(Reuters) - Snap Inc SNAP.N, owner of the popular messaging app Snapchat, set a lower-than-expected valuation range on Thursday, amid mounting investor concern over its unproven business model, slowing growth and tight founder control.

A Snapchat sign hangs on the facade of the New York Stock Exchange (NYSE) in New York City, U.S., January 23, 2017. REUTERS/Brendan McDermid

The company, which filed for an initial public offering earlier this month, was widely expected to be valued at between $20 billion and $25 billion. However it said on Thursday it was targeting a valuation between $19.5 billion and $22.3 billion, ahead of an investor roadshow due to start on Monday in London.

The lower valuation range reflected initial investor feedback. Snap wants to ensure there is sufficient demand for shares of the company that it trades up on its first day in public market.

Investors have been poring over the filing for Snap's upcoming IPO to assess whether the still-unprofitable company will be the next Facebook Inc FB.O, which has figured out how to make money from its social media platform, or if it will be more like Twitter Inc TWTR.N, which is struggling to achieve the same goal.

With platform-hopping millennials as its prime customer base, and constantly evolving competition, the fact that Snapchat’s new user growth has already begun to slow concerns investors, sources said, asking not to be named because the deliberations are confidential.

New active user growth was mostly flat in the early part of the last quarter in 2016, according to the IPO filing. Facebook’s Instagram, which had 600 million users as of late 2016, has introduced its own form of disappearing video content. On average, Snapchat has 158 million daily users.

“Snap is already demonstrating decelerating growth before they have managed to break even,” said Yann Magnan, managing director at Duff & Phelps.

Unlike social media platforms such as Twitter and Facebook, Snapchat can be harder for new users to understand and easier for non-users to avoid, some investors said.

"With Facebook you almost feel left out, socially, if you’re not on it. You may miss a picture or invitations. I don’t get the sense people feel they’re missing out if they’re not on it,” said Chris Carter, portfolio manager for the Buffalo Growth Fund BUFGX.O who has not yet made a decision on whether to buy Snap shares.

Still, Snap proponents argue a more limited user base lends it more loyalty and opportunity for the company to make money.

Snap, which is going public at a much earlier stage in its development than Twitter or Facebook, saw its loss widen to $514.64 million in 2016 from $372.89 million a year earlier. While not rare for a young company to be unprofitable, it is less common for an unprofitable company only five years old to ask for as whopping a valuation as Snap is aiming for.

With Snap’s estimated valuation expected to be around 49 times revenue, and Facebook’s being 27 times, the IPO aspirations “stress how much Snap’s post-IPO growth must exceed Facebook’s to compensate for its lack of short-term profitability” said Magnan at Duff & Phelps.

Snap generates most of its revenue from advertising and will pay Google $2 billion over the next five years to use its cloud computing services.

Investors have also raised concerns over Snap’s first of its kind three-share class structure, which gives no voting rights to IPO investors. Snap’s co-founders Evan Spiegel and Bobby Murphy will have the right of ten votes for every share, and existing investors will have one vote for each of their shares.

“Evan is going to have to earn Wall Street’s trust. If he does that, the ownership issue goes away,” said Nabil Elsheshai, senior research analyst for Thrivent Financial in Minneapolis.

ROADSHOW

The company’s marketing roadshow will take place in London, New York, Boston and San Francisco. Snap is expecting to price its IPO after the U.S. market closes on March 1, according to a confidential document seen by Reuters.

Snap said in a filing on Thursday it expected to raise as much as $3.2 billion from the offering of 200 million Class A shares. The offering is expected to be priced between $14 and $16 per share.

Even at the low end of that expected valuation range, Snap would be the largest tech offering since Alibaba’s IPO in 2014, and after last year’s paucity of tech listings, its public launch will be closely watched.

Selling shareholders, who include Spiegel, Murphy and former Sony CEO Michael Lynton, will sell 55 million shares in total. If the IPO prices on the higher end of the current range, Spiegel and Murphy would both make $256 million on the IPO and Lynton would make $878,000.

Early Snap investors venture firm Benchmark Capital Partners would reap $171 million from the offering if it prices at the top of the range.

Snap will have about 1.16 billion shares outstanding after the offering and list on the New York Stock Exchange under the symbol SNAP.

Snap said it expected to use proceeds of about $2.1 billion for general corporate purposes and to acquire businesses, among other things.

Snap, which launched in 2012 with an app that sends disappearing messages, rebranded itself last year as a camera company and started selling $130 video camera glasses.

Morgan Stanley & Co LLC, Goldman Sachs & Co, JP Morgan Securities LLC, Deutsche Bank Securities Inc, Barclays Capital Inc and Credit Suisse Securities (USA) LLC are among the underwriters to the IPO.