Brindlemoor — Consumer Subscription Exercise
An 8-hour Venture Investment Exercise case study with a complete model answer
Modeled After
Greenoaks
The open exercise format Greenoaks is reported to set, with a firm-provided panel dataset that must be transformed from calendar space into periods-since-acquisition space before it says anything, and which is intentionally wired into nothing else in the model.
Structure and exercise format are modeled after Greenoaks — the take-home exercise format the firm is reported to use. The company, the panel data and every figure in this case are entirely our own.
The Situation
Brindlemoor Audio, Inc. sells a monthly subscription to audiobooks and spoken-word audio.
Brindlemoor Audio, Inc.
- Sector
- Consumer subscription — audiobooks and spoken-word audio, sold at one monthly price with unlimited listening, under publisher agreements that pay a share of subscription revenue
- Size
- Geography
- Established markets, where price is higher and the curve is flatter, and developing markets, where price is roughly two-fifths of it, the curve is steeper and almost all of the subscriber growth is happening
- Ownership
- Situation
The Prompt
You are a candidate for an investment role at a fund that holds positions for years rather than quarters. The exercise arrives by email on a Friday afternoon with a short note:
"Brindlemoor Audio.
Supporting Materials
What you are handed at the start of the case, in the format a real process would use.
Blank modeling template (template.xlsx)
The card panel (given in the template)
Market and third-party data (given in the template)
What You Have to Produce
The deliverables, in the order the committee will read them. The exercise runs 480 minutes.
PART 1
Model retention as a curve, and separate what you can see from what you assume
PART 2
Price the same model with retention read as a RATE, in both directions
PART 3
Say what the terminal value is actually a claim about
PART 4
Take the cost of revenue apart before you assume any of it levers
PART 5
Build the subscriber roll, and print gross adds, churn and net adds separately
PART 6
Read both blended statistics against the components inside them
PART 7
Strike a lifetime value you can defend, and print the flattering one beside it
PART 8
Value it, then back out what the market has to believe
PART 9
Answer the industry question with a counterfactual, and decide what to do with the file
Attempt It First
Blank modelling template
The answer model with every produced cell cleared — the shell you build your attempt in. Work it in Excel against the clock, then check yourself against the model answer below.
How to Approach It
The order a strong candidate works in, and why. This is the shape of the answer — the finished memo and Excel model are in the solution set below.
- 0:00 – 0:40
read everything, and decide about the panel early
- 0:40 – 2:20
the curve, and everything that comes out of it
- 2:20 – 3:40
the subscriber build
- 3:40 – 5:20
the cost of revenue and the cash flows
- 5:20 – 6:40
sensitivities
- 6:40 – 8:00
write it
Key Concepts
The ideas this case is built on. Know these cold and the case becomes a question of execution rather than knowledge.
Retention curve versus retention rate
Consumer churn is front-loaded and the surviving cohort's monthly churn falls with tenure, so retention is a distribution rather than a number. A single blended monthly rate is one point drawn from that distribution, and which point you drew decides the answer — sampled early it destroys the valuation, sampled late it flatters it. Neither is conservative; both are the same mistake.
The tail
What a subscriber does past the last month the data observes. It is one number, it is compounded twelve times into an annual retention rate, and for a business whose terminal value is most of its enterprise value it is what the whole valuation is a claim about. Reading it off a curve fitted on earlier months does not make it observed; it makes the assumption harder to see.
Marginal versus average gross margin
The average margin is what the income statement earns. The marginal margin is what one more subscriber-month leaves behind, and it excludes any cost that a marginal subscriber does not move — a minimum guarantee signed before they arrived is a cost of the business but not a cost of them. The second one is what belongs in a lifetime value, and using the first understates every subscriber.
Gross versus net subscriber adds
Net adds are gross adds less the subscribers the curve removes, and the second term grows with the installed base. So a company can hold gross adds flat, deteriorate in nothing, and still report falling net adds. Printing only one of the two rows is how a subscriber base gets misread in either direction.
Replacement adds at steady state
The gross adds a subscription business must buy every year forever simply to hold its base at the assumed growth rate. It falls out of the stationary tenure mix rather than being assumed, and it is the mechanism by which a retention curve becomes a terminal operating margin: worse retention means more adds, more adds mean more acquisition spend, and that spend goes straight through the margin the terminal value capitalizes.
A royalty stack
A cost of revenue paid as a share of revenue rather than as a fee per unit. It has no operating leverage at all — it is the same percentage at any scale — so a subscription business under one does not converge on software gross margins however large it gets. The only lever is the mix of what is being consumed.
Blended statistics and mix
A blended ARPU can grow more slowly than every component inside it, and a blended acquisition cost can grow faster than every component inside it, purely because the mix underneath is moving. Both are correct arithmetic and both are the wrong instrument for the question they usually get asked.
Implied expectations
Solving for the assumption today's price requires rather than arguing about whether the price is wrong. It converts a valuation disagreement into a specific, testable claim — and the useful follow-up is whether that assumption is free, because an input that can only move if another line pays for it is a much narrower disagreement than the price gap suggests.
What Makes It Hard
The specific traps in this case — the places candidates lose the assessment without noticing.
Check Your Answer
Type the figures you produced and find out how many are right before you open the worked answer. You get a verdict and, where you are off, a pointer to the part of the build to re-check — never the number itself. Everything you type stays on this device.
How to type a figure. Digits, with an optional unit: 1,234.5, $1,234.5, 2.6x, 21.4%. For a negative use (20.0) or -20.0. Enter as many decimals as you carried — precision is never penalised.
What the Case Asked For
The arithmetic is only half of it. Tick off what you actually produced — this half is yours to score, because nothing can grade a written recommendation from a checkbox.
The Model Answer
The worked answer in full: memo and Excel model, built the way a banker would actually build them. It is a reference, not a submission — a strong answer under the clock is far shorter.
What the Solution Covers
- —Subscriber cohort retention from a provided panel
- —ARPU and mix shift
- —Content or catalogue cost as a margin constraint
- —Gross versus net subscriber adds
- —Long-term margin structure under a royalty stack
- —Scratch valuation
Memo
The written recommendation and how it was reached
Upgrade to Diamond
Sign up and upgrade to Diamond to unlock the memo, the Excel model and the audio walkthrough.
Get StartedThe Excel Model
The model is linked and tied out end to end — every schedule, every formula and every check, in the file itself.
Downloads are available to Diamond members
Excel Model and Memo (PDF) — yours to open, edit and rebuild
Walkthrough
A conversational walkthrough of how to approach the case under time pressure — where to start, what to cut, and how the recommendation gets defended.
Audio Walkthrough
How to approach Brindlemoor — Consumer Subscription Exercise
60-second preview — upgrade to Diamond for the full walkthrough
Frequently Asked Questions
Is this a modeling test or a judgment test?
Judgment, and the model exists to make the judgment falsifiable. The brief says explicitly that hygiene is not what is being graded and that the memorandum is the deliverable. A back-of-the-envelope model that announces its own crudeness and makes the written argument checkable beats a polished one attached to two pages of hedging.
How do I decide what a subscriber past three years does?
You cannot decide it from the data. Fit the curve on what you can see, state the tail as its own assumption in its own row, and then price the answer under a tail that settles, one that keeps improving and one that stops improving. Reading how much of the enterprise value moves with that one number is the answer to a question the exercise never asks out loud.
Should I use LTV to CAC?
Yes, and declare all three things that make it checkable: the margin basis, the discount rate and the horizon. Strike it on the marginal gross margin rather than the average one. Then compute the undiscounted, infinite-horizon version most decks print and show how much it flatters — quantifying it is worth more than leaving it out, and it should then drive nothing.
Does net revenue retention apply here?
No, and importing it is the specific way this exercise goes wrong in kind rather than in detail. Net revenue retention measures a customer that grows. A consumer subscriber on a flat monthly price does not add seats, so the instrument reports a number about a different business. The consumer equivalents are the survival curve, the replacement adds a steady state requires, and the mix.
Is there a leveraged buyout in this case?
No. There is no sponsor, no acquisition debt, no cash sweep, no exit multiple and no returns bridge — the company carries no debt at all, so any attribution leaning on deleveraging has nothing to lean on. The question is what steady-state margin structure a business under a royalty stack supports and what that structure is worth.
What do I do with the card panel?
Transform it in separated steps — aggregate, re-align out of calendar space into periods since acquisition, then index each cohort to its own period zero — and write down what you could not resolve about it before you started. Then decide what its window can support. Doing the work and then refusing to build the thesis on it is the behavior this exercise rewards; ignoring it because it is awkward and leaning on it because it was given to you are both wrong.
How much of the eight hours should go on the model?
Less than you think. The workbook is a constraint on the argument rather than the deliverable, and the template's scope table prints the number of distinct formulas so you can plan against it. Finish every tab roughly before you perfect any tab, and leave the last block of the clock for the memorandum.
Is this format still used?
Yes, and it is the most transferable of the long-only and growth formats because it is closest to the actual work. A firm sends three open questions and one imperfect file, and wants to see how you decide what is worth knowing, where you stop, and what you are willing to put your name to.
About This Venture Investment Exercise Case Study
Venture Investment Exercise case study for venture & growth interviews. 480-minute format covering subscriber cohort retention from a provided panel, arpu and mix shift, content or catalogue cost as a margin constraint. Includes the full prompt, a written memo, a tied-out Excel model and an audio walkthrough.
This case study sits in Venture & Growth, under Investment Exercises. Every case ships with the full prompt, the supporting materials, a complete model answer and an audio walkthrough of the judgment behind the recommendation.
480-Minute Format
The time limit a real assessment would give you
Memo
Included in the model answer
Excel Model
Included in the model answer
Audio Walkthrough
How to approach the case under time pressure
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