• 10 BetaLead cab50 plusback L19 is a sum of two impulses recorded with the Lomo 19A19 mic and united into one with phase correction. The mic was placed at two points: 50cm from the cab (aligned with the cab's center) and 25cm behind the open-back cab. This impulse will make you feel like you're playing into a combo placed right next to you. Unlike impulse #3, this one sounds wide, squishy and a little boxy. Switching between #3 and #10, you can hear how different the Sunn Beta Lead can sound.

Our aim was to provide you with 10 really characteristic sounds that the Sunn Beta Lead can offer. Now it's up to you to choose which one you like best!

Terms of Use

Commercial use of the Shift Line SUNN Beta Lead IR Pack or its parts (such as implementing it in third-party hardware or software) is possible with our permission. Please contact us at

Our devices where the impulses can be used